Yarn Technology and QYarn Technology and Quality uality

By Zhang Shangyong ,Wang XungaiBy Zhang Shangyong ,Wang Xungai

► ChapterChapter 1 1 Fundamentals of Yarn Fundamentals of Yarn TechnologyTechnology

► ChapterChapter 2 2 Yarn Evenness Yarn Evenness► ChapterChapter 3 3 Fibre Preparations for Spinning Fibre Preparations for Spinning► ChapterChapter 4 4 Yarn Spinning Systems Yarn Spinning Systems► ChapterChapter 5 5 Yarn Technology Extension Yarn Technology Extension

Chapter 1 Fundamentals of Yarn Chapter 1 Fundamentals of Yarn TechnologyTechnology

► 1.1 Yarn count1.1 Yarn count ► 1.2 Yarn twist 1.2 Yarn twist ► 1.3 The designation of yarn structures 1.3 The designation of yarn structures

1.1 Yarn count1.1 Yarn count （纱线细度）（纱线细度）IntroductionIntroduction

Yarns come in different sizes. They can be Yarns come in different sizes. They can be quite thick, or they can be very thin. Since quite thick, or they can be very thin. Since by their very nature textile yarns are soft by their very nature textile yarns are soft and squashy, the ‘thickness’ of a yarn can and squashy, the ‘thickness’ of a yarn can not be easily measured by yarn diameter. not be easily measured by yarn diameter. But textile yarns are often sold on a weight But textile yarns are often sold on a weight basis, so it is natural to express the size of basis, so it is natural to express the size of a yarn in terms of its weight or mass. a yarn in terms of its weight or mass.

The two basic ways of doing this are by The two basic ways of doing this are by

indicating either how much a given length indicating either how much a given length

of yarn weighs (the direct system)of yarn weighs (the direct system) （定长（定长制）制） or what the length of yarn will be in or what the length of yarn will be in

a given weight (the indirect system)a given weight (the indirect system) （定（定重制）重制） . .

These two broad yarn count systems are These two broad yarn count systems are expressed belowexpressed below

lengthGiven

yarnofWeightcountyarnDirect

weightGiven

yarnofLengthcountyarnIndirect

Because a textile yarn is usually a very Because a textile yarn is usually a very

slender assembly of tiny fibres, it is slender assembly of tiny fibres, it is

conceivable that the weight of a yarn in a conceivable that the weight of a yarn in a

given length will be very small while the given length will be very small while the

length of a yarn in a given weight will be length of a yarn in a given weight will be

quite large. quite large.

Consequently, the yarn count figures would Consequently, the yarn count figures would

get either incredibly small (direct system) get either incredibly small (direct system)

or large (indirect system) unless special or large (indirect system) unless special

units are used. Over the years, many units are used. Over the years, many

different units have been used in different different units have been used in different

sectors of the textile industry. This topic sectors of the textile industry. This topic

describes these different units and the describes these different units and the

conversions involved.conversions involved.

ObjectivesObjectives

At the end of this topic you should be able to:At the end of this topic you should be able to:

understand the definitions for different understand the definitions for different yarn count systemsyarn count systems

know the conversion between yarn know the conversion between yarn countscounts

appreciate the effect of moisture on yarn appreciate the effect of moisture on yarn count results count results

Direct Count SystemsDirect Count Systems

The direct systems are based on the weight or The direct systems are based on the weight or

mass per unit length of yarn. Some typical mass per unit length of yarn. Some typical

direct systems are given below, together direct systems are given below, together

with their definitions. Please note that while with their definitions. Please note that while

the weight unit is gram, different lengths are the weight unit is gram, different lengths are

used in the definitions.used in the definitions.

1.Tex 1.Tex （特克斯）（特克斯） (g/1000m)(g/1000m)

This is the mass in gram of one kilometre, or This is the mass in gram of one kilometre, or 1,000 metres, of the product.1,000 metres, of the product.

If one thousand meters of yarn weigh 20 grams or If one thousand meters of yarn weigh 20 grams or one hundred meters of the yarn weigh 2 grams, one hundred meters of the yarn weigh 2 grams, the yarn would be 20 tex. On the other hand, if the yarn would be 20 tex. On the other hand, if 100 metres of yarn weigh 5 grams, then the count 100 metres of yarn weigh 5 grams, then the count of the yarn will be 50 tex.of the yarn will be 50 tex.

2.Dtex 2.Dtex （分特）（分特） (g/10,000m)(g/10,000m)

This is called deci-tex. It is the mass in gram of ten This is called deci-tex. It is the mass in gram of ten kilometre, or 10,000 metres, of the product. It is a kilometre, or 10,000 metres, of the product. It is a smaller unit than tex (1 tex = 10 dtex), and is smaller unit than tex (1 tex = 10 dtex), and is usually used for fibres and filament yarns.usually used for fibres and filament yarns.

A 167 dtex polyester filament would weigh A 167 dtex polyester filament would weigh 167 grams for every 10,000 meters of the 167 grams for every 10,000 meters of the filament. filament.

3.Ktex3.Ktex （千特） （千特） (g/m)(g/m)

This is called kilo-tex. It is the mass in gram of This is called kilo-tex. It is the mass in gram of one metre of the product. It is a much larger one metre of the product. It is a much larger unit than tex (1 ktex = 1,000 tex), and is unit than tex (1 ktex = 1,000 tex), and is usually used for heavy products such as slivers.usually used for heavy products such as slivers.

If a sliver weighs 5 grams per metre, then the If a sliver weighs 5 grams per metre, then the count of this sliver would be 5 ktex.count of this sliver would be 5 ktex.

The tex system (tex, ktex, dtex) is the preferred The tex system (tex, ktex, dtex) is the preferred standard system. By definition, standard system. By definition,

1 ktex = 1,000 tex = 10,000 dtex1 ktex = 1,000 tex = 10,000 dtex

4.Denier4.Denier （旦尼尔） （旦尼尔） (g/9,000m)(g/9,000m)

Denier is also used extensively in the industry, Denier is also used extensively in the industry, particularly for manufactured fibres and silk. It particularly for manufactured fibres and silk. It is the mass in gram of nine kilometres, or 9,000 is the mass in gram of nine kilometres, or 9,000 metres, of the product. metres, of the product.

By definition,By definition,

1 dtex = 0.9 denier1 dtex = 0.9 denier

If a 300 denier yarn is made up of 1.5 denier If a 300 denier yarn is made up of 1.5 denier individual filaments, there will be a total individual filaments, there will be a total number of filaments in the yarn.number of filaments in the yarn.

Indirect Count SystemsIndirect Count Systems Indirect count systems are not as straightforward Indirect count systems are not as straightforward

as the direct ones. In the early history of yarn as the direct ones. In the early history of yarn manufacture, different spinners, often manufacture, different spinners, often geographically and culturally isolated from one geographically and culturally isolated from one another, devised their own ways of measuring another, devised their own ways of measuring yarn thickness. Consequently, there are numerous yarn thickness. Consequently, there are numerous indirect count systems that have been, and indirect count systems that have been, and continue to be, used in the industry.continue to be, used in the industry.

Some examples are given below, together Some examples are given below, together with the mass and length conversionswith the mass and length conversions ：：

1.Commonly used1.Commonly used

- - MetricMetric （公制）（公制） (N(Nmm)) m/g m/g

- English Cotton- English Cotton （英制棉纱）（英制棉纱） (N(Necec)) No. of 840 yardNo. of 840 yard

hanks per hanks per poundpound

- Worsted- Worsted （精纱毛纱英制）（精纱毛纱英制） (N(Nww) No. of 560 yard) No. of 560 yard

hanks per hanks per poundpound

The metric count (NThe metric count (Nmm) is relatively ) is relatively straightforward. It is the length in metre of straightforward. It is the length in metre of one gram of the product. For example, if one one gram of the product. For example, if one gram of yarn measures 40 metres, then the gram of yarn measures 40 metres, then the metric count of this yarn would be 40 Nmetric count of this yarn would be 40 Nmm. .

Similarly, if one pound of cotton yarn Similarly, if one pound of cotton yarn measures 1,680 yards, or two hanks of 840 measures 1,680 yards, or two hanks of 840 yards, the English cotton count of this yarn yards, the English cotton count of this yarn will be 2 Nwill be 2 Necec. Please note that a hank of yarn . Please note that a hank of yarn is an unsupported coil consisting of wraps of is an unsupported coil consisting of wraps of yarn of a certain length.yarn of a certain length.

The conversions between different units will The conversions between different units will be discussed later. be discussed later.

2.Less commonly used2.Less commonly used

- linen- linen （亚麻）（亚麻） , hemp, hemp （大麻） （大麻） No. of 300 yard No. of 300 yard

,ramie,ramie （苎麻）（苎麻） hanks per pound hanks per pound

- asbestos- asbestos(( 石棉）石棉） " " 50 " " " "" " 50 " " " "

- glass- glass （玻璃丝（玻璃丝 )) " " 100 " " " " " 100 " " "

""

- spun silk- spun silk （绢丝）（绢丝） " " 840 " " " "" " 840 " " " "

- raw silk - raw silk （生丝）（生丝） " " 1000 " " " ounce" " 1000 " " " ounce

3.Occasionally used in the woollen industry3.Occasionally used in the woollen industry

- Yorkshire skein No. of 560 yard hanks- Yorkshire skein No. of 560 yard hanks

per poundper pound

-West of England " " 320 " " " "-West of England " " 320 " " " "

- American cut - American cut " " 300 " " " " " " 300 " " " "

- American run " " 100 " " " ounce- American run " " 100 " " " ounce

- Dewsbury - Dewsbury " " 1 " " " ounce " " 1 " " " ounce

- Galashiels - Galashiels " " 300 " " " " " 300 " " " 24ounces24ounces

You may wonder how the strange length You may wonder how the strange length units such as 840 yard hank and 560 units such as 840 yard hank and 560 yard hank came about. The first mass-yard hank came about. The first mass-production spinner – the spinning-jenny production spinner – the spinning-jenny was able to spin yarns simultaneously was able to spin yarns simultaneously onto several bobbinsonto several bobbins （滚筒）（滚筒） and filled and filled the bobbins up at the same time. The the bobbins up at the same time. The bobbins were changed after 840 yards of bobbins were changed after 840 yards of cotton yarns were wound onto them. To cotton yarns were wound onto them. To estimate the thickness of the yarns, the estimate the thickness of the yarns, the spinner simply counted how many full spinner simply counted how many full bobbins were needed to balance a bobbins were needed to balance a weight of one pound. weight of one pound.

Conversion between Different Yarn CountsConversion between Different Yarn Counts It is often necessary to make conversions It is often necessary to make conversions

between different yarn count systems. For between different yarn count systems. For this purpose, the following mass (weight) and this purpose, the following mass (weight) and length conversions are needed:length conversions are needed:

1 yard (yd)= 0.9144 m1 yard (yd)= 0.9144 m

1 pound (lb)= 0.4536 kg1 pound (lb)= 0.4536 kg

1 ounce (oz)= 1/16 lb1 ounce (oz)= 1/16 lb

1 dram 9dr)= 1/16 oz1 dram 9dr)= 1/16 oz

1 grain (gr)= 1/7000 lb1 grain (gr)= 1/7000 lb

Worked ExamplesWorked Examples

Question1:Question1: What is the conversion factor between What is the conversion factor between

worsted count (Nw) and tex ?worsted count (Nw) and tex ?Solution:Solution: According to definition, one worsted count According to definition, one worsted count

(Nw) = one 560 yard hank per pound, or(Nw) = one 560 yard hank per pound, or

Since 1 yard (yd) = 0.9144 m and 1 pound Since 1 yard (yd) = 0.9144 m and 1 pound

(lb) = 0.4536 kg, the above equation (lb) = 0.4536 kg, the above equation becomes, becomes,

pound

yardNw

56011

g

m

g

m

g

mNw

12892.1

6.453

064.512

6.453

9144.056011

Therefore, for a yarn of NTherefore, for a yarn of Nww worsted count, worsted count, each gram of this yarn would measure each gram of this yarn would measure 1.12892 times N1.12892 times Nww meters. Since tex is the meters. Since tex is the mass in gram of a 1,000 meters of yarn, we mass in gram of a 1,000 meters of yarn, we need the number of grams in 1000 m of the need the number of grams in 1000 m of the yarn.yarn.

The above equation can also be written as: The above equation can also be written as:

So the conversion factor is 885.5So the conversion factor is 885.5..

NwNw

texmpergramsofNo8.885

12892.1

10001000

texNw

8.885

Question2:Question2:

If a yarn is 20 tex, what is the worsted count of If a yarn is 20 tex, what is the worsted count of this yarn?this yarn?

Answer:Answer:

Using the conversion factor given above, the Using the conversion factor given above, the worsted yarn count is worsted yarn count is

Conversion between other count systems can Conversion between other count systems can be worked out in a similar way. Table 1.1 lists be worked out in a similar way. Table 1.1 lists commonly used conversion factors. You may commonly used conversion factors. You may try to work them out yourself. try to work them out yourself.

Nw3.4420

8.885

Moisture and Yarn CountMoisture and Yarn Count

Regardless of the yarn count system used, it is Regardless of the yarn count system used, it is necessary to measure the weight and length of a necessary to measure the weight and length of a yarn in order to determine its count. But most yarn in order to determine its count. But most fibres, particularly natural fibres, absorb moisture fibres, particularly natural fibres, absorb moisture from atmosphere. The weight of the yarn will be from atmosphere. The weight of the yarn will be different at different moisture level. The water different at different moisture level. The water content in textiles can be expressed as either content in textiles can be expressed as either moisture content moisture content （含水率）（含水率） or as regain or as regain （回（回潮率）潮率） . .

Their definitions are:Their definitions are:

From these definitions, the conversion From these definitions, the conversion between regainbetween regain (R)(R) and moisture content (M)and moisture content (M) can be worked out according to the equation can be worked out according to the equation below:below:

100)(

)()(Re

DspecimendryofMass

WspecimeninwaterabsorbedofMassRgain

100)(

)()(

DWspecimenundriedoriginalofMass

WspecimeminwaterabsorbedofMassMcontentMoisture

R

RM

1

In commercial transactions, the mass In commercial transactions, the mass to invoice is worked out on the basis of to invoice is worked out on the basis of an agreed conventional regain level, an agreed conventional regain level, not on the actual regain of the yarns not on the actual regain of the yarns (or other textiles) being traded. This is (or other textiles) being traded. This is very important. Because, in the very important. Because, in the absence of an agreed conventional absence of an agreed conventional regain level, smart sellers may take regain level, smart sellers may take advantage of the moisture absorption advantage of the moisture absorption property of their textiles and rip the property of their textiles and rip the buyers off with large quantity of water buyers off with large quantity of water in their products. in their products.

The conventional regain levels, to be The conventional regain levels, to be used for calculation of the legal used for calculation of the legal commercial mass, have been commercial mass, have been established by national or international established by national or international standards. These commercial regain standards. These commercial regain values are purely arbitrary values values are purely arbitrary values arrived at for commercial purposes for arrived at for commercial purposes for interested parties, and they often vary interested parties, and they often vary from fibre to fibre and from country to from fibre to fibre and from country to country.country.

In Australia, the conventional regain In Australia, the conventional regain rates for some fibres are given in Table rates for some fibres are given in Table 1.21.2

Wool and hair fibresCombed (worsted)

Carded (woollens)CottonNormal cotton

Mercerised cottonSilk

Polyester

Staple fibre

Continuous filament

18.25

17

8.5

10.511

1.5

1.5

Table 1.2: Conventional regain rate for selected fibres

Fibre Conventional regain (%)

Conditioning the whole lot of yarns or other Conditioning the whole lot of yarns or other

textile materials to the conventional regain rates textile materials to the conventional regain rates

given above is not practical, because of the time given above is not practical, because of the time

required etc. In calculating the commercial mass required etc. In calculating the commercial mass

to invoice for a lot, the following procedures are to invoice for a lot, the following procedures are

often followed:often followed:

(1) Extract a sample of mass (gw) from the lot (1) Extract a sample of mass (gw) from the lot (whose total gross weight is GW)(whose total gross weight is GW)

(2) Determine the dry weight (dw) of the sample (2) Determine the dry weight (dw) of the sample by oven drying to completely evaporate the by oven drying to completely evaporate the moisture contained in it.moisture contained in it.

(3) Calculate the commercial mass to invoice (3) Calculate the commercial mass to invoice (cw), based on a conventional regain R%, by (cw), based on a conventional regain R%, by means of the formula:means of the formula:

100

%100 R

gw

dwGWcw

Example:Example: Suppose a lot of worsted yarn is to be shipped Suppose a lot of worsted yarn is to be shipped

to a buyer, and the gross weight of lot is 1000 to a buyer, and the gross weight of lot is 1000 kg. We now need to work out the commercial kg. We now need to work out the commercial mass to invoice for the lot of yarn.mass to invoice for the lot of yarn.

AnswerAnswer::

We first extract a small sample (say 500 grams) We first extract a small sample (say 500 grams) from the lot. After oven drying of this small from the lot. After oven drying of this small sample, the dried mass becomes, say, 450 sample, the dried mass becomes, say, 450 grams. For worsted yarn, the conventional grams. For worsted yarn, the conventional regain rate is 18.25% according to Table 1.2. regain rate is 18.25% according to Table 1.2. Therefore, the commercial mass to invoice Therefore, the commercial mass to invoice should be:should be:

)(25.1064100

25.18100

500

4501000 kg

Review questionsReview questions

1.Suppose you have two cotton yarns. The 1.Suppose you have two cotton yarns. The

count of yarn A is 20 tex, and that of yarn B count of yarn A is 20 tex, and that of yarn B

is 20 Nec. Which yarn is a thicker one? You is 20 Nec. Which yarn is a thicker one? You

need to justify your answer via proper need to justify your answer via proper

count conversions.count conversions.

2.If a worsted yarn has a count of 40 Nw 2.If a worsted yarn has a count of 40 Nw

(worsted count) at a regain level of 20%, (worsted count) at a regain level of 20%,

what would be the count of this yarn, in what would be the count of this yarn, in

tex, when it is oven-dried?tex, when it is oven-dried?

1.2 Yarn twist(1.2 Yarn twist( 纱线捻度纱线捻度 ))IntroductionIntroduction

In the manufacture of staple fibre yarns(In the manufacture of staple fibre yarns( 短纤短纤纱纱 )), twist is inserted into the fine strand of , twist is inserted into the fine strand of fibres to hold the fibres together and impart fibres to hold the fibres together and impart the desired properties to the twisted yarns. the desired properties to the twisted yarns. Without twist, the fine strand of fibres would Without twist, the fine strand of fibres would be very weak and of little practical use. A be very weak and of little practical use. A change in the level of twist also changes many change in the level of twist also changes many yarn properties, such as strength and softness. yarn properties, such as strength and softness. This topic describes the nature of yarn twist, This topic describes the nature of yarn twist, the effect of twist on yarn properties, as well the effect of twist on yarn properties, as well as twist measurement.as twist measurement.

ObjectivesObjectives

At the end of this topic you should be able to:At the end of this topic you should be able to: understand the effect of twist on certain yarn understand the effect of twist on certain yarn

and fabric propertiand fabric properti appreciate the importance of surface twist appreciate the importance of surface twist

angle and of selecting the right twist factor angle and of selecting the right twist factor for different yarnsfor different yarns

know how to calculate the twist contractionknow how to calculate the twist contraction know the basic rules that apply to twist know the basic rules that apply to twist

measurementsmeasurements

Nature of twistNature of twist Types of twistTypes of twist (1) Real twist(1) Real twist To insert a real twist into a length of yarn, To insert a real twist into a length of yarn,

one end of the yarn should be rotated one end of the yarn should be rotated relative to the other end, as indicated in relative to the other end, as indicated in figure2.1(a)figure2.1(a)

(2) False twist((2) False twist( 假捻）假捻） When inserting false twist into a length of When inserting false twist into a length of

yarn, both ends of the yarn are clamped, yarn, both ends of the yarn are clamped, usually by rollers, and twist is inserted with a usually by rollers, and twist is inserted with a false twister between the clamping points, as false twister between the clamping points, as indicated in figure indicated in figure

If the yarn is not traversing along its If the yarn is not traversing along its axis, the twist will be in opposite axis, the twist will be in opposite directions above and below the false directions above and below the false twister. If the false twister is removed, twister. If the false twister is removed, the opposite twists will cancel out one the opposite twists will cancel out one another, leaving no real twist in the another, leaving no real twist in the length of yarn. If the yarn is traversing length of yarn. If the yarn is traversing along its axis, then the section of the along its axis, then the section of the yarn moving away from the false twister yarn moving away from the false twister would have no net twist, as indicated in would have no net twist, as indicated in figure 2.1(b)figure 2.1(b)

False twisting is a very important False twisting is a very important phenomenon, which has considerable phenomenon, which has considerable practical implications in yarn practical implications in yarn technology. False twisting is featured technology. False twisting is featured in many key processes that we will in many key processes that we will discuss later, including woollen ring discuss later, including woollen ring spinning, open-end rotor and friction spinning, open-end rotor and friction spinning, air jet spinning, and filament spinning, air jet spinning, and filament yarn texturing. yarn texturing.

Twist directionTwist direction （捻向）（捻向） A twist can be either in Z direction or S A twist can be either in Z direction or S

direction as indicated in figure 2.2, depending direction as indicated in figure 2.2, depending on the orientation of the surface fibre in relation on the orientation of the surface fibre in relation to yarn axis.to yarn axis.

S-Twist Z-Twist

It is worth noting that twist direction affects It is worth noting that twist direction affects fabric properties. For example , This figure 2.3 fabric properties. For example , This figure 2.3 shows two identical twill-weave fabrics with the shows two identical twill-weave fabrics with the warp yarn of different twist direction. warp yarn of different twist direction.

Twill direction S twist Z twist

(A) (B)

(Short arrows indicate direction of light reflected from the warp and weft yarns)

Fabric A will be more lustrous than fabric B, Fabric A will be more lustrous than fabric B, because light reflected by fibres in the warp because light reflected by fibres in the warp and weft is in the same direction. Fabric A will and weft is in the same direction. Fabric A will be softer while fabric B firmer, because in be softer while fabric B firmer, because in Fabric B, the surface fibres on the warp and Fabric B, the surface fibres on the warp and weft in the region of contact are aligned in the weft in the region of contact are aligned in the same direction and they may ‘get stuck’ inside same direction and they may ‘get stuck’ inside each other and reduce the mobility of the each other and reduce the mobility of the intersection. Whereas for fabric A, the surface intersection. Whereas for fabric A, the surface fibres on the warp and weft in the region of fibres on the warp and weft in the region of contact are crossed over, and they can move contact are crossed over, and they can move about easily. The freedom of movement at the about easily. The freedom of movement at the yarn intersections is the key for fabric softness.yarn intersections is the key for fabric softness.

Self-locking effectSelf-locking effect （自锁效应（自锁效应 ） ）

Because of twist in a yarn, the fibres on yarn Because of twist in a yarn, the fibres on yarn surface take a roughly helical configuration surface take a roughly helical configuration around the yarn. When the yarn is under around the yarn. When the yarn is under tension, these surface fibres are also under tension, these surface fibres are also under tension. However, because of the helical tension. However, because of the helical configuration, part of the tenon is diverted configuration, part of the tenon is diverted radially, which creates a radial pressure. radially, which creates a radial pressure. This is This is illustrated in figure 2.4.illustrated in figure 2.4.

Figure 2.4 Helical fibre under tension (Lord 1981, p. 75)Figure 2.4 Helical fibre under tension (Lord 1981, p. 75)

The radial pressure tends to pack the fibres The radial pressure tends to pack the fibres together, increasing the normal force between together, increasing the normal force between them, and so increasing their frictional them, and so increasing their frictional resistance to slipping past each other. The more resistance to slipping past each other. The more tension is applied to the yarn, the more it locks tension is applied to the yarn, the more it locks together, hence 'self-locking'. An analogy is, together, hence 'self-locking'. An analogy is, when you wind a string around your arm, as you when you wind a string around your arm, as you pull the string along the arm and away from pull the string along the arm and away from each other, the string bites deeper into the flesh. each other, the string bites deeper into the flesh.

Without twist, there won’t be any self-locking Without twist, there won’t be any self-locking effect to prevent fibre slippage. Consequently effect to prevent fibre slippage. Consequently the yarn would have no strength.the yarn would have no strength.

Effect of twist level on yarn strengthEffect of twist level on yarn strength The level of twist is usually expressed in number The level of twist is usually expressed in number

of turns per metre (tpm). Number of turns per of turns per metre (tpm). Number of turns per inch or twist per inch (tpi) is also used in the inch or twist per inch (tpi) is also used in the industry.industry.

Fig. 2.5: Effect of twist level on the strength of staple (spun) yarn

More twist gives greater radial component to More twist gives greater radial component to any applied tension, so increases resistance of any applied tension, so increases resistance of fibres to slip and the strength of yarn increases fibres to slip and the strength of yarn increases as a consequence. This is depicted by the as a consequence. This is depicted by the ‘‘coherence curve’coherence curve’ （（连续性曲线 ）连续性曲线 ） in figure 2.5.in figure 2.5.

On the other hand, if a bundle of parallel On the other hand, if a bundle of parallel filaments is twisted, the twist will put the filaments is twisted, the twist will put the individual filaments under torsional stress. This individual filaments under torsional stress. This stress weakens the filaments and the strength stress weakens the filaments and the strength of the filament would decrease as the level of of the filament would decrease as the level of twist increases. This is depicted by the twist increases. This is depicted by the ‘obliquity curve‘obliquity curve’’（倾斜曲线）（倾斜曲线） in figure 2.5.in figure 2.5.

For staple fibre yarns, these two curves combine For staple fibre yarns, these two curves combine to give the actual to give the actual 'twist-strength curve' 'twist-strength curve' for a for a staple fibre yarn as shown by the heavy line in staple fibre yarn as shown by the heavy line in figure 2.5.figure 2.5.

Figure 2.5 indicates that for staple fibre yarn, Figure 2.5 indicates that for staple fibre yarn,

increasing the twist level will increase yarnincreasing the twist level will increase yarn

It should be noted that for continuous filament It should be noted that for continuous filament yarn, the obliquity curve applies. In other words, yarn, the obliquity curve applies. In other words, twisting a continuous filament yarn only reduces twisting a continuous filament yarn only reduces the yarn strength, regardless of the twist level the yarn strength, regardless of the twist level used. If a continuous multi-filament yarn is used. If a continuous multi-filament yarn is twisted, the reason for the twist is to keep the twisted, the reason for the twist is to keep the individual filaments together, not for strength.individual filaments together, not for strength.

Twist angleTwist angle （捻回角）（捻回角） This is the angle of fibres to yarn axis, and this This is the angle of fibres to yarn axis, and this

angle varies throughout yarn, from zero at centre angle varies throughout yarn, from zero at centre to maximum at yarn surface. The fibres on yarn to maximum at yarn surface. The fibres on yarn surface are the most important, as they bind the surface are the most important, as they bind the others into the yarn (refer to self-locking effect others into the yarn (refer to self-locking effect discussed earlier).discussed earlier).

While it is not common practice to measure the While it is not common practice to measure the yarn twist angle, the surface twist angle made by yarn twist angle, the surface twist angle made by the surface fibres in relation to yarn axis is a very the surface fibres in relation to yarn axis is a very important parameter. It determines the essential important parameter. It determines the essential yarn characteristics such as yarn softness, yarn yarn characteristics such as yarn softness, yarn bulk etc, which in turn govern many essential bulk etc, which in turn govern many essential fabric properties. The following example fabric properties. The following example illustrates the point. illustrates the point.

In figure 2.6, yarn 1 and yarn 2 have the In figure 2.6, yarn 1 and yarn 2 have the same twist level – one turn each. But the same twist level – one turn each. But the surface fibre on the thicker yarn is surface fibre on the thicker yarn is obviously stretched more to accommodate obviously stretched more to accommodate this twist. This would mean the thicker this twist. This would mean the thicker yarn is more closely packed. As a yarn is more closely packed. As a consequence, yarn 2 will not be as soft as consequence, yarn 2 will not be as soft as yarn 1. In other words, even though the yarn 1. In other words, even though the twist level is the same in these two yarns, twist level is the same in these two yarns, the yarn characteristics are quite different. the yarn characteristics are quite different.

Therefore, we can not simply use twist level to Therefore, we can not simply use twist level to represent yarn character. However, the surface represent yarn character. However, the surface twist angles of yarn 1 (θtwist angles of yarn 1 (θ11) and yarn 2 (θ) and yarn 2 (θ22) are ) are different. They can better reflect the yarn different. They can better reflect the yarn characteristics, regardless of the difference in characteristics, regardless of the difference in yarn thickness.yarn thickness.

L

Yarn 1 Yarn 2

d1 d2 L

1 2

d1 d2

L

Figure 2.6 Two yarns of the same twist level, but different surface twist angles

Twist factor (Twist multiplier)Twist factor (Twist multiplier) （（捻系数 ）捻系数 ） This is a very important factor that relates to This is a very important factor that relates to

the angle of twist helix the surface fibres have the angle of twist helix the surface fibres have in a yarn. As we will see later, this factor is very in a yarn. As we will see later, this factor is very important for a spinner because of the following important for a spinner because of the following reasons:reasons:• Like surface twist angle, it governs the yarn Like surface twist angle, it governs the yarn

characteristicscharacteristics• It is used to work out the twist to use in It is used to work out the twist to use in

spinning, in order to maintain the same spinning, in order to maintain the same surface twist angle and similar yarn surface twist angle and similar yarn characteristics when the yarn count is characteristics when the yarn count is changed. The twist worked out from twist changed. The twist worked out from twist factor is also needed for setting up the factor is also needed for setting up the spinning machine.spinning machine.

Relate twist factor to twist angleRelate twist factor to twist angle

Because it is much easier to measure twist level Because it is much easier to measure twist level in turns per metre than twist angle, we should in turns per metre than twist angle, we should relate twist level to twist angle.From figure 2.6, relate twist level to twist angle.From figure 2.6, we get,we get,

Also from figure 2.6, the height (pitch) of one turn Also from figure 2.6, the height (pitch) of one turn of twist is L. Since the twist level is normally of twist is L. Since the twist level is normally specified as the number of turns per metre, the specified as the number of turns per metre, the twist level in one metre of the yarn would be:twist level in one metre of the yarn would be:

so so

L

d = tan

L

1 = twist

twist x d = tan (1)

We also know from experience that yarn We also know from experience that yarn diameter is also very hard to measure, diameter is also very hard to measure, because textile yarns by their very nature because textile yarns by their very nature are soft and squashy. On the other hand, are soft and squashy. On the other hand, yarn count is normally used as we have yarn count is normally used as we have discussed in the first topic of this module. discussed in the first topic of this module. But we can relate yarn diameter to yarn But we can relate yarn diameter to yarn count using the expression below:count using the expression below:

cubic density cubic density （密度）（密度） = = linear density linear density

(Tex)(Tex) （线密度）（线密度） /cross- sectional area (A) /cross- sectional area (A) （横截面积）（横截面积）

Assuming a circular cross section for Assuming a circular cross section for the yarn, we get,the yarn, we get,

Solve ford:Solve ford:

Combining equations (1) and (2):Combining equations (1) and (2):

or or where where K is called the twist factor, and is K is called the twist factor, and is

proportional to if remains constantproportional to if remains constant..

/4d 10 x Tex

= )m( A

(g/m) 10 x Tex = )m(g/

2

-3

2

-33

10 x Tex 4

= d-3

2

/10 x tex 2

= twist

3-

tan

tex

K = twist ) tex (t.p.m /10 0.5 = K 3 tan

(2)

Thus, K is a factor relating twist level to yarn Thus, K is a factor relating twist level to yarn

count. The derivation shows that if two yarns count. The derivation shows that if two yarns

have the same twist factor, they will have the have the same twist factor, they will have the

same surface twist angle, regardless of count. same surface twist angle, regardless of count.

Since surface twist angle is the main factor Since surface twist angle is the main factor

determining yarn character, then twist factor determining yarn character, then twist factor

can be used to define the character of a yarn.can be used to define the character of a yarn.

It is worth noting though there are minor It is worth noting though there are minor errors associated with the use of twist factor errors associated with the use of twist factor for the following reasons:for the following reasons: The cubic density may be different for The cubic density may be different for

different yarns. It is assumed in the above different yarns. It is assumed in the above calculation that this will not change for calculation that this will not change for yarns of the same surface twist angle.yarns of the same surface twist angle.

Different fibres with different frictional Different fibres with different frictional and other properties will create different and other properties will create different yarn character.yarn character.

Nevertheless, the relationship we have Nevertheless, the relationship we have just derived between twist, twist factor just derived between twist, twist factor and yarn count is one of the most and yarn count is one of the most important in the study of yarn important in the study of yarn technology. This relationship is expressed technology. This relationship is expressed in different ways for different yarn count in different ways for different yarn count systems.systems.For the tex systemFor the tex system

For the metric count (NFor the metric count (Nmm) system) system

tex

KFactorTwist = metreperturns Twist t )(

)(

NmAlphaTwist = metreperturns Twist m )()(

For English cotton (NFor English cotton (Necec) count system) count system

For worsted count (NFor worsted count (Nww) system) system

Please note the unit for twist is also different Please note the unit for twist is also different in the above expressions of twist factor. In in the above expressions of twist factor. In addition, twist factor is also known as twist addition, twist factor is also known as twist multiplier, twist alpha, or twist coefficient.multiplier, twist alpha, or twist coefficient.

NecKFactorTwist = inchperturns Twist e )()(

NwKFactorTwist = inchperturns Twist w )()(

Choice of twist factorsChoice of twist factors

Yarns intended for different end uses have Yarns intended for different end uses have different characteristics. Since twist factor different characteristics. Since twist factor (like surface twist angle) determines yarn (like surface twist angle) determines yarn characteristics, the choice of twist factor is characteristics, the choice of twist factor is often governed by the intended use of the often governed by the intended use of the yarns. If maximum yarn strength is of the yarns. If maximum yarn strength is of the utmost importance, one would obviously utmost importance, one would obviously choose the choose the optimumoptimum yarn twist (see figure 2.5) yarn twist (see figure 2.5) and the optimum twist factor for strength. and the optimum twist factor for strength.

However, the end-use of yarn may be However, the end-use of yarn may be such that other properties may be more such that other properties may be more important. For example, a yarn to be important. For example, a yarn to be used for weft or for hosiery may be used for weft or for hosiery may be required to be soft and bulky and required to be soft and bulky and therefore a low twist factor is used. A therefore a low twist factor is used. A yarn to be used for the production of voile yarn to be used for the production of voile or crepe fabric will necessitate the use of or crepe fabric will necessitate the use of a high twist factor. a high twist factor.

If one considers staple yarns for the If one considers staple yarns for the production of plied or cabled sewing production of plied or cabled sewing threads then soft twisted single yarns threads then soft twisted single yarns are used and this results in the highest are used and this results in the highest strength in the final thread. strength in the final thread.

Another important feature to consider Another important feature to consider is that the productivity for spinning is that the productivity for spinning yarns of lower twist factor is higher. yarns of lower twist factor is higher. For these reasons, the majority of For these reasons, the majority of yarns are spun with a twist factor yarns are spun with a twist factor lower than the optimum twist factor lower than the optimum twist factor for maximum strength.for maximum strength.

► Table 2.1 shows the twist factor most Table 2.1 shows the twist factor most commonly used for the various types of commonly used for the various types of yarnsyarns.. Table 2.1: Twist factors most commonly used

Please note these are reference values Please note these are reference values only, and the recommended values only, and the recommended values vary from source to source.vary from source to source.

Once a twist factor is chosen, the level Once a twist factor is chosen, the level of twist required for the yarn can be of twist required for the yarn can be calculated for a given yarn count. This calculated for a given yarn count. This twist level is then used to set up the twist level is then used to set up the spinning machine for yarn production.spinning machine for yarn production.

The distribution of twist in staple spun yarnsThe distribution of twist in staple spun yarns

If someone twists your head, it is your If someone twists your head, it is your

neck that suffers most. That is because neck that suffers most. That is because the neck is a ‘thin’ place and offers little the neck is a ‘thin’ place and offers little resistance to being twisted. By analogy, if resistance to being twisted. By analogy, if a yarn of varying thickness is twisted, it is a yarn of varying thickness is twisted, it is usually the thin spot in the yarn that gets usually the thin spot in the yarn that gets twisted the most. twisted the most.

Invariably, yarns spun from staple Invariably, yarns spun from staple fibres (eg. wool, cotton) are not fibres (eg. wool, cotton) are not perfectly uniform, and there are thick perfectly uniform, and there are thick and thin spots along the yarn length. and thin spots along the yarn length. This variation in yarn thickness will This variation in yarn thickness will lead to variation in the twist level lead to variation in the twist level along the yarn length, because twist along the yarn length, because twist tends to accumulate in the thin placetends to accumulate in the thin place. .

The fact that twist tends to accumulate in The fact that twist tends to accumulate in the thin spot along the yarn has several the thin spot along the yarn has several important implications:important implications:

(1) It exacerbates the variation in yarn (1) It exacerbates the variation in yarn linear density. While variation in yarn linear linear density. While variation in yarn linear density is the fundamental cause of twist density is the fundamental cause of twist variation, concentration of twist in the thin variation, concentration of twist in the thin places will make those places even thinner, places will make those places even thinner, exacerbating the problem of yarn exacerbating the problem of yarn unevennessunevenness. .

(2)It improves the evenness of a fibre (2)It improves the evenness of a fibre assembly during “drafting against twist”assembly during “drafting against twist”

In the drafting stage of woollen ring In the drafting stage of woollen ring spinning, the woollen slubbing is drafted spinning, the woollen slubbing is drafted while twist is inserted into the slubbing while twist is inserted into the slubbing (drafting against twist) to control fibres (drafting against twist) to control fibres during drafting. Because twist tends to during drafting. Because twist tends to accumulate in the thin spots, the fibres in accumulate in the thin spots, the fibres in thin regions in the slubbing are more difficult thin regions in the slubbing are more difficult to draft than those in the thick places, which to draft than those in the thick places, which have less twist. As a result, the thick places have less twist. As a result, the thick places are drafted more than the thin places, thus are drafted more than the thin places, thus improving the evenness of the drafted improving the evenness of the drafted material. This is depicted in figure 2.7. material. This is depicted in figure 2.7.

Thin place with more twist

(a) Before drafting (b) After drafting against twist

(3)It has implication for twist measurements(3)It has implication for twist measurements

Because the twist level varies along the yarn Because the twist level varies along the yarn length, the twist measured at a short length length, the twist measured at a short length of yarn may not reflect the true average twist of yarn may not reflect the true average twist of the yarn. Standard test procedures should of the yarn. Standard test procedures should be followed to measure the yarn twist be followed to measure the yarn twist accurately.accurately.

The relationship between twist and yarn count The relationship between twist and yarn count may be expressed by the following formula:may be expressed by the following formula:

where p is usually greater than 1 but less than where p is usually greater than 1 but less than 2 for most yarns. 2 for most yarns.

Tex

1 Twist

p

Twist contractionTwist contraction （捻缩）（捻缩）

When a bundle of parallel fibres is When a bundle of parallel fibres is twisted, the distance between the two twisted, the distance between the two ends of a fibre will decrease, ends of a fibre will decrease, particularly for fibres near the surface particularly for fibres near the surface of the twisted bundle. As a result, the of the twisted bundle. As a result, the overall length of the twisted bundle is overall length of the twisted bundle is shorter than its length before twist shorter than its length before twist insertion. The reduction in length due insertion. The reduction in length due to twist insertion is known as twist to twist insertion is known as twist contraction.contraction.

The following formula is used to The following formula is used to calculate the amount of twist calculate the amount of twist contraction:contraction:

where Lo = original length before where Lo = original length before twistingtwisting

Lf = final length after twistingLf = final length after twisting

% 100 x L

L-L = ncontractio %o

fo

It should be noted that because of twist It should be noted that because of twist contraction and the associated change in contraction and the associated change in length, the count of a yarn will change length, the count of a yarn will change slightly when twist in the yarn is changed. slightly when twist in the yarn is changed. Twist contraction increases yarn count Twist contraction increases yarn count (tex), because the weight of the yarn is (tex), because the weight of the yarn is distributed over a shorter length. The distributed over a shorter length. The following formula can be usedfollowing formula can be used

wherewhere No = count (tex) before twisting No = count (tex) before twisting

Nf = count (tex) after twistingNf = count (tex) after twisting

C = %contraction C = %contraction

C - 1N = N

of

Measurement of twistMeasurement of twist

Twist measurement is a routine test for Twist measurement is a routine test for

yarns. Because of the variation in twist yarns. Because of the variation in twist along yarn length as discussed earlier, care along yarn length as discussed earlier, care should be taken in measuring the twist of should be taken in measuring the twist of staple spun yarns. Some basic principles are staple spun yarns. Some basic principles are discussed here.discussed here.

• Sampling rulesSampling rules

The following rules should be observed when The following rules should be observed when measuring yarn twist:measuring yarn twist:

a.a. Tests should not be limited to a short Tests should not be limited to a short length of the yarn packagelength of the yarn package..

b.b. Beware of "operator bias" - tendency to Beware of "operator bias" - tendency to select either thicker or thinner regions. select either thicker or thinner regions.

c.c. Discard first few metres from package. Discard first few metres from package. Being a free end, it could have lost twistBeing a free end, it could have lost twist..

d.d. Remove yarn from side of package, not Remove yarn from side of package, not over end. Removing yarn over end will over end. Removing yarn over end will change the twist level in the yarn.change the twist level in the yarn.

e.e. Tension in Yarn during testTension in Yarn during test

e.g. For single worsted yarns: 5 e.g. For single worsted yarns: 5 ++ 1 1 mN/texmN/tex

►Principles of measuring methodsPrinciples of measuring methods The two common methods used in twist The two common methods used in twist

measurement are straightened fibre method measurement are straightened fibre method and untwist/retwist method.and untwist/retwist method.

(1) Straightened fibre method((1) Straightened fibre method( 直接计数法）直接计数法） This method involves counting of the This method involves counting of the

number of turns required to untwist the number of turns required to untwist the yarns until the surface fibres appear to be yarns until the surface fibres appear to be straight and parallel to yarn axis. This straight and parallel to yarn axis. This method is mainly used for ply and method is mainly used for ply and continuous filament yarns.continuous filament yarns.

(2) Untwist / Retwist Method((2) Untwist / Retwist Method( 退捻加捻退捻加捻法）法）

This is the common method used for This is the common method used for staple fibre yarns. It is based on twist staple fibre yarns. It is based on twist contraction (hence also known as twist contraction (hence also known as twist contraction methodcontraction method).).

Review questionsReview questions

1)"For a staple fibre yarn, the higher 1)"For a staple fibre yarn, the higher the twist, the stronger the yarn". Is the twist, the stronger the yarn". Is this statement true? Why?this statement true? Why?

2)A yarn of 40 Nm (metric count) has 2)A yarn of 40 Nm (metric count) has a twist factor of 3,000 . What is the a twist factor of 3,000 . What is the twist level, in turns per metre, of this twist level, in turns per metre, of this yarn?yarn?

3)If a yarn has an alpha metric (αm) of 3)If a yarn has an alpha metric (αm) of 100, what is the twist factor in the tex 100, what is the twist factor in the tex system (Kt) and the English cotton system (Kt) and the English cotton count system (Ke)? You need to show count system (Ke)? You need to show your working.your working.

4)Assuming after twisting, the count of 4)Assuming after twisting, the count of a multi-filament yarn is increased from a multi-filament yarn is increased from 150 dtex to 180 dtex, what is the 150 dtex to 180 dtex, what is the amount of twist contraction amount of twist contraction experienced by this multi-filament experienced by this multi-filament yarn?yarn?

1.3 The designation of yarn 1.3 The designation of yarn structuresstructures

IntroductionIntroduction

This topic describes a method of indicating the This topic describes a method of indicating the

composition of yarns. The yarns can be spun composition of yarns. The yarns can be spun yarns or filament yarns. They may be single, yarns or filament yarns. They may be single, folded or cabled yarns. This topic is adapted folded or cabled yarns. This topic is adapted from “Handbook of textiles standards for from “Handbook of textiles standards for students”, published in 1988 by the Standards students”, published in 1988 by the Standards Association of Australia.Association of Australia.

ObjectivesObjectives

At the end of this topic you should be able At the end of this topic you should be able

to:to: describe a yarn according to its describe a yarn according to its

designationdesignation designate a yarn based on a detailed designate a yarn based on a detailed

description of the yarndescription of the yarn

Systems and rulesSystems and rules

Two systems can be used for yarn designation.Two systems can be used for yarn designation.► Single-to-fold notation (preferred)Single-to-fold notation (preferred)

This is the preferred system, where single This is the preferred system, where single component of the yarn is described first, component of the yarn is described first, followed by a description of how the followed by a description of how the components are combined together to make up components are combined together to make up the resultant yarn.the resultant yarn.

► Fold-to-single notationFold-to-single notation

This notion is opposite to the single-to-fold This notion is opposite to the single-to-fold notation. The whole structure is described first, notation. The whole structure is described first, followed by a description of its components.followed by a description of its components.

►General rulesGeneral rules

The following general rules should be The following general rules should be noted:noted: Use tex for staple spun yarns and dtex for Use tex for staple spun yarns and dtex for

filament yarnsfilament yarns "fn" indicates n filaments in a single mono "fn" indicates n filaments in a single mono

(n=1) or multifilament yarn.(n=1) or multifilament yarn. "t0" indicates components combined without "t0" indicates components combined without

twisttwist "Rxyz tex" specifies the "resultant" count of "Rxyz tex" specifies the "resultant" count of

the yarn (xyz tex) in its final form.the yarn (xyz tex) in its final form. specification after a semi-colon is optionalspecification after a semi-colon is optional The following sections list examples of yarn The following sections list examples of yarn

designations.designations.

Single yarns(Single yarns( 单丝单丝 )) A single yarn, or singles yarn, may be a spun A single yarn, or singles yarn, may be a spun

yarn (or staple yarn), a mono-filament yarn, or yarn (or staple yarn), a mono-filament yarn, or a multi-filament yarn. The ways of designating a multi-filament yarn. The ways of designating these different single yarns are given below.these different single yarns are given below.

Spun yarns(Spun yarns( 短纤纱）短纤纱） The details used in the designation of spun The details used in the designation of spun

yarns include:yarns include:► Linear density (tex)Linear density (tex)► Direction of twist (S or Z)Direction of twist (S or Z)► Amount of twist (turns per metre)Amount of twist (turns per metre)

For example, the designationFor example, the designation 40 tex Z 66040 tex Z 660 describes a spun yarn that has a count of 40 describes a spun yarn that has a count of 40 tex, with a twist level of 600 turns per metre, tex, with a twist level of 600 turns per metre, and the twist is applied in Z directionand the twist is applied in Z direction..

Mono-filament yarnsMono-filament yarns （单丝纱线（单丝纱线）） The details used in the designation of The details used in the designation of

mono-filament yarns include:mono-filament yarns include:Linear density (dtex)Linear density (dtex)Symbol fSymbol fSymbol t0 if not twisted; otherwise Symbol t0 if not twisted; otherwise

twist direction and amounttwist direction and amount For example, the designation For example, the designation 17 dtex 17 dtex

f1 t0f1 t0 describes a mono-filament (f1) describes a mono-filament (f1) yarn with a count of 17 dtex, with any yarn with a count of 17 dtex, with any twist (t0) in the yarn.twist (t0) in the yarn.

Multifilament yarnsMultifilament yarns （复丝）（复丝） The details used in the designation of multi-The details used in the designation of multi-

filament yarns include:filament yarns include:►Linear densityLinear density►Symbol fSymbol f►Number of filamentsNumber of filaments►Symbol t0 if not twisted; otherwise twist Symbol t0 if not twisted; otherwise twist

direction and leveldirection and level►Resultant linear densityResultant linear density

For example, the designationFor example, the designation 140 dtex f40 t0140 dtex f40 t0 means a multi-filament yarn with a count of means a multi-filament yarn with a count of 140 dtex, consisting of 40 individual filaments 140 dtex, consisting of 40 individual filaments which are not twisted. Please note that the which are not twisted. Please note that the linear density of each individual filament will linear density of each individual filament will be . be .

Multiple wound yarnsMultiple wound yarns （并线 ）（并线 ） These are the yarns that have several These are the yarns that have several

components wound up together, without components wound up together, without inserting any twist. This is also known as inserting any twist. This is also known as assembly woundassembly wound yarns yarns

1.Multiple wound yarns with similar 1.Multiple wound yarns with similar componentscomponents

The details used in the designation of such The details used in the designation of such yarns includeyarns include::

►Notation according to single yarn usedNotation according to single yarn used►Multiplication sign, .Multiplication sign, .►Number of single yarns laid togetherNumber of single yarns laid together►Symbol t0Symbol t0

Example:Example: 40 tex S155 2 t040 tex S155 2 t0

2.Multiple wound yarns with dissimilar 2.Multiple wound yarns with dissimilar componentscomponents

The details used in the designation of such The details used in the designation of such yarns include:yarns include:

►Notation according to single yarn used, Notation according to single yarn used, connected by the addition sign + and put connected by the addition sign + and put in brackets in brackets

►Symbol t0Symbol t0

Example:(25 tex S420 + 60 tex Z80) t0Example:(25 tex S420 + 60 tex Z80) t0 (Can (Can you describe this yarn?)you describe this yarn?)

Folded or plied yarnsFolded or plied yarns （多股线）（多股线） These are the yarns that have several These are the yarns that have several

components twisted up together.components twisted up together. 1.Folded yarns having similar components1.Folded yarns having similar components

The details used in the designation of such The details used in the designation of such yarns include:yarns include:

► Notation according to single yarn usedNotation according to single yarn used► Multiplication sign, .Multiplication sign, .► Number of single yarns twisted togetherNumber of single yarns twisted together► Direction of folding twistDirection of folding twist► Amount of folding twistAmount of folding twist► Resultant linear densityResultant linear density

Example:Example: 34 tex S600 2 Z400; R69.3 tex34 tex S600 2 Z400; R69.3 tex

(a singles yarn of 34 tex with a twist of 600 (a singles yarn of 34 tex with a twist of 600 turns per metre in S direction is twisted turns per metre in S direction is twisted together with another yarn of the same together with another yarn of the same descriptions. The folding twist is 400 turns descriptions. The folding twist is 400 turns per metre in Z direction, and the resultant per metre in Z direction, and the resultant yarn count is 69.3 tex (slightly higher than yarn count is 69.3 tex (slightly higher than 34 x 2 due to twist contraction.)34 x 2 due to twist contraction.)

2.Folded yarn having dissimilar 2.Folded yarn having dissimilar componentscomponents

The details used in the designation of such The details used in the designation of such yarns include:yarns include:

► Notation according to single yarn used, Notation according to single yarn used, connected by the addition sign + and put connected by the addition sign + and put in brackets in brackets

► Direction of folding twistDirection of folding twist► Amount of folding twistAmount of folding twist► Resultant linear densityResultant linear density

Example:(25 tex S420 + 60 tex Z80) S360; Example:(25 tex S420 + 60 tex Z80) S360; R89.2 tex (Can you describe this yarn?)R89.2 tex (Can you describe this yarn?)

Cabled yarnsCabled yarns （缆线）（缆线） Cabled yarns have several components, which Cabled yarns have several components, which

can be either similar or dissimilar in can be either similar or dissimilar in structuresstructures..

1.Cabled yarns having similar components1.Cabled yarns having similar components

The details used in the designation of such The details used in the designation of such yarns include:yarns include:

► Notation according to folded yarn usedNotation according to folded yarn used► Multiplication sign, .Multiplication sign, .► Number of folded yarns cabled togetherNumber of folded yarns cabled together► Direction of cabling twistDirection of cabling twist► Amount of cabling twistAmount of cabling twist► Resultant linear densityResultant linear densityExample:20 tex Z700 2 S400 3 Z200; R132 texExample:20 tex Z700 2 S400 3 Z200; R132 tex

2.Cabled yarns having dissimilar 2.Cabled yarns having dissimilar componentscomponents

The details used in the designation of such The details used in the designation of such yarns include:yarns include:

►Notation according to single and folded Notation according to single and folded yarns used, connected by the addition sign yarns used, connected by the addition sign + and put in brackets.+ and put in brackets.

►Direction of cabling twistDirection of cabling twist►Amount of cabling twistAmount of cabling twist►Resultant linear densityResultant linear density

Example:Example: (20 tex Z700 3 S400 + 34 tex S600) (20 tex Z700 3 S400 + 34 tex S600) Z200; R96 texZ200; R96 tex

Single-to- fold versus fold-to-single notationsSingle-to- fold versus fold-to-single notations

So far we have used the preferred single-to-fold So far we have used the preferred single-to-fold notation for yarn designation. Examples of fold-notation for yarn designation. Examples of fold-to-single notation are given below, together with to-single notation are given below, together with their equivalent single-to-fold notation. their equivalent single-to-fold notation.

Example oneExample one 133 dtex f40 S 1000; R 136 dtex (single-to-fold)133 dtex f40 S 1000; R 136 dtex (single-to-fold)

R 136 dtex f 40 S 1000; 133 dtex (fold-to-single)R 136 dtex f 40 S 1000; 133 dtex (fold-to-single)

This describes a multifilament yarn of 136 dtex This describes a multifilament yarn of 136 dtex after twisting to 1000 t/m in the S direction. after twisting to 1000 t/m in the S direction. Before twisting,Before twisting,

the count was 133 dtex, and the individual the count was 133 dtex, and the individual filament filament

linear density is 133/40 = 3.3 dtex.linear density is 133/40 = 3.3 dtex.

Example twoExample two

20 tex Z 700 x 2 S 400 x 3 Z 200; R 20 tex Z 700 x 2 S 400 x 3 Z 200; R 132 tex (single-to-fold)132 tex (single-to-fold)

R 132 tex Z 200 / 3 S 400 / 2 Z 700; 20 R 132 tex Z 200 / 3 S 400 / 2 Z 700; 20 tex (fold-to-single)tex (fold-to-single)

This describes a cabled yarn built up This describes a cabled yarn built up from a singles yarn of 20 tex with 700 from a singles yarn of 20 tex with 700 t/m Z, plied with itself with 400 t/m S, t/m Z, plied with itself with 400 t/m S, which is subsequently three-plied with which is subsequently three-plied with 200 t/m Z twist.200 t/m Z twist.

Example threeExample three

(25 tex S 420 + 60 tex Z 80) S 360; R 89.2 (25 tex S 420 + 60 tex Z 80) S 360; R 89.2 tex (single-to-fold)tex (single-to-fold)

R 89.2 tex S 360 / (S 420 + Z 80); 25 tex + R 89.2 tex S 360 / (S 420 + Z 80); 25 tex + 60 tex (fold-to-single)60 tex (fold-to-single)

This describes a two ply yarn with dissimilar This describes a two ply yarn with dissimilar components, plied together in the S components, plied together in the S direction with 360 t/m.direction with 360 t/m.

Finally, the following points are worth Finally, the following points are worth noting:noting:

(1) The resultant count is of most use (1) The resultant count is of most use to the user of the yarnto the user of the yarn

(2) In textile mills, abbreviated (2) In textile mills, abbreviated notations are often used, i.e. R40/2 notations are often used, i.e. R40/2 tex tex

(3) For indirect count systems, the (3) For indirect count systems, the single yarn count is normally given, single yarn count is normally given, i.e.i.e.

2/20 or 20/2 (2-fold 20s); 3/2/60 (3-2/20 or 20/2 (2-fold 20s); 3/2/60 (3-fold, 2-fold 60s, cabled yarn).fold, 2-fold 60s, cabled yarn).

Review questionsReview questions►Describe yarns with the following Describe yarns with the following

designations:designations:►(25 tex S420 + 60 tex Z80) S360; R89.2 (25 tex S420 + 60 tex Z80) S360; R89.2

textex►(25 tex S420 + 60 tex Z80) t0(25 tex S420 + 60 tex Z80) t0►(20 tex Z700 3 S400 + 34 tex S600) (20 tex Z700 3 S400 + 34 tex S600)

Z200; R96 texZ200; R96 tex►20 tex Z700 2 S400 3 Z200; R13220 tex Z700 2 S400 3 Z200; R132 tex tex

Chapt 2 YarnChapt 2 Yarn Evenness Evenness

► 2.1 Theoretical aspects of evenness2.1 Theoretical aspects of evenness

► 2.2Measurement and benchmarking of yar2.2Measurement and benchmarking of yarn evennessn evenness

Theoretical aspects of evennessTheoretical aspects of evenness

IntroductionIntroduction The foundations for the study of yarn The foundations for the study of yarn

evenness(evenness( 均匀均匀 ) were laid in a 1945 classical ) were laid in a 1945 classical paper by Martindale, entitled “a new method paper by Martindale, entitled “a new method of measuring the irregularity of yarns with of measuring the irregularity of yarns with some observations on the origin of some observations on the origin of irregularities in worsted slivers(irregularities in worsted slivers( 精梳条精梳条 ) and ) and yarns" (Martindale 1945). For this reason, the yarns" (Martindale 1945). For this reason, the evenness theory has often been refereed to as evenness theory has often been refereed to as the Martindale theory. the Martindale theory.

ObjectivesObjectives At the end of this topic you should be able to:At the end of this topic you should be able to:

Understand the statistical limit of evenness (limitiUnderstand the statistical limit of evenness (limiting irregularity)ng irregularity)

Appreciate the effect of fibre finenessAppreciate the effect of fibre fineness(( 细度细度 )) on y on yarn evennessarn evenness

Know the evenness-related calculationsKnow the evenness-related calculations Understand the effect of fibre processing on sliver Understand the effect of fibre processing on sliver

and yarn evennessand yarn evenness

Perfectly even yarnPerfectly even yarn(( 理想均匀纱线理想均匀纱线 ))

For a spun yarnFor a spun yarn(( 细纱细纱 )) (or any other fibre assembly) (or any other fibre assembly) to be perfect even, we need two conditions:to be perfect even, we need two conditions:

(1)(1)The constituent fibres are uniform in thicknessThe constituent fibres are uniform in thickness (2)(2)The yarn has the same number of fibres in allThe yarn has the same number of fibres in all cross sections along its lengthcross sections along its length Figure 1.1 depicts such an ideal fibre assembly Figure 1.1 depicts such an ideal fibre assembly

with perfect evenness.with perfect evenness.

Fig. 1.1: A perfectly even fibre assembly with uniform fibres and ‘butted’ Fig. 1.1: A perfectly even fibre assembly with uniform fibres and ‘butted’ fibre endsfibre ends

While the first condition may be achievable with maWhile the first condition may be achievable with manufactured staple fibres, natural fibres such as cottnufactured staple fibres, natural fibres such as cotton and wool always exhibit variations in thickness aon and wool always exhibit variations in thickness along fibre length.long fibre length.

To satisfy condition (2) would mean that the fibre eTo satisfy condition (2) would mean that the fibre ends are ‘butted’ together (Figure 1.1). In other wnds are ‘butted’ together (Figure 1.1). In other words, as one fibre terminates, another must be introords, as one fibre terminates, another must be introduced to take its place. This would require control aduced to take its place. This would require control and manipulation of each fibre in the fibre assembly nd manipulation of each fibre in the fibre assembly by the processing machinery. This is not possible wiby the processing machinery. This is not possible with current processing technology. th current processing technology.

Because of the variable nature of fibres, particularly Because of the variable nature of fibres, particularly natural fibres, and the difficulty with individual fibre natural fibres, and the difficulty with individual fibre placement in the fibre assembly using current technplacement in the fibre assembly using current technology, a perfectly even yarn is unattainable in practicology, a perfectly even yarn is unattainable in practice. Therefore, a real yarn (or any other fibre assembly) e. Therefore, a real yarn (or any other fibre assembly) would always have some irregularity in linear densitwould always have some irregularity in linear density, because the way fibres are arranged deviates from y, because the way fibres are arranged deviates from what’s required to make a perfectly even yarn. The what’s required to make a perfectly even yarn. The question then is how does the current fibre processiquestion then is how does the current fibre processing machinery arrange fibres? Without this knowledgng machinery arrange fibres? Without this knowledge, we can not possibly know what would be the likely e, we can not possibly know what would be the likely irregularity for such an arrangement.irregularity for such an arrangement.

To answer this question, we need to look at the wholTo answer this question, we need to look at the whole fibre to yarn processes and examine what each pre fibre to yarn processes and examine what each process does to the fibres. In the Introduction to Fibre ocess does to the fibres. In the Introduction to Fibre Science and Textile Technology unit, we have discuScience and Textile Technology unit, we have discussed, separately, the processes involved in manufacssed, separately, the processes involved in manufacturing cotton and worsted yarns. Let us now briefly turing cotton and worsted yarns. Let us now briefly recap the key processes, from the perspective of fibrecap the key processes, from the perspective of fibre arrangement, before we move onto the theoreticre arrangement, before we move onto the theoretical aspects of evenness.al aspects of evenness.

Fibre arrangements during fibre to yarnFibre arrangements during fibre to yarn processprocessinging

Fibres arrive at textile mills(Fibres arrive at textile mills( 纺织厂纺织厂 ) in large ) in large

bales(bales( 纤维包纤维包 ). It is a statement of fact that ). It is a statement of fact that fibres vary in properties, both within a bale and fibres vary in properties, both within a bale and between different bales. We can certainly not between different bales. We can certainly not persuade a sheep to produce identical wool or persuade a sheep to produce identical wool or make a cotton plant to grow identical cotton. make a cotton plant to grow identical cotton. In addition, wool and cotton grown in different In addition, wool and cotton grown in different regions exhibit considerable variations in regions exhibit considerable variations in properties. properties.

To produce a large quantity of uniform To produce a large quantity of uniform yarns from variable fibres, blending yarns from variable fibres, blending and mixing is essential. There are two and mixing is essential. There are two fundamental requirements of the fundamental requirements of the blended product:blended product:

The blend is homogenous, andThe blend is homogenous, andThe blend is intimateThe blend is intimate

These two requirements have different but cThese two requirements have different but complementary connotations. A homogenouomplementary connotations. A homogenous blend means that the blend components as blend means that the blend components are in the right proportion, while an intimate re in the right proportion, while an intimate blend means the blend components lie side blend means the blend components lie side by side without regions of concentration of jby side without regions of concentration of just one component. If a blend satisfy these rust one component. If a blend satisfy these requirements, then fibres in the blend are thoequirements, then fibres in the blend are thoroughly mixed up, in the right proportions throughly mixed up, in the right proportions throughout the bulk (the whole lot or populatiroughout the bulk (the whole lot or population). on).

In other words, within such an ideal blend, In other words, within such an ideal blend, all different fibres are arranged in a complall different fibres are arranged in a completely random way, and all the fibres have tetely random way, and all the fibres have the same chance of being found at any selehe same chance of being found at any selected place in the bulk. Achieving this task icted place in the bulk. Achieving this task is a major objective in fibre to yarn converss a major objective in fibre to yarn conversion. But it is not an easy task, and has to bion. But it is not an easy task, and has to be carried out gradually. e carried out gradually.

In the initial blending of fibres from bales, small tuftIn the initial blending of fibres from bales, small tufts of fibres are picked up and combined to make a hs of fibres are picked up and combined to make a homogenous blend first. For intimate blend, the fibre omogenous blend first. For intimate blend, the fibre tufts need to be opened out into individual fibres, in tufts need to be opened out into individual fibres, in the carding process that follows.the carding process that follows.

A key objective of carding is fibre opening. Only wheA key objective of carding is fibre opening. Only when fibres are opened out into individual fibres can difn fibres are opened out into individual fibres can different fibres lie side by side to achieve an intimate bferent fibres lie side by side to achieve an intimate blend. After blending and carding, fibres are more or lend. After blending and carding, fibres are more or less randomizedless randomized(( 随机排列随机排列 )). Preserving this rando. Preserving this randomness is a key objective of the subsequent drawing mness is a key objective of the subsequent drawing process.process.

During gillingDuring gilling(( 针梳针梳 )) of wool or drawing of cotto of wool or drawing of cotton, several slivers are doubled together first and n, several slivers are doubled together first and drafted to reduce its thickness. Doubling is a randrafted to reduce its thickness. Doubling is a random operation because no deliberate attempt is dom operation because no deliberate attempt is made to compensate for thick places by doublinmade to compensate for thick places by doubling them against selected thin places. If the fibre eg them against selected thin places. If the fibre ends in the individual slivers are randomly distribnds in the individual slivers are randomly distributed, they will still be randomly distributed after uted, they will still be randomly distributed after doubling. If drafting is done properly, this randodoubling. If drafting is done properly, this randomness will persist into the drafted slivermness will persist into the drafted sliver. .

One problem with maintaining the randoOne problem with maintaining the random fibre ends distribution is the fibre lengtm fibre ends distribution is the fibre length variation. If fibre length is very variable oh variation. If fibre length is very variable or if there are many short fibres in the sliverr if there are many short fibres in the slivers before drafting, the short fibres tend to bs before drafting, the short fibres tend to be drafted in tufts rather than individually, e drafted in tufts rather than individually, and a drafting wave appears in the drafted and a drafting wave appears in the drafted sliver. Since a drafting wave is a practicallsliver. Since a drafting wave is a practically periodic variation in the number of fibrey periodic variation in the number of fibres in the cross sections along the sliver, it ds in the cross sections along the sliver, it defeats the randomness of fibre ends distriefeats the randomness of fibre ends distribution. bution.

For this reason, some fibre control devices, For this reason, some fibre control devices, such as pressure barssuch as pressure bars(( 压力棒压力棒 )) in drawing in drawing and faller barsand faller bars(( 针板导棒针板导棒 )) in gilling, are oft in gilling, are often used to minimize the drafting wavesen used to minimize the drafting waves(( 牵牵伸波伸波 )) and improve the random distributio and improve the random distribution of fibre ends. Similarly, in the roving pron of fibre ends. Similarly, in the roving processcess(( 粗纱工序粗纱工序 )) and during the drafting st and during the drafting stage of spinningage of spinning(( 细纱细纱 )), fibres are also cont, fibres are also controlled during drafting.rolled during drafting.

From this brief discussion of the fibre to From this brief discussion of the fibre to yarn conversion, we can see that througyarn conversion, we can see that throughout the different processes involved, rahout the different processes involved, random fibre distribution is a key objective.ndom fibre distribution is a key objective. If all processes perform perfectly, we wil If all processes perform perfectly, we will end up with a completely random distril end up with a completely random distribution of fibre ends in the resultant yarn. bution of fibre ends in the resultant yarn.

We call this yarn an ideal yarn, and the irregWe call this yarn an ideal yarn, and the irregularity of this yarn the limiting irregularity..ularity of this yarn the limiting irregularity.. Limiting irregularity is therefore the mini Limiting irregularity is therefore the minimum irregularity that we must expect fromum irregularity that we must expect from any real yarn or other fibre assemblies. m any real yarn or other fibre assemblies. A thorough understanding of the concept A thorough understanding of the concept of limiting irregularity is essential for the uof limiting irregularity is essential for the understanding of yarn evenness in particulanderstanding of yarn evenness in particular, and yarn quality in general.r, and yarn quality in general.

Limiting irregularityLimiting irregularity(( 不匀率不匀率 )) (CVlim) (CVlim) A common method of expressing the irregularityA common method of expressing the irregularity

(( 不匀率不匀率 )) of a yarn is to use the statistical term CV of a yarn is to use the statistical term CV or coefficient of variationor coefficient of variation(( 变异系数变异系数 )). Obviously t. Obviously the higher the CV value, the more irregular the yarhe higher the CV value, the more irregular the yarn is. The traditional way of obtaining the CV value n is. The traditional way of obtaining the CV value is to dissect a length of yarn into many short sectiis to dissect a length of yarn into many short sections of equal length, say 1 cm, and then weigh eacons of equal length, say 1 cm, and then weigh each of the short sections. Assuming we have dissecth of the short sections. Assuming we have dissected a yarn into n short sections, and the weights oed a yarn into n short sections, and the weights of these sections are: x1, x2, x3 ..... xn respectively. f these sections are: x1, x2, x3 ..... xn respectively.

From these readings we can easily calculate the From these readings we can easily calculate the following statistics regarding the yarn:following statistics regarding the yarn: The mean or average:The mean or average:

The standard deviation:The standard deviation:

n

x

n

xxxx inx

.......321

___

1

)(

1

)(.....)()( 2__

2__

2__

22

__

1

n

x

n

xxxs xxxx in

(1.1)

(1.2)

The coefficient of variation:The coefficient of variation:

The percentage mean deviation (known as The percentage mean deviation (known as the U% value in textiles)the U% value in textiles)

%100__

x

sCV

%100

|

__

__

|

x

xn

x

U

i

(1.3)

(1.3a)

The CV thus calculated will be the measured CV, or The CV thus calculated will be the measured CV, or effective CV. It is the actual CV of the yarn concerneeffective CV. It is the actual CV of the yarn concerned. The U% value is listed here for completeness. Incd. The U% value is listed here for completeness. Increasingly, it is the CV or CV% value that gets used foreasingly, it is the CV or CV% value that gets used for this purpose. For a fault-free yarn with random var this purpose. For a fault-free yarn with random variations in thickness or linear density, the following riations in thickness or linear density, the following relationship exists between the U value and the CV relationship exists between the U value and the CV value.value.

UCV 25.1 (1.3b)

Modern instrument, such as the Uster Modern instrument, such as the Uster Evenness Tester, can measure the U Evenness Tester, can measure the U and CV values of a fibre assembly at a and CV values of a fibre assembly at a high speed. More on evenness high speed. More on evenness measurement will be discussed later.measurement will be discussed later.

Coming back to the concept of limiting irreComing back to the concept of limiting irregularity, we have said before this is the migularity, we have said before this is the minimum irregularity that must be expected nimum irregularity that must be expected from even an ideal yarn with random fibrfrom even an ideal yarn with random fibre ends distribution. The limiting irregularie ends distribution. The limiting irregularity is also expressed as a CV value, denotety is also expressed as a CV value, denoted as CVlim here. Early works in this area hd as CVlim here. Early works in this area have derived the following very important ave derived the following very important expressions for the limiting irregularity of expressions for the limiting irregularity of various yarns with random fibre ends distvarious yarns with random fibre ends distribution.ribution.

(1) Limiting irregularity of an ideal (1) Limiting irregularity of an ideal yarn without fibre variability:yarn without fibre variability:

where n is the average number of where n is the average number of fibres in yarn cross section.fibres in yarn cross section.

nCV

100lim (1.4)

(2)(2)Limiting irregularity for an ideal yarn Limiting irregularity for an ideal yarn with fibre variability:with fibre variability:

where CVA is the coefficient of variation of where CVA is the coefficient of variation of fibre cross sectional area.fibre cross sectional area.

n

CVCV A

2

lim

0001.01100 (1.5)

These expressions indicate that the These expressions indicate that the number of fibres in yarn cross section number of fibres in yarn cross section is overwhelmingly the most important is overwhelmingly the most important factor that determines the irregularity factor that determines the irregularity of a yarn. Irregularity increases with a of a yarn. Irregularity increases with a reduction in the number of fibres in reduction in the number of fibres in yarn cross section. The fibre variability yarn cross section. The fibre variability also has some effect on the also has some effect on the irregularity value. But different fibre irregularity value. But different fibre types vary considerably in terms of types vary considerably in terms of fibre variability.fibre variability.

► Cotton and syntheticsCotton and synthetics(( 合成纤维合成纤维 )) (staple fibre) (staple fibre) Synthetic staple fibres have very little fibre Synthetic staple fibres have very little fibre

variability, and cotton fibres have some small variability, and cotton fibres have some small fibre variability. For these fibres, the number fibre variability. For these fibres, the number of fibres in yarn cross section can be worked of fibres in yarn cross section can be worked as below:as below:

)(

)(sec

texdensitylinearFibre

texdensitylinearYarntioncrossyarninfibresofNo

(1.6)

The fibre variability of synthetic staples may be ignorThe fibre variability of synthetic staples may be ignored and we can simply use equation (1.4) to calculate ed and we can simply use equation (1.4) to calculate the limiting irregularity of a assembly of synthetic stthe limiting irregularity of a assembly of synthetic staple fibres.aple fibres.

Because of the small fibre variability in cotton, we caBecause of the small fibre variability in cotton, we can not simply use equation (1.4) to work out the limitin not simply use equation (1.4) to work out the limiting iregularity. Instead, the following equation is useng iregularity. Instead, the following equation is used to calculate the limiting irregularity of cotton fibre d to calculate the limiting irregularity of cotton fibre assemblies.assemblies.

nstaplesyntheticCV

100)(lim

nCV

106lim

(1.6a)

(1.6b)

Worked example:Worked example:

A cotton yarn of 25s English cotton count (Ne) consiA cotton yarn of 25s English cotton count (Ne) consists of cotton with a micronaire value of 4.1sts of cotton with a micronaire value of 4.1( )( )

What is the limiting irregularity of this cotton yarn?What is the limiting irregularity of this cotton yarn?

Firstly we need to work out the number of Firstly we need to work out the number of fibres in yarn cross section using formula (1.6). fibres in yarn cross section using formula (1.6). To do that we need to use the same count unit, To do that we need to use the same count unit, tex, for both fibres and yarns.tex, for both fibres and yarns.

From the first module, we already know the conversFrom the first module, we already know the conversion between English cotton and tex count systemsion between English cotton and tex count systems ( ( ) )Therefore, the yarn count in tex is Therefore, the yarn count in tex is

inchg

Netex

5.590

tex62.2325

5.590

The following shows how fibre fineness is converted The following shows how fibre fineness is converted into tex:into tex:

Using equation (1.6), the average number of Using equation (1.6), the average number of fibres in yarn cross section is:fibres in yarn cross section is:

Applying equation (1.6b), we get the limiting Applying equation (1.6b), we get the limiting irregularity for this yarn:irregularity for this yarn:

texm

g

m

g

m

g

cm

g

cm

g

inch

g161.0

1000161.0

100010

1061.1

10

1061.1

1061.1

54.2

101.41.45

6

2

666

7.146161.0

62.23

tex

texn

(%)75.87.146

106106lim

nCV

► Wool fibresWool fibres For wool fibre, it is the fibre diameter and diameter CFor wool fibre, it is the fibre diameter and diameter C

V that get measured, not the fibre cross section area aV that get measured, not the fibre cross section area and its CV. In addition, the average number of fibres in nd its CV. In addition, the average number of fibres in yarn cross section is not as easy to get as the yarn couyarn cross section is not as easy to get as the yarn count. The following equation has been derived to calculant. The following equation has been derived to calculate the average number of fibres in the cross section of te the average number of fibres in the cross section of worsted yarns consisting of 100% wool fibres, assumiworsted yarns consisting of 100% wool fibres, assuming a fibre density of 1.31 g/cm3.ng a fibre density of 1.31 g/cm3.

where:where: tex = yarn count in textex = yarn count in texD = mean fibre diameter of wool (in microD = mean fibre diameter of wool (in micro

n)n)CVD = coefficient of variation of fibre diameCVD = coefficient of variation of fibre diame

terter

)0001.01(

97222

DCVD

texn

(1.7)

Since the bulk of the merino wool fibres has a CVD oSince the bulk of the merino wool fibres has a CVD of about 24.5%, the above equation is often simplifief about 24.5%, the above equation is often simplified to:d to:

It should be noted though this simplified equation is It should be noted though this simplified equation is based on the assumption that CVD = 24.5%. based on the assumption that CVD = 24.5%.

If we put equation (1.7) into equation (1.5) and note If we put equation (1.7) into equation (1.5) and note that for wool, we have the following expression for tthat for wool, we have the following expression for the limiting irregularity of wool assemblies:he limiting irregularity of wool assemblies:

2

917

D

texn

tex

CVDwoolCV D

2

lim

0005.012.3)(

(1.7a)

(1.8)

This equation has the following important This equation has the following important implications:implications:

For a given yarn count (tex), the finer For a given yarn count (tex), the finer the fibre in the yarn, the less the yarn the fibre in the yarn, the less the yarn irregularity. This is the main reason why irregularity. This is the main reason why fine fibres are more expensive than fine fibres are more expensive than coarse fibres. coarse fibres.

For fibres of a given fineness (D), the For fibres of a given fineness (D), the finer the yarn, the more irregular it is. This finer the yarn, the more irregular it is. This explains why for a given fibre fineness, explains why for a given fibre fineness, there is a limit on the finest yarn count. It there is a limit on the finest yarn count. It is worth noting that the concept of is worth noting that the concept of irregularity applies to not just yarns, but irregularity applies to not just yarns, but fibre assemblies in general. Therefore, for fibre assemblies in general. Therefore, for a given fibre fineness, the irregularity of a given fibre fineness, the irregularity of sliver will be less than that of roving, and sliver will be less than that of roving, and roving’s irregularity will be less than yarn roving’s irregularity will be less than yarn irregularity. This can also be explained by irregularity. This can also be explained by considering the different number of fibres considering the different number of fibres in those fibre assemblies.in those fibre assemblies.

If you reduce the CV of fibre diameter, the irreguIf you reduce the CV of fibre diameter, the irregularity of the yarn decreases. Put differently, if yolarity of the yarn decreases. Put differently, if you reduce the fibre diameter CV by 5, you may incu reduce the fibre diameter CV by 5, you may increase the fibre diameter by 1 micron without sigrease the fibre diameter by 1 micron without significantly affecting the yarn irregularity. This is tnificantly affecting the yarn irregularity. This is the so-called 5-to-1 rule of thumb.he so-called 5-to-1 rule of thumb.

The equations for wool appear rather complex. A The equations for wool appear rather complex. A simpler equation for wool is given below:simpler equation for wool is given below:

However, this equation should be used with cauHowever, this equation should be used with cau

tion, because it is based on assumption that the tion, because it is based on assumption that the CV of fibre diameter is 25%. If the diameter CV dCV of fibre diameter is 25%. If the diameter CV deviates significantly from 25%, the above formuleviates significantly from 25%, the above formula will lead to error.a will lead to error.

nwoolCV

112)(lim (1.8a)

► Fibre blendsFibre blends Blends of different fibres are common and their Blends of different fibres are common and their

popularity is increasing. How do we work out the popularity is increasing. How do we work out the limiting irregularity of blend yarns then? This limiting irregularity of blend yarns then? This can be tackled by considering the blend yarn as can be tackled by considering the blend yarn as a ply yarn consisting of two or more single a ply yarn consisting of two or more single yarns, each having one fibre component. If yarns, each having one fibre component. If fibres in the blend yarn are randomly fibres in the blend yarn are randomly distributed, it is reasonable to assume the fibres distributed, it is reasonable to assume the fibres in each component are also random. Therefore, in each component are also random. Therefore, we can treat each single yarn the same as we we can treat each single yarn the same as we have treated the 100 cotton or 100% wool have treated the 100 cotton or 100% wool yarnsyarns..

Given the count of the blend yarn Tb, and the blenGiven the count of the blend yarn Tb, and the blend ratio of fibre component Pi, the count of each cod ratio of fibre component Pi, the count of each component Ti can be worked out according to the formponent Ti can be worked out according to the formula below:mula below:

Once we know the count of each component Once we know the count of each component yarn, the limiting irregularity of the blend yarn yarn, the limiting irregularity of the blend yarn of n fibre components is given as follows,of n fibre components is given as follows,

100

PiTbTi

Tb

TnCVnTCVTCVblendCV

22lim2

2lim1

lim

)lim(.....)2()1()(

(1.9)

(1.10)

Worked Example:Worked Example: A wool/polyester blend yarn is manufactured on tA wool/polyester blend yarn is manufactured on t

he worsted processing system. The yarn has a couhe worsted processing system. The yarn has a count of 30 tex and contains 45% wool and 55% polyent of 30 tex and contains 45% wool and 55% polyester. The fibre fineness for the polyester staple is 2.ster. The fibre fineness for the polyester staple is 2.5 dtex. The mean diameter of the wool fibres is 22 5 dtex. The mean diameter of the wool fibres is 22 micron, with a CV of 25%. What is the limiting irregmicron, with a CV of 25%. What is the limiting irregularity of this blend yarn?ularity of this blend yarn?

Solution :Solution :

Assuming the blend yarn is a ply of two single yarns,Assuming the blend yarn is a ply of two single yarns, or 100 wool and 100% polyester respectively, we ca or 100 wool and 100% polyester respectively, we can work out the count of the wool component (Tw) an work out the count of the wool component (Tw) and the polyester component (Tp) according to equand the polyester component (Tp) according to equation (1.9):tion (1.9):

)(5.13100

4530

100tex

PwTbTw

)(5.16100

5530

100tex

PpTbTp

Using equation (1.6), the average number of Using equation (1.6), the average number of fibres in the polyester component (np) can bfibres in the polyester component (np) can be worked out as:e worked out as:

Since polyester staple has little variability in Since polyester staple has little variability in fineness, we can then use equation (2.4) to fineness, we can then use equation (2.4) to work out the limiting irregularity of the work out the limiting irregularity of the polyester component:polyester component:

For the wool component, we can use equation For the wool component, we can use equation (2.8),(2.8),

665.2

165

5.2

5.16

dtex

dtex

dtex

texn p

(%)3.1266

100100lim

nCV p

(%)95.215.13

250005.01222.30005.012.3 22

lim

tex

CVDCV D

w

Finally, we can use equation (2.10) to work out the Finally, we can use equation (2.10) to work out the limiting irregularity of the blend yarn,limiting irregularity of the blend yarn,

So, the blend yarn has a limiting irregularity of So, the blend yarn has a limiting irregularity of 12%.12%.

Finally, since some textile mills still use the U% valFinally, since some textile mills still use the U% value discussed earlier, the limiting U value can be wue discussed earlier, the limiting U value can be worked using the simple equation below:orked using the simple equation below:

(%)1230

)5.163.12()5.1395.21()()()(

222lim

2lim

lim

Tb

TpCVTwCVblendCV

pw

25.1lim

lim

CVU (1.11)

Index of Irregularity (I)Index of Irregularity (I) After the proceeding discussions on limiting irregulAfter the proceeding discussions on limiting irregul

arity, we should be very clear in our minds that the narity, we should be very clear in our minds that the number of fibres in yarn cross section has a decisive eumber of fibres in yarn cross section has a decisive effect on yarn evenness. Because of this, a coarse yarffect on yarn evenness. Because of this, a coarse yarn would always be more even than a thinner yarn mn would always be more even than a thinner yarn made from similar fibres and under similar processing ade from similar fibres and under similar processing conditions. Does this mean the coarse yarn is intrinsiconditions. Does this mean the coarse yarn is intrinsically better, in evenness, than the finer yarn then? cally better, in evenness, than the finer yarn then?

The answer is no. The limiting irregularity provides a reThe answer is no. The limiting irregularity provides a reference point. But this reference point is not fixed, it cference point. But this reference point is not fixed, it changes with yarn count. A fair comparison of yarn quahanges with yarn count. A fair comparison of yarn quality in terms of evenness between similar yarns of difflity in terms of evenness between similar yarns of different counts is to see how close the actual CV of each erent counts is to see how close the actual CV of each yarn is to its respective limit (the limiting irregularity). yarn is to its respective limit (the limiting irregularity). This would be a measure of the degree to which the mThis would be a measure of the degree to which the mass variations of a yarn deviates from the ideal yarn wass variations of a yarn deviates from the ideal yarn with random fibre ends distribution. ith random fibre ends distribution.

The index of irregularity provides such a measure. It is The index of irregularity provides such a measure. It is defined as the ratio between the actual (measured, efdefined as the ratio between the actual (measured, effective) irregularity and the limiting irregularity for thfective) irregularity and the limiting irregularity for the yarn (or other fibre assemblies)e yarn (or other fibre assemblies)

where I = Index of irregulaitywhere I = Index of irregulaity

CVeff = Effective (actual, measured) irregulaCVeff = Effective (actual, measured) irregularityrity

CVlim = Limiting irregularity.CVlim = Limiting irregularity.

limCV

CVI eff (2.12)

TThe index of irregularity is a dimensionless parahe index of irregularity is a dimensionless parameter. In the ideal case, I = 1. Since the actual Cmeter. In the ideal case, I = 1. Since the actual CV of a yarn is almost always higher than its limitV of a yarn is almost always higher than its limiting CV, the I value is usually greater than 1. The ing CV, the I value is usually greater than 1. The higher the I, the worse the yarn is in evenness, rehigher the I, the worse the yarn is in evenness, regardless of the yarn count. Of course, as for limitgardless of the yarn count. Of course, as for limiting irregularity, the index of irregularity also apping irregularity, the index of irregularity also applies to fibre assemblies other than yarns.lies to fibre assemblies other than yarns.

Figure 1.2 shows changes in CV and I of the fibre asFigure 1.2 shows changes in CV and I of the fibre assemblies at different stages of the fibre to yarn consemblies at different stages of the fibre to yarn conversion. It is worth noting that the trends for CV anversion. It is worth noting that the trends for CV and I are quite different. The index of irregularity (I) grd I are quite different. The index of irregularity (I) gradually decreases with further processing. This indiadually decreases with further processing. This indicates that the fibre assembly is increasingly approacates that the fibre assembly is increasingly approaching an ideal one. ching an ideal one.

CVeff I

Carded sliver

Combed sliver

Drawn slivers 1st & 2nd

Roving Yarn

CVeff

I

1

Defective passage

Fig. 1.2: Changes in CV and I values in a combed cotton yarn production

In other words, with further processing, the fibre enIn other words, with further processing, the fibre ends distribution is getting more and more random. Ads distribution is getting more and more random. As mentioned early, promoting random fibre ends dis mentioned early, promoting random fibre ends distribution is a key objective of fibre to yarn processistribution is a key objective of fibre to yarn processing. At the yarn stage, the index of irregularity is appng. At the yarn stage, the index of irregularity is approaching one, suggesting that the yarn is approachiroaching one, suggesting that the yarn is approaching an ideal yarn. ng an ideal yarn.

On the other hand, there is a general trend for thOn the other hand, there is a general trend for the effective (or actual) CV of the fibre assemblies te effective (or actual) CV of the fibre assemblies to increase during fibre to yarn processing, with tho increase during fibre to yarn processing, with the CV of the resultant yarn higher than the rovine CV of the resultant yarn higher than the roving’s and the slivers’. This is a reflection of the dg’s and the slivers’. This is a reflection of the decreasing thickness of the fibre assemblies, and recreasing thickness of the fibre assemblies, and reducing number of fibres in the cross section of teducing number of fibres in the cross section of the fibre assemblies. At the yarn stage, the numbehe fibre assemblies. At the yarn stage, the number of fibres in the cross section is the lowest, hence r of fibres in the cross section is the lowest, hence the CV of the yarn is the highest.the CV of the yarn is the highest.

This example again demonstrates the difference beThis example again demonstrates the difference be

tween the CV value and the I value. The I value ptween the CV value and the I value. The I value p

rovides a good indication of how close a fibre assrovides a good indication of how close a fibre ass

embly is to an idea one with random fibre ends diembly is to an idea one with random fibre ends di

stribution. Because of this, the I value is often usestribution. Because of this, the I value is often use

d as a quality control parameter for assessing the d as a quality control parameter for assessing the

performance of drawing and spinning. performance of drawing and spinning.

For instance, if the I value is obtained at evFor instance, if the I value is obtained at every processing stage, and an increase in I ery processing stage, and an increase in I value is found after the 2nd drawing as invalue is found after the 2nd drawing as indicated by the broken line in Figure 1.2, thdicated by the broken line in Figure 1.2, that immediately tells us that the 2nd drawiat immediately tells us that the 2nd drawing is a defective one and should be fixed. Ing is a defective one and should be fixed. If all processing stages are under control, tf all processing stages are under control, the I values should progressively decrease he I values should progressively decrease from start to the end of the processing as ifrom start to the end of the processing as indicated by the solid line for I values in Findicated by the solid line for I values in Figure 1.2. gure 1.2.

Unlike the CV% and U% values, the index of irregUnlike the CV% and U% values, the index of irregularity (I) is independent of the count of the fibre ularity (I) is independent of the count of the fibre assembly. This makes it an ideal tool for use in thassembly. This makes it an ideal tool for use in the control chart. For instance, if the I value is obtaie control chart. For instance, if the I value is obtained at the roving stage for every processing lot aned at the roving stage for every processing lot and plotted on a control chart, abnormalities may nd plotted on a control chart, abnormalities may be easily identified before the final spinning stagbe easily identified before the final spinning stage. e.

Reduction and addition of irregularitiesReduction and addition of irregularities

Figure 1.2 shows that the measured CV (CVeff) of the Figure 1.2 shows that the measured CV (CVeff) of the cotton sliver gradually reduces from carding to 2nd cotton sliver gradually reduces from carding to 2nd drawing, and then the CV increases again after the rdrawing, and then the CV increases again after the roving and spinning stages. Why is this the case then?oving and spinning stages. Why is this the case then? What is causing the increase and decrease in yarn ir What is causing the increase and decrease in yarn irregularity. To answer this question, we need to learregularity. To answer this question, we need to learn the law of doubling and addition of irregularity.n the law of doubling and addition of irregularity.

► Law of doublingLaw of doubling(( 并合原理并合原理 ))

During drawing, many slivers are combined (doubleDuring drawing, many slivers are combined (doubled) on the input side to feed the drawframe. The law d) on the input side to feed the drawframe. The law of doubling says that if you combine (double) n sliveof doubling says that if you combine (double) n slivers together, the overall irregularity of the combined rs together, the overall irregularity of the combined (doubled) sliver will reduce according to the followi(doubled) sliver will reduce according to the following law:ng law:

where:where: CVCVII = CV of all n slivers at the input to the = CV of all n slivers at the input to the drawframedrawframe

== Mean value of the CV values of all Mean value of the CV values of all the single sliversthe single slivers

n = number of doubled slivers.n = number of doubled slivers.

nCV CV

I

______

CV____

n

CVCVCVCV n

....21

___

(1.13)

Therefore, doubling always reduces the overall irregularity. TTherefore, doubling always reduces the overall irregularity. T

his is not difficult to comprehend if you consider the large inhis is not difficult to comprehend if you consider the large in

crease in the number of fibres in the cross section of the doubcrease in the number of fibres in the cross section of the doub

led material. The doubled material is then subject to drafting, led material. The doubled material is then subject to drafting,

which reduces its thickness. As long as the drawframe is funcwhich reduces its thickness. As long as the drawframe is func

tioning properly, and the output sliver is thicker than, or as thtioning properly, and the output sliver is thicker than, or as th

ink as, the average thickness of the input slivers, the CV of think as, the average thickness of the input slivers, the CV of th

e output sliver will be lower than the average CV of the input e output sliver will be lower than the average CV of the input

slivers. This explains the decrease in measured CV from cardslivers. This explains the decrease in measured CV from card

ing to drawing in Figure 1.2.ing to drawing in Figure 1.2.

► Addition of irregularityAddition of irregularity At the roving and spinning stage, there is no At the roving and spinning stage, there is no

doubling. A sliver is drafted into a thinner rovdoubling. A sliver is drafted into a thinner roving, and a roving is drafted to yarn thickness ing, and a roving is drafted to yarn thickness during spinning. The net result is a reduction during spinning. The net result is a reduction in the number of fibres in yarn cross section. Iin the number of fibres in yarn cross section. In addition, the process itself may introduce an addition, the process itself may introduce additional irregularities to the drafted materiadditional irregularities to the drafted material. l.

Mathematically, if a fibre assembly enters a draftinMathematically, if a fibre assembly enters a drafting process (roving, spinning) with an irregularity of Cg process (roving, spinning) with an irregularity of CVin, and emerges from that process with an irregulaVin, and emerges from that process with an irregularity of CVout, then the additional irregularity due to rity of CVout, then the additional irregularity due to the process itself (CVadd) can be worked out using tthe process itself (CVadd) can be worked out using the following formula:he following formula:

The added irregularity comes from two sources The added irregularity comes from two sources – reduction in the number of fibres in cross – reduction in the number of fibres in cross section and imperfect drafting. section and imperfect drafting.

The following example will help understand the conThe following example will help understand the concepts here.cepts here.

inoutaddaddinout CVCVCVorCVCVCV 22222

Worked exampleWorked example Eight slivers, with an average irregularity CV of 4%, Eight slivers, with an average irregularity CV of 4%,

were fed to a drawframe. The drawn sliver has a CV were fed to a drawframe. The drawn sliver has a CV value of 3%. What is the total irregularity introducevalue of 3%. What is the total irregularity introduced during the drawing process? d during the drawing process?

SolutionSolution : :

The above problem can be graphically represented aThe above problem can be graphically represented as:s: Sliver 1

Sliver 8

CVout = 3%

CVadd = ?

CVave = 4%

First of all, we need to know the CV of the input matFirst of all, we need to know the CV of the input material (CVin). According to the law of doubling (equatierial (CVin). According to the law of doubling (equation 1.13), this can be easily calculated:on 1.13), this can be easily calculated:

Now that we know CVin and CVout is already Now that we know CVin and CVout is already given as 3%, we can calculate the CV introduced given as 3%, we can calculate the CV introduced during drawing (CVadd) using equation 1.14.during drawing (CVadd) using equation 1.14.

As mentioned before, this added CV is due to As mentioned before, this added CV is due to two factors – reduction in the number of fibres in two factors – reduction in the number of fibres in cross section and imperfect drafting caused by cross section and imperfect drafting caused by material and/or machine related reasons.material and/or machine related reasons.

(%)4.18

4___

n

CVin CV

(%)65.24.13 2222 inoutadd CVCVCV

Review questionsReview questions

1.1.In the calculation of limiting irregularity, infoIn the calculation of limiting irregularity, information on fibre length is not used. This implrmation on fibre length is not used. This implies that fibre length has noting to do with the ies that fibre length has noting to do with the theoretical yarn evenness. Yet in practice, fibtheoretical yarn evenness. Yet in practice, fibres with shorter length and higher length varires with shorter length and higher length variations usually make less even yarns, other thations usually make less even yarns, other things being equal. How do you explain this 'diings being equal. How do you explain this 'discrepancy'?screpancy'?

2. 2. A yarn is composed of 40/60 wool/cotton blend A yarn is composed of 40/60 wool/cotton blend and has a linear density of 20 Nec (cotton count).and has a linear density of 20 Nec (cotton count). The cotton has a fineness of 3.8 micronaire () an The cotton has a fineness of 3.8 micronaire () and the wool has an average diameter of 19 μm (1 d the wool has an average diameter of 19 μm (1 μm = 10-6 m) and a diameter CV of 25%. What is μm = 10-6 m) and a diameter CV of 25%. What is the limiting irregularity of this wool/cotton yarn?the limiting irregularity of this wool/cotton yarn? If the blend ratio is changed to 20/80 wool/cotto If the blend ratio is changed to 20/80 wool/cotton, is the yarn evenness likely to improve or detern, is the yarn evenness likely to improve or deteriorate, compared with the 40/60 wool/cotton bliorate, compared with the 40/60 wool/cotton blend ratio? (you need to show your workings).end ratio? (you need to show your workings).

. .

3.3.In his classical book "Studies of quality in In his classical book "Studies of quality in cotton", published by Macmillan and Co., cotton", published by Macmillan and Co., Limited in 1928, W. Lawrence Balls describLimited in 1928, W. Lawrence Balls described such a paradox - the weaker the fibre, ted such a paradox - the weaker the fibre, the stronger the yarn! Please explain this phe stronger the yarn! Please explain this paradox, using the information provided in aradox, using the information provided in this topicthis topic

Measurement and benchmarking Measurement and benchmarking of yarn evennessof yarn evenness(( 纱线均匀度纱线均匀度 ))

IntroductionIntroduction Up till now we have used the term effective CV, actUp till now we have used the term effective CV, act

ual or measured CV of yarns. But how do we measurual or measured CV of yarns. But how do we measure the CV of a yarn or a fibre assembly and what do we the CV of a yarn or a fibre assembly and what do we do with the measured results?e do with the measured results?

This topic discusses evenness measurement and mThis topic discusses evenness measurement and making use of the measured results.aking use of the measured results.

ObjectivesObjectives

At the end of this topic you should be able to:At the end of this topic you should be able to:

Understand the principle of evenness testingUnderstand the principle of evenness testingAppreciate the importance of spectrograms Appreciate the importance of spectrograms

as a diagnostic toolas a diagnostic toolKnow the difference between Uster Statistics Know the difference between Uster Statistics

and Yarnspecand Yarnspec

Principle of evenness testingPrinciple of evenness testing As mentioned before, the traditional way of As mentioned before, the traditional way of

evenness testing is to dissect the fibre assembly into evenness testing is to dissect the fibre assembly into many short sections and weigh each section, and many short sections and weigh each section, and then calculate the CV of the fibre assembly from the then calculate the CV of the fibre assembly from the weights of the individual sections. This is still a weights of the individual sections. This is still a reference method, by which the accuracy of other reference method, by which the accuracy of other methods is judged. Such cutting and weighing methods is judged. Such cutting and weighing method is a very tedious process as you can method is a very tedious process as you can imagine, considering that a sufficiently long length imagine, considering that a sufficiently long length of yarn should be measured to get a CV value of yarn should be measured to get a CV value representative of the bulk material. representative of the bulk material.

Zellweger Uster AG, a textile instrument manufacturZellweger Uster AG, a textile instrument manufacturer based in Switzerland, has produced generations oer based in Switzerland, has produced generations of evenness testing instrument for rapid measuremenf evenness testing instrument for rapid measurement of the evenness of various fibre assemblies. The latt of the evenness of various fibre assemblies. The latest is the Uster Evenness Tester 4, although its predeest is the Uster Evenness Tester 4, although its predecessor (Uster Evenness Tester 3) is still widely used. cessor (Uster Evenness Tester 3) is still widely used. A photo of the Uster tester 3 is given in Figure 2.1.A photo of the Uster tester 3 is given in Figure 2.1.

Fig. 2.1: A photo of Uster evenness tester 3 (Zellweger Uster AG)

The Uster Evenness TesterThe Uster Evenness Tester(Uster(Uster 均匀度测试仪均匀度测试仪 ))

measures mass variations along the length of a fibmeasures mass variations along the length of a fibre assembly. It is based on the capacitance princire assembly. It is based on the capacitance principle as depicted in Figure 2.2. The two capacitors dple as depicted in Figure 2.2. The two capacitors detect the mass variations or weight per unit lengtetect the mass variations or weight per unit length variations of the fibre assembly running betweeh variations of the fibre assembly running between them. These variations are transformed into a pn them. These variations are transformed into a proportional electrical signal. The signal processinroportional electrical signal. The signal processing unit will process this signal, and work out the Ug unit will process this signal, and work out the U% and CV% value, as well as other useful informat% and CV% value, as well as other useful information concerning the mass variations. All the details ion concerning the mass variations. All the details can be displayed or printed out. can be displayed or printed out.

Evenness test resultsEvenness test results The Uster evenness tester provides a considerable The Uster evenness tester provides a considerable

amount of information on the evenness of a fibre asamount of information on the evenness of a fibre assembly, including:sembly, including:

Single overall resultsSingle overall resultsDiagramDiagramSpectrogramSpectrogram

► Single overall resultsSingle overall results

These include the U% and CV% values, the These include the U% and CV% values, the index of irregularity (I), as well as the number index of irregularity (I), as well as the number of imperfections (thin place, thick place, and of imperfections (thin place, thick place, and neps). All those parameters are expressed as neps). All those parameters are expressed as single numbers, which are easy to use, single numbers, which are easy to use, particularly in a mill situation. These single particularly in a mill situation. These single values provide an overall picture of yarn values provide an overall picture of yarn evenness. However, if the results are bad, the evenness. However, if the results are bad, the causes of the poor results can not be causes of the poor results can not be identified from these single valuesidentified from these single values

► DiagramDiagram A diagram is simply a trace of mass (linear A diagram is simply a trace of mass (linear

density) variation along a fibre assembly. For density) variation along a fibre assembly. For instance, if you dissect a long length of yarn instance, if you dissect a long length of yarn into many very short sections and then weigh into many very short sections and then weigh each section, you will get many mass readings each section, you will get many mass readings (xi) as shown in Figure 2.4.(xi) as shown in Figure 2.4.

From this diagram, many useful statistics From this diagram, many useful statistics

(mean, CV etc) can be obtained as shown in (mean, CV etc) can be obtained as shown in the Limiting Irregularity section.the Limiting Irregularity section.

Mass

Length

Mean mass

xi (individual mass readings)

Fig. 2.4: A manually constructed diagram of mass variation

A diagram obtained from the Uster evenness tester A diagram obtained from the Uster evenness tester is given in Figure 2.5. The dip in the middle of this dis given in Figure 2.5. The dip in the middle of this diagram was actually caused by a missing sliver, of aiagram was actually caused by a missing sliver, of about 120 m, in the input material for a drawframe. bout 120 m, in the input material for a drawframe. This example demonstrates the usefulness of diagrThis example demonstrates the usefulness of diagrams in identifying certain faults in the fibre assembams in identifying certain faults in the fibre assembly. Basically, the diagrams can help identify extremly. Basically, the diagrams can help identify extreme thin and thick places, slow changes in the mean e thin and thick places, slow changes in the mean mass value, step changes in the mean value, periodmass value, step changes in the mean value, periodic mass variations of long wave length etc. ic mass variations of long wave length etc.

Fig. 2.5: A diagram showing an extreme thin place iFig. 2.5: A diagram showing an extreme thin place in the sliver (Furter 1982, p.12)n the sliver (Furter 1982, p.12)

► SpectrogramsSpectrograms(( 波谱图波谱图 ))

The single overall results are very useful The single overall results are very useful in that they provide evenness in that they provide evenness information in concise single values. information in concise single values. These single values are easy to use for These single values are easy to use for comparison purpose in particular. For comparison purpose in particular. For instance, the CV% or index of instance, the CV% or index of irregularity of one yarn is higher than irregularity of one yarn is higher than another similar yarn, we can say one another similar yarn, we can say one yarn is better than the other in terms of yarn is better than the other in terms of yarn evenness. yarn evenness.

But that is often not sufficient for But that is often not sufficient for quality control purpose. Suppose we quality control purpose. Suppose we now know from the single overall now know from the single overall results (eg. CV, I) that a yarn is not results (eg. CV, I) that a yarn is not good in evenness, and we want to find good in evenness, and we want to find out what has caused the irregularity in out what has caused the irregularity in the yarn. Once we know what has the yarn. Once we know what has caused the irregularity, we can then caused the irregularity, we can then try to rectify the problem. For this, we try to rectify the problem. For this, we need the spectrograms. need the spectrograms.

Before we discuss the spectrogram, it is necessary to Before we discuss the spectrogram, it is necessary to say a few words about the nature of mass variations isay a few words about the nature of mass variations in a fibre assembly. We already know that random fibn a fibre assembly. We already know that random fibre arrangements lead to mass variation, and this variare arrangements lead to mass variation, and this variation can be precisely calculated as discussed in the lition can be precisely calculated as discussed in the limiting irregularity section. If that is all the variation miting irregularity section. If that is all the variation we get, then we have nothing more to worry about, bwe get, then we have nothing more to worry about, because that is exactly what we aim for in a yarn. Unfecause that is exactly what we aim for in a yarn. Unfortunately we often get more than just the random vaortunately we often get more than just the random variations, for two common reasons:riations, for two common reasons:

(a) (a) Variability in fibre length and the presence Variability in fibre length and the presence of short fibres make fibre control during draftiof short fibres make fibre control during drafting difficult, this leads to non-random variationg difficult, this leads to non-random variations in a fibre assembly. Such non-random varians in a fibre assembly. Such non-random variation is called a drafting wave. It is called a draftion is called a drafting wave. It is called a drafting wave because the mass variation occurs iting wave because the mass variation occurs in a more or less periodic manner in the draften a more or less periodic manner in the drafted material, much like a wave of variations alond material, much like a wave of variations along the length of the fibre assembly.g the length of the fibre assembly.

(b) (b) There may be machine defects or mechThere may be machine defects or mechanical faults in the drafting systems, whicanical faults in the drafting systems, which causes changes in drafting speed and thh causes changes in drafting speed and the actual draft periodically, leading to rathe actual draft periodically, leading to rather strictly periodic mass variations in the der strictly periodic mass variations in the drafted fibre assembly.rafted fibre assembly.

Here we need to reflect upon what has been discusHere we need to reflect upon what has been discussed on Roller Drafting in the Introduction to Fibre Ssed on Roller Drafting in the Introduction to Fibre Science and Textile Technology unit. For roller drafticience and Textile Technology unit. For roller drafting, as depicted in Figure 2.6, the most important cong, as depicted in Figure 2.6, the most important concept is the concept of perfect roller drafting.ncept is the concept of perfect roller drafting.

Front rollers Back rollers

Faster Slower

Ratch setting

Fig. 2.6: A simple roller drafting system

The concept of perfect roller drafting is: every fiThe concept of perfect roller drafting is: every fibre in the drafting zone should travel at the spebre in the drafting zone should travel at the speed of back rollers until its leading end reaches ted of back rollers until its leading end reaches the front roller nip. Then the fibre gets instantly he front roller nip. Then the fibre gets instantly accelerated to the front roller speed.If this is waccelerated to the front roller speed.If this is what actually happens in roller drafting, we will ghat actually happens in roller drafting, we will get a drafted fibre assembly with random variatiet a drafted fibre assembly with random variation of fibre ends only. on of fibre ends only.

However, when there are many short fibres in thHowever, when there are many short fibres in the drafting zone, these short fibres will not move e drafting zone, these short fibres will not move according to the requirements of roller drafting. according to the requirements of roller drafting. They ‘float’ and ‘swim’ together in the drafThey ‘float’ and ‘swim’ together in the drafting zone, the speed at which they travel dependting zone, the speed at which they travel depends on the speed of their neighbouring fibres. The es on the speed of their neighbouring fibres. The end result is some practically (i.e. not strictly) perind result is some practically (i.e. not strictly) periodic mass variation in the drafted material. Such odic mass variation in the drafted material. Such practically periodic mass variation caused by flopractically periodic mass variation caused by floating short fibres is called a drafting wave, and itating short fibres is called a drafting wave, and its wave length is approximately 2.5 to 3 times the s wave length is approximately 2.5 to 3 times the average fibre length of the fibre assembly.average fibre length of the fibre assembly.

With good fibre control, using pressure bars (on cottoWith good fibre control, using pressure bars (on cotton drawframe) and pinned faller basr (on worsted gillbn drawframe) and pinned faller basr (on worsted gillbox), drafting waves can be significantly reduced or eliox), drafting waves can be significantly reduced or eliminated.minated.

A common machine defect or mechanical fault of drafA common machine defect or mechanical fault of drafting elements is roller eccentricity, as indicated in Figuting elements is roller eccentricity, as indicated in Figure 2.7. re 2.7.

r

R

Speed varies with radius

Eccentric front bottom roller

Wave length (Roller circumference)

Drafted material

r

R

Eccentric back bottom roller

Wave length (Roller circumference x draft)

Drafted material

Fig. 2.7: Eccentric rollers cause periodic mass variations

Because of roller eccentricity, the surface speed (v) Because of roller eccentricity, the surface speed (v) of the eccentric roller varies as the radius of rotatioof the eccentric roller varies as the radius of rotation (r) varies (n, where n is the roller rpm). If the front n (r) varies (n, where n is the roller rpm). If the front bottom roller is eccentric, a larger radius of rotatiobottom roller is eccentric, a larger radius of rotation (R) will lead to higher roller surface speed, which n (R) will lead to higher roller surface speed, which means increased drafting, resulting in over draft or means increased drafting, resulting in over draft or a thin section in the drafted material. The opposite a thin section in the drafted material. The opposite happens with the smaller radius of rotation, and thihappens with the smaller radius of rotation, and this cycle repeats for every complete revolution of the s cycle repeats for every complete revolution of the eccentric roller. As a result the wave length of the peccentric roller. As a result the wave length of the periodic variation is exactly the same as the circumfeeriodic variation is exactly the same as the circumference of the offending roller. rence of the offending roller.

On the other hand, if the back bottom roller is eccenOn the other hand, if the back bottom roller is eccentric and front rollers are fine, then at the larger radiutric and front rollers are fine, then at the larger radius of rotation R), the back roller surface speed will be s of rotation R), the back roller surface speed will be faster, leading to a reduction in draft and hence a thfaster, leading to a reduction in draft and hence a thicker section in the drafted material. The opposite is icker section in the drafted material. The opposite is the case at the smaller radius of rotation (r). Not onlthe case at the smaller radius of rotation (r). Not only that, the periodic mass variation caused by the bacy that, the periodic mass variation caused by the back eccentric roller will be lengthened by a factor of thk eccentric roller will be lengthened by a factor of the draft used. In other words, the wave length of the pe draft used. In other words, the wave length of the periodic mass variation caused by a back eccentric roleriodic mass variation caused by a back eccentric roller will be equal to the roller circumference multiplieler will be equal to the roller circumference multiplied by a factor of draft, as indicated in Figure 2.7.d by a factor of draft, as indicated in Figure 2.7.

Periodic mass variations in a yarn often rPeriodic mass variations in a yarn often result in unwanted patterning in fabrics mesult in unwanted patterning in fabrics made from such yarns. They also lead to inade from such yarns. They also lead to increased ends down during spinning and screased ends down during spinning and subsequent processing. It is essential in yaubsequent processing. It is essential in yarn manufacture to prevent the occurrencrn manufacture to prevent the occurrence of such mass variations in slivers, rovine of such mass variations in slivers, rovings or yarns. gs or yarns.

Furthermore, the presence of periodic or pFurthermore, the presence of periodic or practically periodic mass variations in a fibrractically periodic mass variations in a fibre assembly does not necessarily result in se assembly does not necessarily result in significant increases in the CV% value or in ignificant increases in the CV% value or in the index of irregularity. the index of irregularity.

So the CV% value or index of irregularity wSo the CV% value or index of irregularity will not indicate the presence of those mass ill not indicate the presence of those mass variations. But how do we know if a fibre avariations. But how do we know if a fibre assembly has a drafting wave or periodic mssembly has a drafting wave or periodic mass variation then? This question leads us ass variation then? This question leads us back to discussion on spectrograms.back to discussion on spectrograms.

Hypothetically, if a yarn has mass variations tHypothetically, if a yarn has mass variations that resemble a sinusoidal wave as shown in Fhat resemble a sinusoidal wave as shown in Figure 2.8(a), then a mathematical (Fourier) trigure 2.8(a), then a mathematical (Fourier) transformation of such a mass variation signal ansformation of such a mass variation signal will reveal the frequency (f) of such variation will reveal the frequency (f) of such variation as a sharp peak shown in Figure 2.8(b). For a as a sharp peak shown in Figure 2.8(b). For a signal that is not as simple as just a sinusoidasignal that is not as simple as just a sinusoidal wave, it has been proven mathematically thl wave, it has been proven mathematically that it can be constructed by superimposing a sat it can be constructed by superimposing a series of sinusoidal waves of varying frequencieries of sinusoidal waves of varying frequencies. es.

Therefore, if the original mass variation in tTherefore, if the original mass variation in the yarn is of a more complex shape as shohe yarn is of a more complex shape as shown in Figure 2.8(c), then the same mathemwn in Figure 2.8(c), then the same mathematical transformation will reveal the frequeatical transformation will reveal the frequency of each of its sinusoidal components ancy of each of its sinusoidal components as shown Figure 2.8(d). The different amplits shown Figure 2.8(d). The different amplitude reflects the different ‘share’ of the rude reflects the different ‘share’ of the respective component in the original signal.espective component in the original signal.

Amplitude Amplitude

Time

Time

Frequency

Frequency

f

f1 f2 f3

(a)

(d) (c)

(b)

Transformation

Transformation

Fig. 2.8: Transformation of time domain signal to frequency domain

If the original mass variation is of a random nature, thIf the original mass variation is of a random nature, then after transformation, there will be many frequencien after transformation, there will be many frequencies of similar amplitude. Further, if there is a periodic es of similar amplitude. Further, if there is a periodic mass variation in addition to the random variation, thmass variation in addition to the random variation, then the frequency of that periodic mass variation will sen the frequency of that periodic mass variation will show up as a sharp peak after the transformation. Put how up as a sharp peak after the transformation. Put differently, if a mass variation signal is subjected to a differently, if a mass variation signal is subjected to a transformation and a sharp peak (“chimney”) appetransformation and a sharp peak (“chimney”) appears in the transformed signal, then we know there is a ars in the transformed signal, then we know there is a periodic mass variation in the fibre assembly. This is bperiodic mass variation in the fibre assembly. This is basically how spectrogram works. asically how spectrogram works.

Since wave length is more useful than frequencSince wave length is more useful than frequency for textile purposes, the spectrogram indicatey for textile purposes, the spectrogram indicates the different wave lengths (on a logarithmic scs the different wave lengths (on a logarithmic scale) versus their amplitude. Modern evenness tale) versus their amplitude. Modern evenness testing instruments, such as the Uster Evenness esting instruments, such as the Uster Evenness Tester, provide diagrams as well as spectrograTester, provide diagrams as well as spectrograms for the fibre assembly tested. The diagram is ms for the fibre assembly tested. The diagram is a time domain mass variation signal, while the sa time domain mass variation signal, while the spectrogram represents the same mass variation pectrogram represents the same mass variation in the frequency domain. in the frequency domain.

Figure 2.9 shows the diagrams and spectroFigure 2.9 shows the diagrams and spectrograms of 3 different yarns – normal yarn wigrams of 3 different yarns – normal yarn with random variation only, faulty yarn with th random variation only, faulty yarn with additional periodic mass variation, and faadditional periodic mass variation, and faulty yarn with additional drafting wave. ulty yarn with additional drafting wave.

Fig.2.9: Diagrams (left) and spectrograms (right) oFig.2.9: Diagrams (left) and spectrograms (right) of 3 yarns (Uster Spectrograph, Zelleger Uster, PEf 3 yarns (Uster Spectrograph, Zelleger Uster, PE404)404)

With respect to interpreting a spectrogram, the follWith respect to interpreting a spectrogram, the following simple rules can be used as a guide:owing simple rules can be used as a guide:

(a) (a) A fault-free fibre assembly will give a typical norA fault-free fibre assembly will give a typical normal spectrogram (with neither ‘chimnies’ nor ‘hmal spectrogram (with neither ‘chimnies’ nor ‘humps’)umps’)

(b) (b) A ‘chimney’ on top of a normal spectrogram iA ‘chimney’ on top of a normal spectrogram indicates the presence of a periodic mass variation indicates the presence of a periodic mass variation in the fibre assembly. The wave length of this periodin the fibre assembly. The wave length of this periodic mass variation can be read off the horizontal axis c mass variation can be read off the horizontal axis (noting the logarithmic scale)(noting the logarithmic scale)

(c) (c) A ‘hump’ on top of a normal spectrogram indA ‘hump’ on top of a normal spectrogram indicates the presence of a drafting wave in the fibricates the presence of a drafting wave in the fibre assembly. The wave length of the drafting wae assembly. The wave length of the drafting wave is equal to 2.5 to 3 times the mean fibre lengve is equal to 2.5 to 3 times the mean fibre length.th.

Once we get the wave length of a periodic mass varOnce we get the wave length of a periodic mass variation from the spectrogram, and we know this waiation from the spectrogram, and we know this wave length is related to the circumference of the offve length is related to the circumference of the offending roller, we can then identify the roller and rending roller, we can then identify the roller and replace it with a good one to solve the problem. Foeplace it with a good one to solve the problem. For drafting waves, the use of more uniform fibres anr drafting waves, the use of more uniform fibres and proper fibre control during drafting will usually sd proper fibre control during drafting will usually solve the problem.olve the problem.

Spectrogram is therefore a very useful quality contSpectrogram is therefore a very useful quality control tool in a spinning mill. rol tool in a spinning mill.

Benchmarking yarn evennessBenchmarking yarn evenness In management jargon, benchmarking is a total qualIn management jargon, benchmarking is a total qual

ity management tool and denotes the procedure of iity management tool and denotes the procedure of identifying and quantifying topnotch or world-class pdentifying and quantifying topnotch or world-class performance (benchmarks) in a particular business or erformance (benchmarks) in a particular business or product category and comparing the data with the pproduct category and comparing the data with the performance of the own company or product. erformance of the own company or product.

Let’s assume we have already produced some yarnLet’s assume we have already produced some yarns and we have tested the yarns for evenness. Now we s and we have tested the yarns for evenness. Now we want to know how good our yarns are. In other wordwant to know how good our yarns are. In other words, we want to benchmark a product - our yarns. s, we want to benchmark a product - our yarns.

There are several ways of benchmarking yarThere are several ways of benchmarking yarn evenness, including:n evenness, including:

Index of irregularityIndex of irregularityUster StatisticsUster StatisticsYarnspec (for worsted yarn only)Yarnspec (for worsted yarn only)

► Index of irregularityIndex of irregularity Table 2.1 shows a classification of worsted yarns baTable 2.1 shows a classification of worsted yarns ba

sed on the index of irregularity of the yarn. sed on the index of irregularity of the yarn. Table 2.1: Classification of worsted yarns based on tTable 2.1: Classification of worsted yarns based on t

he index of irregularityhe index of irregularity

Since processing technology is improving and so is Since processing technology is improving and so is yarn quality, the data in this table may not reflect thyarn quality, the data in this table may not reflect the quality of worsted yarns in the future. Generally se quality of worsted yarns in the future. Generally speaking, a good quality worsted yarn should not hapeaking, a good quality worsted yarn should not have an index of irregularity greater than 1.2 by todave an index of irregularity greater than 1.2 by today’s standard.y’s standard.

► Uster statisticsUster statistics(Uster(Uster 统计值统计值 ))

While the evenness index value is of use to the While the evenness index value is of use to the yarn manufacturers for internal quality control yarn manufacturers for internal quality control purpose, what matters to the users of yarn (i.e purpose, what matters to the users of yarn (i.e the weavers and knitters) is the actual the weavers and knitters) is the actual irregularity in the yarn they are going to use. irregularity in the yarn they are going to use. For this reason, the Uster Statistics is of great For this reason, the Uster Statistics is of great practical importance.practical importance.

So what is the Uster Statistics then? So what is the Uster Statistics then? The following excerpts from the 1997 UsteThe following excerpts from the 1997 Uste

r Statistics Book (produced by Zellweger Ur Statistics Book (produced by Zellweger Uster) answer this question briefly:“Almost ster) answer this question briefly:“Almost half a century ago, in 1949, the first Uster Shalf a century ago, in 1949, the first Uster Standards were presented to the textile putandards were presented to the textile public in numerical form. This started a new blic in numerical form. This started a new era in the assessment of the technological era in the assessment of the technological and commercial value of spun yarns. and commercial value of spun yarns.

Over the years, the Uster Standards have dOver the years, the Uster Standards have developed into the Uster Statistics, which heveloped into the Uster Statistics, which have been regularly updated until today anave been regularly updated until today and additional quality parameters for sliver, d additional quality parameters for sliver, roving, and yarns have been introduced proving, and yarns have been introduced progressively. Simultaneously, the methodrogressively. Simultaneously, the methods and procedures applied to establish the s and procedures applied to establish the Uster Statistics have been gradually enhaUster Statistics have been gradually enhanced.”nced.”

Today, the Uster Statistics represent the only truly cToday, the Uster Statistics represent the only truly comprehensive survey of the quality of textile materiaomprehensive survey of the quality of textile materials produced in the major textile hubs around the worlls produced in the major textile hubs around the world and they constitute the mainstay of global market id and they constitute the mainstay of global market intelligence related to textile quality. ntelligence related to textile quality.

The Uster Statistics are first and foremost a The Uster Statistics are first and foremost a practical guide to ‘good textile practices’ in the practical guide to ‘good textile practices’ in the field of yarn manufacturing.field of yarn manufacturing.

The Uster Statistics just seem to have been The Uster Statistics just seem to have been made for quality benchmarking on the corporate made for quality benchmarking on the corporate level.level.

Uster Statistics 1997 provide data on the following Uster Statistics 1997 provide data on the following major types of yarn:major types of yarn:100% CO, carded, ring spinning – 100% 100% CO, carded, ring spinning – 100%

carded cotton (ring spun)carded cotton (ring spun)100% CO, carded, rotor spinning – 100% carded 100% CO, carded, rotor spinning – 100% carded

cotton (rotor spun) cotton (rotor spun) 100% CO, combed, ring spinning – 100% combed 100% CO, combed, ring spinning – 100% combed

cotton (ring spun)cotton (ring spun)100% CO, combed, rotor spinning – 100% combe100% CO, combed, rotor spinning – 100% combe

d cotton (rotor spun) d cotton (rotor spun) 100% CO, carded, rotor spinning – 100$ carded c100% CO, carded, rotor spinning – 100$ carded c

otton (rotor spun)otton (rotor spun)100% WO, worsted spinning – 100% wool yarn (w100% WO, worsted spinning – 100% wool yarn (w

orsted ring spun)orsted ring spun)

Provisional data is also provided for the following Provisional data is also provided for the following types of yarn:types of yarn:

100% PES, ring spinning – 100% polyester (ring spun)100% PES, ring spinning – 100% polyester (ring spun)100% CV, ring spinning - 100% Rayon (ring spu100% CV, ring spinning - 100% Rayon (ring spu

n)n)100% CV, rotor spinning – 100% Rayon (rotor sp100% CV, rotor spinning – 100% Rayon (rotor sp

un)un)65/35, 67/33 PES/CO, combed, ring spinning – 665/35, 67/33 PES/CO, combed, ring spinning – 6

5% polyester/35% cotton blend, combed (ring s5% polyester/35% cotton blend, combed (ring spun) and 67% polyester/33% cotton blend, compun) and 67% polyester/33% cotton blend, combed (ring spun)bed (ring spun)

65/35, 67/33 PES/CV, ring spinning – 65% 65/35, 67/33 PES/CV, ring spinning – 65% polyester/35% Rayon blend (ring spun) and polyester/35% Rayon blend (ring spun) and 67% polyester/33% Rayon blend (ring spun)67% polyester/33% Rayon blend (ring spun)

50/50 PES/CO, rotor spinning – 50% 50/50 PES/CO, rotor spinning – 50% polyester/50% cotton blend (rotor spun)polyester/50% cotton blend (rotor spun)

50/50 PES/CO, air-jet spinning – 50% 50/50 PES/CO, air-jet spinning – 50% polyester/50% cotton blend (air-jet spun)polyester/50% cotton blend (air-jet spun)

65/35 PES/CO, air-jet spinning – 65% 65/35 PES/CO, air-jet spinning – 65% polyester/35% cotton blend (air-jet spun)polyester/35% cotton blend (air-jet spun)

55/45 PES/WO, worsted spinning – 55% 55/45 PES/WO, worsted spinning – 55% polyester/45% wool blend (worsted ring spun)polyester/45% wool blend (worsted ring spun)

The key quality attributes listed for these yarns The key quality attributes listed for these yarns are:are:

Yarn count variation (between bobbins or Yarn count variation (between bobbins or packages)packages)

Mass variation (U% and CV%)Mass variation (U% and CV%) Imperfections (thick and thin places, neps)Imperfections (thick and thin places, neps) Uster Hairiness Index Uster Hairiness Index Tensile properties (strength and elongation) Tensile properties (strength and elongation)

► Yarnspec (for worsted yarns)Yarnspec (for worsted yarns) Yarnspec is a computer program developed by ScienYarnspec is a computer program developed by Scien

tists at CSIRO Textile and Fibre Technology in Geelotists at CSIRO Textile and Fibre Technology in Geelong. Since the work was funded by Australian wool grng. Since the work was funded by Australian wool growers, the program has been specifically designed fowers, the program has been specifically designed for the prediction of properties of worsted yarns and or the prediction of properties of worsted yarns and the performance of worsted spinning, based on the the performance of worsted spinning, based on the properties of worsted tops and the spinning conditiproperties of worsted tops and the spinning conditions. The predicted results are what a worsted spinnons. The predicted results are what a worsted spinner can expect in terms of spinning performance and er can expect in terms of spinning performance and yarn quality if the operation follows “best commeryarn quality if the operation follows “best commercial practice”. In other words, Yarnspec can be usecial practice”. In other words, Yarnspec can be used to benchmark the performance of worsted spinnerd to benchmark the performance of worsted spinners.s.

For single worsted yarns, the program requires the For single worsted yarns, the program requires the following details as the input:following details as the input:

(a) Wool properties (from tops)(a) Wool properties (from tops)Fibre diameter (micron) and diameter CVFibre diameter (micron) and diameter CVHauteur length (mm), CV of Hauteur and Hauteur length (mm), CV of Hauteur and Fibre bundle tenacity (cN/tex)Fibre bundle tenacity (cN/tex)

(b)(b)Processing details (spinning)Processing details (spinning)Spinning draftSpinning draftSpindle speed (rpm)Spindle speed (rpm)Ring size (mm)Ring size (mm)Traveller numberTraveller number

(c)(c)Yarn detailsYarn detailsYarn countYarn count(( 纱线支数纱线支数 )) Yarn twistYarn twist(( 纱线捻度纱线捻度 )) Dyed or undyedDyed or undyed(( 染色与否染色与否 ))

The predicted outcome includes the following details:The predicted outcome includes the following details:Yarn evennessYarn evenness(( 纱线均匀度纱线均匀度 )) (I, CV%, U%) (I, CV%, U%)Yarn ImperfectionsYarn Imperfections(( 纱线疵点纱线疵点 )) (Thin places/km, (Thin places/km,

thick places/km, and neps/km) thick places/km, and neps/km)(( 粗节，细节粗节，细节 ))Yarn tenacity and breaking elongation%Yarn tenacity and breaking elongation%(( 纱线纱线

强度与断裂伸长强度与断裂伸长 ))Spinning ends-down per 1,000 spindle hoursSpinning ends-down per 1,000 spindle hours

(( 细纱断头率细纱断头率 ))

For a worsted spinner, Yarnspec is a step ahead of For a worsted spinner, Yarnspec is a step ahead of Uster Statistics for performance benchmarking, becUster Statistics for performance benchmarking, because it takes into consideration of the fibre propertiause it takes into consideration of the fibre properties used in spinning the yarn. In addition, it provides es used in spinning the yarn. In addition, it provides information on yarn strength as well as on the criticinformation on yarn strength as well as on the critical spinning performance in terms of ends-down per al spinning performance in terms of ends-down per 1,000 spindle hours. Yarnspec can also be used to p1,000 spindle hours. Yarnspec can also be used to predict the properties of two folded yarns. redict the properties of two folded yarns.

Review questionsReview questions

1.1.An ideal sliver of 70 mm mean fibre length is roller drafted wiAn ideal sliver of 70 mm mean fibre length is roller drafted with a draft of 10 under the following three conditions:th a draft of 10 under the following three conditions:

(a)(a)Perfect roller draftingPerfect roller drafting (b)(b)Presence of a large number of uncontrolled short fibresPresence of a large number of uncontrolled short fibres (c)(c)An eccentric back drafting roller with a diameter of 3 cm.An eccentric back drafting roller with a diameter of 3 cm.

Explain how drafting under each condition will affect the eveExplain how drafting under each condition will affect the evenness of the drafted sliver, and sketch and label the spectronness of the drafted sliver, and sketch and label the spectrogram for each drafting condition.gram for each drafting condition.

2.2.A 50 tex worsted yarn of 100% wool is measured for its evenA 50 tex worsted yarn of 100% wool is measured for its evenness on the Uster evenness tester. If the CV of this yarn is 15ness on the Uster evenness tester. If the CV of this yarn is 15%, how good is this yarn in relation to world production of si%, how good is this yarn in relation to world production of similar yarns? milar yarns?

Fibre preparation for Fibre preparation for spinningspinning

Short Staple ProcessingShort Staple ProcessingIntroductionIntroduction Short staple fibres(Short staple fibres( 短纤维短纤维 ) refer to fibres less than 2 ) refer to fibres less than 2

inches in length. Cotton is a typical example of short inches in length. Cotton is a typical example of short staple fibre. The short staple system(staple fibre. The short staple system( 短纤维纺纱系短纤维纺纱系统统 ) is used to process cotton mainly, cotton/polyest) is used to process cotton mainly, cotton/polyester(er( 涤纶涤纶 ) blends are the next most commonly proces) blends are the next most commonly processed fibres on the short staple system. Other fibres, sused fibres on the short staple system. Other fibres, such as viscose(ch as viscose( 粘胶粘胶 ), are also processed occasionally ), are also processed occasionally using the system. Short staple yarns make up the bulusing the system. Short staple yarns make up the bulk of international yarn market.k of international yarn market.

Since cotton is the dominant fibres used, the emphaSince cotton is the dominant fibres used, the emphasis of this topic will be on cotton processing. The actsis of this topic will be on cotton processing. The actual spinning of yarns is discussed in a separate moduual spinning of yarns is discussed in a separate module. le.

ObjectivesObjectivesAt the end of this topic you should be able to:At the end of this topic you should be able to:

Know the flow chart of cotton processingKnow the flow chart of cotton processingUnderstand the principles and objectives of Understand the principles and objectives of

carding, drawing, and combingcarding, drawing, and combingAppreciate the differences in the process and Appreciate the differences in the process and

property of carded ring spun yarnproperty of carded ring spun yarn(( 环锭纺粗梳环锭纺粗梳纱纱 )), combed ring spun yarn, combed ring spun yarn(( 环锭纺精梳纱环锭纺精梳纱 )), , carded rotor spun yarncarded rotor spun yarn(( 转杯纺粗梳纱转杯纺粗梳纱 )), and , and combed rotor spun yarncombed rotor spun yarn(( 转杯纺精梳纱转杯纺精梳纱 ))..

Process overvieProcess overvieww

The process flow cThe process flow chart for cotton prohart for cotton processing from fibre cessing from fibre to yarn is shown in to yarn is shown in Figure Figure

1.1. 1.1.

Blow-room processes (blend, open & clean)

Carding

Drawing

Lap forming

Combing

Drawing (x 2)

Rotor spinning Roving

Ring spinning

Short staple yarns Carded rotor spun yarn, Carded ring spun yarn Combed rotor spun yarn, Combed ring spun yarn

Cotton growing

Ginning

COTTON LINT

(Transport to textile mill)

Baling, HVI Classing

Engineered Fibre Selection EFS

(Marshalling into “mixes” or laydowns)

Cotton seed - by product

Agricultural Processes

Textile Processes

Harvest

Fig. 1.1: Fibre to yarn processing for cotton

The agricultural processes include cotton The agricultural processes include cotton growing, harvesting and ginning(growing, harvesting and ginning( 轧棉轧棉 ). C). Cotton grown in different regions have diffeotton grown in different regions have different properties. Modern cotton harvesting rent properties. Modern cotton harvesting uses machine pickers or strippers. Since cuses machine pickers or strippers. Since cotton fibres do not mature at the same timotton fibres do not mature at the same time and machine picking is less discriminative and machine picking is less discriminative than traditional hand picking, large quane than traditional hand picking, large quantities of impurities such as green bolls, leaf,tities of impurities such as green bolls, leaf, stick, and trash are also picked up during stick, and trash are also picked up during cotton harvesting, together with the seed cotton harvesting, together with the seed cotton. cotton.

On a weight basis, “seed cotton” contaiOn a weight basis, “seed cotton” contains approximately 35% fibre (lint), 55% sens approximately 35% fibre (lint), 55% seed, and 10% trash. Obviously the cotton sed, and 10% trash. Obviously the cotton seed and other impurities need to be remoeed and other impurities need to be removed from the fibres. This is largely done in ved from the fibres. This is largely done in a gin, which removes all green balls and ca gin, which removes all green balls and cotton seeds, about 95% burrs, 92% sticks, otton seeds, about 95% burrs, 92% sticks, and about 85% fine trash. and about 85% fine trash.

The actual process (in a gin) that separates cThe actual process (in a gin) that separates cotton fibres and the seed they grow attached otton fibres and the seed they grow attached to is called ginning. Other machines are also uto is called ginning. Other machines are also used before and after ginning to mechanically sed before and after ginning to mechanically clean the fibres. The ginned cotton is now knclean the fibres. The ginned cotton is now known as cotton lint or lint cotton. The fibres in own as cotton lint or lint cotton. The fibres in the cotton lint vary considerably in length becthe cotton lint vary considerably in length because of fibre breakage caused by the severe ause of fibre breakage caused by the severe mechanical actions during ginning and cleanimechanical actions during ginning and cleaning. The cotton lint is then sampled and packeng. The cotton lint is then sampled and packed into bales weighing 227 kg (or 500 pounds), d into bales weighing 227 kg (or 500 pounds), containing over 60 billion individual fibres. containing over 60 billion individual fibres.

Fibre samples are now tested on the High VolFibre samples are now tested on the High Volume Instrument (HVI) for a range of fibre propume Instrument (HVI) for a range of fibre properties, including strength, elongation, length, erties, including strength, elongation, length, uniformity, micronaire, colour, and trash. The uniformity, micronaire, colour, and trash. The HVI system was developed in the late 1960s aHVI system was developed in the late 1960s and has been increasingly accepted since the 1nd has been increasingly accepted since the 1980s. Before the introduction of the HVI syste980s. Before the introduction of the HVI system, cotton in a bale was graded subjectively bm, cotton in a bale was graded subjectively by experienced cotton classers for properties sy experienced cotton classers for properties such as staple length, colour, and trash contenuch as staple length, colour, and trash content. t.

The results were then used to assign cottoThe results were then used to assign cotton bales into lots or categories. When the cn bales into lots or categories. When the cotton was ready for consumption, the balotton was ready for consumption, the bales were grouped into mixes or laydowns. es were grouped into mixes or laydowns. Bales from different regions were mixed in Bales from different regions were mixed in proportion to the number of bales in each proportion to the number of bales in each lot and fed into the opening line machinerlot and fed into the opening line machinery in the blow-room. y in the blow-room.

TToday, objective measurement is widely used. Woday, objective measurement is widely used. When the bales arrive at a textile mill to start the then the bales arrive at a textile mill to start the textile processes, the test results are used as a baextile processes, the test results are used as a basis for fibre selection and mixing according to thsis for fibre selection and mixing according to the end product requirements. The modern cotton e end product requirements. The modern cotton mill will "engineer" its yarn to meet specific end-mill will "engineer" its yarn to meet specific end-use requirements. The engineered fibre selectiouse requirements. The engineered fibre selection (EFS) system, introduced by Cotton Inc. (USA) in (EFS) system, introduced by Cotton Inc. (USA) in 1982, has been used increasingly by cotton miln 1982, has been used increasingly by cotton mills to facilitate this important task. ls to facilitate this important task.

It is most useful in bale management, partiIt is most useful in bale management, particularly for storing and retrieving bales, for cularly for storing and retrieving bales, for selecting bales with fibre properties withiselecting bales with fibre properties within specified ranges and average values, for n specified ranges and average values, for composing consistent bale laydowns and composing consistent bale laydowns and for predicting yarn strength and other yarfor predicting yarn strength and other yarn properties based on tailer-made regressn properties based on tailer-made regression analyses. The bulk of the cotton bales ion analyses. The bulk of the cotton bales consumed in America is now managed at tconsumed in America is now managed at the mill level by the engineered fibre selecthe mill level by the engineered fibre selection system (EFS). ion system (EFS).

Adequate fibre blending and mixing is also vital to eAdequate fibre blending and mixing is also vital to ensure processing efficiency and yarn quality. The cotnsure processing efficiency and yarn quality. The cotton lint still contains some small trash particles, whiton lint still contains some small trash particles, which have to be removed by the textile processes, such ch have to be removed by the textile processes, such as carding and combing. The textile processes also pas carding and combing. The textile processes also perform fibre opening, fibre alignment, fibre mixing aerform fibre opening, fibre alignment, fibre mixing and attenuation to get the fibres ready for spinning. And attenuation to get the fibres ready for spinning. As indicated in Figure 1.1, depending on the particular s indicated in Figure 1.1, depending on the particular processing route followed, four major types of cottoprocessing route followed, four major types of cotton yarn may be produced – carded rotor spun, carded n yarn may be produced – carded rotor spun, carded ring spun, combed rotor spun, combed ring spun. ring spun, combed rotor spun, combed ring spun.

An overview of the key stages is given in Table An overview of the key stages is given in Table 1.1.1.1.

It is important to keep in mind at this stage that befIt is important to keep in mind at this stage that before fibres can be made into useful yarns, they shoulore fibres can be made into useful yarns, they should be:d be:

Free from impuritiesFree from impuritiesWell individualised and alignedWell individualised and alignedWell mixedWell mixedOf adequate length and strengthOf adequate length and strength

Knowing these requirements will help us understaKnowing these requirements will help us understand why the fibres need to go through many textile nd why the fibres need to go through many textile processes before the actual spinning process. For iprocesses before the actual spinning process. For instance, in order to remove impurities imbedded instance, in order to remove impurities imbedded in fibres, we need to open the fibres first to expose tn fibres, we need to open the fibres first to expose those impurities. Fibre opening needs to be graduallhose impurities. Fibre opening needs to be gradually carried out so as not to stress and damage the fiby carried out so as not to stress and damage the fibres too much. In fact, there are two opening stages:res too much. In fact, there are two opening stages:

Stage 1: Breaking apart (break large tufts of fibres iStage 1: Breaking apart (break large tufts of fibres into small tufts)nto small tufts)

Stage 2: Opening out (open small tufts into individStage 2: Opening out (open small tufts into individual fibres)ual fibres)

Individualising the fibres is very important. As mentioIndividualising the fibres is very important. As mentioned in the module on yarn evenness, poorly separatened in the module on yarn evenness, poorly separated fibres will travel in groups during drafting, which wild fibres will travel in groups during drafting, which will lead to reduced evenness and increased imperfectiol lead to reduced evenness and increased imperfections in the final yarn. For a yarn to have adequate strenns in the final yarn. For a yarn to have adequate strength, fibres in the yarn should be well aligned in order tgth, fibres in the yarn should be well aligned in order to share the applied load on the yarn. The different deo share the applied load on the yarn. The different degrees of fibre alignment in different yarns often explaigrees of fibre alignment in different yarns often explain the differences in yarn properties. n the differences in yarn properties.

Because of the variability that exists both within and Because of the variability that exists both within and between fibres, fibres should be well mixed before thbetween fibres, fibres should be well mixed before the actual spinning stage. There are two basic requireme actual spinning stage. There are two basic requirements for a good fibre mix or blend:ents for a good fibre mix or blend:

Requirement 1: The blend (mix) is homogenousRequirement 1: The blend (mix) is homogenous Requirement 2: The blend (mix) is intimateRequirement 2: The blend (mix) is intimate

The first requirement entails that different fibres arThe first requirement entails that different fibres are mixed in the right proportion, while the second ree mixed in the right proportion, while the second requirement can only be achieved with different indiquirement can only be achieved with different individual fibres lying side by side. vidual fibres lying side by side.

Preserving the quality of fibres during processing iPreserving the quality of fibres during processing is also essential to ensure yarn quality. Damage to fis also essential to ensure yarn quality. Damage to fibre length and strength will lead to reduced yarn stbre length and strength will lead to reduced yarn strength.rength.

With this overall picture in mind, we can now discuWith this overall picture in mind, we can now discuss the individual textile processes applied to fibres.ss the individual textile processes applied to fibres.

► ObjectivesObjectives The blowroom is the section of a cotton spinning The blowroom is the section of a cotton spinning

mill where the preparatory processes of opening, mill where the preparatory processes of opening, blending and cleaning are carried out. The blending and cleaning are carried out. The blowroom machines blend, open and clean the blowroom machines blend, open and clean the ginned cotton before feeding it to the cotton card.ginned cotton before feeding it to the cotton card.

The ginned cotton, still contaminated with some The ginned cotton, still contaminated with some impurities, arrives in the textile mill in compressed impurities, arrives in the textile mill in compressed bales, fibre properties often vary from bale to bale. bales, fibre properties often vary from bale to bale. Blending is regarded as the most important Blending is regarded as the most important process in a cotton spinning mill. It reduces process in a cotton spinning mill. It reduces variation of fibre characteristics, permits uniform variation of fibre characteristics, permits uniform processing and improves yarn quality. In the processing and improves yarn quality. In the blending process, different cottons of known blending process, different cottons of known physical properties are combined to give a mix physical properties are combined to give a mix with the required or pre-determined average with the required or pre-determined average characteristics. characteristics.

For example, the general formula for calculating the For example, the general formula for calculating the theoretical fineness (micronaire, μg/in.) is as followstheoretical fineness (micronaire, μg/in.) is as follows

where Fwhere Fbb is the fineness of a blend of n is the fineness of a blend of n components; Wt is the total weight of the blend; components; Wt is the total weight of the blend; and W is the weight of any one component and and W is the weight of any one component and F is its fineness. In terms of weight percentages, F is its fineness. In terms of weight percentages, the above equation becomes:the above equation becomes:

where P is the percentage by weight of any one where P is the percentage by weight of any one component and F is its fineness.component and F is its fineness.

F

WWt

F

W

F

W

F

WW

F

n

n

tb

.....2

2

1

1

F

P

F

P

F

P

F

PF

n

nb

100

.....

100

2

2

1

1

The group of different bales to be mixed is referred The group of different bales to be mixed is referred to as the "laydown", with laydowns containing betto as the "laydown", with laydowns containing between 10 and 100 bales. In a modern cotton spinning ween 10 and 100 bales. In a modern cotton spinning mill, automatic bale pluckers are used to extract anmill, automatic bale pluckers are used to extract and blend fibres from the laydowns. The bale plucker d blend fibres from the laydowns. The bale plucker extracts, at controlled rates, small tufts of cotton frextracts, at controlled rates, small tufts of cotton from each bale (in the laydown) and delivers the fibreom each bale (in the laydown) and delivers the fibres through pneumatic ducting (hence the name “bls through pneumatic ducting (hence the name “blow-room”) to the subsequent opening and cleaninow-room”) to the subsequent opening and cleaning machines. g machines.

In the opening and cleaning processes, clumIn the opening and cleaning processes, clumps of fibres from the bale plucker are opened ps of fibres from the bale plucker are opened to smaller tufts to facilitate further processinto smaller tufts to facilitate further processing and to allow removal of impurities, such as g and to allow removal of impurities, such as dust, sand, seed particles, leaf and stem fragdust, sand, seed particles, leaf and stem fragments and motes (undeveloped seeds). A numents and motes (undeveloped seeds). A number of machines are employed to perform tmber of machines are employed to perform the opening and cleaning actions gradually, she opening and cleaning actions gradually, so as not to cause too much fibre damage. In oo as not to cause too much fibre damage. In other words, the opening action in blow-room ther words, the opening action in blow-room is largely the “breaking apart” stage mentiis largely the “breaking apart” stage mentioned in the previous section. oned in the previous section.

“ “Opening-out” or individualising the fibrOpening-out” or individualising the fibres is not intended in the blow-room. But ses is not intended in the blow-room. But some fibre damage is inevitable. In additioome fibre damage is inevitable. In addition, the opening processes also create neps, n, the opening processes also create neps, or highly entangled fibres. At the end of thor highly entangled fibres. At the end of the blowroom processes, the opened and cle blowroom processes, the opened and cleaned cotton fibres are condensed in a laeaned cotton fibres are condensed in a lap form to feed into the carding process. p form to feed into the carding process.

► Blowroom installationsBlowroom installations In a typical blowroom installation, six In a typical blowroom installation, six

distinguishable zones can be identified as distinguishable zones can be identified as indicated in figure 1.2. These are:indicated in figure 1.2. These are:

ZONE 1 - Bale openingZONE 1 - Bale opening ZONE 2 - Coarse blendingZONE 2 - Coarse blending ZONE 3 - Blending (Mixing)ZONE 3 - Blending (Mixing) ZONE 4 - Fine cleaning and dust removalZONE 4 - Fine cleaning and dust removal ZONE 5 - Intensive opening/cleaning (optional)ZONE 5 - Intensive opening/cleaning (optional) ZONE 6 - Card feedZONE 6 - Card feed

If the cotton contains only few impurities, then the zoIf the cotton contains only few impurities, then the zone of intensive cleaning is not necessary. ne of intensive cleaning is not necessary.

Figure 1.2 Operating zones in a typical blowroom (Klein 1987a, p.13)

The zone 1 opening machine is usually an automatic The zone 1 opening machine is usually an automatic bale plucker, an example of which is given in figure 1.bale plucker, an example of which is given in figure 1.3. As mentioned in the previous section, the bale pluc3. As mentioned in the previous section, the bale plucker extracts, at controlled rates, small tufts of cotton fker extracts, at controlled rates, small tufts of cotton from different bales in the laydown and delivers the firom different bales in the laydown and delivers the fibres through pneumatic ducting to the subsequent obres through pneumatic ducting to the subsequent opening and cleaning machines.pening and cleaning machines.

Figure 1.3 An automatic bale opening machine (Fritz Figure 1.3 An automatic bale opening machine (Fritz and Cant 1986, p.327, courtesy of Rieter Machine Worand Cant 1986, p.327, courtesy of Rieter Machine Works)ks)

The zone 2 coarse cleaning (and opening) machine The zone 2 coarse cleaning (and opening) machine is usually a step cleaner (figure 1.4) or a dual roller is usually a step cleaner (figure 1.4) or a dual roller cleaner (figure 1.5). Both cleaners feature widely scleaner (figure 1.5). Both cleaners feature widely spaced striker elements working on fibres in relativpaced striker elements working on fibres in relatively free flight. So the action on fibres are gentle. ely free flight. So the action on fibres are gentle.

Figure 1.4 A step cleaner (Shrigley 1973, p91)Figure 1.4 A step cleaner (Shrigley 1973, p91)

For the step cleaner, fibres enter through the entry For the step cleaner, fibres enter through the entry point (A). They are worked on by a series of 6 inclinpoint (A). They are worked on by a series of 6 inclined beaters (B, D), under which is fitted a grid-bar syed beaters (B, D), under which is fitted a grid-bar system (C). The grid bars support the upward flow of fstem (C). The grid bars support the upward flow of fibres while allowing impurities to fall through into tibres while allowing impurities to fall through into the trash box (F). The action of opposing spikes bethe trash box (F). The action of opposing spikes between adjacent beaters helps opening fibres and disween adjacent beaters helps opening fibres and dislodging impurities. The baffle plates (E) prevent the lodging impurities. The baffle plates (E) prevent the beaters from creating a circular air current by deflebeaters from creating a circular air current by deflecting the air and fibre to the next beater. The coarscting the air and fibre to the next beater. The coarsely cleaned fibres come out the step cleaner througely cleaned fibres come out the step cleaner through exit (G).h exit (G).

Figure 1.5 A dual-roller cleaning (Shrigley 1973, p93)Figure 1.5 A dual-roller cleaning (Shrigley 1973, p93)

The dual-roller cleaner, shown in figure 1.5, has two The dual-roller cleaner, shown in figure 1.5, has two spiked rollers (beaters A and B) mounted horizontaspiked rollers (beaters A and B) mounted horizontally, with grid bars beneath each beater. A condenselly, with grid bars beneath each beater. A condenser fan downstream the cleaner draws fibres through r fan downstream the cleaner draws fibres through the machine by suction. Fibres are opened by the sthe machine by suction. Fibres are opened by the spikes gradually. As can be seen from figure 1.5, the pikes gradually. As can be seen from figure 1.5, the outlet is positioned higher than the inlet, ensuring toutlet is positioned higher than the inlet, ensuring that only the relatively small and light tufts of fibres hat only the relatively small and light tufts of fibres can fly straight through. The residence time of fibre can fly straight through. The residence time of fibre materials within the machine can be adjusted by thmaterials within the machine can be adjusted by the baffle plate D.e baffle plate D.

An example of zone 3 blending machine is shown in An example of zone 3 blending machine is shown in figure 1.6. This machine comprises several adjacenfigure 1.6. This machine comprises several adjacent chambers into which the fibres are blown from abt chambers into which the fibres are blown from above. The chambers are filled successively, but the fiove. The chambers are filled successively, but the fibre material is removed from all chambers simultabre material is removed from all chambers simultaneously. This gives good long-term mixing.neously. This gives good long-term mixing.

Figure 1.6: The Hergeth Hollingsworth multiple mixer (Klein 1987a, p.19)

Fine cleaning requires further opening of fibres to expose the Fine cleaning requires further opening of fibres to expose the impurities. For this reason, finer opening elements are used.impurities. For this reason, finer opening elements are used.

Dust removal is not confined to one particular zone. But fine Dust removal is not confined to one particular zone. But fine dust can only be effectively removed when the fibres are reldust can only be effectively removed when the fibres are relatively open. Dust removal equipment is usually incorporateatively open. Dust removal equipment is usually incorporated into the pneumatic ducting system, with the dust separated into the pneumatic ducting system, with the dust separated from fibre by air suction through perforated surfaces. The d from fibre by air suction through perforated surfaces. The principle of a condenser type dust extractor is shown in figurprinciple of a condenser type dust extractor is shown in figure 1.7. The condenser also helps even the flow of fibres, becae 1.7. The condenser also helps even the flow of fibres, because the thin spots in the fibre sheet laying on the perforated use the thin spots in the fibre sheet laying on the perforated screen will allow more air to flow, hence carrying more fibrescreen will allow more air to flow, hence carrying more fibres to the thin spots.s to the thin spots.

Figure 1.7: Sketch of a condenser type dust extracter (Lord 198Figure 1.7: Sketch of a condenser type dust extracter (Lord 1981, p.137) 1, p.137)

Finally, the opened and cleaned fibres are fed to a Finally, the opened and cleaned fibres are fed to a card through a chute feed device. An example of a card through a chute feed device. An example of a chute feed is shown in figure 1.8. It is vital that a unchute feed is shown in figure 1.8. It is vital that a uniform sheet of fibres be fed to the card. For this reaiform sheet of fibres be fed to the card. For this reason, chute feeds have control systems to ensure fison, chute feeds have control systems to ensure fibres are uniformly packed inside the chute.bres are uniformly packed inside the chute.

Figure 1.8: An example of a chute feed (Lord 1981, p.Figure 1.8: An example of a chute feed (Lord 1981, p.138)138)

Cotton cardingCotton carding► ObjectivesObjectives An old spinning mill adage states that "well An old spinning mill adage states that "well

carded is half spun". Card is also referred to as carded is half spun". Card is also referred to as the heart of a spinning mill. This highlights the the heart of a spinning mill. This highlights the importance of the carding process. The main importance of the carding process. The main objectives of carding are:objectives of carding are:

Fibre opening/individualisingFibre opening/individualising Fibre cleaningFibre cleaningFibre mixingFibre mixing Fibre aligningFibre aligningSliver formingSliver forming

Understanding how a card achieves these objectiveUnderstanding how a card achieves these objectives requires knowledge of its operating principle.s requires knowledge of its operating principle. Figu Figure 1.9 shows a diagram of a modern high performanre 1.9 shows a diagram of a modern high performance flat-top card. ce flat-top card.

Fibres from the blow-room are supplied pneumatiFibres from the blow-room are supplied pneumatically via pipe ducting (1) to the feed chute (2) of the cally via pipe ducting (1) to the feed chute (2) of the card. An evenly compressed fibre batt of about 500 card. An evenly compressed fibre batt of about 500 – 900 ktex (g/m) is formed in the chute. A transport r– 900 ktex (g/m) is formed in the chute. A transport roller (3) forwards fibres from this matt to the card’oller (3) forwards fibres from this matt to the card’s feed device (4), consisting of a feed roller and a fees feed device (4), consisting of a feed roller and a feed plate. The licker-in or taker-in (5), covered with strd plate. The licker-in or taker-in (5), covered with strong metal teeth, snatches fibres from the feed devicong metal teeth, snatches fibres from the feed device, dislodges heavy impurities via the gaps of grid sege, dislodges heavy impurities via the gaps of grid segments (6), and carries the fibres to the main cylinder ments (6), and carries the fibres to the main cylinder (8). The suction ducts (7) carry away the dislodged i(8). The suction ducts (7) carry away the dislodged impurities. The sawtooth elements (or clothing elemmpurities. The sawtooth elements (or clothing elements) on the main cylinder (8), which has a higher suents) on the main cylinder (8), which has a higher surface speed than the taker-in, strip the fibres off the rface speed than the taker-in, strip the fibres off the taker-in (5) and carry them to the main carding zone taker-in (5) and carry them to the main carding zone between the cylinder (8) and the flats (10) (hence thbetween the cylinder (8) and the flats (10) (hence the name ‘flat-top’ card). e name ‘flat-top’ card).

The flats comprise some 80 – 120 carding bars coThe flats comprise some 80 – 120 carding bars combined into a band moving on an endless path. mbined into a band moving on an endless path. When in the carding zone, the teeth on the cardiWhen in the carding zone, the teeth on the carding bars and that on the main cylinder act togethng bars and that on the main cylinder act together to repeatedly tear apart fibres into individual er to repeatedly tear apart fibres into individual ones, to remove neps (highly entangled fibres) aones, to remove neps (highly entangled fibres) and some impurities. As the ‘action’ carding bnd some impurities. As the ‘action’ carding bars emerge from the carding zone, a cleaning unars emerge from the carding zone, a cleaning unit (11) strips fibres, neps and impurities from the it (11) strips fibres, neps and impurities from the bars, and the bars then return for further action ibars, and the bars then return for further action in the carding zone. Obviously, the main carding n the carding zone. Obviously, the main carding zone is where most of the card’s objectives are zone is where most of the card’s objectives are achieved. Extra carding bars (9, 12) are also used achieved. Extra carding bars (9, 12) are also used to increase the level of fibre opening in carding. to increase the level of fibre opening in carding. The underside of the main cylinder is enclosed bThe underside of the main cylinder is enclosed by grids or cover plates (13). y grids or cover plates (13).

Fibres coming out of the main carding zone are indFibres coming out of the main carding zone are individualised and aligned. They are carried by the teividualised and aligned. They are carried by the teeth on the main cylinder to meet the teeth on the eth on the main cylinder to meet the teeth on the doffer (14), which has a slower surface speed than doffer (14), which has a slower surface speed than the cylinder. The doffer snatches some (not all) fibthe cylinder. The doffer snatches some (not all) fibres from the cylinder surface and combines the fibres from the cylinder surface and combines the fibres into a web because of its substantially lower sres into a web because of its substantially lower surface speed relative to the main cylinder. Fibres urface speed relative to the main cylinder. Fibres not snatched by the doffer continue to travel with not snatched by the doffer continue to travel with the main cylinder. These fibres are called “recyclithe main cylinder. These fibres are called “recycling fibres”. The recycling fibres will soon meet witng fibres”. The recycling fibres will soon meet with “fresh fibres” from the taker-in and together th “fresh fibres” from the taker-in and together these fibres are worked on in the main carding zonhese fibres are worked on in the main carding zone. e.

This is how fibre mixing is achieved in cardiThis is how fibre mixing is achieved in carding. In fact, carding is the only process wheng. In fact, carding is the only process where intimate mixing can be achieved. A fibre re intimate mixing can be achieved. A fibre may go around the main cylinder many timay go around the main cylinder many times and get mixed with many fresh fibres mes and get mixed with many fresh fibres before it is finally removed by the doffer. Tbefore it is finally removed by the doffer. The stripping device (15) then removes the fhe stripping device (15) then removes the fibre web from the doffer. The web is brougibre web from the doffer. The web is brought together as a sliver and compressed by ht together as a sliver and compressed by a pair of calender rolls (16). Finally, the coia pair of calender rolls (16). Finally, the coiler (18) deposits the sliver into a sliver can ler (18) deposits the sliver into a sliver can (17). (17).

The carding action of a flat-top card like this is quitThe carding action of a flat-top card like this is quite intensive, and may cause considerable fibre dame intensive, and may cause considerable fibre damage and breakage, particularly for long fibres. For tage and breakage, particularly for long fibres. For this reason, flat-top card is not used to card long fibrhis reason, flat-top card is not used to card long fibres such as wool. Carding also creates some neps, or es such as wool. Carding also creates some neps, or highly entangled fibres. While carding is supposed thighly entangled fibres. While carding is supposed to align and straighten individual fibres, most fibres o align and straighten individual fibres, most fibres in a carded sliver have hooked ends. The reason for in a carded sliver have hooked ends. The reason for this will be discussed later.this will be discussed later.

► Card clothingCard clothing The tern 'card clothing' refers to the large The tern 'card clothing' refers to the large

number of pins or teeth covering the surfaces of number of pins or teeth covering the surfaces of various rollers on the card. There are three various rollers on the card. There are three major types of card clothing - flexible fillet wire, major types of card clothing - flexible fillet wire, semi-rigid wire, and metallic sawtooth wire, as semi-rigid wire, and metallic sawtooth wire, as shown in figure 1.10shown in figure 1.10..

Knee

Backing material

(a) Flexible fillet wire

(b) Semi-regid wire

(c) Metallic sawtooth wire

carding angle

Figure 1.10 Different types of card clothing

The flexible fillet wire was developed to mimic the flThe flexible fillet wire was developed to mimic the flexibility of natural teazles used in the past. This type exibility of natural teazles used in the past. This type of clothing is believed to minimise fibre damage durof clothing is believed to minimise fibre damage during carding. The fillet wire is designed with a knee oing carding. The fillet wire is designed with a knee on each needle, so that when the needle bends back n each needle, so that when the needle bends back as force is applied during carding, the point of the nas force is applied during carding, the point of the needle does not project too far outwards. Otherwise teedle does not project too far outwards. Otherwise the points on two adjacent surfaces will touch each ohe points on two adjacent surfaces will touch each other, causing damage to the needles. In other word, ther, causing damage to the needles. In other word, the knee is designed to prevent point-rise to avoid the knee is designed to prevent point-rise to avoid wire damage. The needles are embedded in the bacwire damage. The needles are embedded in the backing material. Dirt and short fibres tend to accumulking material. Dirt and short fibres tend to accumulate under the knees of flexible fillet wire. If not remoate under the knees of flexible fillet wire. If not removed, carding efficiency will drop. Removing the dirts ved, carding efficiency will drop. Removing the dirts and short fibres from the card clothing is called card and short fibres from the card clothing is called card fettling.fettling.

The semi-rigid wire is often used on the flats of cottThe semi-rigid wire is often used on the flats of cotton cards. It is more rigid than the flexible fillet wire on cards. It is more rigid than the flexible fillet wire and has no knee. During carding, some short fibres and has no knee. During carding, some short fibres and impurities will also accumulate in the semi-rigiand impurities will also accumulate in the semi-rigid wire. Long fibres have more contacts with the mad wire. Long fibres have more contacts with the main cylinder clothing and will tend to move with the in cylinder clothing and will tend to move with the main cylinder. The short fibres and impurities remomain cylinder. The short fibres and impurities removed from the clothing of flats are called flat strippinved from the clothing of flats are called flat strippings. Compared with flexible fillet wire, the semi-rigid gs. Compared with flexible fillet wire, the semi-rigid wire has the advantage of not choking with fibres awire has the advantage of not choking with fibres and correspondingly eliminating less flat strippings. nd correspondingly eliminating less flat strippings.

The metallic wire, also known as sawtooth wire, is a The metallic wire, also known as sawtooth wire, is a later development. It is less prone to damage and allater development. It is less prone to damage and allows higher production rate. Modern high productiolows higher production rate. Modern high production cards are usually fitted with metallic fillet wire. Thn cards are usually fitted with metallic fillet wire. The carding angle as indicated in figure 1.10 is the mose carding angle as indicated in figure 1.10 is the most important of the tooth. The higher the carding anglt important of the tooth. The higher the carding angle, the more aggressive the tooth is, and more fibres ie, the more aggressive the tooth is, and more fibres it will hold during carding. For this reason, the taker-t will hold during carding. For this reason, the taker-in clothing usually has a very small carding angle, or in clothing usually has a very small carding angle, or even a negative carding angle so that fibres on the teven a negative carding angle so that fibres on the taker-in can be easily transferred to the cylinder. Simaker-in can be easily transferred to the cylinder. Similarly, the doffer clothing usually has a higher cardinilarly, the doffer clothing usually has a higher carding angle than the cylinder clothing to allow fibre trang angle than the cylinder clothing to allow fibre transfer from cylinder to doffer.sfer from cylinder to doffer.

► Basic actions in cardingBasic actions in carding There are two basic actions in cotton carding: There are two basic actions in cotton carding:

carding (or working) action and stripping carding (or working) action and stripping action.action.

The tooth direction and relative surface speed decThe tooth direction and relative surface speed decide which action occurs between two adjacent and ide which action occurs between two adjacent and clothed (or toothed) surfaces.clothed (or toothed) surfaces.

(a) Point-to-point carding(a) Point-to-point carding Each tooth has a point and a back, as indicated in fiEach tooth has a point and a back, as indicated in fi

gure 1.11a.gure 1.11a. If the tip of the tooth on one surface points to the tiIf the tip of the tooth on one surface points to the ti

p of the tooth on the other surface, a point-to-point p of the tooth on the other surface, a point-to-point carding (or working) action occurs (figure 1.11b). carding (or working) action occurs (figure 1.11b).

(a) The Point and Back of a tooth

back back

point

point

(b) Carding action (Point-to-point) (c) Stripping action (Point-to-back)

Fig. 1.11: Carding and stripping actions

For instance, the teeth arrangements on flats and For instance, the teeth arrangements on flats and main cylinder, and on main cylinder and doffer (Fimain cylinder, and on main cylinder and doffer (Figure 1.9) are typical point-to-point arrangements. gure 1.9) are typical point-to-point arrangements. Therefore carding action occurs between flats anTherefore carding action occurs between flats and main cylinder, and between main cylinder and dd main cylinder, and between main cylinder and doffer.offer.

It is through the carding action that fibre opening It is through the carding action that fibre opening occurs. Both surfaces contest for fibres and as a reoccurs. Both surfaces contest for fibres and as a result, fibres are separated.sult, fibres are separated.

The level of fibre opening in carding can be represenThe level of fibre opening in carding can be represented by points-per-fibre. This is the ratio of the total ited by points-per-fibre. This is the ratio of the total infeed fibres per unit time over the number of workinnfeed fibres per unit time over the number of working points available in the same time. As the card prodg points available in the same time. As the card production rate increases, more fibres must pass through uction rate increases, more fibres must pass through the card, this would reduce the number of points-pethe card, this would reduce the number of points-per-fibre, hence the carding effect on the fibres. To mair-fibre, hence the carding effect on the fibres. To maintain the carding effect, extra working points are adntain the carding effect, extra working points are added on modern cardsded on modern cards..

((b) Point-to-back strippingb) Point-to-back stripping If the tip of the tooth on one surface points to the baIf the tip of the tooth on one surface points to the ba

ck of the tooth on the other surface, a stripping actiock of the tooth on the other surface, a stripping action occurs (figure 1.11). The point n occurs (figure 1.11). The point strips fibres off the strips fibres off the back.back.

For instance, a stripping action occurs between the For instance, a stripping action occurs between the main cylinder and the taker-in. The teeth on the maimain cylinder and the taker-in. The teeth on the main cylinder point to the back of teeth on the taker-in, n cylinder point to the back of teeth on the taker-in, so the fibres on the taker-in are stripped by the teeth so the fibres on the taker-in are stripped by the teeth on the main cylinder.on the main cylinder.

It is through the stripping action that fibres are tranIt is through the stripping action that fibres are transferred from one surface to another during carding.sferred from one surface to another during carding.

► Quality of carded sliverQuality of carded sliver The important quality considerations for the cardThe important quality considerations for the card

ed slivers are:ed slivers are:

Fibre lengthFibre lengthNumber of nepsNumber of nepsFibre alignmentFibre alignmentSliver evennessSliver evenness

(1) Fibre length(1) Fibre length As mentioned earlier, the intensive carding action As mentioned earlier, the intensive carding action

causes considerable fibre damage and breakage, lcauses considerable fibre damage and breakage, leading to reduction in fibre length and increase in eading to reduction in fibre length and increase in short fibre content. Changes in mean fibre length short fibre content. Changes in mean fibre length before and after carding has also been used to estibefore and after carding has also been used to estimate the level of fibre breakage in carding, using tmate the level of fibre breakage in carding, using the formula below:he formula below:

cardingafterlengthfibreean

cardingafterlengthfibremaincardingbeforelengthfibreMeanbreakageFibre

%

(2) Number of neps(2) Number of neps► Neps are highly entangled fibres. Usually a nep contaNeps are highly entangled fibres. Usually a nep conta

ins ten or more fibres. It is a very serious problem in tins ten or more fibres. It is a very serious problem in the textile industry. he textile industry.

► The ease with which a fibre forms part of a nep is relaThe ease with which a fibre forms part of a nep is related to its bending rigidity. Immature cotton and fine fted to its bending rigidity. Immature cotton and fine fibres bend easily. They are prone to nep formation dibres bend easily. They are prone to nep formation during carding. Many neps often persist into the final furing carding. Many neps often persist into the final fabrics. Neps contain many immature cotton fibres, wabrics. Neps contain many immature cotton fibres, which have less cellulosic materials than mature fibres.hich have less cellulosic materials than mature fibres. During fabric dyeing, they do not take up as much dy During fabric dyeing, they do not take up as much dye as the rest of the fabric, causing a serious fabric faue as the rest of the fabric, causing a serious fabric fault known as “white specks”.lt known as “white specks”.

► Closer card settings between adjacent surfaces, sharCloser card settings between adjacent surfaces, sharper teeth, and higher doffer speed (reducing “recyclper teeth, and higher doffer speed (reducing “recycling fibres”) can be used to reduce the number of neing fibres”) can be used to reduce the number of neps in carding.ps in carding.

(3) Fibre alignment(3) Fibre alignment Ideally, fibres in a carded sliver should be straight anIdeally, fibres in a carded sliver should be straight an

d parallel. This is not quite the case. In a typical card d parallel. This is not quite the case. In a typical card sliver, the fibre configuration may be:sliver, the fibre configuration may be:

20% fibres 20% fibres -- straight fibresstraight fibres 50% fibres 50% fibres - having trailing hooks (hooks at trailing fibre end- having trailing hooks (hooks at trailing fibre end

s)s) 15% fibres15% fibres -having leading hooks (hooks at leading fibre en-having leading hooks (hooks at leading fibre en

ds)ds) 15% fibres15% fibres -having hooks at both fibre ends-having hooks at both fibre ends

You may wonder how fibres get hooked up during cYou may wonder how fibres get hooked up during carding. arding.

Fibre hooks are created in carding by the doffer maiFibre hooks are created in carding by the doffer mainly. The doffer picks up fibres on the cylinder by allnly. The doffer picks up fibres on the cylinder by allowing the fibre leading ends to hook around its teetowing the fibre leading ends to hook around its teeth. The teeth on the fast-moving cylinder surface theh. The teeth on the fast-moving cylinder surface then comb and 'brush forward' the other ends of the fin comb and 'brush forward' the other ends of the fibres. Therefore, the fibres on the doffer surface havbres. Therefore, the fibres on the doffer surface have a majority of trailing hooks. This configuration pere a majority of trailing hooks. This configuration persists to the carded sliver. sists to the carded sliver.

The generation of trailing hooks by the doffer is graThe generation of trailing hooks by the doffer is graphically illustrated below.phically illustrated below.

Further processing is therefore necessary to help strFurther processing is therefore necessary to help straighten up these fibre hooks. aighten up these fibre hooks.

Card sliver

1

2

3

4

5

Main cylinder

Doffer

1 - a fibre approaching the doffer 2 - fibre leading end picked up by doffer 3 - fibre trailing end combed forward by cylinder 4 - trailing hook fibre formed on differ 5 - the trailing hook persists to carded sliver

Fig. 1.12: Formation of trailing hooks in carding

(4) Sliver evenness(4) Sliver evenness It would be very difficult, if not impossible, to obtain It would be very difficult, if not impossible, to obtain

an even yarn from irregular slivers. an even yarn from irregular slivers.

Uniform feed to the card is essential for the Uniform feed to the card is essential for the uniformity of card sliver. Modern chute feed uniformity of card sliver. Modern chute feed regulates the amount of fibres fed to the card to regulates the amount of fibres fed to the card to improve uniformity. In addition, some cards are improve uniformity. In addition, some cards are fitted with an autoleveller or autolevelling system to fitted with an autoleveller or autolevelling system to ensure uniformity. An autoleveller is a system fitted ensure uniformity. An autoleveller is a system fitted to carding (and drawing) machines to automatically to carding (and drawing) machines to automatically reduce the variation of the linear density of the reduce the variation of the linear density of the output material. This is achieved by monitoring the output material. This is achieved by monitoring the linear density of the input or output material and, if linear density of the input or output material and, if necessary, changing the machine speed to necessary, changing the machine speed to compensate for any deviation from a pre-set value. compensate for any deviation from a pre-set value.

Two main types of autolevelling systems have been Two main types of autolevelling systems have been used on the carding machines: the open-loop (or feeused on the carding machines: the open-loop (or feed forward) and closed-loop (feed backward) autolevd forward) and closed-loop (feed backward) autolevelling systems. The principles of these two types are ielling systems. The principles of these two types are indicated in Figure 1.13.ndicated in Figure 1.13.

Measuringunit

Regulatorunit

Controlunit

Ref.Signal

Materialinput

Materialoutput

An open-loop (feed-forward) controlsystem

Measuringunit

Regulatorunit

Controlunit

Ref.Signal

Materialinput

Materialoutput

A closed-loop control system

Fig. 1.13: Open-loop and closed-loop autolevelling systems

For the open-loop aultolevelling system, the linear For the open-loop aultolevelling system, the linear density (or thickness) of the input material is measudensity (or thickness) of the input material is measured by a measuring unit. The result is compared witred by a measuring unit. The result is compared with a set value or the reference signal. If there is any dh a set value or the reference signal. If there is any deviation, the control unit will direct the regulator unieviation, the control unit will direct the regulator unit to change the process speed to maintain a regular t to change the process speed to maintain a regular output. In this case, the measured signal is fed forwoutput. In this case, the measured signal is fed forward from input to output, and this autolevelling systard from input to output, and this autolevelling system is also known as feed forward autolevelling systeem is also known as feed forward autolevelling system. This system is often used to correct short-term vm. This system is often used to correct short-term variations in linear density.ariations in linear density.

For the closed-loop autolevelling system, the linear dFor the closed-loop autolevelling system, the linear density (or thickness) of the output material is monitorensity (or thickness) of the output material is monitored by a measuring unit. It is then compared with the sed by a measuring unit. It is then compared with the set value or the reference signal. If the measured value et value or the reference signal. If the measured value deviates from the set value, the control unit will direcdeviates from the set value, the control unit will direct the regulator unit to change the process speed so tht the regulator unit to change the process speed so that the deviation can be reduced. Since the measured at the deviation can be reduced. Since the measured signal is fed backwards from output to input, this systsignal is fed backwards from output to input, this system is also known as feedback autolevelling system. Tem is also known as feedback autolevelling system. This system is suitable for correcting medium to long-this system is suitable for correcting medium to long-term variations in linear density.erm variations in linear density.

Figure 1.13a shows an open-loop autolevelling sysFigure 1.13a shows an open-loop autolevelling system on a cotton card . In this example, the thicknetem on a cotton card . In this example, the thickness of the feed stock is measured at the feed roller. ss of the feed stock is measured at the feed roller. The thickness signal is then fed into a programmaThe thickness signal is then fed into a programmable controller which processes the signal and workble controller which processes the signal and works out the correct draft required to adjust the weighs out the correct draft required to adjust the weight of the material being processed, and commands t of the material being processed, and commands a servo-motor to change the relevant roller speed ta servo-motor to change the relevant roller speed to maintain a uniform output.o maintain a uniform output.

Figure 1.13a Open-loop autolevelling on a card Figure 1.13a Open-loop autolevelling on a card (Lennox-Kerr 1983, p. 46)(Lennox-Kerr 1983, p. 46)

A closed-loop autolevelling on a cotton card is shoA closed-loop autolevelling on a cotton card is shown in figure 1.13b. In this case, the thickness of the wn in figure 1.13b. In this case, the thickness of the output sliver is monitored by a pneumatic measurioutput sliver is monitored by a pneumatic measuring unit. The signal is fed back to the feed roller so tng unit. The signal is fed back to the feed roller so that it can either slow down or speed up to change that it can either slow down or speed up to change the draft. he draft.

Figure 1.13b Closed-loop autolevelling on a card (KFigure 1.13b Closed-loop autolevelling on a card (Klein 1987a, p54. Courtesy of Zellweger Uster). lein 1987a, p54. Courtesy of Zellweger Uster).

DrawingDrawing Converting bales of fibres to a thin strand of fibres Converting bales of fibres to a thin strand of fibres

or yarns requires enormous fibre attenuation. Put sor yarns requires enormous fibre attenuation. Put simply, attenuation (drafting) is to make input materimply, attenuation (drafting) is to make input material longer and thinner. In this sense, carding can alsial longer and thinner. In this sense, carding can also be regarded as a fibre attenuation process. Drawio be regarded as a fibre attenuation process. Drawing continues the fibre attenuation, it also performs ng continues the fibre attenuation, it also performs several other functions.several other functions.

► ObjectivesObjectives The drawing process aims at achieving the followinThe drawing process aims at achieving the followin

g objectives:g objectives:Attenuate the card sliversAttenuate the card sliversReduce the fibre hooks and improve fibre alignReduce the fibre hooks and improve fibre align

mentmentBlend and mix fibresBlend and mix fibresReduce the irregularity of card slivers by doublReduce the irregularity of card slivers by doubl

inging Drawing usually implies the actions of doubling anDrawing usually implies the actions of doubling an

d drafting. Doubling is the combing of several sliverd drafting. Doubling is the combing of several slivers and drafting is attenuation.s and drafting is attenuation.

By now we already know that fibres in card slivers arBy now we already know that fibres in card slivers are by no means straight and parallel, and there are me by no means straight and parallel, and there are many hooked fibres, particularly trailing hooks, in the cany hooked fibres, particularly trailing hooks, in the card slivers. Many of these hooks should be straightenard slivers. Many of these hooks should be straightened as fibres slide past each other in the drawing proced as fibres slide past each other in the drawing process. Slivers from different cards vary evenness and otess. Slivers from different cards vary evenness and other properties, and should be blended to reduce the her properties, and should be blended to reduce the irregularity. Cotton and synthetics are often blended irregularity. Cotton and synthetics are often blended in drawing in sliver form. Finally, when card slivers arin drawing in sliver form. Finally, when card slivers are combined (doubled), attenuation is necessary to ree combined (doubled), attenuation is necessary to reduce the thickness of the drawn sliver. Drawing plays duce the thickness of the drawn sliver. Drawing plays a crucial role in the final quality of yarn, and a good ua crucial role in the final quality of yarn, and a good understanding of the fundamentals of drawing is essenderstanding of the fundamentals of drawing is essential.ntial.

► Basics of roller draftinBasics of roller draftin The basic elements of a roller drafting unit is The basic elements of a roller drafting unit is

shown in Figure 1.14. shown in Figure 1.14.

Figure 1.14 Basic elements of drafting

There are two sets of rollers, the front rollers There are two sets of rollers, the front rollers (top and bottom) and the back rollers (top and (top and bottom) and the back rollers (top and bottom). The front rollers are also known as bottom). The front rollers are also known as the delivery rollers while the back rollers the the delivery rollers while the back rollers the feed rollers. For drafting to occur, the front feed rollers. For drafting to occur, the front roller surface speed Vroller surface speed VFRFR is faster than the back is faster than the back roller surface speed Vroller surface speed VBRBR. The bottom rollers . The bottom rollers are the driving rollers, which drive the top are the driving rollers, which drive the top rollers by frictional contacts. The top rollers rollers by frictional contacts. The top rollers are loaded by spring or dead weight to apply are loaded by spring or dead weight to apply pressure to the fibre material running pressure to the fibre material running between the two sets of top and bottom between the two sets of top and bottom rollers. rollers.

There are several important definitions with There are several important definitions with respect to roller drafting:respect to roller drafting:

(a)Material Draft= (a)Material Draft=

(b)Mechanical Draft = (b)Mechanical Draft =

(c)Drafting Zone = the region between the front (c)Drafting Zone = the region between the front and back rollers, where drafting occurs. and back rollers, where drafting occurs.

A drawframe usually has at least two drafting A drawframe usually has at least two drafting zones, and the total draft of the drawframe is zones, and the total draft of the drawframe is not the addition, but multiplication, of the drafts not the addition, but multiplication, of the drafts in separate zones. For instance, if a drawframe in separate zones. For instance, if a drawframe has 3 drafting zones with drafts of D1, D2 and has 3 drafting zones with drafts of D1, D2 and D3 respectively, then the total draft of the D3 respectively, then the total draft of the drawframe should be .drawframe should be .

(tex) count Output

(tex) count Input

speed surfaceInput

speed surfaceOutput

(d)Ratch = distance between the nip points of the fro(d)Ratch = distance between the nip points of the front nt and back rollers.and back rollers.

(e)(e)Doublings = number of slivers fed to the drafting sDoublings = number of slivers fed to the drafting system for one output sliver.ystem for one output sliver.

The material draft and mechanical draft are not alwThe material draft and mechanical draft are not always equal. The material draft is the real draft. The raays equal. The material draft is the real draft. The ratch is also known as the ratch length or ratch settintch is also known as the ratch length or ratch setting. It is set according to the length of the longest fibrg. It is set according to the length of the longest fibres in order to prevent these fibres from being stretces in order to prevent these fibres from being stretched to break.hed to break.

► Perfect Roller DraftingPerfect Roller Drafting Assuming all fibres are uniform in length and Assuming all fibres are uniform in length and

diameter, and straight and parellel to sliver axis. diameter, and straight and parellel to sliver axis. The position of each fibre in the sliver will be The position of each fibre in the sliver will be fully described by position of its fibre leading fully described by position of its fibre leading end (FLE) and its length. Existing textile end (FLE) and its length. Existing textile processes can not arrange these fibres in such a processes can not arrange these fibres in such a perfect manner that a sliver would have the perfect manner that a sliver would have the same number of fibres in its cross sections same number of fibres in its cross sections along its length (we call this sliver a perfect along its length (we call this sliver a perfect sliver). The best sliver that can be expected sliver). The best sliver that can be expected under optimum processing conditions is one in under optimum processing conditions is one in which the fibre leading ends (FLEs) are which the fibre leading ends (FLEs) are randomly distributed. A sliver with random FLEs randomly distributed. A sliver with random FLEs distribution is called an ideal sliver. distribution is called an ideal sliver.

For an ideal sliver to remain ideal after drafting, the For an ideal sliver to remain ideal after drafting, the random FLEs distribution should be maintained. Thirandom FLEs distribution should be maintained. This requires that the drafting should increase the distas requires that the drafting should increase the distance between fibre leading ends by a factor exactly ence between fibre leading ends by a factor exactly equal to the draft used, which can only be achieved tqual to the draft used, which can only be achieved through perfect roller drafting. hrough perfect roller drafting.

Achieving perfect roller drafting requires individual Achieving perfect roller drafting requires individual control and manipulation of single fibres during the control and manipulation of single fibres during the drafting process, which is not possible with existing drafting process, which is not possible with existing technology. Nevertheless, near-perfect roller draftintechnology. Nevertheless, near-perfect roller drafting may be obtainable if the pressure distribution in tg may be obtainable if the pressure distribution in the drafting zone is ideal.he drafting zone is ideal.

► Ideal Pressure DistributionIdeal Pressure Distribution The ideal pressure distribution indicated in Figure The ideal pressure distribution indicated in Figure

1.15 has the following features:1.15 has the following features:

(a)(a) Back roller pressure is enlarged, in order to kBack roller pressure is enlarged, in order to keep fibres move at back roller speed.eep fibres move at back roller speed.

Figure 1.15 Ideal and real pressure distributions in simple roller drafting

(b)(b) Front roller pressure is more concentrated Front roller pressure is more concentrated or narrow, so that fibres under the influence of or narrow, so that fibres under the influence of the front roller pressure can change speed the front roller pressure can change speed near the nip of the front rollers.near the nip of the front rollers.

(c)(c) Pressure from back rollers decreases Pressure from back rollers decreases gradually, so fibres are not held back while gradually, so fibres are not held back while they get accelerated at the front roller nip.they get accelerated at the front roller nip.

With an ideal pressure distribution in the drafting zWith an ideal pressure distribution in the drafting zone, near-perfect roller drafting can be achieved. one, near-perfect roller drafting can be achieved.

The pressure distribution provided by a simple rollThe pressure distribution provided by a simple roller drafting system is indicated by the broken line in er drafting system is indicated by the broken line in Figure 1.15. Such a pressure distribution does not fFigure 1.15. Such a pressure distribution does not facilitate a near perfect roller drafting and often soacilitate a near perfect roller drafting and often some fibre control devices are needed in the drafting me fibre control devices are needed in the drafting zone. Fibre control during drafting will be discussezone. Fibre control during drafting will be discussed later.d later.

► Real DraftingReal Drafting In a real roller drafting situation, both the pressure In a real roller drafting situation, both the pressure

distribution in the drafting zone and the slivers themdistribution in the drafting zone and the slivers themselves are not as ideal as the ones mentioned above. selves are not as ideal as the ones mentioned above. Fibres in a real sliver are of different lengths and diaFibres in a real sliver are of different lengths and diameters. They are often not straight and parellel to slimeters. They are often not straight and parellel to sliver axis. Fibre leading ends may not follow a perfect ver axis. Fibre leading ends may not follow a perfect random distribution. There are also grouping of fibrrandom distribution. There are also grouping of fibres in the sliver due to fibre entanglements and frictioes in the sliver due to fibre entanglements and frictional contacts. Besides, there may be variatiosn in rollnal contacts. Besides, there may be variatiosn in roller speed and slippage between fibres and rollers etc. er speed and slippage between fibres and rollers etc. All these factors contribute to the fact that perfect roAll these factors contribute to the fact that perfect roller drafting is not achieved in real drafting.ller drafting is not achieved in real drafting.

Because the ratch of a drafting zone is set accordinBecause the ratch of a drafting zone is set according to the length of the longest fibres, many fibres arg to the length of the longest fibres, many fibres are not gripped by either the front roller or the back re not gripped by either the front roller or the back roller nip for some part of their journey through the oller nip for some part of their journey through the drafting zone. Figure 1.16 shows a simple roller dradrafting zone. Figure 1.16 shows a simple roller drafting unit with three typical fibres of different lengtfting unit with three typical fibres of different lengths in the drafting zone. The three fibres a, b and c hs in the drafting zone. The three fibres a, b and c will behave differently during drafting.will behave differently during drafting.

Figure 1.16 Movements of fibres in the drafting zone

Fibre a:Fibre a: The front rollers exsert more pressure oThe front rollers exsert more pressure on this fibre than the back rollers. It has been accelern this fibre than the back rollers. It has been accelerated to the front roller speed and is a 'fast-moving' fiated to the front roller speed and is a 'fast-moving' fibre, travelling at the speed of front rollers.bre, travelling at the speed of front rollers.

Fibre b:Fibre b: This fibre is under heavy control of the baThis fibre is under heavy control of the back rollers. It is a 'slow-moving' fibre. ck rollers. It is a 'slow-moving' fibre.

Fibre c:Fibre c: This fibre is not under direct control of eitThis fibre is not under direct control of either roller nip. Fibres which are not gripped by either her roller nip. Fibres which are not gripped by either nip are known as 'floating fibres'. The movement of nip are known as 'floating fibres'. The movement of a floating fibre will depend on its surrounding fibres. a floating fibre will depend on its surrounding fibres. If it is surrounded by some slow moving fibres and sIf it is surrounded by some slow moving fibres and some fast moving fibres, it may be accelerated before ome fast moving fibres, it may be accelerated before its leading end reaches the front roller nip if the sum its leading end reaches the front roller nip if the sum of the frictional forces between it and the fast movinof the frictional forces between it and the fast moving fibres is greater than the sum of the frictional forceg fibres is greater than the sum of the frictional forces between it and the slow moving fibres. A floating fis between it and the slow moving fibres. A floating fibre like fibre c may also accelerate to immediate velbre like fibre c may also accelerate to immediate velocities depending on the ratio of the frictional forces.ocities depending on the ratio of the frictional forces. Floating fibres are obviously short fibres. Another fe Floating fibres are obviously short fibres. Another feature of this floating fibre is that once it gets accelerature of this floating fibre is that once it gets accelerated, it moves faster than other longer ones because ated, it moves faster than other longer ones because there is less restraining force on its short training enthere is less restraining force on its short training end.d.

The following observations can be made from this The following observations can be made from this simplified description of fibre movements.simplified description of fibre movements.

(1)(1)Speed change zoneSpeed change zone

Not all fibres change their speeds, or get acceleratNot all fibres change their speeds, or get accelerated at the front roller nip as required by perfect rolled at the front roller nip as required by perfect roller drafting, because fibre lengths are different and er drafting, because fibre lengths are different and fibres at the edges of the drafting zone are unpredifibres at the edges of the drafting zone are unpredictable (edge fibres can not be controlled effectivelctable (edge fibres can not be controlled effectively). There is a speed change zone near the front rolly). There is a speed change zone near the front roller nip. This speed change zone will be more localiser nip. This speed change zone will be more localised towards the front roller nip if fibre length is mored towards the front roller nip if fibre length is more uniform.e uniform.

(2)(2)Drafting wave due to floating fibresDrafting wave due to floating fibres

Since the movement of a floating fibre depends on Since the movement of a floating fibre depends on its contacts with neighbouring fibres. Some floatinits contacts with neighbouring fibres. Some floating fibres may be pulled forward out of turn by the ng fibres may be pulled forward out of turn by the neighbouring fibres that have already been acceleraeighbouring fibres that have already been accelerated. Floating fibres accelerating out of turn can cauted. Floating fibres accelerating out of turn can cause adjacent fibres to also accelerate, creating a thise adjacent fibres to also accelerate, creating a thick place. The thick place is then drawn forward by ck place. The thick place is then drawn forward by the front roller nip, leaving a thin place behind. Thithe front roller nip, leaving a thin place behind. This process repeats to produce alternatively thick ans process repeats to produce alternatively thick and thin places in the drafted fibre assembly. This is a d thin places in the drafted fibre assembly. This is a practically periodic irregularity, and is widely knowpractically periodic irregularity, and is widely known as a 'drafting wave', because it is caused by floatin as a 'drafting wave', because it is caused by floating fibres during drafting. The wavelength of a draftng fibres during drafting. The wavelength of a drafting wave is about 2.5 times the mean fibre length. ing wave is about 2.5 times the mean fibre length.

(3)(3)Drafting wave due to sliver elasticityDrafting wave due to sliver elasticity Due to crimp and poor orientation and entanglement of fibrDue to crimp and poor orientation and entanglement of fibr

es, slivers are elastic over small strains. They can stretch unes, slivers are elastic over small strains. They can stretch under the drafting force. As the fast moving fibres are withdrader the drafting force. As the fast moving fibres are withdrawn from the bulk of the sliver, their frictional contacts with twn from the bulk of the sliver, their frictional contacts with the sliver create a withdrawal force, which then extends the he sliver create a withdrawal force, which then extends the sliver. This extension will cause the fibre leading ends to reasliver. This extension will cause the fibre leading ends to reach the front roller nip and accelerate ahead of their turn, anch the front roller nip and accelerate ahead of their turn, and so produce a thick place. A thick place means more fast md so produce a thick place. A thick place means more fast moving fibres and higher withdrawal forces and more extensioving fibres and higher withdrawal forces and more extension, causing more fibres to accelerate ahead of their turn unton, causing more fibres to accelerate ahead of their turn until the sliver reaches the limit of its extension. At this level of il the sliver reaches the limit of its extension. At this level of extension, the number of fibres reaching the front roller nip extension, the number of fibres reaching the front roller nip settles back down to the normal level, and so the number of settles back down to the normal level, and so the number of fast moving fibres (& withdrawal force) decreases. The redufast moving fibres (& withdrawal force) decreases. The reduction in withdrawal force causes the sliver to retract, so fibrction in withdrawal force causes the sliver to retract, so fibres reach the front roller nip later than expected, producing es reach the front roller nip later than expected, producing a thin place. Again, this process repeats and drafting wave ia thin place. Again, this process repeats and drafting wave is produced. The wave length of this drafting wave is also abs produced. The wave length of this drafting wave is also about 2.5 times the mean fibre length.out 2.5 times the mean fibre length.

(4)(4)Periodic mass variations due to mechanical faultsPeriodic mass variations due to mechanical faults If there are mechanical faults in the drafting If there are mechanical faults in the drafting

system, such as eccentric drafting rollers, system, such as eccentric drafting rollers, periodic mass variation will result in the periodic mass variation will result in the drafted material. This phenomenon has been drafted material. This phenomenon has been discussed in the module on yarn evenness. discussed in the module on yarn evenness.

In summary, real drafting may deviate from perfecIn summary, real drafting may deviate from perfect roller drafting because of either material related ot roller drafting because of either material related or machine related factors. In practice, fibre control r machine related factors. In practice, fibre control during drafting is necessary to reduce this deviatioduring drafting is necessary to reduce this deviation.n.

► Fibre Control in Roller DraftingFibre Control in Roller Drafting The main aim of fibre control is to keep the The main aim of fibre control is to keep the

floating fibres at the speed of back rollers until floating fibres at the speed of back rollers until they reach the front roller nip (i.e. to prevent they reach the front roller nip (i.e. to prevent fibres being accelerated out of turn), while still fibres being accelerated out of turn), while still allowing long fibres to be drafted. allowing long fibres to be drafted.

Figure 1.17 Examples of fibre control for the Short Staple Drawframes

Different yarn manufacture systems, and different pDifferent yarn manufacture systems, and different process in the same system, often apply different conrocess in the same system, often apply different control device in drafting. Two examples of fibre control trol device in drafting. Two examples of fibre control in short staple drawing machines (drawframes) are sin short staple drawing machines (drawframes) are shown in Figure 1.17. The control roller and pressure hown in Figure 1.17. The control roller and pressure bar force the fibre assembly (in the drafting zone) to bar force the fibre assembly (in the drafting zone) to take a curved path, thus increasing the pressure on ftake a curved path, thus increasing the pressure on fibres at the control roller or pressure bar. The increaibres at the control roller or pressure bar. The increased pressure helps to control fibre movement during sed pressure helps to control fibre movement during drafting. drafting.

► Doubling in DrawingDoubling in Drawing As mentioned in the beginning, drawing often As mentioned in the beginning, drawing often

implies the actions of doubling and drafting. We implies the actions of doubling and drafting. We have already discussed drafting at length. have already discussed drafting at length. Doubling simply means combining several slivers Doubling simply means combining several slivers together as the input to a drawframe. According together as the input to a drawframe. According to the law of doubling discussed in the module to the law of doubling discussed in the module on yarn evenness, if n slivers are doubled on yarn evenness, if n slivers are doubled together, the CV of the doubled material will be together, the CV of the doubled material will be reduced by a factor of orreduced by a factor of or

where is the average CV of the where is the average CV of the individual slivers before doublingindividual slivers before doubling

n1

n

doubling beforeCV _______

doublingafterCV

doublingbeforeCV

______

Usually 8 slivers are doubled up to give one output Usually 8 slivers are doubled up to give one output sliver, as indicated in Figure 1.18. The linear density sliver, as indicated in Figure 1.18. The linear density of the output sliver is determined by the amount of of the output sliver is determined by the amount of total draft applied in the draft zone. total draft applied in the draft zone.

Draft zone

Main draft Measuring

unit

Signal processing unit

Servomotor (for speed change)

Creel with feed rolers (variable speed)

Autolevelling System

Cans of input slivers

Break draft

Figure 1.18 A drawframe with 8 doublings and an autolevelling unit

► Autolevelling in DrawingAutolevelling in Drawing Fibre control and doubling are necessary in drawinFibre control and doubling are necessary in drawin

g to improve the quality, particularly evenness, of dg to improve the quality, particularly evenness, of drawn slivers. As in carding, autolevelling is often usrawn slivers. As in carding, autolevelling is often used in drawing to further improve the evenness of dred in drawing to further improve the evenness of drawn materials. The principle of autolevelling has bawn materials. The principle of autolevelling has been discussed in the carding section. An example of een discussed in the carding section. An example of autolevelling in drawing is shown in figure 1.18. Thiautolevelling in drawing is shown in figure 1.18. This is an open-loop or feed forward autolevelling systs is an open-loop or feed forward autolevelling system. The input material is measured for linear densiem. The input material is measured for linear density or thickness by a measuring unit, the signal is prty or thickness by a measuring unit, the signal is processed and compared with set value by the signal ocessed and compared with set value by the signal processing unit. If deviation exists, then the servomprocessing unit. If deviation exists, then the servomotor is instructed to change the speed of the draftinotor is instructed to change the speed of the drafting rollers to adjust the draft in other to reduce the irg rollers to adjust the draft in other to reduce the irregularity of the output material.regularity of the output material.

► Fibre Straightening in DrawingFibre Straightening in Drawing We already know that most fibres in card We already know that most fibres in card

slivers are hooked fibres, and one of the key slivers are hooked fibres, and one of the key objectives of drawing is to straighten out these objectives of drawing is to straighten out these hooked fibres.hooked fibres.

Consider a trailing hook (T) and a leading hook Consider a trailing hook (T) and a leading hook (L) in drawing as shown in Figure 1.19. (L) in drawing as shown in Figure 1.19.

Front rollers

Back rollers

Front rollers

Back rollers

T L

Trailing hook in the drafting zone (straightens out easily)

Leading hook in the drafting zone (does not straighten out easily)

Figure 1.19 Fibre straightening during drafting

For the trailing hook, it will travel initially at the speeFor the trailing hook, it will travel initially at the speed of the back drafting rollers. Soon its leading end, ed of the back drafting rollers. Soon its leading end, embedded in ‘fast-moving’ fibres under the influenmbedded in ‘fast-moving’ fibres under the influence of the front drafting rollers, will travel with the ‘fce of the front drafting rollers, will travel with the ‘fast-moving’ fibres at the front roller speed. Since thast-moving’ fibres at the front roller speed. Since the hooked end of the fibre is still embedded in a relatie hooked end of the fibre is still embedded in a relatively thick body of ‘slow-moving’ fibres controlled vely thick body of ‘slow-moving’ fibres controlled by the back rollers, the difference in speed between tby the back rollers, the difference in speed between the leading end and trailing (hooked) end will straighthe leading end and trailing (hooked) end will straighten out the hook. For the fibre with leading hook (L), ten out the hook. For the fibre with leading hook (L), the hook can get caught easily by the ‘fast moving’ he hook can get caught easily by the ‘fast moving’ fibres and travel at the front roller speed, while the ufibres and travel at the front roller speed, while the unhooked trailing end offers little resistance to its accnhooked trailing end offers little resistance to its acceleration. As a result, the leading hook (L) is likely to eleration. As a result, the leading hook (L) is likely to persist into the output material. From this brief discupersist into the output material. From this brief discussion, it is clear that one passage through a drawfrassion, it is clear that one passage through a drawframe only effectively removes trailing hooks.me only effectively removes trailing hooks.

In a card sliver, the majority of fibre hooks are trailing In a card sliver, the majority of fibre hooks are trailing hooks. But as the card sliver is deposited into a can anhooks. But as the card sliver is deposited into a can and gets taken out to feed a drawframe, it follows a ‘fird gets taken out to feed a drawframe, it follows a ‘first-in-last-out’ principle and a reversal of hook directist-in-last-out’ principle and a reversal of hook direction occurs. This is known as natural reversal of fibre diron occurs. This is known as natural reversal of fibre direction. Because of this natural reversal, most fibres (in ection. Because of this natural reversal, most fibres (in the card slivers) entering the first drawframe have leathe card slivers) entering the first drawframe have leading hooks, which do not get effectively straightened ding hooks, which do not get effectively straightened out as we have just discussed. In addition, a short stapout as we have just discussed. In addition, a short staple combing machine (the comber) straightens out leadle combing machine (the comber) straightens out leading hooks effectively (which is different from a worsteing hooks effectively (which is different from a worsted comb for long staple fibres), and trailing hooks must d comb for long staple fibres), and trailing hooks must be presented to a ring spinning machine (the drafting ibe presented to a ring spinning machine (the drafting in ring spinning does not straighten out leading hooks).n ring spinning does not straighten out leading hooks).

For these reasons, there must be an even number of For these reasons, there must be an even number of passages between the short staple carding and compassages between the short staple carding and combing machines, and an odd number between the shbing machines, and an odd number between the short staple carding and ring spinning machines. You cort staple carding and ring spinning machines. You can see this arrangement from Figure 1.1.an see this arrangement from Figure 1.1.

Figure 1.1 indicates that after two drawing Figure 1.1 indicates that after two drawing passages, the sliver can go directly to rotor passages, the sliver can go directly to rotor spinning to produce a carded rotor spun yarn. spinning to produce a carded rotor spun yarn. However, if a high quality ring spun cotton yarn However, if a high quality ring spun cotton yarn is required, the sliver should go through a is required, the sliver should go through a combing stage, followed by further drawing, combing stage, followed by further drawing, roving and finally the ring spinning process. roving and finally the ring spinning process. Combing is discussed next.Combing is discussed next.

CombingCombing► IntroductionIntroduction Combing is a key process that makes the difference bCombing is a key process that makes the difference b

etween an ordinary yarn and a quality yarn. It enableetween an ordinary yarn and a quality yarn. It enables the ultimate yarn to be smoother, finer, stronger, as the ultimate yarn to be smoother, finer, stronger, and more uniform than otherwise would be possible, nd more uniform than otherwise would be possible, at a cost of course.at a cost of course.

The basic objectives of combing are:The basic objectives of combing are:

(a) Removal of a pre-determined amount of short (a) Removal of a pre-determined amount of short fibresfibres

(b) Removal of neps and impurities(b) Removal of neps and impurities(c) Straightening of the retained long fibres (c) Straightening of the retained long fibres

The continuous assembly of long and parallThe continuous assembly of long and parallel fibres delivered by the combing process is el fibres delivered by the combing process is called a comb sliver. Just as long and well-alcalled a comb sliver. Just as long and well-aligned fibre polymers (molecules) make stroigned fibre polymers (molecules) make strong fibres, long and straight fibres in the comng fibres, long and straight fibres in the comb sliver will make strong and smooth yarns. b sliver will make strong and smooth yarns.

The materials rejected in the combing proceThe materials rejected in the combing process is called noil. Noil contains short fibres, nss is called noil. Noil contains short fibres, neps and impurities. The amount of noil prodeps and impurities. The amount of noil produced may be expressed as either percentage uced may be expressed as either percentage noil or tear ratio:noil or tear ratio:

The relationship between the two expressions is gThe relationship between the two expressions is given below:iven below:

For example, a 10% noil is equivalent to a tear ratiFor example, a 10% noil is equivalent to a tear ratio of 9 : 1, and a 16% noil is equivalent to a tear ratio of 9 : 1, and a 16% noil is equivalent to a tear ratio of 5.25 : 1.o of 5.25 : 1.

100)(

slivercombnoilofweight

noilofweightnoilPercentage

1:noilofweight

slivercombofweightratioTear

1100

)1(

100

noilpercentageTearor

tearnoilPercentage

The amount of noil produced is of significant importThe amount of noil produced is of significant importance. A higher noil means longer fibres in the comb ance. A higher noil means longer fibres in the comb sliver, but less comb sliver will be produced.sliver, but less comb sliver will be produced.

Yarns made from the combed sliver are called combYarns made from the combed sliver are called combed yarns. Without combing, a carded yarn would be ed yarns. Without combing, a carded yarn would be produced. Combed yarns, consisting of longer and produced. Combed yarns, consisting of longer and more parallel fibres, are of better quality and commmore parallel fibres, are of better quality and command a higher price than carded yarns or yarns produand a higher price than carded yarns or yarns produced without the combing stage. A brief comparison ced without the combing stage. A brief comparison of combed and carded cotton yarns is given in Table of combed and carded cotton yarns is given in Table 1.2 below. `1.2 below. `

► The combThe comb A combing machine is usually referred to as a combA combing machine is usually referred to as a comb

er, or simply a comb. The short-staple spinning mill er, or simply a comb. The short-staple spinning mill uses only the rectilinear comb with swinging nipperuses only the rectilinear comb with swinging nippers and stationary detaching rollers, as originally concs and stationary detaching rollers, as originally conceived in 1845 by J. Heilman in Alsace and further deeived in 1845 by J. Heilman in Alsace and further developed in 1902 by the Englishman Nasmith and in 1veloped in 1902 by the Englishman Nasmith and in 1948 by the Whitin company. 948 by the Whitin company.

The most common machine layouts used in practice The most common machine layouts used in practice comprise single-sided machines with eight heads. Dcomprise single-sided machines with eight heads. Double-sided machines with six-plus-six head are alsouble-sided machines with six-plus-six head are also manufactured by the Platt Saco Lowell company.o manufactured by the Platt Saco Lowell company.

A typical comb head is sketched in Figure 1.20. A typical comb head is sketched in Figure 1.20.

Top comb

Nipper jaws

Feed rolls

Input sliver lap

Cylinder comb (Circular comb)

Detaching rolls

Combed sliver

Figure 1.20 Sketch of a rectilinear cotton comb

The sliver lap, or the thick sheet of fibres formed The sliver lap, or the thick sheet of fibres formed on a sliver lapper before combing, is fed to the on a sliver lapper before combing, is fed to the comb in an intermittent fashion. In each operating comb in an intermittent fashion. In each operating cycle, the lap is advanced a short distance (4 to cycle, the lap is advanced a short distance (4 to 6.5 mm) and then gripped (by the nippers) so that 6.5 mm) and then gripped (by the nippers) so that a fringe of fibres is presented to the toothed a fringe of fibres is presented to the toothed section of a cylinder comb. The fibre fringe is then section of a cylinder comb. The fibre fringe is then combed by the teeth on the cylinder comb and in combed by the teeth on the cylinder comb and in the process, short fibres, neps and impurities are the process, short fibres, neps and impurities are removed from the fringe. The short fibres, neps removed from the fringe. The short fibres, neps and impurities are collectively called noils. When and impurities are collectively called noils. When the un-toothed portion of the comber roll comes the un-toothed portion of the comber roll comes into contact with the fringe, the nippers open and into contact with the fringe, the nippers open and swing towards the detaching rollers to allow the swing towards the detaching rollers to allow the fringe to be drawn off by the detaching (or draw-fringe to be drawn off by the detaching (or draw-off) rolls. off) rolls.

The closest distance between the nipping points of thThe closest distance between the nipping points of the nippers and the detaching rollers is called by several e nippers and the detaching rollers is called by several names – gauge setting, detachment setting, noil settinames – gauge setting, detachment setting, noil setting. This setting is the most important setting on a cong. This setting is the most important setting on a comb. It has the largest impact on the percentage noil amb. It has the largest impact on the percentage noil and the mean fibre length of the comb sliver. During thnd the mean fibre length of the comb sliver. During the drawing off process, the fibre fringe is pressed into te drawing off process, the fibre fringe is pressed into the needles of the top comb, so that the portion of the he needles of the top comb, so that the portion of the fringe not combed by the cylinder comb can now be cfringe not combed by the cylinder comb can now be combed by the top comb. The neps and impurities will ombed by the top comb. The neps and impurities will not be able to pass through the closely pinned top conot be able to pass through the closely pinned top comb and are removed by the cylinder comb in the next mb and are removed by the cylinder comb in the next combing cycle. combing cycle.

The detaching rolls bring the combed fringe to the tThe detaching rolls bring the combed fringe to the tail end of the previously combed material to make a ail end of the previously combed material to make a joint or piecing. The combed fibres, from many comjoint or piecing. The combed fibres, from many combing heads, are then brought together and consolidabing heads, are then brought together and consolidated into a sliver and coiled into a sliver can. ted into a sliver and coiled into a sliver can.

The comb operates intermittently in cycles. Its speeThe comb operates intermittently in cycles. Its speed is described in terms of cycles per minute or nips pd is described in terms of cycles per minute or nips per minute. Modern cotton combs run in excess of 35er minute. Modern cotton combs run in excess of 350 nips/minute0 nips/minute

► Sequence of operationsSequence of operations The sequence of operations of a cotton comb is The sequence of operations of a cotton comb is

described below described below

(a) The feed rollers S move the sheet W 4 – 6.5 (a) The feed rollers S move the sheet W 4 – 6.5 mm forward, while the nippers ZO/ZU are held mm forward, while the nippers ZO/ZU are held open (feed).open (feed).

(b) The upper nipper plate ZO is lowered onto the (b) The upper nipper plate ZO is lowered onto the cushion plate ZU so that the fibres are clamped cushion plate ZU so that the fibres are clamped between them (nipping).between them (nipping).

(c) The combing segment (K), mounted on (c) The combing segment (K), mounted on rotating cylinder (Z), sweeps its needles or saw-rotating cylinder (Z), sweeps its needles or saw-teeth through the fibre fringe (B) and carries away teeth through the fibre fringe (B) and carries away anything not held by the nippers (rotary combing).anything not held by the nippers (rotary combing).

(d) The nippers open again and move towards the (d) The nippers open again and move towards the detaching rollers A (nippers forward).detaching rollers A (nippers forward).Figure 1.21 Sequence of operations of a cotton comb (Klein, 1987b, p2-4)

(e)(e)Meanwhile, the detaching rollers A have returneMeanwhile, the detaching rollers A have returned part of the previously drawn off stock (web V) by d part of the previously drawn off stock (web V) by means of a reverse rotation, so that the web protrumeans of a reverse rotation, so that the web protrudes from the back of the detaching device (web retdes from the back of the detaching device (web return).urn).

(f)(f)In the course of the forward movement of the niIn the course of the forward movement of the nippers, the projecting fibre fringe B is placed upon tppers, the projecting fibre fringe B is placed upon the returned web V (piecing).he returned web V (piecing).

(g)(g)The detaching rollers begin to rotate in the forwThe detaching rollers begin to rotate in the forward direction again and draw the clamped fibres oard direction again and draw the clamped fibres out of the sheet W held fast by the feed rollers (detaut of the sheet W held fast by the feed rollers (detaching).ching).

(h)(h)Before the start of the detaching operation, the tBefore the start of the detaching operation, the top comb F has thrust its single row of needles into top comb F has thrust its single row of needles into the fibre fringe. As the fibres are pulled through the he fibre fringe. As the fibres are pulled through the needles of the top comb during detaching, the trailineedles of the top comb during detaching, the trailing part of the fringe is combed, thus making up for tng part of the fringe is combed, thus making up for the inability of the cylinder comb to reach this part ohe inability of the cylinder comb to reach this part of the fringe (combing by the top comb).f the fringe (combing by the top comb).

(i)(i)As the nipper assembly is retracted, the nippers oAs the nipper assembly is retracted, the nippers open for the next feeding step. The top comb is withpen for the next feeding step. The top comb is withdrawn. A new combing cycle begins.drawn. A new combing cycle begins.

► Fibre selection in combingFibre selection in combing The theory of combing deals with the key issue of fibThe theory of combing deals with the key issue of fib

re selection in the combing process, i.e. what goes inre selection in the combing process, i.e. what goes into the noil and what goes into the comb sliver. The pto the noil and what goes into the comb sliver. The percentage noil is largely a function of the detachmenercentage noil is largely a function of the detachment setting and the feed distance per combing cycle. It it setting and the feed distance per combing cycle. It is worth pointing out here that there are two types of s worth pointing out here that there are two types of feeding arrangements – concurrent feed and countefeeding arrangements – concurrent feed and counter-feed. With concurrent feed, the fibre sheet is fed forr-feed. With concurrent feed, the fibre sheet is fed forward into the nippers while the nippers are swinging ward into the nippers while the nippers are swinging towards the detaching rollers. With counter-feed, thtowards the detaching rollers. With counter-feed, the fibre sheet is fed forward during the return of the nie fibre sheet is fed forward during the return of the nippers. The type of feeding also affects the percentagppers. The type of feeding also affects the percentage noil in combing.e noil in combing.

According to Charles Gegauff’s noil theory, the According to Charles Gegauff’s noil theory, the percentage noil (N%) are related to the percentage noil (N%) are related to the detachment setting (D), feed distance (F), and detachment setting (D), feed distance (F), and the longest fibre length (L), according to the the longest fibre length (L), according to the formula below:formula below:

It should be noted that these formulas are used It should be noted that these formulas are used to reflect the relationship between percentage to reflect the relationship between percentage noil and important comb settings, not to noil and important comb settings, not to calculate the actual percentage noils. The calculate the actual percentage noils. The implication of this relationship on the quality of implication of this relationship on the quality of comb sliver is discussed in the following section.comb sliver is discussed in the following section.

)(1002%

2

feedcocurrentForL

FDN

)(1002%

2

feedcounterForL

FDN

► Quality issues in combingQuality issues in combing The theory of combing or noil theory discussed The theory of combing or noil theory discussed

in the previous section provides a good in the previous section provides a good starting point on the quality issues in combing. starting point on the quality issues in combing. Research at Rieter has shown that the Research at Rieter has shown that the percentage noil has a major impact on the percentage noil has a major impact on the important quality attributes of the resultant important quality attributes of the resultant yarns, as depicted in Figure 1.22.yarns, as depicted in Figure 1.22.

Percentage noil 5% 10% 15% 20%

Improvement in yarn quality (%)

Yarn imperfections

Yarn evenness

Yarn strength

100

50

Figure 1.22 The effect of percentage noil on yarn quality attributes

In a normal combing process for cotton, a percentage In a normal combing process for cotton, a percentage noil between 10 to 20% is expected. Combing with a nnoil between 10 to 20% is expected. Combing with a noil percentage below 10% is often referred to as upgroil percentage below 10% is often referred to as upgrading combing, while combing with a noil percentage ading combing, while combing with a noil percentage about 20% is known as super combing. Super combinabout 20% is known as super combing. Super combing is only used when superfine combed yarns are to be g is only used when superfine combed yarns are to be produced.produced.

Now that we know the importance of percentage Now that we know the importance of percentage noil, what are the major factors that affect noil, what are the major factors that affect percentage noil in combing then? We will need to percentage noil in combing then? We will need to refer to the noil theory to answer this question. refer to the noil theory to answer this question.

(1)(1)The detachment setting (D)The detachment setting (D)

As mentioned before, this setting is the closest distanAs mentioned before, this setting is the closest distance between the bite of the nippers and the nip line of ce between the bite of the nippers and the nip line of the detaching rollers. According to the noil theory, ththe detaching rollers. According to the noil theory, the percentage noil increases as the detachment settine percentage noil increases as the detachment setting increases. At larger detachment setting, more fibres g increases. At larger detachment setting, more fibres are removed into the noil and the average fibre lengtare removed into the noil and the average fibre length in the comb sliver is longer. Because of the increaseh in the comb sliver is longer. Because of the increased fibre loss with increase in detachment setting, the cd fibre loss with increase in detachment setting, the cost of production will be higher. In practice, spinners ost of production will be higher. In practice, spinners need to find the optimum detachment setting based need to find the optimum detachment setting based on a balance of quality and cost. The detachment seton a balance of quality and cost. The detachment setting on a cotton comb normally lies in the range 15 to ting on a cotton comb normally lies in the range 15 to 25 mm.25 mm.

(2)(2)The feedThe feed

According to the noil theory, both the type of feed anAccording to the noil theory, both the type of feed and the feed distance affect the percentage noil. For thd the feed distance affect the percentage noil. For the same feed distance, counter-feed results in higher e same feed distance, counter-feed results in higher noil percentage than concurrent feed. In other words,noil percentage than concurrent feed. In other words, there are more short fibres in the comb sliver with c there are more short fibres in the comb sliver with concurrent feed than with counter-feed. In upgrading oncurrent feed than with counter-feed. In upgrading combing where the quality requirement is low and prcombing where the quality requirement is low and production rate needs to be high, concurrent feed is oftoduction rate needs to be high, concurrent feed is often used. On the other hand, if the quality requiremenen used. On the other hand, if the quality requirement is very rigorous, counter-feed should be used. Some t is very rigorous, counter-feed should be used. Some modern combs allow selection of the feed type accormodern combs allow selection of the feed type according to needs.ding to needs.

The feed distance affects the noil, the quality and The feed distance affects the noil, the quality and the production rate of combing. According to the the production rate of combing. According to the noil theory, noil increases with feed distance for noil theory, noil increases with feed distance for counter-feed, and decreases with feed distance counter-feed, and decreases with feed distance for concurrent feed. Increase in the feed for concurrent feed. Increase in the feed distance will increase production rate, because distance will increase production rate, because more fibres go into the comb sliver at a larger more fibres go into the comb sliver at a larger feed distance. But the cleanliness of the combed feed distance. But the cleanliness of the combed web, i.e. its freedom from impurities and neps, web, i.e. its freedom from impurities and neps, will deteriorate at a higher feed distance. will deteriorate at a higher feed distance. Therefore, a lower feed distance needs to be Therefore, a lower feed distance needs to be used for higher quality requirements. used for higher quality requirements.

(3)(3)Effect of fibre hooksEffect of fibre hooks

The cotton comb deals with relatively short fibres, coThe cotton comb deals with relatively short fibres, compared with worsted comb. The hooks on short fibrempared with worsted comb. The hooks on short fibres are small. As a result, leading hooks can be removes are small. As a result, leading hooks can be removed easily by the cylinder comb, with little damage or brd easily by the cylinder comb, with little damage or breakage to the hooked fibres. An exception is when theakage to the hooked fibres. An exception is when that both limbs of a leading fibre hook are held in the niat both limbs of a leading fibre hook are held in the nippers while the protruding loop is still long enough tppers while the protruding loop is still long enough to be engaged by the teeth on the cylinder comb. This o be engaged by the teeth on the cylinder comb. This event is much rarer in short staple combing than in loevent is much rarer in short staple combing than in long staple combing. ng staple combing.

Trailing hooks can cause serious problems in short stTrailing hooks can cause serious problems in short staple combing. Some trailing hooks may persist into taple combing. Some trailing hooks may persist into the comb sliver or cause fibre breakage during detachhe comb sliver or cause fibre breakage during detaching, particularly if concurrent feed is used. Consider a ing, particularly if concurrent feed is used. Consider a fibre with a trailing hook just lying in the bite of the nfibre with a trailing hook just lying in the bite of the nippers. With concurrent feed, the trailing hook will be ippers. With concurrent feed, the trailing hook will be pushed forward out of the nippers as the nippers swipushed forward out of the nippers as the nippers swing towards the detaching rollers. The subsequent deng towards the detaching rollers. The subsequent detaching action may drag this fibre (and its trailing hotaching action may drag this fibre (and its trailing hook) into the comb sliver, particularly if this fibre is neok) into the comb sliver, particularly if this fibre is near the bottom of the fibre sheet where the top comb ar the bottom of the fibre sheet where the top comb has not yet penetrated. If this fibre’s trailing hook is has not yet penetrated. If this fibre’s trailing hook is engaged by the top comb, fibre breakage is likely to engaged by the top comb, fibre breakage is likely to occur because of the high friction between the hook occur because of the high friction between the hook and the top comb needle. With the counter-feed, no fand the top comb needle. With the counter-feed, no feeding occurs during the forward movement of the needing occurs during the forward movement of the nippers.ippers.

During detaching, the fibre fringe gets pressed into tDuring detaching, the fibre fringe gets pressed into the top comb in front of the nippers, and the trailing hhe top comb in front of the nippers, and the trailing hook in the fibre concerned is likely to be combed by took in the fibre concerned is likely to be combed by the top comb. In such case, the fibre could be combed he top comb. In such case, the fibre could be combed straight unharmed and dragged into the comb sliver, straight unharmed and dragged into the comb sliver, or the fibre may be broken because of the friction betor the fibre may be broken because of the friction between the fibre and the needles of the top comb. The fween the fibre and the needles of the top comb. The fibre breakage will generate two short fibres, one procibre breakage will generate two short fibres, one proceeding to the comb sliver, and the other blocked by teeding to the comb sliver, and the other blocked by the top comb but removed as noil in the next combing he top comb but removed as noil in the next combing cycle. This has two major undesirable consequences cycle. This has two major undesirable consequences – short fibres in the comb sliver and increased combi– short fibres in the comb sliver and increased combing waste. ng waste.

The trailing hook, or other forms of fibre disorientatThe trailing hook, or other forms of fibre disorientation, may also carry its neighbouring short fibres forion, may also carry its neighbouring short fibres forward to be detached by the detaching rollers, again ward to be detached by the detaching rollers, again increasing the number of short fibres in the comb slincreasing the number of short fibres in the comb sliver. Large trailing hooks will also reduce the effectiiver. Large trailing hooks will also reduce the effective length of even a relatively long fibre. The comb is ve length of even a relatively long fibre. The comb is likely to treat this fibre just like an ordinary short fiblikely to treat this fibre just like an ordinary short fibre and remove it into the noil. In other words, trailinre and remove it into the noil. In other words, trailing hooks (or other forms of fibre disorientation) can g hooks (or other forms of fibre disorientation) can also increase the number of long fibres in the noil, also increase the number of long fibres in the noil, which of course is undesirablewhich of course is undesirable..

From this discussion, it is clear that good fibre alignFrom this discussion, it is clear that good fibre alignment in the feed lap is essential for quality combing.ment in the feed lap is essential for quality combing. Trailing hooks are particularly troublesome. This re Trailing hooks are particularly troublesome. This requires good lap preparation before combing. It also quires good lap preparation before combing. It also requires that an even (i.e. two) number of machines requires that an even (i.e. two) number of machines between the card and the comb, as indicated in Figbetween the card and the comb, as indicated in Figure 1.1. This ensures leading hooks mainly are fed iure 1.1. This ensures leading hooks mainly are fed into the cotton comb.nto the cotton comb.

(4) Comb overlap effect in piecing(4) Comb overlap effect in piecing

At the end of each combing cycle, a small tuft of coAt the end of each combing cycle, a small tuft of combed fibres is detached. This tuft is then partially ombed fibres is detached. This tuft is then partially overlapped on the previously detached tufts, like shiverlapped on the previously detached tufts, like shingles on a roof or roofing tiles. Such pieced structurngles on a roof or roofing tiles. Such pieced structure, or the comb overlap effect, is an inherent source e, or the comb overlap effect, is an inherent source of faults in the operation of rectilinear combs. Becaof faults in the operation of rectilinear combs. Because of this, the combed sliver exhibits periodic masuse of this, the combed sliver exhibits periodic mass variations along its length, which can be revealed s variations along its length, which can be revealed using the spectrogram. using the spectrogram.

The combing process is normally followed by one oThe combing process is normally followed by one or two passages of drawing before spinning. The drar two passages of drawing before spinning. The drawing subsequent to combing will reduce the comb wing subsequent to combing will reduce the comb overlap effect. If a combed ring spun yarn is to be proverlap effect. If a combed ring spun yarn is to be produced, a roving process is needed before the ring soduced, a roving process is needed before the ring spinning process. pinning process.

RovingRoving► IntroductionIntroduction A roving is a fine strand (slubbing) intended to be feA roving is a fine strand (slubbing) intended to be fe

d into the ring spinning machines (ring frames) for d into the ring spinning machines (ring frames) for making yarns. Rotor spinning machine and other nemaking yarns. Rotor spinning machine and other new spinning systems use slivers as feed materials. Buw spinning systems use slivers as feed materials. But conventional ring frames still use rovings as the fet conventional ring frames still use rovings as the feed material. A roving is much thinner than a sliver, ed material. A roving is much thinner than a sliver, but thicker than a yarn.but thicker than a yarn.

The main objective of the roving machine is to furthThe main objective of the roving machine is to further attenuate the drawn sliver (to make it longer and er attenuate the drawn sliver (to make it longer and thinner) and get it ready for spinning.thinner) and get it ready for spinning.

The drawframe has already produced a sliver that is The drawframe has already produced a sliver that is clean, and consists of more or less parallel fibres. Suclean, and consists of more or less parallel fibres. Such a sliver satisfies the essential requirements for yach a sliver satisfies the essential requirements for yarn production. The question is why is there a need forn production. The question is why is there a need for the roving process and why can’t we feed slivers tr the roving process and why can’t we feed slivers to conventional ring frames? There are two major reao conventional ring frames? There are two major reasons for this need. First, a very high draft, in the ordesons for this need. First, a very high draft, in the order of 300 to 500, is required to bring the thickness of a r of 300 to 500, is required to bring the thickness of a sliver into the thickness of a yarn. Conventional ring sliver into the thickness of a yarn. Conventional ring frames can not cope with such a high draft. Second, frames can not cope with such a high draft. Second, the drawframe slivers are deposited in bulky sliver cthe drawframe slivers are deposited in bulky sliver cans, which are difficult to transport and present to tans, which are difficult to transport and present to the ring frames as feed material. The much smaller rhe ring frames as feed material. The much smaller roving packages are better suited for the purpose. oving packages are better suited for the purpose.

► Roving frameRoving frame The commonly used roving machine for cotton is a The commonly used roving machine for cotton is a

flyer frame (or speed frame) as shown in Figure 1.2flyer frame (or speed frame) as shown in Figure 1.23. 3.

Sliver can (carded or combed sliver)

Drafting Unit

Flyer

Vd

nf

nb

Dr Roving bobbin

Flyer leg

Presser arm

Front rollers

Double aprons

Back rollers

Bobbin drive

Flyer drive

Figure 1.23 Diagram of a roving frame

There are three basic steps in the operation of thThere are three basic steps in the operation of the roving frame – drafting, twisting, and winding. e roving frame – drafting, twisting, and winding. These basic steps are exactly the same as the baThese basic steps are exactly the same as the basic steps required in spinning. Consequently, an sic steps required in spinning. Consequently, an understanding of the roving process will help us understanding of the roving process will help us understand the spinning process to be discussed understand the spinning process to be discussed in the next module.in the next module.

The input to this roving frame is a drawn sliver (eithThe input to this roving frame is a drawn sliver (either carded or combed) from the last drawing process.er carded or combed) from the last drawing process. The sliver is drafted by a roller drafting unit. Betwe The sliver is drafted by a roller drafting unit. Between the front and back rollers (the drafting zone), the en the front and back rollers (the drafting zone), the fibres pass between the double aprons, which contrfibres pass between the double aprons, which control the fibre movement during drafting. The front nool the fibre movement during drafting. The front nose of the double aprons is set close to the front rollese of the double aprons is set close to the front roller nip for good drafting performance. You may recall r nip for good drafting performance. You may recall the concept of perfect roller drafting, which requirethe concept of perfect roller drafting, which requires that fibres in the drafting zone travel at the speed s that fibres in the drafting zone travel at the speed of back rollers until the fibre leading ends reach the of back rollers until the fibre leading ends reach the front roller nip. The double aprons travel at about tfront roller nip. The double aprons travel at about the same speed as the back rollers, and they control he same speed as the back rollers, and they control the fibres until they reach the front roller nip. the fibres until they reach the front roller nip.

A small amount of twist (30 to 65 turns per meter) is iA small amount of twist (30 to 65 turns per meter) is inserted into the drafted fibre strand via the rotation nserted into the drafted fibre strand via the rotation of the flyer. The bobbin (on a spindle) is driven at a spof the flyer. The bobbin (on a spindle) is driven at a speed different to that of the flyer. The different in bobbeed different to that of the flyer. The different in bobbin and flyer speeds allows the slightly twisted fibre strin and flyer speeds allows the slightly twisted fibre strand or roving to be wound on the bobbin. If the rotatiand or roving to be wound on the bobbin. If the rotations of the bobbin and the flyer are synchronised, the ons of the bobbin and the flyer are synchronised, the roving will not be wound up onto the bobbin. The flyeroving will not be wound up onto the bobbin. The flyer arm through which the roving passes helps to suppor arm through which the roving passes helps to support the relatively weak roving due to its low twist level. rt the relatively weak roving due to its low twist level.

In addition, a presser arm is attached to the lower eIn addition, a presser arm is attached to the lower end of the hollow flyer leg (through which the roving nd of the hollow flyer leg (through which the roving runs). This presser arm guides the roving from the eruns). This presser arm guides the roving from the exit of the flyer leg to the roving package. The roving ixit of the flyer leg to the roving package. The roving is wrapped two or three times around the presser ars wrapped two or three times around the presser arm. The friction between the roving and the presser am. The friction between the roving and the presser arm will increase the roving tension at the winding orm will increase the roving tension at the winding on point. This will give a compact roving package. A cn point. This will give a compact roving package. A compact package has more roving and is more stable ompact package has more roving and is more stable as well.as well.

On the roving bobbin, each coil of roving material is aOn the roving bobbin, each coil of roving material is arranged very closely and almost parallel to one anothrranged very closely and almost parallel to one another (parallel wind) so that as much material as possible er (parallel wind) so that as much material as possible is taken up in the package. For this purpose, the bobbis taken up in the package. For this purpose, the bobbin rail (not shown in the diagram) with the package on in rail (not shown in the diagram) with the package on it moves up and down steadily. The build-up of roving it moves up and down steadily. The build-up of roving package leads to an increase in the wound length of rpackage leads to an increase in the wound length of roving per coil. The speed of the bobbin rail movement oving per coil. The speed of the bobbin rail movement is reduced by a small amount after each completed lais reduced by a small amount after each completed layer. With the increase in package diameter (Dr), the byer. With the increase in package diameter (Dr), the bobbin rotation rate is also changed to maintain a consobbin rotation rate is also changed to maintain a constant difference between the surface speeds of the pactant difference between the surface speeds of the package and the flyer. This speed difference is the windinkage and the flyer. This speed difference is the winding on speed and should be the same as the speed at wg on speed and should be the same as the speed at which the fibre strand is delivered by the front drafting hich the fibre strand is delivered by the front drafting rollers.rollers.

The working principle of the flyer roving frame can bThe working principle of the flyer roving frame can be summarised as below:e summarised as below:

roller drafting, delivers fibre strand at a roller drafting, delivers fibre strand at a constant speed Vconstant speed Vdd

flyer rotate at nf (constant) to twist the strandflyer rotate at nf (constant) to twist the strand

bobbin rotates at nb (different to nf) to wind on bobbin rotates at nb (different to nf) to wind on the rovingthe roving

- either bobbin lead or flyer lead, as long as - either bobbin lead or flyer lead, as long as there is a difference in rotational speedthere is a difference in rotational speed

- winding on speed - winding on speed ( ( Dr= roving diameter on Dr= roving diameter on

bobbinbobbin))

V

n = level Twist

d

f

)n- n( Dr = V bfW

Dr varies as the roving package builds up, chanDr varies as the roving package builds up, change nb to match VW with Vd ge nb to match VW with Vd

fibre strand is supported by a flyer arm (no ballfibre strand is supported by a flyer arm (no ballooning, best for thick weak strand)ooning, best for thick weak strand)

- flyer speed is limited by the mechanical design.- flyer speed is limited by the mechanical design.

► Quality issues in rovingQuality issues in roving Since ring spun yarns are produced directly Since ring spun yarns are produced directly

from rovings, the quality of the roving is very from rovings, the quality of the roving is very important. The roving process is essentially a important. The roving process is essentially a drafting process (not a drawing process because drafting process (not a drawing process because there is no doubling). In fibre drafting, fibre there is no doubling). In fibre drafting, fibre control is important. Good condition of the control is important. Good condition of the double aprons, the right ratch setting (distance double aprons, the right ratch setting (distance between the front and back drafting rollers) are between the front and back drafting rollers) are important in ensuing good fibre control.important in ensuing good fibre control.

Rovings should be routinely sampled and tested for eRovings should be routinely sampled and tested for evenness. Particular attention should be paid to the spvenness. Particular attention should be paid to the spectrogram to see if any drafting wave or periodic masectrogram to see if any drafting wave or periodic mass variation exists in the rovings. s variation exists in the rovings.

The small amount of twist inserted in the roving is nThe small amount of twist inserted in the roving is necessary to ensure trouble-free transport of the roviecessary to ensure trouble-free transport of the roving package, smooth unwinding of the roving at the rng package, smooth unwinding of the roving at the ring frame, and to prevent accidental drafting of the ring frame, and to prevent accidental drafting of the roving during roving winding. This twist should be as oving during roving winding. This twist should be as small as practically possible for two reasons. First, if small as practically possible for two reasons. First, if the flyer rotation speed is fixed, a higher twist level the flyer rotation speed is fixed, a higher twist level means lower delivery speed or lower production ratmeans lower delivery speed or lower production rate. Second, high twist in the roving may cause problee. Second, high twist in the roving may cause problem in drafting of the roving at the ring frame, because m in drafting of the roving at the ring frame, because fibres may not be able to slide past one another freelfibres may not be able to slide past one another freely. The machine manufacturers will recommend the ry. The machine manufacturers will recommend the right level of twist for different fibre materials used.ight level of twist for different fibre materials used.

Review questionsReview questions1.1.The key processing stages for cotton includeThe key processing stages for cotton include

opening and blendingopening and blendingcardingcardingdrawingdrawingcombingcombing

Describe the objectives and principle of each of thesDescribe the objectives and principle of each of these processes, using sketches if necessary and use aboe processes, using sketches if necessary and use about 200 words for each process.ut 200 words for each process.

2.2.Four bales of cotton, of 500 pounds each, are to be mFour bales of cotton, of 500 pounds each, are to be mixed together for the blow-room process. If the cottoixed together for the blow-room process. If the cotton fineness in these bales is, 3.8, 4.1, 4.4, and 3.3 micrn fineness in these bales is, 3.8, 4.1, 4.4, and 3.3 micronaire (mic., μg/in.) respectively, what would be the onaire (mic., μg/in.) respectively, what would be the theoretical fineness of the cotton in the mix? You neetheoretical fineness of the cotton in the mix? You need to show your calculations. d to show your calculations.

3.3.On a draw-frame or drawing machine, why is it ofteOn a draw-frame or drawing machine, why is it often necessary to adjust the ratch setting according to n necessary to adjust the ratch setting according to the fibres to be processed?the fibres to be processed?

4.4.With reference to the two-zone drawframe in figure With reference to the two-zone drawframe in figure 1.18 and assuming a break draft of 1.5 and a main dr1.18 and assuming a break draft of 1.5 and a main draft of 4. If the average count of the eight input sliveraft of 4. If the average count of the eight input slivers is 12 ktex, what is the count of the single output slis is 12 ktex, what is the count of the single output sliver? If the delivery (front) roller speed is 400 m/min, ver? If the delivery (front) roller speed is 400 m/min, what would be the approximate speed of the feed (bwhat would be the approximate speed of the feed (back) rollers?ack) rollers?

5.5.With reference to fibre hooks, explain why two passWith reference to fibre hooks, explain why two passages of drawing are necessary between cotton cardiages of drawing are necessary between cotton carding and cotton combing. You should consider the follng and cotton combing. You should consider the following points:owing points:Hook generation in cardingHook generation in cardingHook removal during draftingHook removal during draftingEffect of hook direction on combing Effect of hook direction on combing

Worsted ProcessingWorsted ProcessingIntroductionIntroduction Long staple fibres are fibres longer than about 2 inLong staple fibres are fibres longer than about 2 in

ches. Fibres such as merino wool, mohair and alpaches. Fibres such as merino wool, mohair and alpaca fibres are typical long staple fibres. Synthetic stca fibres are typical long staple fibres. Synthetic staples of similar length are long staple synthetic fibaples of similar length are long staple synthetic fibres. Long staple fibres are processed on the worsteres. Long staple fibres are processed on the worsted processing system mainly, to make worsted yarnd processing system mainly, to make worsted yarns. s.

This topic focuses on the principle and quality of This topic focuses on the principle and quality of worsted processing of wool fibres. worsted processing of wool fibres.

ObjectivesObjectives

At the end of this topic you should be able to:At the end of this topic you should be able to:

Understand the principles and functions of Understand the principles and functions of worsted processing from raw wool to topworsted processing from raw wool to top

Appreciate the effect of raw wool quality on Appreciate the effect of raw wool quality on the quality of topsthe quality of tops

Know the applications of the TEAM formula in Know the applications of the TEAM formula in top-makingtop-making

Appreciate how fibre processing affects fibre Appreciate how fibre processing affects fibre propertiesproperties

Process overviewProcess overview The worsted industry is more fragmented than The worsted industry is more fragmented than

the cotton or short staple industry. The the cotton or short staple industry. The processing from greasy wool to worsted yarn is processing from greasy wool to worsted yarn is often carried out separately in different mills - often carried out separately in different mills - early stage processing (ESP) mill, top-making early stage processing (ESP) mill, top-making mill and spinning mill. The early stage mill and spinning mill. The early stage processor cleans the greasy wool. The top-processor cleans the greasy wool. The top-maker buys the clean wool from the early maker buys the clean wool from the early stage processor and converts the wool into a stage processor and converts the wool into a top (a sliver ready for worsted drawing and top (a sliver ready for worsted drawing and spinning). The spinner sources the top from spinning). The spinner sources the top from the topmaker and processes it into worsted the topmaker and processes it into worsted yarns. yarns.

Some mills engage in both early stage Some mills engage in both early stage processing and topmaking, others are processing and topmaking, others are vertically integrated and do the whole vertically integrated and do the whole processing from greasy wool to yarn. processing from greasy wool to yarn. Early stagEarly stage processing and top-making are also used synonye processing and top-making are also used synonymously to refer to all the greasy wool to top procesmously to refer to all the greasy wool to top processing stages. Worsted processing utilises relatively fising stages. Worsted processing utilises relatively fine (< 27 micron) and long (> 45 mm) virgin wool anne (< 27 micron) and long (> 45 mm) virgin wool and other long staple fibres. A typical sequence of wod other long staple fibres. A typical sequence of worsted processing of wool is given in Figure 2.1. rsted processing of wool is given in Figure 2.1.

Raw Wool

Opening & Blending

Scouring & Drying

Worsted Carding

Intermediate Gillings (usually 3)

Combing

Finishing Gillings (usually 2)

Drawings (2 to 5)

Spinning

WORSTED TOP

WORSTED SINGLES YARN

SCOURED WOOL

Early stage processing

Top-making

Spinning

Figure 2.1 A typical worsted processing sequence for wool

Before wool processing can start, we need to first of aBefore wool processing can start, we need to first of all source the raw wool. Sourcing the right raw wool is ll source the raw wool. Sourcing the right raw wool is vital and requires a good understanding between the vital and requires a good understanding between the raw wool, wool top, worsted yarn and fabric. Even thoraw wool, wool top, worsted yarn and fabric. Even though raw wool is the starting point for wool processing,ugh raw wool is the starting point for wool processing, the decision to source a certain type of raw wool is go the decision to source a certain type of raw wool is governed by the intended end use of the fibre. Fabric reverned by the intended end use of the fibre. Fabric requirements govern yarn requirements; yarn requiremquirements govern yarn requirements; yarn requirements govern top requirements, which in turn govern tents govern top requirements, which in turn govern the raw wool specifications. This relationship is represhe raw wool specifications. This relationship is represented in Figure 2.2.ented in Figure 2.2.

Fabric RequirementsFabric Requirements

Yarn RequirementsYarn Requirements

Top RequirementsTop Requirements

Raw Wool SpecificationsRaw Wool Specifications

Figure 2.2 End use governs raw wool purchase

Traditionally, translating the end use requirements tTraditionally, translating the end use requirements to raw wool requirements calls for considerable skills o raw wool requirements calls for considerable skills and experience. However, tools have been developeand experience. However, tools have been developed in recent years to facilitate this translation in the wd in recent years to facilitate this translation in the worsted industry. The notable examples of such tools orsted industry. The notable examples of such tools are TEAM formulae and Yarnspec software developeare TEAM formulae and Yarnspec software developed by the CSIRO Textile and Fibre Technology (formerld by the CSIRO Textile and Fibre Technology (formerly known as CSIRO Division of Wool Technology). y known as CSIRO Division of Wool Technology).

The TEAM formulae and applicationsThe TEAM formulae and applications► IntroductionIntroduction The bulk of Australian wool clip is now The bulk of Australian wool clip is now

scientifically sampled and the samples are scientifically sampled and the samples are objectively measured before sale for a range of objectively measured before sale for a range of properties. When objective measurements of properties. When objective measurements of greasy wool started in Australia in the early 70s, greasy wool started in Australia in the early 70s, only Yield (i.e. the amount of clean fibre that can only Yield (i.e. the amount of clean fibre that can be produced from the greasy wool), Vegetable be produced from the greasy wool), Vegetable Matters (VM) and Mean Fibre Diameter (in micron) Matters (VM) and Mean Fibre Diameter (in micron) were measured. While these measurements are were measured. While these measurements are very important for raw wool sales, they can not be very important for raw wool sales, they can not be used to adequately predict the processing used to adequately predict the processing performance of the measured wool. In the late performance of the measured wool. In the late 70s, technology for additional measurements of 70s, technology for additional measurements of raw wool became available. raw wool became available.

These include measurements of staple length, staplThese include measurements of staple length, staple strength and position of break using the ATLAS ine strength and position of break using the ATLAS instrument developed in CSIRO. The use of these meastrument developed in CSIRO. The use of these measurement results has become an indispensable tool surement results has become an indispensable tool for modern wool processing mills worldwide. There for modern wool processing mills worldwide. There are three major advantages associated with the use are three major advantages associated with the use of objectively measured and specified wool:of objectively measured and specified wool:

Maintaining control of the quality of wool deliverMaintaining control of the quality of wool delivered to the mill,ed to the mill,

Monitoring processing performance and quality Monitoring processing performance and quality management in the mill, and,management in the mill, and,

Optimising wool blend selection and minimising Optimising wool blend selection and minimising raw wool cost by taking advantage of the wool prraw wool cost by taking advantage of the wool price differentials.ice differentials.

To make use of these advantages, the wool processTo make use of these advantages, the wool processing mills should have some knowledge of the TEAM ing mills should have some knowledge of the TEAM prediction formulae. prediction formulae.

TEAM stands for Trials Evaluating Additional MeasuTEAM stands for Trials Evaluating Additional Measurements. These trials were conducted between 198rements. These trials were conducted between 1981 and 1988 by the former Australian Wool Corporati1 and 1988 by the former Australian Wool Corporation, the Australian Wool Testing Authority Ltd (AWTA on, the Australian Wool Testing Authority Ltd (AWTA Ltd) and the CSIRO Division of Wool Technology (noLtd) and the CSIRO Division of Wool Technology (now known as CSIRO Textile and Fibre Technology). Ow known as CSIRO Textile and Fibre Technology). Over 20 mills in 12 different countries were involved iver 20 mills in 12 different countries were involved in the trails. n the trails.

As a result of these trials, a series of prediction formAs a result of these trials, a series of prediction formulae (known as the TEAM formulae) were released, ulae (known as the TEAM formulae) were released, which can be used to predict the processing perforwhich can be used to predict the processing performance of fully measured wool in terms of the followimance of fully measured wool in terms of the following:ng:

- Hauteur - Hauteur - CV of Hauteur- CV of Hauteur

- Barbe - Barbe - Romaine- Romaine

Hauteur and Barbe are two different measures of thHauteur and Barbe are two different measures of the average fibre length. Their calculations may be exe average fibre length. Their calculations may be explained with the simple case of two fibres indicated iplained with the simple case of two fibres indicated in figure 2.3. The average length of these two fibres n figure 2.3. The average length of these two fibres may be different, depending on how we calculate it.may be different, depending on how we calculate it.

L1

A1

Fibre 1 Fibre 2

A2

L2

Figure 2.3 A simplified example for calculating the mean fibre length

For example, if L1 = 60 mm, L2 = 80 mm, A1 = 300 mFor example, if L1 = 60 mm, L2 = 80 mm, A1 = 300 m2, A2 = 400 m2 , then the above calculations will giv2, A2 = 400 m2 , then the above calculations will give: Ln = 70 mm, H = 71.4 mm, B = 72.8 mm.e: Ln = 70 mm, H = 71.4 mm, B = 72.8 mm.

.

2211

2211

)22()11(

2)22(1)11(

:)(

21

2211:)(sec

2

21:

22

densityfibreiswhere

LALA

LALA

LALA

LLALLAB

BarbelengthfibremeanbiasedWeight

AA

LALAHHauteurlengthfibremeanbiasedtionCross

LLLlengthfibremeanNumerical N

The numerical mean length is the true average length The numerical mean length is the true average length of the fibres. But it is difficult to obtain in practice. Haof the fibres. But it is difficult to obtain in practice. Hauteur length has been the most commonly used in thuteur length has been the most commonly used in the worsted industry. It can be easily obtained from coe worsted industry. It can be easily obtained from commercial instruments such as the Almeter and WIRA fmmercial instruments such as the Almeter and WIRA fibre length meter. ibre length meter.

Romaine is the term used in the worsted industry to dRomaine is the term used in the worsted industry to describe the amount of noil produced during the combescribe the amount of noil produced during the combing process, expressed as a percentage of the total (ning process, expressed as a percentage of the total (noil and combed sliver).oil and combed sliver).

These prediction formulae can be applied to any comThese prediction formulae can be applied to any com

bing wool with full objective measurements, whether bing wool with full objective measurements, whether that be individual lots or entire consignments, of whothat be individual lots or entire consignments, of wholly measured Australian wool. Computer softwares hally measured Australian wool. Computer softwares have also been developed to assist with the calculationve also been developed to assist with the calculations of the predicted results. s of the predicted results.

The general formula for HauteurThe general formula for Hauteur As discussed above, Hauteur is the (cross As discussed above, Hauteur is the (cross

section biased) mean length of fibres in the section biased) mean length of fibres in the wool top (a top is a sliver of parallel fibres, wool top (a top is a sliver of parallel fibres, obtained after the processes of scouring, obtained after the processes of scouring, carding and combing of greasy wool). It is carding and combing of greasy wool). It is normally measured by using an instrument normally measured by using an instrument called Almeter. Hauteur value has a significant called Almeter. Hauteur value has a significant effect on top price and the subsequent yarn effect on top price and the subsequent yarn properties. Hauteur has traditionally been properties. Hauteur has traditionally been estimated subjectively by wool buyers and estimated subjectively by wool buyers and processors.processors.

However, the TEAM project has demonstrated that However, the TEAM project has demonstrated that the theoretical Hauteur value may be predicted frothe theoretical Hauteur value may be predicted from measurements on raw wool according to the follm measurements on raw wool according to the following general formula:owing general formula:

H = 0.52 L + 0.47 S + 0.95 D - 0.19 M* - 0.45 V - 3.5H = 0.52 L + 0.47 S + 0.95 D - 0.19 M* - 0.45 V - 3.5

wherewhere H = Predicted Hauteur (mm)H = Predicted Hauteur (mm) L = Mean Staple Length (mm)L = Mean Staple Length (mm) S = Mean Staple Strength (N/ktex)S = Mean Staple Strength (N/ktex) D = Mean Fibre Diameter (micron)D = Mean Fibre Diameter (micron) M* = Adjusted Percentage of Middle Breaks M* = Adjusted Percentage of Middle Breaks

(%)(%) 3.5 = A Constant3.5 = A Constant

NB 1:NB 1: The value of M* is determined from the percentage of The value of M* is determined from the percentage of staples which broke in the middle portion (PM) as displayed staples which broke in the middle portion (PM) as displayed on an AWTA Test Certificate for Staple Length and Strength aon an AWTA Test Certificate for Staple Length and Strength as follows:s follows:

for PM values between 0 to 45% thenfor PM values between 0 to 45% then M* = 45M* = 45for PM values between 46 - 100% thenfor PM values between 46 - 100% then M* = PMM* = PM

For example, if a consignment has objective measurements For example, if a consignment has objective measurements of Mean Staple of Mean Staple Length (90mm), Mean Staple Strength (40 N/Length (90mm), Mean Staple Strength (40 N/ktex), Mean Fibre Diameter (21 microns), adjusted Percentagktex), Mean Fibre Diameter (21 microns), adjusted Percentage of Middle Breaks (50%), and Mean VM Base e of Middle Breaks (50%), and Mean VM Base (2.0%), then th(2.0%), then the Hauteur predicted from the general formula is:e Hauteur predicted from the general formula is:

H = 0.52 * 90 + 0.47 * 40 + 0.95 * 21 - 0.19 * 50 - 0.45 * 2.0 - 3.5 H = 0.52 * 90 + 0.47 * 40 + 0.95 * 21 - 0.19 * 50 - 0.45 * 2.0 - 3.5 = 71.7 (mm) = 71.7 (mm)

NB 2:NB 2: The TEAM formula for predicting Hauteur is baThe TEAM formula for predicting Hauteur is based on the processing results of 545 consignments csed on the processing results of 545 consignments combed at 20 different mills worldwide. Raw wool teombed at 20 different mills worldwide. Raw wool test data for the consignments fell into the following rst data for the consignments fell into the following ranges:anges:

Mean Staple LengthMean Staple Length 59 - 123 mm59 - 123 mmMean Staple StrengthMean Staple Strength 23 - 60 N/ktex23 - 60 N/ktexMean Fibre DiameterMean Fibre Diameter 17 - 31 microns17 - 31 micronsVM BaseVM Base 0.1 - 10.0%0.1 - 10.0%

Application of the above formula to data which falls Application of the above formula to data which falls outside these ranges should be treated with cautiooutside these ranges should be treated with caution.n.

The mill adjustment factorThe mill adjustment factor(( 工厂修正因数工厂修正因数 ))

All wool processing mills are different. They mAll wool processing mills are different. They may use different raw materials and have differeay use different raw materials and have different processing machinery installed. While the gnt processing machinery installed. While the general formula for Hauteur gives a satisfactory eneral formula for Hauteur gives a satisfactory general prediction for mills, as adjustment to rgeneral prediction for mills, as adjustment to reflect performance for individual mills are ofteeflect performance for individual mills are often needed, particularly if a mill produces tops tn needed, particularly if a mill produces tops that are consistently longer or shorter than the hat are consistently longer or shorter than the length predicted by the general formula. The Tlength predicted by the general formula. The TEAM prediction represents the world average EAM prediction represents the world average of processing performance.of processing performance.

The constant (-3.5) in the TEAM formula can be adjustThe constant (-3.5) in the TEAM formula can be adjusted when a mill has monitored the processing performed when a mill has monitored the processing performance of 10 to 15 consignments. The mean value of the ance of 10 to 15 consignments. The mean value of the difference between the Hauteur predicted by the TEAdifference between the Hauteur predicted by the TEAM formula and the actual Hauteur achieved can be caM formula and the actual Hauteur achieved can be calculated. This mean value then becomes the "Mill Corlculated. This mean value then becomes the "Mill Correction Factor" and is added or subtracted from the crection Factor" and is added or subtracted from the constant in the TEAM formula. onstant in the TEAM formula.

If changes are made to the mill processing conditions,If changes are made to the mill processing conditions, such as the installation of new machinery, difference such as the installation of new machinery, differences will be expected and alterations to the Mill Correctis will be expected and alterations to the Mill Correction Factor will be necessary. It is also worth noting thaon Factor will be necessary. It is also worth noting that the Mill Adjustment Factors are commercially sensitt the Mill Adjustment Factors are commercially sensitive, individual traders are unlikely to be advised of thive, individual traders are unlikely to be advised of them by the commissioning combers.em by the commissioning combers.

An example of calculating a Mill Correction Factor is An example of calculating a Mill Correction Factor is given in Table 2.1 below:given in Table 2.1 below:

Processors can also calculate their own tailor-madProcessors can also calculate their own tailor-made 'mill specific prediction formula' using a regressioe 'mill specific prediction formula' using a regression equation based on the greasy wool characteristicn equation based on the greasy wool characteristics found to be the most important for the mill. Any sts found to be the most important for the mill. Any standard computer package containing regression anandard computer package containing regression analysis can do this. However, it must be stressed that alysis can do this. However, it must be stressed that new formulae should only be developed on large danew formulae should only be developed on large databases. When a small database is available, the abtabases. When a small database is available, the above approach for calculating the Mill Correction Facove approach for calculating the Mill Correction Factor should suffice.tor should suffice.

TEAM formulae for the predictions of CV of Hauteur, TEAM formulae for the predictions of CV of Hauteur, Romaine & BarbeRomaine & Barbe

Besides the formula for the prediction of Hauteur, the Besides the formula for the prediction of Hauteur, the TEAM projects also developed prediction formulae for TEAM projects also developed prediction formulae for the Coefficient of Variation of Hauteur, the Romaine athe Coefficient of Variation of Hauteur, the Romaine and the Barbe.nd the Barbe.

The CV of Hauteur (CVH) is an important feature of the The CV of Hauteur (CVH) is an important feature of the top length distribution, since it may affect the subseqtop length distribution, since it may affect the subsequent drafting and spinning performances. Romaine is uent drafting and spinning performances. Romaine is the term used to describe the quantity of noil expressthe term used to describe the quantity of noil expressed as a percentage in relation to the combined quantied as a percentage in relation to the combined quantity of top and noil. It reflects the combing efficiency. Bty of top and noil. It reflects the combing efficiency. Barbe is a weight biased measurement of fibre length iarbe is a weight biased measurement of fibre length in the top and is not as widely used as Hauteur.n the top and is not as widely used as Hauteur.

The three prediction formulae are:The three prediction formulae are:

CVH = 0.12 L - 0.41 S - 0.35 D + 0.20 M* + 49.3CVH = 0.12 L - 0.41 S - 0.35 D + 0.20 M* + 49.3Romaine = (-0.11) L - 0.14 S - 0.35 D + 0.94 V + 27.Romaine = (-0.11) L - 0.14 S - 0.35 D + 0.94 V + 27.

77Barbe (B) = 0.73 L + 0.32 S + 0.96 D - 0.51 V - 0.08Barbe (B) = 0.73 L + 0.32 S + 0.96 D - 0.51 V - 0.08

6 M* - 5.36 M* - 5.3

The symbols L, S, D, M* and V are as previously definThe symbols L, S, D, M* and V are as previously defined for TEAM Hauteur Formula. The above three formed for TEAM Hauteur Formula. The above three formulae can also be adjusted to any particular mill in the ulae can also be adjusted to any particular mill in the same way as the TEAM Hauteur Formula, by adding osame way as the TEAM Hauteur Formula, by adding or subtracting a mill adjustment factor to the constantr subtracting a mill adjustment factor to the constants, when appropriate.s, when appropriate.

It is also worth noting that the TEAM formulae have It is also worth noting that the TEAM formulae have been developed for general use and therefore do nbeen developed for general use and therefore do not take into account variations in processing perforot take into account variations in processing performance between and within specific mills. If the premance between and within specific mills. If the predictions are outside the following ranges, care musdictions are outside the following ranges, care must be taken in interpreting the prediction results:t be taken in interpreting the prediction results:

Hauteur:Hauteur: Less than 55 mm and greater than 80 Less than 55 mm and greater than 80 mmmmCVHa:CVHa: Less than 40% and greater than 55%Less than 40% and greater than 55%Romaine*Romaine* Less than 3% and greater than 12%Less than 3% and greater than 12%

In summary, the TEAM project has demonstrated the iIn summary, the TEAM project has demonstrated the importance of additional measurements on raw wool. mportance of additional measurements on raw wool. Without these additional staple measurements, the prWithout these additional staple measurements, the prediction of Hauteur and Romaine are not as accurate ediction of Hauteur and Romaine are not as accurate and it is impossible to predict CVHa or other top lengtand it is impossible to predict CVHa or other top length distribution specifications important to the spinner. h distribution specifications important to the spinner. Many topmakers and spinners worldwide are willing tMany topmakers and spinners worldwide are willing to pay premiums to have their raw wool measured for so pay premiums to have their raw wool measured for staple length, strength and position of break. Wool usetaple length, strength and position of break. Wool users, whether mills, exporters, or traders, should maintairs, whether mills, exporters, or traders, should maintain a record of the greasy wool measurement data and tn a record of the greasy wool measurement data and the difference between the processing characteristics he difference between the processing characteristics predicted by the TEAM formulae and those actually acpredicted by the TEAM formulae and those actually achieved for each processing consignment. By doing this,hieved for each processing consignment. By doing this, a 'mill specific' database can be built and used to imp a 'mill specific' database can be built and used to improve the predictions for that mill.rove the predictions for that mill.

Applications of TEAM formulaeApplications of TEAM formulae The TEAM formulae have a number of applications. TThe TEAM formulae have a number of applications. T

he major ones include assisting mill quality control ahe major ones include assisting mill quality control and raw wool specification.nd raw wool specification.

When a wool processing mill uses fully measured AusWhen a wool processing mill uses fully measured Australian wool, the mill performance can be monitored tralian wool, the mill performance can be monitored with the help of TEAM formulae. For instance, the diffwith the help of TEAM formulae. For instance, the differences between actual and predicted Hauteur of the erences between actual and predicted Hauteur of the tops produced in a mill can be plotted on a time-serietops produced in a mill can be plotted on a time-series graph. By setting boundary limits for the size of the s graph. By setting boundary limits for the size of the deviations, a control chart can be established to indicdeviations, a control chart can be established to indicate whether the mill's topmaking process is 'in contrate whether the mill's topmaking process is 'in control'. ol'.

Another impartant application of TEAM is in assisting Another impartant application of TEAM is in assisting with raw wool specification. As mentioned in the overwith raw wool specification. As mentioned in the overview, producing the right worsted yarn requires the riview, producing the right worsted yarn requires the right tops, which in turn require the right raw wool. To ght tops, which in turn require the right raw wool. To explain this point, let's assume that we (a spinner) neexplain this point, let's assume that we (a spinner) need to spin 2/52 Nm weaving yarns for a fabric manufaed to spin 2/52 Nm weaving yarns for a fabric manufacturer. The question is what is the right raw material fcturer. The question is what is the right raw material for efficient spinning of this yarn?or efficient spinning of this yarn?

To answer this question, we need to get the right tops To answer this question, we need to get the right tops first. The two critical parameters for a wool top are thfirst. The two critical parameters for a wool top are the average fibre diameter and length. Determining the e average fibre diameter and length. Determining the average fibre diameter is relatively easy, because the faverage fibre diameter is relatively easy, because the fibre should be fine enough to ensure adequate averagibre should be fine enough to ensure adequate average number of fibres in yarn cross section. As discussed ie number of fibres in yarn cross section. As discussed in the module on yarn evenness, the minimum numben the module on yarn evenness, the minimum number of fibres in the cross section of a worsted yarn shoulr of fibres in the cross section of a worsted yarn should be about 40. Below this limit, yarn quality drops rapid be about 40. Below this limit, yarn quality drops rapidly and spinning becomes inefficient due to increased dly and spinning becomes inefficient due to increased ends-down. Table 2.2 gives the approximate diameter ends-down. Table 2.2 gives the approximate diameter range used in majority of commercial weaving and knrange used in majority of commercial weaving and knitting yarns, and the corresponding average number oitting yarns, and the corresponding average number of fibres in yarn cross section.f fibres in yarn cross section.

So for a 52/2 Nm weaving yarn, if we wish to So for a 52/2 Nm weaving yarn, if we wish to have 40 fibres on average in the singles yarn chave 40 fibres on average in the singles yarn cross section, then the average diameter of thross section, then the average diameter of the wool should be:e wool should be:

)(21

,40

2.199172

micronD

D

Now that the average fibre diameter is decided, thNow that the average fibre diameter is decided, the appropriate Hauteur (mean fibre length) of the toe appropriate Hauteur (mean fibre length) of the top is needed. For this purpose, we may check previop is needed. For this purpose, we may check previous record as to the likely Hauteur value for a given fus record as to the likely Hauteur value for a given fibre diameter (micron) processed on our machineribre diameter (micron) processed on our machinery. In the absence of previous record, experience valy. In the absence of previous record, experience values given in Table 2.3 can be used as a starting poiues given in Table 2.3 can be used as a starting point.nt.

From this Table, a Hauteur value of at least 68 to From this Table, a Hauteur value of at least 68 to 69 mm is necessary for the 21 micron wool. If our 69 mm is necessary for the 21 micron wool. If our machinery is in good condition, the minimum Hamachinery is in good condition, the minimum Hauteur can be used. Otherwise, higher Hauteur valuteur can be used. Otherwise, higher Hauteur values should be used to ensure efficient spinning. Fues should be used to ensure efficient spinning. For the current example, we can set the Hauteur vor the current example, we can set the Hauteur value at 70 mm.alue at 70 mm.

By now we know that to spin a 2/52 Nm weaving yarBy now we know that to spin a 2/52 Nm weaving yarn, the top specifications should have an average min, the top specifications should have an average micron value of 21, and a Hauteur value of 70 mm. The cron value of 21, and a Hauteur value of 70 mm. The next step is to translate these values into raw wool next step is to translate these values into raw wool specifications. Again determining the micron of the specifications. Again determining the micron of the raw wool is the first necessary step. In a typical top-raw wool is the first necessary step. In a typical top-making process, it is normal that the average fibre making process, it is normal that the average fibre diameter increases by about 0.3 micron after top-mdiameter increases by about 0.3 micron after top-making, the reason for this is briefly discussed in the saking, the reason for this is briefly discussed in the section on combing. Again an individual mill's past pection on combing. Again an individual mill's past performance should be looked at in terms of diameterformance should be looked at in terms of diameter increase (occasionally, fibre diameter increase caer increase (occasionally, fibre diameter increase can be up to 1 micron). Keeping this in mind, the avern be up to 1 micron). Keeping this in mind, the average diameter of the raw wool should be finer than tage diameter of the raw wool should be finer than that of the top.hat of the top.

We can use 20.7 micron for this example. Now that tWe can use 20.7 micron for this example. Now that the average micron for the raw wool is determined, whe average micron for the raw wool is determined, we need to know other raw wool characteristics, such e need to know other raw wool characteristics, such as staple length, staple strength etc. This is where thas staple length, staple strength etc. This is where the TEAM formulae play an important role. Using the Te TEAM formulae play an important role. Using the TEAM formulae, we can play with different combinatiEAM formulae, we can play with different combinations of values for the parameters in the TEAM predictons of values for the parameters in the TEAM prediction formula for Hauteur, such as different staple lenion formula for Hauteur, such as different staple length, staple strength, mid breaks etc, to get the right gth, staple strength, mid breaks etc, to get the right Hauteur value (70 mm in this example). Hauteur value (70 mm in this example).

One possible combination is:One possible combination is:Mean fibre diameter (D): 20.7 micron (already determined)Mean fibre diameter (D): 20.7 micron (already determined)Mean staple length (L): 87 mmMean staple length (L): 87 mmMean staple strength (S): 40 N/texMean staple strength (S): 40 N/texVegetable matter base (V): 1%Vegetable matter base (V): 1%Percentage of mid breaks: 50%Percentage of mid breaks: 50%

Using the TEAM formula for Hauteur,Using the TEAM formula for Hauteur,

H = 0.52 L + 0.47 S + 0.95 D - 0.19 M* - 0.45 V H = 0.52 L + 0.47 S + 0.95 D - 0.19 M* - 0.45 V - 3.5- 3.5

H = 0.52 x 87 + 0.47 x 40 + 0.95 x 20.7 - 0.19 H = 0.52 x 87 + 0.47 x 40 + 0.95 x 20.7 - 0.19 x 50 - 0.45 x 1 - 3.5 = 70.3 (mm) x 50 - 0.45 x 1 - 3.5 = 70.3 (mm)

It should be pointed out here that the Hauteur valIt should be pointed out here that the Hauteur value predicted by the TEAM equation is an average ue predicted by the TEAM equation is an average value. This means half of the actual Hauteur valuevalue. This means half of the actual Hauteur values may fall above the prediction, and the other half s may fall above the prediction, and the other half fall below prediction. In other words, there is a 50fall below prediction. In other words, there is a 50% probability for the actual Hauteur to be less tha% probability for the actual Hauteur to be less than that required. This is not an acceptable situation that required. This is not an acceptable situation. In practice, it is common to ensure that the raw n. In practice, it is common to ensure that the raw wool purchased will perform better than predictewool purchased will perform better than predicted, so that there is only about 5% chance of not med, so that there is only about 5% chance of not meeting the requirement.eting the requirement.

It should also be pointed out though that in additioIt should also be pointed out though that in addition to average fibre diameter and fibre length, fibre din to average fibre diameter and fibre length, fibre diameter and length variations, short fibre content in tameter and length variations, short fibre content in the top, are also important considerations. Furthermhe top, are also important considerations. Furthermore, the amount of noil produced during combing is ore, the amount of noil produced during combing is another important consideration. The value of combanother important consideration. The value of combing noil is only about 30% of the value of a top. If we ing noil is only about 30% of the value of a top. If we apply the TEAM formulae for Hauteur CV and for Roapply the TEAM formulae for Hauteur CV and for Romaine to our example, we get:maine to our example, we get:

CVH = 0.12 L - 0.41 S - 0.35 D + 0.20 M* + 49.3CVH = 0.12 L - 0.41 S - 0.35 D + 0.20 M* + 49.3 = 0.12 x 87 - 0.41 x 40 - 0.35 x 20.7 + 0.20 x 50 + 49.3= 0.12 x 87 - 0.41 x 40 - 0.35 x 20.7 + 0.20 x 50 + 49.3 = 46.1 (%)= 46.1 (%)

Romaine = (-0.11) L - 0.14 S - 0.35 D + 0.94 V + 27.7Romaine = (-0.11) L - 0.14 S - 0.35 D + 0.94 V + 27.7 = (- 0.11) x 87 - 0.14 x 40 - 0.35 x 20.7 + 0.94 x 1 + 27.= (- 0.11) x 87 - 0.14 x 40 - 0.35 x 20.7 + 0.94 x 1 + 27.

77 = 6.2%= 6.2%

The CV of Hauteur (CVH) may affect drafting performaThe CV of Hauteur (CVH) may affect drafting performance. Too high a CVH may lead to poor evenness of yarnce. Too high a CVH may lead to poor evenness of yarns. For this reason, the experiences have shown that Cns. For this reason, the experiences have shown that CVH value should be less than 50%. The 46.1% CVH for VH value should be less than 50%. The 46.1% CVH for our example is below this figure. If we wish to have a lour example is below this figure. If we wish to have a lower CVH than 46.1%, we can change some parameteower CVH than 46.1%, we can change some parameter in the CVH formula, bearing in mind that any change r in the CVH formula, bearing in mind that any change will also affect the predicted Hauteur and Romaine valwill also affect the predicted Hauteur and Romaine values. As indicated earlier, computer packages are availues. As indicated earlier, computer packages are available to assist with these calculations.able to assist with these calculations.

On the basis of this information, a specification of the On the basis of this information, a specification of the raw wool required for producing the 2/52 Nm weaving raw wool required for producing the 2/52 Nm weaving yarn can be worked out. With a proper specification, wyarn can be worked out. With a proper specification, we will get the right raw materials. Once we get the righe will get the right raw materials. Once we get the right raw materials, we can start the processing. The first t raw materials, we can start the processing. The first processing stage is scouring, which is discussed next.processing stage is scouring, which is discussed next.

ScouringScouring(( 洗毛洗毛 ))

A number of processes are carried out in a scouring A number of processes are carried out in a scouring mill, including:mill, including:

preparation of wool for scouring by opening and preparation of wool for scouring by opening and blending, blending,

scouring itself, and,scouring itself, and,drying of scoured wool. drying of scoured wool.

Raw wool contains a number of impurities. Some of tRaw wool contains a number of impurities. Some of the impurities are removed in scouring, others are rehe impurities are removed in scouring, others are removed in further processing. Table 2.4 lists the impurmoved in further processing. Table 2.4 lists the impurities that are found in raw wool, and the ways of remities that are found in raw wool, and the ways of removing these impurities. Figure 2.4 gives the average coving these impurities. Figure 2.4 gives the average compositions of Australian merino and crossbred fleecompositions of Australian merino and crossbred fleeces.es.

Figure 2.4 Average composition of a Merino fleece (a) and Australian crossbred (b) (Humphries 1996, p.90 [courtesy of International Wool Secretariat])

The main objectives of scouring are:The main objectives of scouring are:To remove various impurities (grease, suint, mineTo remove various impurities (grease, suint, mine

ral) from wool in such a way that the scoured wooral) from wool in such a way that the scoured wool is clean, full and open (with little felting of wool). l is clean, full and open (with little felting of wool).

To leave a small amount (about 0.5%) of residual To leave a small amount (about 0.5%) of residual grease on the wool to facilitate further mechanicagrease on the wool to facilitate further mechanical processing.l processing.

Wool grease and suint are the key impurities removWool grease and suint are the key impurities removed during scouring in the so called aqueous emulsioed during scouring in the so called aqueous emulsion scouring process using detergent and hot water. Gn scouring process using detergent and hot water. Grease can also be removed by dissolving in organic srease can also be removed by dissolving in organic solvent using the solvent scouring process. But beforolvent using the solvent scouring process. But before we talk about the actual scouring processes, we ne we talk about the actual scouring processes, we need to understand the chemistry of these impurities.eed to understand the chemistry of these impurities.

► The chemistry of impuritiesThe chemistry of impurities(( 杂质杂质 ))SuintSuint

Suint consists of potassium salts of the various lowSuint consists of potassium salts of the various lower fatty and amino acids, plus some inorganic salts. er fatty and amino acids, plus some inorganic salts. Like the table salt used for cooking, suint is soluble iLike the table salt used for cooking, suint is soluble in water, particularly warm water (~ 30oC). So removn water, particularly warm water (~ 30oC). So removal of suint in aqueous scouring is not a problem.al of suint in aqueous scouring is not a problem.

Grease/WaxGrease/Wax Grease is a mixture of higher fatty acids (CnHmCOOGrease is a mixture of higher fatty acids (CnHmCOO

H, or RCOOH) and alcohols. There is about 2 - 15% frH, or RCOOH) and alcohols. There is about 2 - 15% free fatty acid in raw grease. At pH > 9, free fatty acid cee fatty acid in raw grease. At pH > 9, free fatty acid can be saponified (turned into soap by decompositioan be saponified (turned into soap by decomposition with alkali). The Saponifying (soap making) procesn with alkali). The Saponifying (soap making) process is indicated below:s is indicated below:

Na2CO3 + 2H2O ---> 2NaOH + H2CO3Na2CO3 + 2H2O ---> 2NaOH + H2CO3 NaOH + RCOOH ---> H2O + RCOONa (soap!)NaOH + RCOOH ---> H2O + RCOONa (soap!)

Grease has a relatively low melting point (38 to 43oGrease has a relatively low melting point (38 to 43oC). In aqueous scouring, it is important to raise the liC). In aqueous scouring, it is important to raise the liquor temperature above this value to facilitate greaquor temperature above this value to facilitate grease removal. Since grease usually forms a stable film se removal. Since grease usually forms a stable film around fibre surface. The attraction between grease around fibre surface. The attraction between grease and wool needs to be reduced to dislodge grease frand wool needs to be reduced to dislodge grease from fibre surface. In aqueous emulsion scouring, thiom fibre surface. In aqueous emulsion scouring, this is achieved with the help of scouring agents such as is achieved with the help of scouring agents such as detergents detergent

Vegetable matter (VM)Vegetable matter (VM)(( 草杂草杂 ))

Vegetable matter is cellulose material. Scouring rVegetable matter is cellulose material. Scouring removes very little vegetable matter from wool. A emoves very little vegetable matter from wool. A small amount of VM is removed during the pre-scsmall amount of VM is removed during the pre-scour opening, and the rest is removed in the post-sour opening, and the rest is removed in the post-scour carding and combing.cour carding and combing.

► The scouring agentsThe scouring agents(( 洗涤剂洗涤剂 )) Detergent (Natural or Synthetic)Detergent (Natural or Synthetic)

Detergents are surfactants or surface-active agents. Detergents are surfactants or surface-active agents. Surfactant molecules have a hydrophilic head and a Surfactant molecules have a hydrophilic head and a hydrophobic tail as indicated in figure 2.5 below.hydrophobic tail as indicated in figure 2.5 below.

In the presence of an interface (eg. air/water, greaseIn the presence of an interface (eg. air/water, grease/water), the surfactant molecules are adsorbed at th/water), the surfactant molecules are adsorbed at the interface due to differing polarities of head and tail.e interface due to differing polarities of head and tail. This then lowers the interfacial surface tension. The This then lowers the interfacial surface tension. The importance of reducing interfacial surface tension in importance of reducing interfacial surface tension in scouring will be discussed later.scouring will be discussed later.

Hydrophobic tail Hydrophilic head

Fig. 2.5: The molecule of a surfactant with a hydrophilic head and a hydrophobic tail

The two main types of detergent are natural soap and The two main types of detergent are natural soap and synthetic detergent. synthetic detergent.

Natural soap is made from action of alkali with a fatty Natural soap is made from action of alkali with a fatty acid. It can also be created by the saponifying process acid. It can also be created by the saponifying process in scouring, as indicated in the section on the chemistin scouring, as indicated in the section on the chemistry of impurities. The water for wool scouring should bry of impurities. The water for wool scouring should be soft water. Synthetic detergents are not destroyed be soft water. Synthetic detergents are not destroyed by lime salts. They can be used under neutral pH (so lesy lime salts. They can be used under neutral pH (so less wool damage) but scouring is more efficient in slight s wool damage) but scouring is more efficient in slight alkalinity. Synthetic detergents have very high detergalkalinity. Synthetic detergents have very high detergent efficiency, even at low concentrations (when scouent efficiency, even at low concentrations (when scouring fabrics in the finishing stage, this may be a drawbring fabrics in the finishing stage, this may be a drawback. Because a thorough degreasing often leads to a ack. Because a thorough degreasing often leads to a worsening fabric handle. Most modern scouring mills worsening fabric handle. Most modern scouring mills use synthetic detergents rather than natural soaps.use synthetic detergents rather than natural soaps.

WaterWater The water used in aqueous scouring should be of miThe water used in aqueous scouring should be of mi

nimum hardness, particularly when natural soap is nimum hardness, particularly when natural soap is used as the detergent. Hard water containing calciuused as the detergent. Hard water containing calcium salts (lime) will reduce the effectiveness of soap: m salts (lime) will reduce the effectiveness of soap:

soap + calcium salts (lime) = lime soap (insoluble!)soap + calcium salts (lime) = lime soap (insoluble!)

The insoluble lime soap can adhere firmly to wool aThe insoluble lime soap can adhere firmly to wool and cause difficulty in the subsequent carding, combnd cause difficulty in the subsequent carding, combing and dyeing.ing and dyeing.

Aqueous wool scouring consumes a large quantity oAqueous wool scouring consumes a large quantity of water. One kilo of greasy wool may require up to 2f water. One kilo of greasy wool may require up to 20 litres of water for scouring. If a scour has a capacit0 litres of water for scouring. If a scour has a capacity of 1,200 kg/hour, then a staggering 24,000 litres of y of 1,200 kg/hour, then a staggering 24,000 litres of water will be consumed in every hour of the scour's water will be consumed in every hour of the scour's working life. Researchers and industrialists have put working life. Researchers and industrialists have put considerable effort into reducing water consumptioconsiderable effort into reducing water consumption in scouring and treating scouring effluent. n in scouring and treating scouring effluent. AlkaliAlkali(( 碱碱 ))

The addition of alkali adds to the efficiency of scouriThe addition of alkali adds to the efficiency of scouring. It is usually in the form of sodium carbonate (song. It is usually in the form of sodium carbonate (soda ash) rather than caustic alkali, since caustic alkalda ash) rather than caustic alkali, since caustic alkali attacks wool. As mentioned before, alkali reacts wii attacks wool. As mentioned before, alkali reacts with the fatty acid (in grease) to produce soap in scourth the fatty acid (in grease) to produce soap in scouring. ing.

► The principle of aqueous emulsionThe principle of aqueous emulsion(( 水乳状液水乳状液 )) sc scouringouring

As mentioned earlier, aqueous scouring As mentioned earlier, aqueous scouring removes suint and grease mainly from wool, removes suint and grease mainly from wool, and suint removal is relatively easy, because it and suint removal is relatively easy, because it is soluble in water. Grease removal is more is soluble in water. Grease removal is more complicated, and this section focuses on how complicated, and this section focuses on how grease gets removed from wool in scouring. grease gets removed from wool in scouring. The role played by detergent is highlighted in The role played by detergent is highlighted in this section. Generally speaking, there are this section. Generally speaking, there are three stages involved in grease removal during three stages involved in grease removal during aqueous scouring. aqueous scouring.

Stage 1Stage 1

This stage has the following functions:This stage has the following functions:-- Wet out greasy woolWet out greasy wool-- Raise temperature above grease melting pointRaise temperature above grease melting point-- Add alkali (demands of wool, saponification,Add alkali (demands of wool, saponification,

optimum scouring pH)optimum scouring pH) -- Deliver detergent molecules to fibres by liquor flDeliver detergent molecules to fibres by liquor fl

ow ow and diffusionand diffusion

Wetting is the first necessary step for aqueous scouriWetting is the first necessary step for aqueous scouring. The more water molecules on fibre surface, the bng. The more water molecules on fibre surface, the better the fibre wetting. How easily a greasy wool can etter the fibre wetting. How easily a greasy wool can get wetted depends upon the fibre/water/air interfaget wetted depends upon the fibre/water/air interfacial surface tensions. Ironically, the wettability of wacial surface tensions. Ironically, the wettability of water on wool textiles is quite poor. When a drop of watter on wool textiles is quite poor. When a drop of water is placed on a surface of wool fibres, the water droer is placed on a surface of wool fibres, the water drop does not spread out on the surface. The attraction p does not spread out on the surface. The attraction between molecules in the water drop is quite strong, between molecules in the water drop is quite strong, which tends to keep the water molecules together in which tends to keep the water molecules together in a ball shape. To increase the wettability of water, its a ball shape. To increase the wettability of water, its surface tension needs to be reduced so that the watsurface tension needs to be reduced so that the water can spread out on the fibre surface to achieve gooer can spread out on the fibre surface to achieve good wetting of the fibre. d wetting of the fibre.

Figure 2.6 depicts poor and good wetting behaviour Figure 2.6 depicts poor and good wetting behaviour of water on a surface.of water on a surface.

..

(poor wetting) (good wetting)

Figure 2.6 Poor and good wetting behaviour of water on a surface

In relation to scouring greasy wool, we are looking at In relation to scouring greasy wool, we are looking at a wool/liquor/air system as shown in figure 2.7 beloa wool/liquor/air system as shown in figure 2.7 beloww

In equlibrium, the three interfacial surface tensions sIn equlibrium, the three interfacial surface tensions should be balanced. We havehould be balanced. We have

.T

T-T= ,*T+T=Tal

WlwaalWlwa coscos

Figure 2.7 Wetting the wool fibre with a drop of liquor - the wool/liquor/air system

This simple relationship can be used to explain how dThis simple relationship can be used to explain how detergent helps the wetting process. Detergents are suretergent helps the wetting process. Detergents are surfactants, which have the power of reducing surface tefactants, which have the power of reducing surface tension. When detergent is added to the liquor, it greatlnsion. When detergent is added to the liquor, it greatly reduces the interfacial surface tension between the ly reduces the interfacial surface tension between the liquor and its contact surfaces, such as air and wool in iquor and its contact surfaces, such as air and wool in this case. Therefore, with the addition of detergent, bthis case. Therefore, with the addition of detergent, both Twl and Tal will be reduced. According to the abooth Twl and Tal will be reduced. According to the above equations, should decrease when Twl and Tal reduve equations, should decrease when Twl and Tal reduce. A lower means the water drop is more spread out ce. A lower means the water drop is more spread out on the wool fibre, hence better wetting. Therefore, froon the wool fibre, hence better wetting. Therefore, from the change in , we can tell how detergents help to wm the change in , we can tell how detergents help to wet the wool fibres. In household washing, if you add det the wool fibres. In household washing, if you add detergent to the water in the washing machine and theetergent to the water in the washing machine and then put the clothing items in, the clothing items will get in put the clothing items in, the clothing items will get immersed into the water more quickly than when thermmersed into the water more quickly than when there is no detergent in the water. e is no detergent in the water.

Stage 2Stage 2This is the key stage, and has the following functions:This is the key stage, and has the following functions:

Form surface film of detergent molecules Form surface film of detergent molecules Gather grease into droplets Gather grease into droplets Sweep droplets from fibre by liquor flowSweep droplets from fibre by liquor flow

In this stage, we are looking at a grease/wool/liquor syIn this stage, we are looking at a grease/wool/liquor system as shown in figure 2.8 below.stem as shown in figure 2.8 below.

Figure 2.8 Removal of grease from wool - the grease/wool/liquor system

Again, in equlibrium, we haveAgain, in equlibrium, we have

.T

T-T= *T+T=T

gl

wlwgglwgwl cos),180cos(

In the presence of detergent (surfactant) in the liquor, In the presence of detergent (surfactant) in the liquor, both Twl and Tgl will be reduced. According to the abboth Twl and Tgl will be reduced. According to the above equations, cosф should increase (and ф should dove equations, cosф should increase (and ф should decrease) when Twl and Tgl reduce. A gradually reduciecrease) when Twl and Tgl reduce. A gradually reducing ф would mean the grease is rolling up as droplets. ng ф would mean the grease is rolling up as droplets. When ф becomes zero, the grease ball would come ofWhen ф becomes zero, the grease ball would come off the wool fibre easily with the help of liquor flow. Whf the wool fibre easily with the help of liquor flow. When the grease droplets are detached from the wool, then the grease droplets are detached from the wool, they are surrounded by surfactant molecules. The hydrey are surrounded by surfactant molecules. The hydrophobic tails of the surfactant molecules will stick to tophobic tails of the surfactant molecules will stick to the grease, while the hydrophilic heads will stay in the he grease, while the hydrophilic heads will stay in the liquor. In addition, the like-charged hydrophobic healiquor. In addition, the like-charged hydrophobic heads on the surfaces of the grease droplets will be mutuds on the surfaces of the grease droplets will be mutually repulsive. This keeps the grease droplets separate ally repulsive. This keeps the grease droplets separate and suspended in the liquor, without aggregating and and suspended in the liquor, without aggregating and re-depositing back onto the fibre surface. re-depositing back onto the fibre surface.

TThe grease removal process can also be described he grease removal process can also be described without using the force balance equations given abwithout using the force balance equations given above. When the scouring liquor containing surfactant ove. When the scouring liquor containing surfactant molecules comes in contact with grease particles omolecules comes in contact with grease particles on fibre surface, the water-hating tails of surfactant n fibre surface, the water-hating tails of surfactant molecules will compete for places in the grease, bemolecules will compete for places in the grease, because they don’t like water molecules in the liquocause they don’t like water molecules in the liquor. The competition gets tougher and tougher as morr. The competition gets tougher and tougher as more and more surfactant molecules try to stick their tae and more surfactant molecules try to stick their tails into the oil. They only way of easing the tension ils into the oil. They only way of easing the tension of competition is to create more surface of grease, of competition is to create more surface of grease, and the only way of doing this is by breaking the greand the only way of doing this is by breaking the grease apart and lifting the grease away from fibre surfase apart and lifting the grease away from fibre surface gradually.ace gradually.

Once removed from the fibre surface, the grease will bOnce removed from the fibre surface, the grease will be surrounded by the surfactant molecules with the taile surrounded by the surfactant molecules with the tails inside the grease. In the mean time, the fibre surface s inside the grease. In the mean time, the fibre surface originally occupied by the grease will now be occupieoriginally occupied by the grease will now be occupied by the surfactant molecules, again with their tails stid by the surfactant molecules, again with their tails sticking to the fibres and heads inside the liquor. The likcking to the fibres and heads inside the liquor. The like-charged heads on the fibre surface and on the grease-charged heads on the fibre surface and on the grease surface repel each other so they try to stay away froe surface repel each other so they try to stay away from each other, thus preventing the grease from being rm each other, thus preventing the grease from being re-deposited on the fibre surface. Similarly, the grease e-deposited on the fibre surface. Similarly, the grease particles broken apart by the surfactant will stay apart particles broken apart by the surfactant will stay apart as well. Therefore, after scouring, the scouring liquor as well. Therefore, after scouring, the scouring liquor becomes an emulsion of suspended oil or grease partibecomes an emulsion of suspended oil or grease particles, which can be easily removed by rinsing. For this rcles, which can be easily removed by rinsing. For this reason, aqueous scouring is also known as emulsion sceason, aqueous scouring is also known as emulsion scouring or aqueous emulsion scouring. In other words, ouring or aqueous emulsion scouring. In other words, surfactant helps to emulsify the oil or grease to facilitasurfactant helps to emulsify the oil or grease to facilitate its removal. Similar principle applies to house-hold te its removal. Similar principle applies to house-hold washing.washing.

The processes of grease or oil removal with The processes of grease or oil removal with surfactant are illustrated below in Figure 2.9.surfactant are illustrated below in Figure 2.9.

Fibre

grease

Water only With surfactant

Figure 2.9 The process of grease removal from wool

Stage 3Stage 3

This is the final stage which has the following functions:This is the final stage which has the following functions:

- - Remove excess detergent and alkali from wool Remove excess detergent and alkali from wool -- Remove contaminants from liquorRemove contaminants from liquor

Rinsing with fresh water achieves the first function. Rinsing with fresh water achieves the first function. Removing contaminants from liquor requires compleRemoving contaminants from liquor requires complex effluent treatment system. In fact, a well-known dilx effluent treatment system. In fact, a well-known dilemma of wool scouring is the environment friendlineemma of wool scouring is the environment friendliness-versus-cost compromise. ss-versus-cost compromise.

► Commercial aqueous scouring systemsCommercial aqueous scouring systems 1.The basic configuration1.The basic configuration

In a typical process of aqueous emulsion In a typical process of aqueous emulsion scouring, 5 or 6 scouring bowls are used. Figure scouring, 5 or 6 scouring bowls are used. Figure 2.10 gives a simplified representation of a 6-2.10 gives a simplified representation of a 6-bowl aqueous wool scouring process. bowl aqueous wool scouring process.

Bowl 2 Bowl 3 Bowl 4 Bowl 5 Bowl 6

Settlingtank

Centrifuge

Effluent TreatmentGrease Recovery

Greasywool in

Scouredwool todryer

Fresh water in(Scour) (Scour) (Scour) (Rinse) (Rinse)

Scouring agents

Bowl 1(De suint)

Figure 2.10 A 6-bowl aqueous scouring process

The first de-suint bowl is used to remove water-solubThe first de-suint bowl is used to remove water-soluble contaminants such as suint (or sheep sweat) from tle contaminants such as suint (or sheep sweat) from the wool. The next three bowls contain hot water, dethe wool. The next three bowls contain hot water, detergent and alkali for grease removal, while the remaiergent and alkali for grease removal, while the remaining two bowls contain clean water for rinsing. Fibres ning two bowls contain clean water for rinsing. Fibres are propelled through each bowl and there is a pair oare propelled through each bowl and there is a pair of squeeze rollers between the adjacent bowls. Becausf squeeze rollers between the adjacent bowls. Because of the scale structure on the wool surface, excessive e of the scale structure on the wool surface, excessive agitation of wool during scouring will lead to felting oagitation of wool during scouring will lead to felting of wool, which in turn will lead to increased fibre damaf wool, which in turn will lead to increased fibre damage during the subsequent processes, carding process ge during the subsequent processes, carding process in particular.in particular.

Fresh water is introduced from the last bowl for rinsiFresh water is introduced from the last bowl for rinsing, and flows backward to the scouring bowls ('counng, and flows backward to the scouring bowls ('counter-current' flow). The water temperature in the threter-current' flow). The water temperature in the three scouring bowls is usually set at about 55 to 60e scouring bowls is usually set at about 55 to 60OOC, wiC, with the temperature in the rinsing bowls set at about th the temperature in the rinsing bowls set at about 45 to 50 45 to 50 OOC.C.

2.Scouring bowls2.Scouring bowls

Three types of scouring bowls used in the industry arThree types of scouring bowls used in the industry are given in figure 2.11.e given in figure 2.11.

(a) Conventional long bowl

(b) WRONZ Mini-bowl

(c) Fleissner suction drums

The conventional long bowl uses dunkers to push the The conventional long bowl uses dunkers to push the wool sheet into the scouring liquor. The ranks then prwool sheet into the scouring liquor. The ranks then propel the sheet of wool through the bowl, dislodging topel the sheet of wool through the bowl, dislodging the mineral dirt from the fibres in the process. The scrahe mineral dirt from the fibres in the process. The scratching of fibres against the perforated screen (the falstching of fibres against the perforated screen (the false bottom) also helps dirt removal. There is considerabe bottom) also helps dirt removal. There is considerable agitation of wool during scouring, which tends to inle agitation of wool during scouring, which tends to increase the level of wool felting. As mentioned earlier, crease the level of wool felting. As mentioned earlier, wool felting is very undesirable, because it leads to inwool felting is very undesirable, because it leads to increased fibre breakage in the subsequent processes screased fibre breakage in the subsequent processes such as carding.uch as carding.

The WRONZ mini-bowl is the most widely used bowl dThe WRONZ mini-bowl is the most widely used bowl design. The agitation on the wool sheet in the bowl is nesign. The agitation on the wool sheet in the bowl is not as severe as in the conventional long-bowl. In additot as severe as in the conventional long-bowl. In addition, the hopper shaped bowl facilitates fast settling of ion, the hopper shaped bowl facilitates fast settling of the dirt in the bottom of the bowl. the dirt in the bottom of the bowl.

The Fleissner suction drum type is the gentlest of the tThe Fleissner suction drum type is the gentlest of the three. Each bowl has several perforated rotating drums hree. Each bowl has several perforated rotating drums half immersed in the scour bath. The scouring liquor inhalf immersed in the scour bath. The scouring liquor inside each drum is pumped into circulation loop and thside each drum is pumped into circulation loop and then back to the bowl. When the wool sheet enters the ben back to the bowl. When the wool sheet enters the bowl, it is pushed into the liquor by a rotating dunker (nowl, it is pushed into the liquor by a rotating dunker (not shown in fig. 2.11c) first. The sheet of wool then gets ot shown in fig. 2.11c) first. The sheet of wool then gets held against the suction drum surface by in-flowing liqheld against the suction drum surface by in-flowing liquor and released as it emerges at liquor surface on the uor and released as it emerges at liquor surface on the other side. The sheet of wool then flows to the next druother side. The sheet of wool then flows to the next drum. Since there is little mechanical agitation on the wom. Since there is little mechanical agitation on the wool, wool felting is minimised during scouring. This is thol, wool felting is minimised during scouring. This is the biggest advantage of the suction drum system. But the biggest advantage of the suction drum system. But the reduced agitation also means less dirt removal durine reduced agitation also means less dirt removal during scouring. This is the well-known cleanliness-versus-eg scouring. This is the well-known cleanliness-versus-entanglement compromise in wool scouring. Reduced entanglement compromise in wool scouring. Reduced entanglement often means reduced cleanliness as well.ntanglement often means reduced cleanliness as well.

In addition to scouring bowls, the squeeze rollers are In addition to scouring bowls, the squeeze rollers are also very important cleaning mechanisms. Inadequatalso very important cleaning mechanisms. Inadequate roller pressure will lead to scoured wool with a high e roller pressure will lead to scoured wool with a high level of residual grease. Poor opening of the wool beflevel of residual grease. Poor opening of the wool before scouring will have a similar effect. Fibre opening ore scouring will have a similar effect. Fibre opening and blending before scouring is discussed in the folloand blending before scouring is discussed in the following section.wing section.

► Fibre openingFibre opening(( 开毛开毛 )) and blending and blending(( 混和混和 )) before s before scouringcouring

Most consignments of greasy wool are made up Most consignments of greasy wool are made up of a number of farm lots or inter-lots. Each lot of a number of farm lots or inter-lots. Each lot sold at auction should have a minimum number sold at auction should have a minimum number of 4 bales of greasy wool. On average, each bale of 4 bales of greasy wool. On average, each bale weighs about 180 kg. The properties of wool in weighs about 180 kg. The properties of wool in the different lots are usually quite different. the different lots are usually quite different. Blending of the greasy wool in different lots is Blending of the greasy wool in different lots is therefore one of the most important functions in therefore one of the most important functions in the whole topmaking process. The blend should the whole topmaking process. The blend should be prepared to ensure a good mix across all the be prepared to ensure a good mix across all the different lots in a given consignment.different lots in a given consignment.

As an example, let's assume that we have a consignmAs an example, let's assume that we have a consignment of 50 bales of greasy wool, consisting of 4 lots of went of 50 bales of greasy wool, consisting of 4 lots of wool from different farms. It would be very bad practice ool from different farms. It would be very bad practice to feed the lots of wool one after another, because fibto feed the lots of wool one after another, because fibre properties differ from lot to lot. One way of mixing tre properties differ from lot to lot. One way of mixing the lots and feeding the bales of wool to a scour line is he lots and feeding the bales of wool to a scour line is sketched in figure 2.12. Other ways of mixing and feedsketched in figure 2.12. Other ways of mixing and feeding the opening process has also been used to minimiing the opening process has also been used to minimise the irregularity in the final product.se the irregularity in the final product.

Lot 1 (5 bales)

Lot 2 (20 bales)

Lot 3 (15 bales)

Lot 4 (10 bales)

Opening Scouring

Figure 2.12 Blending of greasy wool bales before scouring

TThe typical opening systems used are the feed he typical opening systems used are the feed hopper and drum opener, as indicated in figure hopper and drum opener, as indicated in figure 2.13.2.13.

(a) Feed hopper(a) Feed hopper (b) Double drum (b) Double drum openeropener

Figure 2.13 Pre-scouring fibre opening systems Figure 2.13 Pre-scouring fibre opening systems (Stewart 1985, p.5, p.7)(Stewart 1985, p.5, p.7)

A usual combination of the opening systems is: A usual combination of the opening systems is:

Feed Hopper 1 Double Drum Opener Feed Feed Hopper 1 Double Drum Opener Feed Hopper 2 Scouring Hopper 2 Scouring

With the feed hopper 1, greasy wool from different balWith the feed hopper 1, greasy wool from different bales is placed on the feed apron in the hopper, which foes is placed on the feed apron in the hopper, which forwards the wool to the spiked apron. The spikes pick rwards the wool to the spiked apron. The spikes pick up tufts of wool and move them upwards. Upon meetiup tufts of wool and move them upwards. Upon meeting the comb drum, large tufts are separated into smalng the comb drum, large tufts are separated into smaller ones and some small tufts continue with the spikeler ones and some small tufts continue with the spiked apron until doffed off by the doffer drum, others are d apron until doffed off by the doffer drum, others are returned by the comb drum to the hopper. The retunereturned by the comb drum to the hopper. The retuned tufts will mix with others already in the hopper, so sd tufts will mix with others already in the hopper, so some blending is also achieved with the feed hopper oome blending is also achieved with the feed hopper opening system.pening system.

The double drum opener has two toothed drums betThe double drum opener has two toothed drums between which fibres are opened. There are usually perfween which fibres are opened. There are usually perforated screens underneath each drum, which allow diorated screens underneath each drum, which allow dirt and dust to fall away. So apart from fibre opening, srt and dust to fall away. So apart from fibre opening, some cleaning is also achieved with the double drum oome cleaning is also achieved with the double drum opener. Feed hopper 2 will deliver a uniform, opened lapener. Feed hopper 2 will deliver a uniform, opened layer of greasy wool to the scour. yer of greasy wool to the scour.

IIt is worth pointing out that all tri-pack wool (three bt is worth pointing out that all tri-pack wool (three bales compressed into one for ease of storage and traales compressed into one for ease of storage and transport) and some farm bales which have had prolonnsport) and some farm bales which have had prolonged storage need to be warmed up prior to scouring. ged storage need to be warmed up prior to scouring. Even for ordinary bales, cold climates may warrant bEven for ordinary bales, cold climates may warrant bale warming before processing. Warming the bales wale warming before processing. Warming the bales will loosen and open fibres in the bale, which leads to ill loosen and open fibres in the bale, which leads to better scouring and reduced fibre breakage. Bale warbetter scouring and reduced fibre breakage. Bale warming is achieved in a number of ways, the most popuming is achieved in a number of ways, the most popular being steam or hot-air heating. A recent developlar being steam or hot-air heating. A recent development is to heat the bales with the microwave techniqment is to heat the bales with the microwave technique. ue.

► Drying of scoured woolDrying of scoured wool The wool leaving the last pair of squeeze rollers The wool leaving the last pair of squeeze rollers

has a moisture content of about 40%, or a regain has a moisture content of about 40%, or a regain of about 66% ( )It is typical to of about 66% ( )It is typical to dry the scoured wool to around 8 to 12% regain.dry the scoured wool to around 8 to 12% regain.

There are three main types of dryers available There are three main types of dryers available for wool - suction drum dryer, conveyer dryer, for wool - suction drum dryer, conveyer dryer, and Unidryer. They use either gas or steam for and Unidryer. They use either gas or steam for heating. Figure 2.14 shows a side view of the heating. Figure 2.14 shows a side view of the three dryers.three dryers.

Figure 2.14 Side view of wool dryers (Teasdale Figure 2.14 Side view of wool dryers (Teasdale 1996, p. 97) 1996, p. 97)

wooldryofmass

waterofmassregain

1.Suction drum dryer1.Suction drum dryer

Upon entering the dryer, the sheet of wet wool is held on Upon entering the dryer, the sheet of wet wool is held on rotating perforated drums by suction created by fans on rotating perforated drums by suction created by fans on the end of each drum. An internal baffle in each drum the end of each drum. An internal baffle in each drum blocks half of its circumference so that wool is only held blocks half of its circumference so that wool is only held on half of its surface by the suction. As the drums rotate, on half of its surface by the suction. As the drums rotate, the sheet of wool is passed from drum to drum so that the the sheet of wool is passed from drum to drum so that the heated air passes in alternate directions through the wool heated air passes in alternate directions through the wool for even drying. There is a 'counter-current' airflow inside for even drying. There is a 'counter-current' airflow inside the dryer. In other words, the direction of air flow is the dryer. In other words, the direction of air flow is opposite to the direction of wool flow. Fresh (cool) air is opposite to the direction of wool flow. Fresh (cool) air is fanned in from the delivery end, which cools the dried fanned in from the delivery end, which cools the dried wool at exit. The air is recirculated to the drums via wool at exit. The air is recirculated to the drums via heating batteries. As the heated air is drawn through the heating batteries. As the heated air is drawn through the wool, it carries moisture with it to dry the wool. The air is wool, it carries moisture with it to dry the wool. The air is then heated again and drawn through the layer of wool then heated again and drawn through the layer of wool towards the wool inlet, where the wet air is finally towards the wool inlet, where the wet air is finally exhausted to the atmosphere. Drum dryers usually have exhausted to the atmosphere. Drum dryers usually have between 4 to 8 drums.between 4 to 8 drums.

2.2.Conveyer dryerConveyer dryer This is the traditional hot air dryer where the This is the traditional hot air dryer where the

sheet of wool is carried through on a perforated sheet of wool is carried through on a perforated conveyer. Similar to the drum dryer, fresh (ccol) conveyer. Similar to the drum dryer, fresh (ccol) air is introduced at the wool outlet to cool the air is introduced at the wool outlet to cool the exiting wool. This air is then heated and blown exiting wool. This air is then heated and blown down through the layer of wool, carrying down through the layer of wool, carrying moisture with in to dry the wool. The now moist moisture with in to dry the wool. The now moist air is then heated again and blown through the air is then heated again and blown through the wool layer towards the wool inlet, where the wool layer towards the wool inlet, where the wet air is finally exhausted to the atmosphere. wet air is finally exhausted to the atmosphere.

UnidryerUnidryer

This dryer was developed at the University of New SoThis dryer was developed at the University of New South wales. It carries wool between two porous conveuth wales. It carries wool between two porous conveyer belts. The conveyer belts pass next to a perforateyer belts. The conveyer belts pass next to a perforated screen. Again there is a 'counter-current' airflow insd screen. Again there is a 'counter-current' airflow inside the dryer, with the fresh air coming into the dryer ide the dryer, with the fresh air coming into the dryer from wool outlet and wet air exhausted at the wool infrom wool outlet and wet air exhausted at the wool inlet. The direction of airflow in the two chambers is oplet. The direction of airflow in the two chambers is opposite so that wool is dried evenly from both sides. Tposite so that wool is dried evenly from both sides. The unidryer is a powerful dryer and is much smaller the unidryer is a powerful dryer and is much smaller than the other two. han the other two.

Worsted CardingWorsted Carding The same adage - "well carded is half spun", as quoteThe same adage - "well carded is half spun", as quote

d in the cotton carding section also applies to worsted in the cotton carding section also applies to worsted carding. Carding is a vital process in the fibre to yard carding. Carding is a vital process in the fibre to yarn processing chain.n processing chain.

► ObjectivesObjectives

The main objectives of worsted carding are:The main objectives of worsted carding are: --to disentangle and align the scoured wool, to disentangle and align the scoured wool, --to remove the vegetable matters left in the scoured wto remove the vegetable matters left in the scoured w

ool, ool, --to intimately mix the fibres, and, to intimately mix the fibres, and, --to deliver the carded fibres in a continuous rope-like fto deliver the carded fibres in a continuous rope-like f

orm called a card sliver.orm called a card sliver.

Owing to the scale structure on wool surface, it is unOwing to the scale structure on wool surface, it is unavoidable that some degree of fibre entanglement oavoidable that some degree of fibre entanglement occurs during aqueous wool scouring. Carding is the ccurs during aqueous wool scouring. Carding is the only process that can untangle and individualise the only process that can untangle and individualise the fibres. After scouring and drying, the vegetable mattfibres. After scouring and drying, the vegetable matters still remain in the wool. The bulk of these foreign ers still remain in the wool. The bulk of these foreign matters are removed in carding. Carding also achievmatters are removed in carding. Carding also achieves intimate mixing of wool fibres, which is only possies intimate mixing of wool fibres, which is only possible with individualised fibres. Considerable fibre breble with individualised fibres. Considerable fibre breakage occurs during carding, mainly because of the akage occurs during carding, mainly because of the fibre entanglement. To minimise fibre damage, adefibre entanglement. To minimise fibre damage, adequate fibre preparation between wool drying and caquate fibre preparation between wool drying and carding is essential.rding is essential.

► Fibre preparation before cardingFibre preparation before carding After the wool is scoured and dried, the After the wool is scoured and dried, the

moisture content and total fatty matter (TFM) moisture content and total fatty matter (TFM) left in the wool are checked. This will allow left in the wool are checked. This will allow correct addition of oil/water to facilitate wool correct addition of oil/water to facilitate wool carding. Usually the scoured/dried wool is gently carding. Usually the scoured/dried wool is gently opened first by a simple opener as shown in opened first by a simple opener as shown in figure 2.15. figure 2.15.

Oil/water spray

Wool to storage bin via pneumatic duct

Spiked lattice

Beater

Doffer

(wool from dryer)

Figure 2.15 A simple opener for scoured and dried wool

A mixture of processing oil and water is sprayed A mixture of processing oil and water is sprayed on to the wool, preferably at the delivery end on to the wool, preferably at the delivery end just before the wool enters the pneumatic just before the wool enters the pneumatic transport ducts to the storage bins. The wool is transport ducts to the storage bins. The wool is allowed to stand for a minimum of 12 hours in allowed to stand for a minimum of 12 hours in the bins to allow oil and water to spread evenly the bins to allow oil and water to spread evenly throughout the wool before carding. Insufficient throughout the wool before carding. Insufficient moisture in the wool will cause static problems moisture in the wool will cause static problems during carding, while too much oil will cause during carding, while too much oil will cause wool lapping on the card rollers.wool lapping on the card rollers.

► Roller-top cardRoller-top card Unlike the flat-top card used for carding cotton Unlike the flat-top card used for carding cotton

fibres (or other staples of similar length to fibres (or other staples of similar length to cotton), a roller-top card is used for carding wool cotton), a roller-top card is used for carding wool fibres. A simple roller-top card is shown in figure fibres. A simple roller-top card is shown in figure 2.16. 2.16.

In the simple card depicted in figure 2.16, the brokeIn the simple card depicted in figure 2.16, the broken line represents the flow of fibres. The incoming fibn line represents the flow of fibres. The incoming fibres are first picked up or 'licked in' by the teeth of thres are first picked up or 'licked in' by the teeth of the lickerin or takerin. e lickerin or takerin.

Feed rollers

Licker-in

cylinder

Doffer

Doffer comb

Burr beater

Transfer roller

worker stripper

Figure 2.16 A simple roller-top card

As the name implies, a roller-top card has As the name implies, a roller-top card has rollers, rather than flats, on top of the cylinder. rollers, rather than flats, on top of the cylinder. Roller-top cards are relatively gentle on fibres, Roller-top cards are relatively gentle on fibres, which is important in minimising damage to the which is important in minimising damage to the delicate fibres such as wool. The rollers are delicate fibres such as wool. The rollers are clothed with metallic teeth pointing to certain clothed with metallic teeth pointing to certain directions. As discussed in cotton carding, the directions. As discussed in cotton carding, the teeth direction, the relative speed between two teeth direction, the relative speed between two adjacent roller surfaces, and the rotating adjacent roller surfaces, and the rotating direction of the roller surface govern the basic direction of the roller surface govern the basic actions (point-to-point carding or point-to-back actions (point-to-point carding or point-to-back stripping) between the two adjacent rollers. stripping) between the two adjacent rollers.

In the simple card depicted in figure 2.16, the broken In the simple card depicted in figure 2.16, the broken line represents the flow of fibres. The incoming fibres line represents the flow of fibres. The incoming fibres are first picked up or 'licked in' by the teeth of the licare first picked up or 'licked in' by the teeth of the lickerin or takerin. The sheet of fibres travels with the likerin or takerin. The sheet of fibres travels with the lickerin and presents the relatively exposed vegetable ckerin and presents the relatively exposed vegetable matters (VM) in the fibres to the flicking action of the matters (VM) in the fibres to the flicking action of the beater for removal. Between the lickerin and the tranbeater for removal. Between the lickerin and the transfer roller, a point-to-back stripping action occurs ansfer roller, a point-to-back stripping action occurs and the sheet of fibres on the lickerin is stripped by the d the sheet of fibres on the lickerin is stripped by the teeth of the trasnfer roller. Another point-to-back striteeth of the trasnfer roller. Another point-to-back stripping action occurs between the cylinder and the trapping action occurs between the cylinder and the transfer roller, which allows the sheet of fibres to be strinsfer roller, which allows the sheet of fibres to be stripped off the transfer roller by the cylinder teeth. The pped off the transfer roller by the cylinder teeth. The cylinder now carries the sheet of fibres to the very imcylinder now carries the sheet of fibres to the very important stripper/worker pair. portant stripper/worker pair.

The relative surface speed (V) here is: VThe relative surface speed (V) here is: Vcylindercylinder>Vs>Vstrippertripper>V>Vww

orkerorker. This, together with the tooth direction and the s. This, together with the tooth direction and the surface rotating direction as indicated in figure 2.16, urface rotating direction as indicated in figure 2.16, gives the following basic actions in the cylinder/worgives the following basic actions in the cylinder/worker/stripper unit:ker/stripper unit:

--Cylinder/stripper: point-to-back stripping action; cCylinder/stripper: point-to-back stripping action; cylinder strips the stripper.ylinder strips the stripper.

- - Cylinder/worker: point-to-point working action; bCylinder/worker: point-to-point working action; both surfaces will grab some fibres to untangle them.oth surfaces will grab some fibres to untangle them.

- - Worker/stripper: point-to-back stripping action; stWorker/stripper: point-to-back stripping action; stripper strips the worker.ripper strips the worker.

With this arrangement, the fibres carried by the cylinWith this arrangement, the fibres carried by the cylinder will 'by-pass' the stripper and proceed to the worder will 'by-pass' the stripper and proceed to the working (or carding) action of the cylinder/worker pair. Tking (or carding) action of the cylinder/worker pair. This is where much of the fibre untangling and alignmhis is where much of the fibre untangling and alignment occur in the card. The fibres picked up by the worent occur in the card. The fibres picked up by the worker will soon meet the stripper and be stripped by thker will soon meet the stripper and be stripped by the stripper. The stripper then returns these fibres to the stripper. The stripper then returns these fibres to the cylinder for further action. The fibres that are not pie cylinder for further action. The fibres that are not picked by the worker will continue their journey with ocked by the worker will continue their journey with on the cylinder surface, until they reach the doffer. Thn the cylinder surface, until they reach the doffer. The doffer has a lower surface speed than the cylinder, e doffer has a lower surface speed than the cylinder, and a working or carding action happens between thand a working or carding action happens between them. This would mean that the fibres entering the cyliem. This would mean that the fibres entering the cylinder/doffer zone is further opened, and a fraction of nder/doffer zone is further opened, and a fraction of the fibres will be picked up by the doffer teeth, and tthe fibres will be picked up by the doffer teeth, and this sheet of fibre will then be stripped off the doffer shis sheet of fibre will then be stripped off the doffer surface by the rapidly oscillating doffer comb. urface by the rapidly oscillating doffer comb.

The fibres not picked up by the doffer will stay on thThe fibres not picked up by the doffer will stay on the cylinder surface as 'recycled fibre'. The 'recycled fie cylinder surface as 'recycled fibre'. The 'recycled fibres' on the cylinder surface will soon meet with the bres' on the cylinder surface will soon meet with the 'fresh fibres' that have just been picked up by the cyl'fresh fibres' that have just been picked up by the cylinder from the transfer roller. Together, the recycled inder from the transfer roller. Together, the recycled and fresh fibres are then presented to the cylinder/and fresh fibres are then presented to the cylinder/worker/stripper unit and the process repeats. The 'lworker/stripper unit and the process repeats. The 'looping' of fibres on the cylinder/worker/stripper uniooping' of fibres on the cylinder/worker/stripper unit and the recycled fibres meeting with fresh fibres ot and the recycled fibres meeting with fresh fibres on the cylinder are also important for intimate fibre n the cylinder are also important for intimate fibre mixing. From this brief description, we can see that tmixing. From this brief description, we can see that the cyliner/worker/stripper unit achieves the importhe cyliner/worker/stripper unit achieves the important key objectives of fibre untangling, fibre alignmeant key objectives of fibre untangling, fibre alignment, and fibre mixing. On a modern worsted card, mant, and fibre mixing. On a modern worsted card, many such units are employed to ensure sufficient fibre ny such units are employed to ensure sufficient fibre opening, aligning and mixing in carding. opening, aligning and mixing in carding.

Figure 2.17 shows a schematic diagram of a Figure 2.17 shows a schematic diagram of a modern worsted card. modern worsted card.

Feed rollers

Worker

Stripper

Licker-in

Breast cylinder

Main cylinder (Sw ift)

Doffer

Doffer comb

Burr beater

Morel roller (usually 2) Transfer

roller

Worker/stripper units

Figure 2.17 Diagram of worsted roller top card

A total of nine cylinder/worker/stripper units are emplA total of nine cylinder/worker/stripper units are employed on the card to achieve the desired level of fibre ooyed on the card to achieve the desired level of fibre opening, aligning, and mixing. In addition, the worsted pening, aligning, and mixing. In addition, the worsted card is often equipped with specially designed burr recard is often equipped with specially designed burr removal rollers (eg. Morel roller) and burr beaters to free moval rollers (eg. Morel roller) and burr beaters to free the opened fibres from burrs and other vegetable matthe opened fibres from burrs and other vegetable matters. The morel roller is clothed with special teeth, whters. The morel roller is clothed with special teeth, whose gaps are large enough to accommodate the fibres ose gaps are large enough to accommodate the fibres but are too small for the vegetable matter, so that the but are too small for the vegetable matter, so that the vegetable matter can be beaten off by the bur beaters vegetable matter can be beaten off by the bur beaters on top of the morel roller. The thin web of fibres remoon top of the morel roller. The thin web of fibres removed from the doffer by the doffer comb is usually condved from the doffer by the doffer comb is usually condensed into a sliver or rope form, and deposited into a sensed into a sliver or rope form, and deposited into a sliver can or coiler can for further processing. Figure 2.1liver can or coiler can for further processing. Figure 2.17a shows a sketch of a sliver can with coils of sliver insi7a shows a sketch of a sliver can with coils of sliver inside.de.

► Important settings in cardingImportant settings in carding (1)Card loading or production rate(1)Card loading or production rate

The theoretical production rate of a worsted The theoretical production rate of a worsted card can be calculated using the formula below:card can be calculated using the formula below:

This is the production rate at 100% efficiency, This is the production rate at 100% efficiency, and is related to the mean fibre diameter and is related to the mean fibre diameter (MFD), card width, and the swift surface speed.(MFD), card width, and the swift surface speed.

000,1

min)/()()(9.2)/(

mspeedSwiftmwidthCardmicronMFDhkgrateproductionlTheoretica

If the card is in good condition and set properly, it caIf the card is in good condition and set properly, it can produce quality products at this theoretical producn produce quality products at this theoretical production rate. Otherwise a lower rate is necessary to redution rate. Otherwise a lower rate is necessary to reduce fibre breakage during carding. The usual way of chce fibre breakage during carding. The usual way of checking card performance is to process the card slivers ecking card performance is to process the card slivers to tops, and examine the length characteristics of the to tops, and examine the length characteristics of the tops on the Almeter and calculate the coming yield atops on the Almeter and calculate the coming yield and noil figures.nd noil figures.

(2)(2)Fresh fibre density (FFD)Fresh fibre density (FFD) Research at CSIRO has demonstrated that the density Research at CSIRO has demonstrated that the density

of fresh fibres on the main cylinder (swift) has a major of fresh fibres on the main cylinder (swift) has a major effect on fibre breakage in the carding process. The freffect on fibre breakage in the carding process. The fresh fibre density (FFD) is calculated using the formula esh fibre density (FFD) is calculated using the formula below:below:

By combining this equation with the formula for producBy combining this equation with the formula for production rate, we can derive the formula for theoretical fretion rate, we can derive the formula for theoretical fresh fibre density (FFDt):sh fibre density (FFDt):

)(min)/(60

000,1)/(Pr)/( 2

mwidthcardmspeedSwift

hkgrateoductionmgDenstyFibreFresh

60

)(9.2)/( 2 micronMFD

mgdensityfibrefreshlTheoretica

If the actual fresh fibre density is significantly higher If the actual fresh fibre density is significantly higher than the theoretical fresh fibre density, considerable than the theoretical fresh fibre density, considerable fibre breakage may arise during carding. On the othefibre breakage may arise during carding. On the other hand, if the actual fresh fibre density is kept below ir hand, if the actual fresh fibre density is kept below its theoretical value, increasing the card production rts theoretical value, increasing the card production rate will have little effect on the quality of the carded ate will have little effect on the quality of the carded sliver. It is worth reiterating that the only way to confsliver. It is worth reiterating that the only way to confirm card performance is to check the fibre length chirm card performance is to check the fibre length characteristics on the Almeter and calculate combing yaracteristics on the Almeter and calculate combing yield and noil figures at each different setting.ield and noil figures at each different setting.

(3)(3)Roller settingsRoller settings The clearance between adjacent roller surfaces The clearance between adjacent roller surfaces

and the relative surface speeds are important and the relative surface speeds are important settings that affect carding quality. The settings that affect carding quality. The clearances gradually decreases from the feed to clearances gradually decreases from the feed to delivery end of the card as the fibre materials delivery end of the card as the fibre materials become thinner. The card manufacturer will become thinner. The card manufacturer will advise on the best settings for the particular type advise on the best settings for the particular type of fibre being processed by its card. Incorrect of fibre being processed by its card. Incorrect settings may reduce the mean fibre length, and settings may reduce the mean fibre length, and increase the number of neps in the carded sliver.increase the number of neps in the carded sliver.

The reading material "The pressure on fibres in cardinThe reading material "The pressure on fibres in carding" by Harrowfield, Eley and Robinson (1986), reports rg" by Harrowfield, Eley and Robinson (1986), reports relevant research carried out at CSIRO.elevant research carried out at CSIRO.

Like the cotton card, a properly set worsted card also generLike the cotton card, a properly set worsted card also generates a majority of trailing fibre hooks in the carded sliver, whates a majority of trailing fibre hooks in the carded sliver, which are then straightened in the gilling (drawing) processes fich are then straightened in the gilling (drawing) processes following carding. Despite of the best effort, fibre breakage aollowing carding. Despite of the best effort, fibre breakage and other less dramatic forms of fibre damage are unavoidabnd other less dramatic forms of fibre damage are unavoidable in carding. Poor scouring leading to increased fibre entanle in carding. Poor scouring leading to increased fibre entanglement, excessive fresh fibre density, and poor lubrication glement, excessive fresh fibre density, and poor lubrication are the main causes of fibre breakage in carding. In addition,are the main causes of fibre breakage in carding. In addition, highly entangled balls of fibres (called neps) are also genera highly entangled balls of fibres (called neps) are also generated in carding. Card surfaces with blunt teeth may lead to rolted in carding. Card surfaces with blunt teeth may lead to rolling of fibres between adjacent surfaces and create neps in tling of fibres between adjacent surfaces and create neps in the process. Grinding of card clothing to maintain sharpness he process. Grinding of card clothing to maintain sharpness of the teeth will reduce this problem. Another possible mechof the teeth will reduce this problem. Another possible mechanism of nep formation in carding is the 'snap back' effect. Ianism of nep formation in carding is the 'snap back' effect. In carding, many fibres are stretched at high extension rates. n carding, many fibres are stretched at high extension rates. When one fibre breaks, the broken end may 'snap back' and When one fibre breaks, the broken end may 'snap back' and entangle with neighbouring fibres to form neps. Most of the entangle with neighbouring fibres to form neps. Most of the broken short fibres plus the neps generated in carding are sbroken short fibres plus the neps generated in carding are subsequently removed as waste fibres (noils) in the combing ubsequently removed as waste fibres (noils) in the combing process. This is also why the combing yield and noil can reflprocess. This is also why the combing yield and noil can reflect the performance of carding. ect the performance of carding.

Preparatory GillingsPreparatory Gillings(( 预针梳预针梳 ))► ObjectivesObjectives The main objectives of the gilling machine are to furThe main objectives of the gilling machine are to fur

ther align the fibres in card sliver and to blend the slther align the fibres in card sliver and to blend the slivers from different cards. ivers from different cards.

A gilling machine is also known as a gillbox, or simpA gilling machine is also known as a gillbox, or simply a gill. ly a gill.

As discussed before, most fibres in the card slivers As discussed before, most fibres in the card slivers have hooked ends, with the trailing hooks at a majohave hooked ends, with the trailing hooks at a majority. These hooks and other poorly aligned fibres shrity. These hooks and other poorly aligned fibres should be straightened out before combing to increasould be straightened out before combing to increase the average fibre length and reduce the percentage the average fibre length and reduce the percentage of noil during combing. e of noil during combing.

► Gilling processGilling process Gilling is basically a roller drafting process in Gilling is basically a roller drafting process in

which fibre movements are controlled by pins which fibre movements are controlled by pins fixed on moving pinned bars (faller bars). fixed on moving pinned bars (faller bars). Figure 2.18 shows a schematic of a gillbox with Figure 2.18 shows a schematic of a gillbox with intersecting upper and lower faller bars intersecting upper and lower faller bars controlling fibre movement during drafting. controlling fibre movement during drafting. Such a gillbox is also called an intersecting Such a gillbox is also called an intersecting gillbox. gillbox.

Figure 2.18 Schematic of an intersecting Figure 2.18 Schematic of an intersecting gillbox (Grosberg and Iype 1999, p.14)gillbox (Grosberg and Iype 1999, p.14)

You may recall that perfect roller drafting requires fibYou may recall that perfect roller drafting requires fibres in the drafting zone travel at the speed of back rolres in the drafting zone travel at the speed of back rollers until their leading ends reach the front roller nip, lers until their leading ends reach the front roller nip, where they get accelerated to the front roller speed iwhere they get accelerated to the front roller speed instantly. In gilling, several slivers (eg. from different cnstantly. In gilling, several slivers (eg. from different cards) are combined as the input material, which is drards) are combined as the input material, which is drafted to produce a single sliver at the output. During afted to produce a single sliver at the output. During drafting, the faller bars move at about the same speedrafting, the faller bars move at about the same speed as the back rollers and the pins on the faller bars ked as the back rollers and the pins on the faller bars keep the fibres moving at a similar speed. Once the leadep the fibres moving at a similar speed. Once the leading end of a fibre gets gripped by the nip of the front ring end of a fibre gets gripped by the nip of the front rollers, that fibre gets pulled through the pins on the follers, that fibre gets pulled through the pins on the faller bars and has its trailing end straightened. So eacaller bars and has its trailing end straightened. So each passage of gilling straightens fibre trailing ends maih passage of gilling straightens fibre trailing ends mainly. nly.

The distance between the front roller nip and the closest fallThe distance between the front roller nip and the closest faller bar is called the front ratch setting. This setting is very imer bar is called the front ratch setting. This setting is very important for gilling. If it is set too large, then many fibres in thportant for gilling. If it is set too large, then many fibres in the critical region near the front rollers are not properly controe critical region near the front rollers are not properly controlled by the pinned faller bars during drafting. We already knolled by the pinned faller bars during drafting. We already know that lack of fibre control during drafting will lead to increaw that lack of fibre control during drafting will lead to increased irregularity in the drafted material. On the other hand, if sed irregularity in the drafted material. On the other hand, if the front ratch setting is too small, pulling the fibres through the front ratch setting is too small, pulling the fibres through the pins on the faller bars may cause fibre breakage. In practthe pins on the faller bars may cause fibre breakage. In practice, the front ratch setting is set at about half of the average fice, the front ratch setting is set at about half of the average fibre length. Using this value as a starting point, the final settiibre length. Using this value as a starting point, the final setting should be optimised based on sliver evenness results, parng should be optimised based on sliver evenness results, particularly the spectrograms obtained from the Uster evenness ticularly the spectrograms obtained from the Uster evenness tester. As discussed in the Module on Yarn Evenness, the spetester. As discussed in the Module on Yarn Evenness, the spectrograms allow us to identify the presence of drafting faults ctrograms allow us to identify the presence of drafting faults such as drafting waves. If a drafting wave is identified from tsuch as drafting waves. If a drafting wave is identified from the spectrogram, a closer front ratch setting should be used the spectrogram, a closer front ratch setting should be used to improve fibre control and reduce the number of floating fio improve fibre control and reduce the number of floating fibres during gilling.bres during gilling.

► Three intermediate gillingsThree intermediate gillings It is common practice in the worsted industry to have It is common practice in the worsted industry to have

three intermediate gillings between carding and combthree intermediate gillings between carding and combing. You may ask why this is necessary. To answer this ing. You may ask why this is necessary. To answer this question, we need to keep in mind the following three question, we need to keep in mind the following three points:points:

(1) (1) Fibres in card slivers have a majority of trailing hooksFibres in card slivers have a majority of trailing hooks(2) (2) There is a natural reversal of fibre ends between twoThere is a natural reversal of fibre ends between two processing stages ('first-in-last-out') processing stages ('first-in-last-out') (3) (3) In feeding a worsted comb, fibres with leading hooks In feeding a worsted comb, fibres with leading hooks

tend to cause more fibre breakage in combing (note thtend to cause more fibre breakage in combing (note the difference between worsted combing and cotton coe difference between worsted combing and cotton combing!)mbing!)

Figure 2.19 shows the configuration of fibre hooks dFigure 2.19 shows the configuration of fibre hooks during gilling. uring gilling.

Card 1st Gill 2nd Gill

3rd Gill

1st Gill

Comb

Can Can

Can Can

Figure 2.19 Fibre configurations from card to comb

The card produces fibres with a majority of trailing hooks. WThe card produces fibres with a majority of trailing hooks. When the card sliver is deposited into a can and then taken ouhen the card sliver is deposited into a can and then taken out to feed the 1st gill, there is a reversal of fibre ends, so that tt to feed the 1st gill, there is a reversal of fibre ends, so that the fibres entering the 1he fibres entering the 1st st gill have a majority of leading hooks.gill have a majority of leading hooks. Because gilling straightens trailing hooks only, the fibres wil Because gilling straightens trailing hooks only, the fibres will emerge from the 1st gill still with the leading hooks. Now thl emerge from the 1st gill still with the leading hooks. Now the 1e 1st st gilled sliver is stored in a can and taken out again for the gilled sliver is stored in a can and taken out again for the 22nd nd gilling operation. The reversal of fibre ends mean that fibgilling operation. The reversal of fibre ends mean that fibre entering the 2re entering the 2ndnd gill have a majority of trailing hooks, most gill have a majority of trailing hooks, most of which are straightened during this 2of which are straightened during this 2nd nd gilling. So after the gilling. So after the 22nd nd gilling, most fibres are straight except for a few which magilling, most fibres are straight except for a few which may still have some trailing hooks. After a further can storage ay still have some trailing hooks. After a further can storage and removal from the can, the sliver now enters the 3nd removal from the can, the sliver now enters the 3rd rd gill witgill with a few fibres with leading hooks, which can not be straighteh a few fibres with leading hooks, which can not be straightened and will persist to the 3ned and will persist to the 3rdrd gilled sliver. But when the 3 gilled sliver. But when the 3rd rd gigilling sliver is stored in a can and taken out for combing, any rlling sliver is stored in a can and taken out for combing, any remaining hooks in the sliver would be trailing, which is fine emaining hooks in the sliver would be trailing, which is fine as far as worsted combing is concerned. Feeding a worsted cas far as worsted combing is concerned. Feeding a worsted comb with leading hooks is likely to increase fibre breakage domb with leading hooks is likely to increase fibre breakage during combing, as will be discussed in the following section.uring combing, as will be discussed in the following section.

From figure 2.19, you may think that the 3From figure 2.19, you may think that the 3rd rd gill has dogill has done nothing to the fibres. This is not quite true. In gillinne nothing to the fibres. This is not quite true. In gilling as in cotton drawing, there is a doubling function as g as in cotton drawing, there is a doubling function as well. Many slivers are fed to a gill together, and there well. Many slivers are fed to a gill together, and there is a doubling and blending function by each gill, whicis a doubling and blending function by each gill, which improves the evenness of the gilled sliver.h improves the evenness of the gilled sliver.

Five intermediate gillings between worsted carding aFive intermediate gillings between worsted carding and combing have been tried before, but the benefit is nd combing have been tried before, but the benefit is too marginal to justify the cost for two extra gillings.too marginal to justify the cost for two extra gillings.

After the 3After the 3rdrd gilling, the slivers are ready for combing. gilling, the slivers are ready for combing. Combing is discussed next.Combing is discussed next.

Worsted CombingWorsted Combing(( 精梳精梳 ))► ObjectivesObjectives Combing is a critical step in worsted processing. SiCombing is a critical step in worsted processing. Si

milar to cotton combing, worsted combing achievemilar to cotton combing, worsted combing achieves the objectives of:s the objectives of:

(a) removing short fibres, neps, and impurities(a) removing short fibres, neps, and impurities (collectively known as noils) (collectively known as noils)

(b) further mixing and aligning fibres(b) further mixing and aligning fibres(c) forming a continuous rope-like comb sliver(c) forming a continuous rope-like comb sliver

Since longer and cleaner wool fibres make better yaSince longer and cleaner wool fibres make better yarns, combing improves the yarn quality and comberns, combing improves the yarn quality and combed yarns command a high price. d yarns command a high price.

• Combing processCombing process A schematic diagram of a rectilinear worsted comb is sA schematic diagram of a rectilinear worsted comb is s

hown in figure 2.20. Up to 32 carded and gilled slivers hown in figure 2.20. Up to 32 carded and gilled slivers may be fed to the comb via a pair of feed rollers and thmay be fed to the comb via a pair of feed rollers and the feed gill assembly. Like the cotton comb, worsted coe feed gill assembly. Like the cotton comb, worsted comb also runs in an intermittent fashion. In each cycle, tmb also runs in an intermittent fashion. In each cycle, the following actions are performed:he following actions are performed:

(1) (1) Feeding a short distance of slivers to the combFeeding a short distance of slivers to the comb (2) (2) Initial combing of fibre leading ends by the cylinder Initial combing of fibre leading ends by the cylinder comb or comb cylindercomb or comb cylinder (3) (3) Final combing of fibre trailing ends by the intersectFinal combing of fibre trailing ends by the intersect

oror comb or top comb comb or top comb (4) (4) Detaching the fully combed tuft and overlapping it Detaching the fully combed tuft and overlapping it with previously combed oneswith previously combed ones Figure 2.20 A side elevation of a worsted comb (Brearley Figure 2.20 A side elevation of a worsted comb (Brearley

1964, p50).1964, p50).

During the initial combing stage, the fibres are firmly gripped During the initial combing stage, the fibres are firmly gripped by the nips or nipper jaws. Fibre leading ends protruding froby the nips or nipper jaws. Fibre leading ends protruding from the nipper jaws are combed by the comb cylinder (also knm the nipper jaws are combed by the comb cylinder (also known as the circular comb). Fibre penetration of the pins is aidown as the circular comb). Fibre penetration of the pins is aided by a nipper brush (not shown in figure 2.20) attached to thed by a nipper brush (not shown in figure 2.20) attached to the upper nipper. In the initial combing process, short fibres, ne upper nipper. In the initial combing process, short fibres, neps and impurities are removed as noils by the comb cylindeeps and impurities are removed as noils by the comb cylinder, which itself is then cleaned by the noil brush. If some fibres r, which itself is then cleaned by the noil brush. If some fibres have large leading hooks, there is a possibility for the leading have large leading hooks, there is a possibility for the leading hooks to be engaged by the teeth on the comb cylinder and fihooks to be engaged by the teeth on the comb cylinder and fibre breakage will occur as a result. This is why it is preferable bre breakage will occur as a result. This is why it is preferable that no leading hooks exist in the feed stock. In contrast, the that no leading hooks exist in the feed stock. In contrast, the presence of leading hooks in the feed stock to cotton combs ipresence of leading hooks in the feed stock to cotton combs is normal, since there are only two passages of drawing betws normal, since there are only two passages of drawing between cotton carding and combing. The difference is that for sheen cotton carding and combing. The difference is that for short staple fibres such as cotton, the fibre length is much shortort staple fibres such as cotton, the fibre length is much shorter than long staples such as wool. Even if there are leading her than long staples such as wool. Even if there are leading hooks, the extent of the hooks will be considerably smaller anooks, the extent of the hooks will be considerably smaller and the small hooks are unlikely to be engaged by the teeth of td the small hooks are unlikely to be engaged by the teeth of the comb cylinder to cause fibre breakage. he comb cylinder to cause fibre breakage.

In the final combing by the intersector comb (also knIn the final combing by the intersector comb (also known as the top comb), the trailing ends not combed own as the top comb), the trailing ends not combed by the comb cylinder are combed. The short fibres, nby the comb cylinder are combed. The short fibres, neps and impurities are held back by the intersector ceps and impurities are held back by the intersector comb, and will be removed in the next combing cycle. omb, and will be removed in the next combing cycle. The noils or combing noils (i.e. short fibres, neps and The noils or combing noils (i.e. short fibres, neps and impurities) represent combing waste. The value of noimpurities) represent combing waste. The value of noils is about one third of that of tops, so any increase iils is about one third of that of tops, so any increase in the percentage of noil is going to cost the topmaken the percentage of noil is going to cost the topmaker large sum of money. But an increase in noil is usuallr large sum of money. But an increase in noil is usually accompanied with an increase in the mean fibre leny accompanied with an increase in the mean fibre length of the combed sliver, because more short fibres agth of the combed sliver, because more short fibres are removed. This improves the value of the tops. So cre removed. This improves the value of the tops. So choosing the right percentage noil is a balancing act. hoosing the right percentage noil is a balancing act. A 6% noil is typical in modern topmaking mills. A 6% noil is typical in modern topmaking mills.

Each fully combed tuft of fibres is drawn off by the dEach fully combed tuft of fibres is drawn off by the drawing-off rollers and laid on top of the previously corawing-off rollers and laid on top of the previously combed ones, like shingles on the roof. This overlappembed ones, like shingles on the roof. This overlapped web of fully combed fibres is then consolidated by d web of fully combed fibres is then consolidated by the calender rollers and deposited in the sliver can. the calender rollers and deposited in the sliver can. Because fibres in the combed sliver simply overlap, tBecause fibres in the combed sliver simply overlap, the cohesion between fibres is very small, therefore the cohesion between fibres is very small, therefore the combed sliver is very weak. To improve the strenghe combed sliver is very weak. To improve the strength of combed slivers, the slivers may be crimped by a th of combed slivers, the slivers may be crimped by a crimping mechanism before they are deposited into crimping mechanism before they are deposited into the coiler can. the coiler can.

Figure 2.21 shows the worsted combing in seFigure 2.21 shows the worsted combing in separate stages, noting that the upper nipper hparate stages, noting that the upper nipper has a brush attached to it to assist with fibre pas a brush attached to it to assist with fibre penetration into the pins of the circular comb.enetration into the pins of the circular comb.

Figure 2.21 A graphical representation of woFigure 2.21 A graphical representation of worsted combing process (CSIRO Wool Textile rsted combing process (CSIRO Wool Textile News, Feb. 1969).News, Feb. 1969).

► Settings on the combSettings on the comb(( 精梳机工艺参数精梳机工艺参数 ))

(1)Noil(1)Noil(( 落毛落毛 )) setting setting

Noil setting is also known as detachment setting or Noil setting is also known as detachment setting or gauge setting. It is the closest distance between the gauge setting. It is the closest distance between the bite of the nippers and the nip line of the detaching bite of the nippers and the nip line of the detaching rollers. On a worsted comb, this setting may vary frrollers. On a worsted comb, this setting may vary from 26 mm to 40 mm. A large ratch setting will lead tom 26 mm to 40 mm. A large ratch setting will lead to increased noil, and longer mean fibre length in tho increased noil, and longer mean fibre length in the top. This will be further discussed in the following e top. This will be further discussed in the following section on the geometrical model of worsted combisection on the geometrical model of worsted combing.ng.

(2)(2)FeedFeed(( 喂入喂入 ))

Normally about 12 to 32 slivers are fed to a worsteNormally about 12 to 32 slivers are fed to a worsted comb, depending on sliver weight and machine d comb, depending on sliver weight and machine design. A practical rule of thumb is:design. A practical rule of thumb is:

Rule of thumb for feed:Rule of thumb for feed: Input ktex = 20 x MicroInput ktex = 20 x Micronn

For example, if the comb is processing 22 micron wFor example, if the comb is processing 22 micron wool, then the total density of the feed stock may be ool, then the total density of the feed stock may be set at 20 x 22 = 440 ktex.set at 20 x 22 = 440 ktex.

As mentioned earlier, the comb operates in an intAs mentioned earlier, the comb operates in an intermittent fashion. On a worsted comb, the feed lenermittent fashion. On a worsted comb, the feed length is usually adjustable between 4.5 to 9 mm per gth is usually adjustable between 4.5 to 9 mm per combing cycle.combing cycle.

(3)(3)Production rateProduction rate(( 产量产量 ))

The comb production rate can be calculated using tThe comb production rate can be calculated using the formulas below:he formulas below:

A practical rule of thumb is:A practical rule of thumb is: Rule of thumb for production rate:Rule of thumb for production rate: Prod.Rate = 1.4 x MicronProd.Rate = 1.4 x Micron It is typical for a worsted comb to have a productioIt is typical for a worsted comb to have a productio

n rate between 20 to 40 kg/hour.n rate between 20 to 40 kg/hour.Geometrical theory of worsted combingGeometrical theory of worsted combing

► Geometrical theory of worsted combingGeometrical theory of worsted combing Belin and Walls (1963) developed a geometrical modBelin and Walls (1963) developed a geometrical mod

el of fibre selection in worsted combing. This model iel of fibre selection in worsted combing. This model is represented in figure 2.22 below.s represented in figure 2.22 below.

Nip of detaching rollers B

Nipper position E

A

Top comb

C

D

f

f

Feed mechanism

F

(a)

(b)

(a) Fibre beard in the combing zone BD combed by circular comb and about to be presented to the detachingrollers. DE is the ‘dead zone’ in front of the nipper, where pins on the comb cylinder can not reach (b) Fibre beard advanced a distance ‘f ’ by the feed mechanism F. Fibres with ends inside detaching zone AB removed to combed sliver, their tail ends combed by the top comb C

section combed by circular comb

Noil Setting N

f A’

Figure 2.22 Geometrical model of fibre selection in worsted combing

This model shows that for fibres not held by the nippers, the This model shows that for fibres not held by the nippers, the combing action of the circular comb will remove them as noilcombing action of the circular comb will remove them as noils. These are the relatively short fibres, i.e. fibres shorter than ts. These are the relatively short fibres, i.e. fibres shorter than the noil setting (N). Longer but poorly aligned fibres not grippehe noil setting (N). Longer but poorly aligned fibres not gripped by the nippers will also be removed as noil. After the initial cd by the nippers will also be removed as noil. After the initial combing by the circular comb, the fibre beard is fed forward a ombing by the circular comb, the fibre beard is fed forward a short distance represented by 'f' in figure 2.22. Combed fibres short distance represented by 'f' in figure 2.22. Combed fibres with leading ends reaching the detaching zone A'B (AB after fwith leading ends reaching the detaching zone A'B (AB after feeding) will be pulled through the top comb by the detaching eeding) will be pulled through the top comb by the detaching rollers and they will end up in the combed sliver. If a fibre has rollers and they will end up in the combed sliver. If a fibre has its trailing end just gripped by the nippers and its leading end its trailing end just gripped by the nippers and its leading end just reaching the detaching zone A'B, this fibre will end up in tjust reaching the detaching zone A'B, this fibre will end up in the combed sliver, even though its length is relatively short (slihe combed sliver, even though its length is relatively short (slightly longer than N - f). On the other hand, if a relatively long fghtly longer than N - f). On the other hand, if a relatively long fibre of length N is not gripped by the nippers, it will end up as ibre of length N is not gripped by the nippers, it will end up as noil regardless of the fact that its leading end is well inside thnoil regardless of the fact that its leading end is well inside the detaching zone A'B. Therefore, it is inevitable that a few fibre detaching zone A'B. Therefore, it is inevitable that a few fibres in the noil are longer than some fibres in the combed sliver.es in the noil are longer than some fibres in the combed sliver. This will be more so if the fibres are not well aligned before c This will be more so if the fibres are not well aligned before combing. This also highlights the importance of pre-comb gilliombing. This also highlights the importance of pre-comb gillings and the necessity to straighten fibres before combing.ngs and the necessity to straighten fibres before combing.

For any fibre that is shorter than (N - f), there is no wFor any fibre that is shorter than (N - f), there is no way that this fibre will be able to get gripped by the niay that this fibre will be able to get gripped by the nipper and in the same time having its leading end inspper and in the same time having its leading end inside the detaching zone A'B, so this fibre will always ide the detaching zone A'B, so this fibre will always end up in the noil.end up in the noil.

During detaching, the top comb is inserted just a shDuring detaching, the top comb is inserted just a short distance in front of the 'dead zone' DE to ensure ort distance in front of the 'dead zone' DE to ensure that fibres are fully combed along their entire lengththat fibres are fully combed along their entire lengths. The 'dead zone' exists because the pins on the cirs. The 'dead zone' exists because the pins on the circular comb can not reach right up to the nipping poicular comb can not reach right up to the nipping points of the nippers. In practice, this 'dead zone' lengtnts of the nippers. In practice, this 'dead zone' length is reduced with the aid of a nipper brush, which puh is reduced with the aid of a nipper brush, which pushes the fibres into the pins on the circular comb (fishes the fibres into the pins on the circular comb (figure 2.21). The impurities, short fibres and neps blogure 2.21). The impurities, short fibres and neps blocked by the top comb during detaching are removecked by the top comb during detaching are removed as noil in the next combing cycle.d as noil in the next combing cycle.

► Effect of combing on fibre propertiesEffect of combing on fibre properties In addition to the obvious changes in fibre length, combing aIn addition to the obvious changes in fibre length, combing a

lso changes fibre diameter slightly. With wool fibres, finer fibrlso changes fibre diameter slightly. With wool fibres, finer fibres are usually shorter ones, and are also easier to break durines are usually shorter ones, and are also easier to break during carding and combing. Since combing removes short fibres g carding and combing. Since combing removes short fibres mainly, the average diameter of fibres in the noil is about 10mainly, the average diameter of fibres in the noil is about 10% finer than the raw wool from which they have been produc% finer than the raw wool from which they have been produced. With the removal of relatively shorter and finer wools, the ed. With the removal of relatively shorter and finer wools, the combed sliver has an average fibre diameter that is about 1% combed sliver has an average fibre diameter that is about 1% coarser than the raw wool from which the combed sliver is prcoarser than the raw wool from which the combed sliver is produced. In absolute terms, it is usual for the average fibre diaoduced. In absolute terms, it is usual for the average fibre diameter to increase by about 0.3 micron after combing. This incmeter to increase by about 0.3 micron after combing. This increase should be considered when selecting raw wool, as discrease should be considered when selecting raw wool, as discussed in the section on TEAM formulae and applications.ussed in the section on TEAM formulae and applications.

The reading material "ITMA'99 - long staple gilling and combiThe reading material "ITMA'99 - long staple gilling and combing" by Atkinson (1999) discusses the latest developments in ng" by Atkinson (1999) discusses the latest developments in worsted gilling and combing, as exhibited at the 1999 internaworsted gilling and combing, as exhibited at the 1999 international textile machinery exhibition.tional textile machinery exhibition.

Worsted TopWorsted Top(( 精梳毛条精梳毛条 )) Finishing Finishing The worsted top finishing usually consists of two gilThe worsted top finishing usually consists of two gil

ling operations on the combed slivers.ling operations on the combed slivers.

► ObjectivesObjectives The objectives of top finishing are:The objectives of top finishing are:

--Randomise comb overlap effectRandomise comb overlap effect --Mixing of fibres from different combsMixing of fibres from different combs --Producing tops of the right count, regain, and packProducing tops of the right count, regain, and pack

age formage form --Improving the evennessImproving the evenness

An explanation of some of these objectives is given iAn explanation of some of these objectives is given in the following section.n the following section.

► The processThe process As with gilling before combing, the top finishing gilAs with gilling before combing, the top finishing gil

ling processes combine drafting, doubling and pin ling processes combine drafting, doubling and pin control. control.

As the combed slivers are removed from the storagAs the combed slivers are removed from the storage cans to feed the 1st finishing gillbox, they follow te cans to feed the 1st finishing gillbox, they follow the 'first-in-last-out' order (i.e. natural reversal of fihe 'first-in-last-out' order (i.e. natural reversal of fibre ends). Because of this natural reversal, fibres in bre ends). Because of this natural reversal, fibres in slivers fed to the 1st finishing gilling are drafted in tslivers fed to the 1st finishing gilling are drafted in the reverse direction, i.e. opposite to the direction he reverse direction, i.e. opposite to the direction of fibres as they came out of the comb. This is knoof fibres as they came out of the comb. This is known as 'reverse drafting'. The reverse drafting helps wn as 'reverse drafting'. The reverse drafting helps to randomise the overlapping fibre ends in the coto randomise the overlapping fibre ends in the combed slivers, leading to improved sliver strength dmbed slivers, leading to improved sliver strength due to the increased inter-fibre cohesion. This is shoue to the increased inter-fibre cohesion. This is shown in figure 2.23.wn in figure 2.23.

Overlapping points

Combed sliver with overlapping points

Reverse drafting randomises fibre ends in the combed sliver

Drafting direction

Figure 2.23 Reverse drafting randomising comb overlapping effect

TThe first finishing gillbox feeds on slivers from he first finishing gillbox feeds on slivers from many combs. This doubling of slivers (from difmany combs. This doubling of slivers (from different combs) in the gilling process improves tferent combs) in the gilling process improves the evenness of the gilled sliver, as discussed in he evenness of the gilled sliver, as discussed in the module on yarn evenness. A special controthe module on yarn evenness. A special control mechanism is often used in the finishing gill tl mechanism is often used in the finishing gill to automatically level or regulate the sliver eveo automatically level or regulate the sliver evenness, such a mechanism is called an autolevenness, such a mechanism is called an autoleveller. ller.

► The principle of autolevelling has been discussed in the first The principle of autolevelling has been discussed in the first topic of this module. Figure 2.24 shows a gillbox with an topic of this module. Figure 2.24 shows a gillbox with an autolevelling system. The slivers are fed into the gillbox via a autolevelling system. The slivers are fed into the gillbox via a condenser funnel and a pair of measuring rollers. This condenser funnel and a pair of measuring rollers. This measuring rollers are known as tongue and groove or shoe and measuring rollers are known as tongue and groove or shoe and groove rollers. The bottom roller has a groove through which groove rollers. The bottom roller has a groove through which the slivers run. The tongue or shoe roller is the top one, which the slivers run. The tongue or shoe roller is the top one, which sits in the groove roller, pressing on the slivers. Variations in sits in the groove roller, pressing on the slivers. Variations in the amount of fibre materials running through the tongue and the amount of fibre materials running through the tongue and groove rollers will cause the tongue roller to move up or down. groove rollers will cause the tongue roller to move up or down. This movement reflects the variation in material thickness and This movement reflects the variation in material thickness and is automatically recorded as a 'pattern line' on the memory is automatically recorded as a 'pattern line' on the memory unit. The memory unit then feeds this information forward to unit. The memory unit then feeds this information forward to the transmitter unit, which controls a variable speed the transmitter unit, which controls a variable speed mechanism. This mechanism can change the speed of the back mechanism. This mechanism can change the speed of the back rollers to vary the draft. For example, if the tongue and groove rollers to vary the draft. For example, if the tongue and groove measuring unit detects a thick section running through, this measuring unit detects a thick section running through, this information is recorded and fed forward to the transmitter. information is recorded and fed forward to the transmitter. When the thick section arrives in the drafting zone, the variable When the thick section arrives in the drafting zone, the variable speed mechanism will reduce the back roller speed to increase speed mechanism will reduce the back roller speed to increase the draft on this thick section. Conversely, if the measuring unit the draft on this thick section. Conversely, if the measuring unit detects a thin spot section coming through, the draft on the thin detects a thin spot section coming through, the draft on the thin section will be reduced by increasing the speed of the back section will be reduced by increasing the speed of the back rollers.rollers.

► Figure 2.24 Autolevelling gillbox (Brearley and Iredale 1980, Figure 2.24 Autolevelling gillbox (Brearley and Iredale 1980, p.83)p.83)

After two finishing gillings, we get worsted 'tops'. TAfter two finishing gillings, we get worsted 'tops'. The tops are usually packaged in balls or in bumps. Bhe tops are usually packaged in balls or in bumps. Balls are self-supporting cross wound tops, while bualls are self-supporting cross wound tops, while bumps are press-packed layers of coiled tops. mps are press-packed layers of coiled tops.

The tops should be of the right moisture content. TThe tops should be of the right moisture content. The standard regain for tops is about 18%. It is normhe standard regain for tops is about 18%. It is normal to spray moisture on the sliver at the delivery enal to spray moisture on the sliver at the delivery end of the first finishing gill, to bring the regain up to ad of the first finishing gill, to bring the regain up to about 19% first. At the 2nd finishing gilling process, about 19% first. At the 2nd finishing gilling process, about 1% of the moisture is lost through evaporatiobout 1% of the moisture is lost through evaporation.n.

► Quality of wool topsQuality of wool tops From a spinner's point of view, tops should be From a spinner's point of view, tops should be

produced to the spinner's specifications. These produced to the spinner's specifications. These specifications usually include requirements on specifications usually include requirements on the following:the following:

--Fibre diameter (micron) and CV of fibre diameterFibre diameter (micron) and CV of fibre diameter --Average fibre length (Hauteur) and CV of HauteurAverage fibre length (Hauteur) and CV of Hauteur --Count or size of the topCount or size of the top --Short fibre contentShort fibre content

In addition, the tops should be free from contamiIn addition, the tops should be free from contaminations (coloured fibre, vegetable matters, bale pnations (coloured fibre, vegetable matters, bale packing materials etc), and of the correct shape anacking materials etc), and of the correct shape and density.d density.

The TEAM equations discussed before have been rThe TEAM equations discussed before have been routinely used by top-makers to select the right woutinely used by top-makers to select the right wool for the tops, and for predicting the important ool for the tops, and for predicting the important quality attributes of tops according to raw wool squality attributes of tops according to raw wool specifications.pecifications.

Worsted DrawingWorsted Drawing► ObjectivesObjectives After the tops arrive at a worsted spinning mill (or After the tops arrive at a worsted spinning mill (or

the spinning department of a vertical worsted milthe spinning department of a vertical worsted mill), they go through a series of drawing processes. Tl), they go through a series of drawing processes. The main objectives of worsted drawing are:he main objectives of worsted drawing are:

--Reduce the count of tops gradually before spinniReduce the count of tops gradually before spinningng

--Mix tops of different propertiesMix tops of different properties --Minimise irregularity in count, colour etc.Minimise irregularity in count, colour etc.

► Drawing processDrawing process The drawing sequence differs from mill to mill. A typiThe drawing sequence differs from mill to mill. A typi

cal sequence of producing a 21 tex worsted yarn is gical sequence of producing a 21 tex worsted yarn is given in Table 2.5ven in Table 2.5

The roving frame used in the worsted system The roving frame used in the worsted system is mainly of the rub finisher type, although a fis mainly of the rub finisher type, although a flyer roving frame is also used. A schematic of lyer roving frame is also used. A schematic of the rub finisher roving frame is shown in Figuthe rub finisher roving frame is shown in Figure 2.25.re 2.25.

Fig. 2.25: Schematic of a rub finisher roving frFig. 2.25: Schematic of a rub finisher roving frame (Grosberg and Iype 1999, p.16)ame (Grosberg and Iype 1999, p.16)

The rub finisher roving frame uses roller drafting to atThe rub finisher roving frame uses roller drafting to attenuate the input sliver. The roving straight after drafttenuate the input sliver. The roving straight after drafting is weak, since no twist is inserted into the roving. ing is weak, since no twist is inserted into the roving. To increase the strength of the roving, rubbing aprons To increase the strength of the roving, rubbing aprons are used to consolidate the roving to increase fibre coare used to consolidate the roving to increase fibre cohesion. Each roving package normally has two rovinghesion. Each roving package normally has two rovings wound up side by side without being twisted togeths wound up side by side without being twisted together (parallel winding). The rovings are then used to feeer (parallel winding). The rovings are then used to feed a worsted ring spinning machine.d a worsted ring spinning machine.

Because the roving stage is the last process before spiBecause the roving stage is the last process before spinning, it is important that rovings are of good quality. nning, it is important that rovings are of good quality. The Uster spectrograms are often used to check whetThe Uster spectrograms are often used to check whether there is any periodic mass variation in the roving. Iher there is any periodic mass variation in the roving. If there is, it should be rectified as soon as possible beff there is, it should be rectified as soon as possible before further processing.ore further processing.

Once we have the rovings, spinning can commence Once we have the rovings, spinning can commence to make yarns. Spinning is discussed in the next mto make yarns. Spinning is discussed in the next module.odule.

While we have devoted this topic to worsted proceWhile we have devoted this topic to worsted processing, it is also important to know the system of wossing, it is also important to know the system of woollen processing. The reading material “Woollen pollen processing. The reading material “Woollen processing system” by Osborne (1998) provides essrocessing system” by Osborne (1998) provides essential information on the differences between worsential information on the differences between worsted and woollen processing.ted and woollen processing.

Review questionsReview questions

(1)(1)If a 20 tex weaving yarn is to be produced with an aIf a 20 tex weaving yarn is to be produced with an average number of 40 fibres in yarn cross section. Whverage number of 40 fibres in yarn cross section. What would be the right average diameter of the raw wat would be the right average diameter of the raw wool for the top-making process? You need to show thool for the top-making process? You need to show the calculations involved and consider changes in fibre calculations involved and consider changes in fibre diameter during top-making.e diameter during top-making.

(2)(2)In your own words and use sketches if necessary, exIn your own words and use sketches if necessary, explain how detergent helps to remove grease from thplain how detergent helps to remove grease from the surface of wool during the aqueous wool scouring.e surface of wool during the aqueous wool scouring.

(3)(3)An important unit on a card is the cylinder/worker/An important unit on a card is the cylinder/worker/stripper unit. Explain, with the help of sketches, how stripper unit. Explain, with the help of sketches, how this unit helps achieve the objectives of fibre openinthis unit helps achieve the objectives of fibre opening, aligning, and mixing during carding.g, aligning, and mixing during carding.

(4)(4)With reference to carding, gilling and combinWith reference to carding, gilling and combing processes, explain why three intermediate gig processes, explain why three intermediate gillings are commonly used in worsted top-makillings are commonly used in worsted top-making.ng.

(5)(5)With reference to the geometrical model of fiWith reference to the geometrical model of fibre selection in worsted combing, explain:bre selection in worsted combing, explain:

(a) (a) Why is possible to find a few fibres in the nWhy is possible to find a few fibres in the noil that are actually longer than some fibres in oil that are actually longer than some fibres in the combed sliver?the combed sliver?

(b) (b) What happens to the noil% and the mean What happens to the noil% and the mean fibre length of the combed sliver is the feed 'f' ifibre length of the combed sliver is the feed 'f' is increased?s increased?

SStaple Spinning and taple Spinning and Filament TexturingFilament Texturing

Ring spinningRing spinningIntroductionIntroduction Ring spinning has been and will continue to be an Ring spinning has been and will continue to be an

important spinning system for making important spinning system for making staple spun staple spun yarnsyarns ( ( 环锭短纤纱环锭短纤纱 )from different fibres. Since its )from different fibres. Since its invention in 1828, little has changed in terms of the invention in 1828, little has changed in terms of the principle of ring spinning. Furthermore, the principle of principle of ring spinning. Furthermore, the principle of ring spinning for short staples such as cotton and for ring spinning for short staples such as cotton and for long staples such as wool is exactly the same. So the long staples such as wool is exactly the same. So the discussion in this topic applies to both discussion in this topic applies to both short staple and short staple and long staple ring spinninglong staple ring spinning （短纤和长纤环锭纺纱）（短纤和长纤环锭纺纱） . This . This topic discusses the three basic stages of ring spinning, topic discusses the three basic stages of ring spinning, the physics of ring spinning, and the developments as the physics of ring spinning, and the developments as well as limitations of ring spinning. The detailed well as limitations of ring spinning. The detailed differences in machine design for long staple and short differences in machine design for long staple and short staple ring spinning are beyond the scope of this topic. staple ring spinning are beyond the scope of this topic.

ObjectivesObjectives At the end of this topic you should be able to:At the end of this topic you should be able to: Explain the basic principle of ring spinningExplain the basic principle of ring spinning Know the features of Know the features of ring spun yarnsring spun yarns （环（环

锭短纤纱）锭短纤纱） Understand the theory of yarn balloon and Understand the theory of yarn balloon and

its implicationsits implications Appreciate the advantages and Appreciate the advantages and

disadvantages of ring spinningdisadvantages of ring spinning

The principle and processThe principle and process A schematic diagram of a ring spinning process A schematic diagram of a ring spinning process

is shown in Figure 1.1. is shown in Figure 1.1.

Figure 1.1Figure 1.1 Diagram of a ring spinning system (Mathews & Diagram of a ring spinning system (Mathews &

Hardingham 1994, p.9)Hardingham 1994, p.9)

It consists of a It consists of a roller drafting unitroller drafting unit （罗拉牵伸系统，（罗拉牵伸系统，罗拉牵伸装置）罗拉牵伸装置） , a , a ringring （钢领）（钢领） and and travellertraveller （钢丝（钢丝圈）圈） assembly, and a assembly, and a bobbinbobbin （筒管，筒子）（筒管，筒子） mounted on a mounted on a spindlespindle 锭子锭子 (driven by a tape). A (driven by a tape). A yarn guideyarn guide 导纱钩导纱钩 (pigtail guide) is also used to (pigtail guide) is also used to guide the yarn. To start ring spinning, a guide the yarn. To start ring spinning, a seed yarnseed yarn 接头纱，引头纱接头纱，引头纱 (on an empty bobbin) is threaded (on an empty bobbin) is threaded through the traveller and the pigtail guide. It is then through the traveller and the pigtail guide. It is then brought to the nip of the front rollers where a thin brought to the nip of the front rollers where a thin strandstrand 须条须条 of fibres emerges. As the bobbin/spindle of fibres emerges. As the bobbin/spindle rotates, the seed yarn is twisted and the twist flows rotates, the seed yarn is twisted and the twist flows upwards to trap the thin strand of fibres emerging upwards to trap the thin strand of fibres emerging from the front rollers. A continuous twisted strand of from the front rollers. A continuous twisted strand of fibres (i.e. the yarn) is thus formed. The newly fibres (i.e. the yarn) is thus formed. The newly formed yarn is wound up onto the bobbin. To avoid formed yarn is wound up onto the bobbin. To avoid the newly formed yarn being wound onto just one the newly formed yarn being wound onto just one spot of the bobbin, the spot of the bobbin, the ring railring rail 钢领板钢领板 oscillates oscillates upwards and downwards during spinning to build up upwards and downwards during spinning to build up the yarn package along the bobbin length.the yarn package along the bobbin length.

The three basic steps of ring spinning, i.e. The three basic steps of ring spinning, i.e. draftingdrafting 牵伸牵伸 , , twistingtwisting 加捻加捻 , and , and winding-onwinding-on 卷绕卷绕 , are discussed below., are discussed below.

► DraftingDrafting The The rovingroving 粗纱粗纱 is drafted by a roller drafting unit on the is drafted by a roller drafting unit on the

ring framering frame 环锭细纱机环锭细纱机 . Figure 1.2a shows the typical . Figure 1.2a shows the typical drafting arrangement. They comprise three drafting arrangement. They comprise three fluted fluted bottom rollersbottom rollers 沟槽下罗拉沟槽下罗拉 (a), against which are pressed (a), against which are pressed three three top rollerstop rollers 上罗拉，胶辊上罗拉，胶辊 (b) that carry the (b) that carry the pivoted pivoted weighting armweighting arm 摆动加压臂，摆动加压杆摆动加压臂，摆动加压杆 (c). The top rollers (c). The top rollers are driven via frictional contacts by the bottom rollers, to are driven via frictional contacts by the bottom rollers, to which the drive is applied. The three pairs of rollers form which the drive is applied. The three pairs of rollers form two two drafting zonesdrafting zones 牵伸区牵伸区 . The . The break draftbreak draft zone zone 后牵伸后牵伸区，预牵伸区区，预牵伸区 formed between the back and middle pairs of formed between the back and middle pairs of rollers has a small draft only, and there is little fibre rollers has a small draft only, and there is little fibre control in this zone. control in this zone.

Figure 1.2 The roller drafting arrangement (Klein1987, p.5)Figure 1.2 The roller drafting arrangement (Klein1987, p.5)

The The main draftmain draft zone zone 主牵伸区 主牵伸区 is formed is formed between the middle and front pairs of rollers. between the middle and front pairs of rollers. Fibre control is achieved by the revolving Fibre control is achieved by the revolving double double apronaprons s 胶圈胶圈 (e) in this zone.(e) in this zone.

► (a) The drafting arrangeme(a) The drafting arrangeme► (b) Cross-section through the drafting (b) Cross-section through the drafting

arrangement arrangement

You may recall the concept of perfect roller You may recall the concept of perfect roller drafting. It requires fibres in the drafting zone drafting. It requires fibres in the drafting zone travel at the speed of back rollers until the travel at the speed of back rollers until the fibre leading endsfibre leading ends 纤维头端纤维头端 reach the reach the front front roller niproller nip 前钳口前钳口 , where they get accelerated , where they get accelerated instantly to front roller speed. Because of this instantly to front roller speed. Because of this requirement, the apron speed is close to the requirement, the apron speed is close to the back roller speed (break draft is small), and the back roller speed (break draft is small), and the aprons have a ‘aprons have a ‘nosenose’’鼻状物，胶圈顶端即胶圈钳口 鼻状物，胶圈顶端即胶圈钳口 which is very close to the front roller nip (see which is very close to the front roller nip (see figure 1.2b). The distance between the apron figure 1.2b). The distance between the apron nose and the front roller nip should be as small nose and the front roller nip should be as small as practically possible to ensure the best fibre as practically possible to ensure the best fibre control during drafting. control during drafting.

Figure 1.2b also shows that the front top roller Figure 1.2b also shows that the front top roller has a slight has a slight ‘overhang‘overhang’ ’ 前倾 前倾 (a) relative to the (a) relative to the front bottom roller, while the middle top roller is front bottom roller, while the middle top roller is set a short distance (b) behind the middle bottom set a short distance (b) behind the middle bottom roller. Such position is found to give smooth roller. Such position is found to give smooth running of the top rollers. In addition, the running of the top rollers. In addition, the ‘overhang’ of the front top roller shortens the ‘overhang’ of the front top roller shortens the spinning triangle (figure 1.3b), which tends to spinning triangle (figure 1.3b), which tends to reduce the rate of yarn breakage (ends-down) in reduce the rate of yarn breakage (ends-down) in spinning. More on spinning. More on spinning trianglespinning triangle 纺纱三角区纺纱三角区is discussed in the following section on twisting.is discussed in the following section on twisting.

Figure 1.3 Front top roller without overhang (a) and with overhang (b)

► TwistingTwisting 加捻加捻 The essence of The essence of staple spinningstaple spinning 短纤维纺纱短纤维纺纱 is is

about twist insertion. In ring spinning, about twist insertion. In ring spinning, twisttwist 捻度，捻度，捻回捻回 is inserted into the thin strand of fibres is inserted into the thin strand of fibres emerging from the front roller nip to form the emerging from the front roller nip to form the yarn. During ring spinning, the spindle is yarn. During ring spinning, the spindle is positively driven by a belt or tape at a constant positively driven by a belt or tape at a constant speed. The speed. The travellertraveller 钢丝圈钢丝圈 is dragged around is dragged around the the ringring 钢领钢领 by the yarn being wound onto the by the yarn being wound onto the bobbin. The rotation of the traveller allows the bobbin. The rotation of the traveller allows the yarn between the traveller and the yarn between the traveller and the pigtail pigtail guideguide 猪尾形导纱钩即导纱钩猪尾形导纱钩即导纱钩 to rotate at the same to rotate at the same speed. The persistence of vision will give us the speed. The persistence of vision will give us the impression of a yarn balloonimpression of a yarn balloon 气圈 气圈 as the yarn as the yarn rotates at a high speed. It is the rotating balloon rotates at a high speed. It is the rotating balloon that inserts the actual twist into the yarn.that inserts the actual twist into the yarn.

As twist is generated in the yarn balloon, it travels As twist is generated in the yarn balloon, it travels past the yarn guide towards the front roller nip. But past the yarn guide towards the front roller nip. But the twist can not quite reach the the twist can not quite reach the nip linenip line 钳口线钳口线 of of the front rollers, because the fibres emerging from the front rollers, because the fibres emerging from the nip have to be diverted inwards to be twisted the nip have to be diverted inwards to be twisted around each other. So a small triangle of fibres, around each other. So a small triangle of fibres, without any twist, is formed between the front without any twist, is formed between the front roller nip and the fibre convergence point as shown roller nip and the fibre convergence point as shown in figure 1.3. This triangle is called the in figure 1.3. This triangle is called the spinning spinning triangletriangle or or twist triangletwist triangle 加捻三角区加捻三角区 . It is also . It is also known as the yarn formation zone. Because there known as the yarn formation zone. Because there is no twist in this zone, it is a weak point and is no twist in this zone, it is a weak point and ends-ends-downdown 断头断头 most often occurs in this region. For most often occurs in this region. For this reason, a large triangle is not desirable. The this reason, a large triangle is not desirable. The height of the spinning triangle is affected by the height of the spinning triangle is affected by the spinning geometry and the twist level in the yarn. spinning geometry and the twist level in the yarn. Overhang of front top roller and high twist will Overhang of front top roller and high twist will reduce the height, hence the level of ends-down in reduce the height, hence the level of ends-down in spinning. spinning.

Because of Because of air dragair drag 空气阻力空气阻力 on the yarn on the yarn balloon and friction between the traveller and balloon and friction between the traveller and ring, the yarn balloon and the traveller rotate at ring, the yarn balloon and the traveller rotate at a slower speed than the spindle. As we will see a slower speed than the spindle. As we will see shortly, the balloon speed keeps changing as shortly, the balloon speed keeps changing as spinning continues. Theoretically, we should spinning continues. Theoretically, we should use the balloon speed to work out the twist use the balloon speed to work out the twist level in the yarn. But this is obviously difficult level in the yarn. But this is obviously difficult because of the changing speed of the balloon. because of the changing speed of the balloon.

In practice, the nominal twist level in the yarn In practice, the nominal twist level in the yarn is calculated using the constant spindle is calculated using the constant spindle rotational speed rather than the balloon rotational speed rather than the balloon speed. The discrepancy arising from this speed. The discrepancy arising from this approximation is quite small. approximation is quite small.

The yarn delivery speed is surface speed of The yarn delivery speed is surface speed of the front rollers. It is also referred to as the the front rollers. It is also referred to as the yarn production speed (rate). yarn production speed (rate).

.)min(

.)min()(

permetresspeeddeliveryYarn

perrevsrpmSpindlemetreperturnsTwist

(1.1)

► Winding-onWinding-on 卷绕卷绕 As mentioned earlier, the yarn balloon rotates As mentioned earlier, the yarn balloon rotates

at a slower speed than the spindle due to air at a slower speed than the spindle due to air drag (resistance) on yarn and the friction drag (resistance) on yarn and the friction between traveller and ring. It is this difference between traveller and ring. It is this difference in rotational speeds of the balloon and the in rotational speeds of the balloon and the spindle (bobbin) that allows the yarn to be spindle (bobbin) that allows the yarn to be wound up onto the bobbin. Without this wound up onto the bobbin. Without this difference in rotational speed or if the traveller difference in rotational speed or if the traveller and spindle rotate in sync, there will be no and spindle rotate in sync, there will be no winding of yarn onto the bobbin. In addition, winding of yarn onto the bobbin. In addition, the linear winding-on speed needs to match the linear winding-on speed needs to match the delivery (surface) speed of the front rollers, the delivery (surface) speed of the front rollers, otherwise the yarn will be too taut or too slack otherwise the yarn will be too taut or too slack during spinning.during spinning.

Figure 1.4 shows a cross-sectional view of the Figure 1.4 shows a cross-sectional view of the bobbin/ring/traveller assembly, with a yarn bobbin/ring/traveller assembly, with a yarn being wound onto the bobbin via the traveller. being wound onto the bobbin via the traveller.

Figure 1.4 The cross-section of the bobbin/ring/traveller assembly

If the diameter of the bobbin at the yarn wind-If the diameter of the bobbin at the yarn wind-on point is dwind-on, the linear winding-on on point is dwind-on, the linear winding-on speed (Vwind-on) should equal the speed (Vwind-on) should equal the circumference of yarn package (π dwind-on) circumference of yarn package (π dwind-on) multiplied by the difference in traveller and multiplied by the difference in traveller and bobbin rotational speeds (nbobbin - ntraveller), bobbin rotational speeds (nbobbin - ntraveller), i.e.i.e.

)( travellerbobbinonwindonwind nndV

This wind-on speed should match the speed at This wind-on speed should match the speed at which the fibre strand is delivered by the front which the fibre strand is delivered by the front rollers. But as the yarn package builds up, its rollers. But as the yarn package builds up, its circumference changes. With a constant circumference changes. With a constant bobbin rotation speed (nbobbin), the traveller bobbin rotation speed (nbobbin), the traveller needs to change its rotation speed (ntraveller) needs to change its rotation speed (ntraveller) so that the winding speed (Vwind-on) remains so that the winding speed (Vwind-on) remains constant and matches the front roller delivery constant and matches the front roller delivery speed. The beauty of ring spinning is that the speed. The beauty of ring spinning is that the traveller can self-adjust its rotational speed traveller can self-adjust its rotational speed during spinning. It's all done automatically by during spinning. It's all done automatically by the traveller itself. the traveller itself.

► Characteristics of ring spun yarnsCharacteristics of ring spun yarns Ring spun yarns are characterised by their good Ring spun yarns are characterised by their good

strength and smoothnessstrength and smoothness 光滑光滑 , and their , and their relatively high relatively high hairinesshairiness 毛羽毛羽 ..

Ring spun yarns feature near-helical fibre Ring spun yarns feature near-helical fibre

configuration in the yarn structure. This is a configuration in the yarn structure. This is a result of twisting a strand of well-aligned and result of twisting a strand of well-aligned and parallel fibres. In the whole processing stages parallel fibres. In the whole processing stages from from cardingcarding 梳理梳理 right up to ring spinning, right up to ring spinning, fibre alignment has been an essential aim. By fibre alignment has been an essential aim. By having well-aligned fibres within the yarn having well-aligned fibres within the yarn structure, the fibres are able to share the stress structure, the fibres are able to share the stress in the yarn when a force is applied to stretch in the yarn when a force is applied to stretch the yarn. This is why ring spun yarns have the yarn. This is why ring spun yarns have excellent strength. The good fibre alignment excellent strength. The good fibre alignment and the near-helical configuration of surface and the near-helical configuration of surface fibres also impart the yarn with a smooth and fibres also impart the yarn with a smooth and neat surfaceneat surface..

During ring spinning, the fibres on the two edges of During ring spinning, the fibres on the two edges of the spinning triangle must be strongly deflected to the spinning triangle must be strongly deflected to get bound into the yarn at the get bound into the yarn at the convergence pointconvergence point汇合点汇合点 . The deflection is higher with a smaller . The deflection is higher with a smaller triangle (figure 1.3b). Not all fibres will be bound triangle (figure 1.3b). Not all fibres will be bound into the yarn, particularly those fibres with a high into the yarn, particularly those fibres with a high rigidityrigidity 刚度，硬挺度刚度，硬挺度 and low and low cohesioncohesion 抱合性，粘合抱合性，粘合性性 with neighbouring fibres. As a consequence, some with neighbouring fibres. As a consequence, some of these fibres escape the twisting action and are of these fibres escape the twisting action and are lost as lost as flyfly 飞花飞花 , others may only get partially bound , others may only get partially bound in with their remaining parts projecting outside the in with their remaining parts projecting outside the yarn surface as hair fibres. This is why ring spinning yarn surface as hair fibres. This is why ring spinning produces relatively hairy yarns, especially when produces relatively hairy yarns, especially when spinning short and coarse fibres. The majority of spinning short and coarse fibres. The majority of these hair fibres have their tail ends sticking out of these hair fibres have their tail ends sticking out of the yarn surface. This is because as the tail ends the yarn surface. This is because as the tail ends emerge from the front roll nip, they are no longer emerge from the front roll nip, they are no longer under any positive control and the under any positive control and the centrifugal centrifugal forceforce 离心力离心力 from the yarn rotation tends to throw from the yarn rotation tends to throw these uncontrolled tail ends out away from the yarn these uncontrolled tail ends out away from the yarn body, making them protruding hair fibres. body, making them protruding hair fibres.

Figure 1.5 shows a photo of the spinning Figure 1.5 shows a photo of the spinning triangle and the hair fibres (trailing ends) on triangle and the hair fibres (trailing ends) on the newly formed yarn.the newly formed yarn.

Figure 1.5 Formation of trailing hairs in the spinning triangle (Wang et al 1999)

The hairiness is a desirable feature of staple The hairiness is a desirable feature of staple spun yarns. But too much of it can be a costly spun yarns. But too much of it can be a costly nuisance. The latest nuisance. The latest compact spinningcompact spinning 紧密纺，紧密纺，聚集纺聚集纺 technology, released at the 1999 technology, released at the 1999 international textile machinery exhibition in international textile machinery exhibition in Paris, eliminates the spinning triangle all Paris, eliminates the spinning triangle all together by using a modified drafting together by using a modified drafting arrangement to compact the fibres before arrangement to compact the fibres before twist is inserted. The compact spun yarns are twist is inserted. The compact spun yarns are very smooth with few protruding fibre ends.very smooth with few protruding fibre ends.

► Twist variation within yarn packageTwist variation within yarn package We mentioned in the previous section that as We mentioned in the previous section that as

the yarn package builds up, the traveller the yarn package builds up, the traveller adjusts its rotational speed automatically. This adjusts its rotational speed automatically. This would suggest that within a yarn package, the would suggest that within a yarn package, the twist level would be different. This is true. But twist level would be different. This is true. But the difference is only marginal as the following the difference is only marginal as the following examples demonstrates.examples demonstrates.

Assume:Assume: (1) (1) CopCop 管纱，纬管，纡子管纱，纬管，纡子 dimensions as in the diadimensions as in the dia

gram belowgram below (2) Front roll delivery speed is 15 m/min(2) Front roll delivery speed is 15 m/min (3) Spindle speed is 10,000 rpm(3) Spindle speed is 10,000 rpm

Since the linear wind-on speed = winding rpm Since the linear wind-on speed = winding rpm x circumference of the wind-on point = front x circumference of the wind-on point = front roll delivery speed, we have:roll delivery speed, we have:

revs 191 = 10 x 2.5 x

15 = A at rpm Winding

2-

revs 80 = 10 x 6 x

15 = B at rpm Winding

2-

IIgnoring the effect of up and down movement gnoring the effect of up and down movement of ring rail, we have:of ring rail, we have:

Traveller speed at A = 10,000 - 191 = 9,809 Traveller speed at A = 10,000 - 191 = 9,809 rpmrpm

Traveller speed at B = 10,000 - 80 = 9,920 Traveller speed at B = 10,000 - 80 = 9,920 rpmrpm

Therefore, Therefore,

twists/m 662 = 15

9920 B at Twist

twists/m, 654 = 15

9809= A at Twist

The difference in twist is about 1% only. If the The difference in twist is about 1% only. If the effect of added potential twist due to unwinding effect of added potential twist due to unwinding the yarn axially (at the next process) is taken the yarn axially (at the next process) is taken into account, then at the minimum diameter A, into account, then at the minimum diameter A, more twists will be added and at the maximum more twists will be added and at the maximum diameter B less twists will be added thus diameter B less twists will be added thus bringing the twist levels more or less equal at bringing the twist levels more or less equal at both points. Therefore, the effect of traveller both points. Therefore, the effect of traveller speed change (and cop build-up) on yarn twist speed change (and cop build-up) on yarn twist is very small.is very small.

Physics of ring spinningPhysics of ring spinning

The physics of ring spinning considers the The physics of ring spinning considers the various forces acting on the yarn in the balloon, various forces acting on the yarn in the balloon, as well as the forces acting on the traveller. as well as the forces acting on the traveller. This consideration is necessary in order to gain This consideration is necessary in order to gain an insight into the nature of ring spinning, and an insight into the nature of ring spinning, and how different parameters/settings affect the how different parameters/settings affect the spinning performance. spinning performance.

► Balloon theoryBalloon theory

Consider the section of yarn between the Consider the section of yarn between the pigtail and the traveller as shown in figure pigtail and the traveller as shown in figure 1.6. 1.6.

: angular velocity of balloon; m: yarn mass/unit length Tc: centrifugal force = m ds 2 y; H: balloon height

R: ring radius; T: yarn tensionFigure 1.6 Forces acting on the balloon

The centrifugal forces associated with the The centrifugal forces associated with the rotation of the yarn makes this section of the rotation of the yarn makes this section of the yarn balloon out to form a yarn balloon. Now yarn balloon out to form a yarn balloon. Now consider a small element, of length ds, in the consider a small element, of length ds, in the balloon. Ignoring the balloon. Ignoring the air dragair drag 空气阻力空气阻力 and and other small forces, the only forces acting on other small forces, the only forces acting on this small element would be the this small element would be the tensiontensions Ts T（张力（张力 TT ） ） and T+dT at the two ends of the and T+dT at the two ends of the element, plus the centrifugal force (m ds element, plus the centrifugal force (m ds 2 y) 2 y) acting on the element.acting on the element.

In equilibrium, the forces acting on each In equilibrium, the forces acting on each element in the balloon should be balanced in element in the balloon should be balanced in both X and Y directions. So we haveboth X and Y directions. So we have

0)(cos)(cos ddT + T T

0)(sin)(sin ddTTTc T

or

y ds m- = Td

0 =Td2

)sin(

)cos(

If we assume the balloon is slim, i.e. If we assume the balloon is slim, i.e. , , and yarn and yarn tension (T) is constant and equals To (the tension (T) is constant and equals To (the tension at the pigtail guide), we get the tension at the pigtail guide), we get the following balloon equation.following balloon equation.

It should be stressed that this is the simplified It should be stressed that this is the simplified balloon equation. The detailed derivation need balloon equation. The detailed derivation need not concern us here. What we are interested in not concern us here. What we are interested in is the practical implications of this so called is the practical implications of this so called balloon theory.balloon theory.

x) T

m(

H) T

m(

R =y

O

2

O

2

sin

sin(1.2)(1.2)

The shape of the balloon is sinusoidal, and its The shape of the balloon is sinusoidal, and its amplitude (A) and wavelength (amplitude (A) and wavelength () are:) are:

H) T

m(

R = A

O

2sin

(1.3)(1.3)

mT

2 =

T

m

2 = O

O

2

(1.4)

A A sine curvesine curve 正弦曲线正弦曲线 can contain one or more can contain one or more points where the curve crosses the axis, and points where the curve crosses the axis, and these crossing points are called these crossing points are called nodesnodes 节点节点 as as shown in figure 1.7. shown in figure 1.7.

Figure 1.7 Formation of node in yarn balloons

For normal spinning, it is obvious from figure 1.7 For normal spinning, it is obvious from figure 1.7 (left diagram) that the (left diagram) that the balloon heightballoon height 气圈高度气圈高度(H) should be less than half the wavelength (H) should be less than half the wavelength ((/2). If the balloon height is more than half the /2). If the balloon height is more than half the wavelength (i.e. H > wavelength (i.e. H > /2), a node appears in the /2), a node appears in the balloon as indicated in figure 1.7 (right balloon as indicated in figure 1.7 (right diagram). What this means is that during diagram). What this means is that during spinning, the yarn at the node would always spinning, the yarn at the node would always want to be in the space occupied by the yarn want to be in the space occupied by the yarn package, so that the yarn at the node strikes the package, so that the yarn at the node strikes the rotating package during spinning, resulting in an rotating package during spinning, resulting in an end-breakend-break 断头断头 . Therefore, this node should be . Therefore, this node should be avoided for normal spinning. avoided for normal spinning.

We now know that it is impossible to operate a We now know that it is impossible to operate a ring spinning machine with a ring spinning machine with a multiple-node multiple-node balloonballoon 多节多节气圈气圈 (H > (H > /2). However, means /2). However, means that the yarn package height or size is limited. that the yarn package height or size is limited. Since, to spin yarn onto a large package, H Since, to spin yarn onto a large package, H should be large, this requires a large to avoid a should be large, this requires a large to avoid a node. A large is achievable (according to the node. A large is achievable (according to the equation 1.4) through:equation 1.4) through:

either a large yarn tension which may lead to either a large yarn tension which may lead to yarn yarn breakage;breakage;

or a low spindle speed , which usually means or a low spindle speed , which usually means low production rate. low production rate.

In practice, a In practice, a BALLOON CONTROL RINGBALLOON CONTROL RING 气圈控制气圈控制环环 is normally used to restrict balloon expansion, is normally used to restrict balloon expansion, so that large yarn package may be used without so that large yarn package may be used without having to reduce the production or increase the having to reduce the production or increase the yarn tension. yarn tension.

Figure 1.8 shows a sketch of the ring spinning Figure 1.8 shows a sketch of the ring spinning process with a balloon control ring restricting the process with a balloon control ring restricting the balloon size. It should be pointed out though that balloon size. It should be pointed out though that the balloon control (restriction) ring tends to hinder the balloon control (restriction) ring tends to hinder doffingdoffing 落纱落纱 (removal of full package from (removal of full package from spindle). For this reason, balloon control rings are spindle). For this reason, balloon control rings are not universally popular on modern ring frames not universally popular on modern ring frames fitted with automatic doffing systems. Instead, fitted with automatic doffing systems. Instead, these ring frames use very small package sizes to these ring frames use very small package sizes to reduce balloon size and yarn tension. reduce balloon size and yarn tension.

Figure 1.8 Sketch of ring spinning with a balloon control ring

► Forces acting on the travellerForces acting on the traveller Figure 1.9 shows the different forces acting on a Figure 1.9 shows the different forces acting on a

traveller during spinning.traveller during spinning.

Tt = yarn tension at traveller; TwTt = yarn tension at traveller; Tw = yarn wind-on tension= yarn wind-on tensionN = normal force between ring and traveller; Fa = air drag on travellerN = normal force between ring and traveller; Fa = air drag on travellerF = frictional drag between ring and traveller (= N ); mg = traveller F = frictional drag between ring and traveller (= N ); mg = traveller weightweightTc = centripetal forces on traveller = m R Tc = centripetal forces on traveller = m R (where m = traveller mass; R = ring radius; = spindle speed)(where m = traveller mass; R = ring radius; = spindle speed)

RT

Figure 1.9 Forces acting on a traveller during spinning

All these forces must be balanced during All these forces must be balanced during spinning. It is possible to derive equations for spinning. It is possible to derive equations for this force balance to show the effect of variables this force balance to show the effect of variables such as traveller weight, balloon size, spindle such as traveller weight, balloon size, spindle speed, speed, yarn countyarn count 纱线号数，纱线支数纱线号数，纱线支数 etc on the etc on the spinning tension.spinning tension.

In equilibrium:In equilibrium:

Ignoring Fa and mg, this gives the yarn Ignoring Fa and mg, this gives the yarn wind-on wind-on tensiontension 卷绕张力卷绕张力 ,,

0 = forces vertical 0; = forces radial 0; = forces tangential

) - (

+

R m = Tw

RT

2

tansincossin

cos(1.5)

Again, the detailed derivation need not concern us Again, the detailed derivation need not concern us here, and we should focus on the following here, and we should focus on the following implications of this equation.implications of this equation.

(1)(1) Wind-on tension increases with the square of Wind-on tension increases with the square of the spindle speed (the spindle speed (). Since wind-on tension is ). Since wind-on tension is directly related to spinning tension in the yarn directly related to spinning tension in the yarn above the pigtail guide, increasing the spindle above the pigtail guide, increasing the spindle rotational speed will drastically increase the yarn rotational speed will drastically increase the yarn tension, which may lead to increased ends-down. tension, which may lead to increased ends-down. This limits the maximum spindle speed in ring This limits the maximum spindle speed in ring spinning. If spindle speed is reduced to reduce spinning. If spindle speed is reduced to reduce yarn tension, the production rates will drop.yarn tension, the production rates will drop.

(2) (2) Winding tension increases as package Winding tension increases as package diameter decreases. This puts a limit on the diameter decreases. This puts a limit on the minimum diameter of the empty bobbin.minimum diameter of the empty bobbin.

This is not obvious from equation 1.5. But if we This is not obvious from equation 1.5. But if we look at figure 1.9a, we will see that as the yarn look at figure 1.9a, we will see that as the yarn package diameter decreases, the winding angle package diameter decreases, the winding angle or or angle of leadangle of lead 卷绕角卷绕角 (() decreases. As the ) decreases. As the angle of lead decreases, the tangential angle of lead decreases, the tangential componentcomponent 切向分力 切向分力 (T') of the winding tension (T') of the winding tension (Tw) reduces, since T' = Tw sin(Tw) reduces, since T' = Tw sin. But T' needs to . But T' needs to be sufficient to be able to move the traveller be sufficient to be able to move the traveller around the ring during spinning. Therefore, as around the ring during spinning. Therefore, as the package diameter reduces, the winding the package diameter reduces, the winding tension (Tw) will have to increase to maintain tension (Tw) will have to increase to maintain the T' required to move the traveller.the T' required to move the traveller.

Figure 1.9a Winding tension and winding angle as indicated in figure 1.9

(3)Since larger balloon means higher yarn tension, (3)Since larger balloon means higher yarn tension, the winding tension increases as the balloon gets the winding tension increases as the balloon gets longer. This limits the length of the bobbin.longer. This limits the length of the bobbin.

Points (2) & (3) suggest that a yarn is most likely Points (2) & (3) suggest that a yarn is most likely to break when spinning at the bottom of an empty to break when spinning at the bottom of an empty bobbin when the winding angle (bobbin when the winding angle () is the smallest. ) is the smallest. This has been confirmed in practice. For this This has been confirmed in practice. For this reason, some machines operate at a lower speed reason, some machines operate at a lower speed at the start (since spinning tension increases with at the start (since spinning tension increases with the square of spindle speed) to avoid the ends-the square of spindle speed) to avoid the ends-down during start-up. down during start-up.

This also explains the general rule used in practice This also explains the general rule used in practice that the angle of lead (that the angle of lead () should not be less than ) should not be less than 28O. This minimum angle of lead is equivalent to a 28O. This minimum angle of lead is equivalent to a minimum ratio of minimum ratio of (empty bobbin or tube (empty bobbin or tube diameter)/(ring diameter) = 0.47diameter)/(ring diameter) = 0.47. .

(4)Winding tension increases as ring radius (4)Winding tension increases as ring radius 钢领钢领半径半径 (R) increases. This limits the size of the full (R) increases. This limits the size of the full package that must fit inside the ring.package that must fit inside the ring.

Points (2), (3) & (4) mean that there is a limit to Points (2), (3) & (4) mean that there is a limit to how much yarn can fit onto the yarn package how much yarn can fit onto the yarn package enclosed by the ring.enclosed by the ring.

The The package capacitypackage capacity 管纱卷装容量管纱卷装容量 is is approximately proportional to (ring diameter)2, approximately proportional to (ring diameter)2, so a large ring diameter is desirable for so a large ring diameter is desirable for increased package capacity. But in practice, the increased package capacity. But in practice, the ring diameter is restricted by considerations of ring diameter is restricted by considerations of the yarn tension, the minimum angle of lead the yarn tension, the minimum angle of lead previously discussed, as well as other factors previously discussed, as well as other factors such as such as power consumptionpower consumption 功率消耗功率消耗 , spindle , spindle rpm, and traveller speed limitations (see rpm, and traveller speed limitations (see relationships below).relationships below).

diameterRingspeedspindleMax

1.

diameterRingspeedtravellerlinearMax .

This is why we do not see ring spinning machines This is why we do not see ring spinning machines with very large rings and very small bobbins with very large rings and very small bobbins (tubes). For coarser and stronger yarns, large (tubes). For coarser and stronger yarns, large ring radius and yarn packages are used to allow ring radius and yarn packages are used to allow for more yarns on the package. For finer yarns, for more yarns on the package. For finer yarns, both ring radius and the package size are both ring radius and the package size are smaller. Most smaller. Most worsted yarnsworsted yarns 精梳纱线精梳纱线 are spun are spun using rings between 45 and 75 mm in diameter using rings between 45 and 75 mm in diameter at spindle rotational speeds between 7,000 and at spindle rotational speeds between 7,000 and 12,000 rpm. Short staple yarns are spun with 12,000 rpm. Short staple yarns are spun with smaller rings, but at about twice the spindle smaller rings, but at about twice the spindle speeds used for worsted yarns.speeds used for worsted yarns.

(5)Winding tension increases with traveller (5)Winding tension increases with traveller mass. Heavier yarns require a greater mass. Heavier yarns require a greater centripetal force to keep them rotating. centripetal force to keep them rotating. Traveller mass is used as a variable to increase Traveller mass is used as a variable to increase the tension and generate the higher centripetal the tension and generate the higher centripetal force for heavier yarns. The traveller mass is force for heavier yarns. The traveller mass is usually chosen according to the linear density usually chosen according to the linear density of the yarn being spun.of the yarn being spun.

(6)Winding tension increases with an increase (6)Winding tension increases with an increase in the frictional coefficient between the ring in the frictional coefficient between the ring and the traveller (and the traveller (RT). RT).

While we talk about the winding tension here, While we talk about the winding tension here, we should note that the spinning tension in the we should note that the spinning tension in the yarn is directly related to winding tension, so yarn is directly related to winding tension, so any factor that contributes to an increase in any factor that contributes to an increase in winding tension will also increase the tension in winding tension will also increase the tension in the yarn during ring spinning. In fact all the the yarn during ring spinning. In fact all the implications for winding tension apply to tension implications for winding tension apply to tension in the yarn or spinning tension.in the yarn or spinning tension.

Developments and limitations of ring Developments and limitations of ring spinningspinning

As indicated in the beginning of this module, As indicated in the beginning of this module, ring spinning is the most versatile spinning ring spinning is the most versatile spinning process. It can spin yarns of a wide range of process. It can spin yarns of a wide range of counts (from very fine to coarse) from different counts (from very fine to coarse) from different types of fibres (short as well as long staple types of fibres (short as well as long staple fibres). The quality of ring spun yarns has been a fibres). The quality of ring spun yarns has been a benchmark against which the quality of yarns benchmark against which the quality of yarns produced on other spinning systems is judged. produced on other spinning systems is judged.

The basic principle of ring spinning has not The basic principle of ring spinning has not

changed much since its invention by Thorpe in changed much since its invention by Thorpe in 1828. But there have been numerous 1828. But there have been numerous developments of the ring spinning system, developments of the ring spinning system, particularly in the short staple sector. These particularly in the short staple sector. These developments include:developments include:

► Automatic doffing of full cops (bobbins)Automatic doffing of full cops (bobbins)► Linkage to Linkage to roving frameroving frame 粗纱机，此处指粗细联粗纱机，此处指粗细联

装置的发展。装置的发展。► Linkage to Linkage to automatic winding machineautomatic winding machine 自动自动

络纱机，此处指细络联装置的发展。络纱机，此处指细络联装置的发展。

Developments of worsted ring frames are Developments of worsted ring frames are relatively slow, because the market of worsted relatively slow, because the market of worsted spinning is much smaller than short staple spinning is much smaller than short staple spinning. Therefore the incentive for spinning. Therefore the incentive for manufacturers of worsted ring frame is not very manufacturers of worsted ring frame is not very high.high.

Over the years, the ring spinning system has also Over the years, the ring spinning system has also been modified to improve the properties of ring been modified to improve the properties of ring spun yarns. Examples of such modifications spun yarns. Examples of such modifications include:include:

► Sirospun Sirospun 赛洛纺赛洛纺 (see the reading “Sirospun - A (see the reading “Sirospun - A yarn with character" by Waldauser)yarn with character" by Waldauser)

► Compact spinningCompact spinning 紧密纺紧密纺 (see the reading “The (see the reading “The Suessen Elite Spinning system for long and short Suessen Elite Spinning system for long and short staple fibres”, courtesy of Suessen, Germany)staple fibres”, courtesy of Suessen, Germany)

Ring spinning also has several major limitations. Ring spinning also has several major limitations. These limitations include:These limitations include:

► High power consumptionHigh power consumption► Small package sizeSmall package size► Low production rateLow production rate

Staple spinning is basically about twist Staple spinning is basically about twist insertion. In ring spinning, twist insertion insertion. In ring spinning, twist insertion requires the rotation of the whole yarn package requires the rotation of the whole yarn package on the spindle. About 95% of the power used in on the spindle. About 95% of the power used in ring spinning is consumed by rotating the yarn ring spinning is consumed by rotating the yarn package to insert twist. This leads to the package to insert twist. This leads to the relatively high power consumption for the ring relatively high power consumption for the ring spinning systems.spinning systems.

The package size is limited in ring spinning due The package size is limited in ring spinning due to the need to reduce the balloon height and to the need to reduce the balloon height and yarn tension, as discussed in the section on the yarn tension, as discussed in the section on the physics of ring spinning.physics of ring spinning.

Perhaps the most serious limitation of ring Perhaps the most serious limitation of ring spinning is its low production rate. We already spinning is its low production rate. We already know the relationship between yarn twist level, know the relationship between yarn twist level, spindle speed, and yarn production or delivery spindle speed, and yarn production or delivery speed (equation 1.1). According to its end-use, a speed (equation 1.1). According to its end-use, a ring spun yarn needs to have a certain level of ring spun yarn needs to have a certain level of twist, which is determined before spinning is twist, which is determined before spinning is started. From equation 1.1, we know that the started. From equation 1.1, we know that the only way of speeding up the yarn delivery speed only way of speeding up the yarn delivery speed or production rate is to increase the spindle or production rate is to increase the spindle rotation speed.rotation speed.

We already know that any increase in spindle We already know that any increase in spindle speed will lead to significant increase in yarn speed will lead to significant increase in yarn tension, hence the possibility of ends-down. In tension, hence the possibility of ends-down. In addition, with the increase in spindle speed, the addition, with the increase in spindle speed, the traveller speed increases. This increases the traveller speed increases. This increases the friction between the traveller and the ring. friction between the traveller and the ring. Considerable heat is generated because of this Considerable heat is generated because of this friction, which may result in traveller burning friction, which may result in traveller burning during spinning. Because of these, spindle during spinning. Because of these, spindle speed can not be increased at will, and yarn speed can not be increased at will, and yarn production is limited as a consequence. production is limited as a consequence. Currently, the maximum spindle speed for short Currently, the maximum spindle speed for short staple ring spinning is about 25,000 rpm, and staple ring spinning is about 25,000 rpm, and that for long staple ring spinning is about that for long staple ring spinning is about 15,000 rpm. 15,000 rpm.

The following example further illustrates this The following example further illustrates this point.point.

Suppose a Suppose a spinning millspinning mill 纺纱厂纺纱厂 produces a produces a standard 49 tex yarn, with a twist factor of standard 49 tex yarn, with a twist factor of 3500 tpm , on 1,000 spindles operating at 3500 tpm , on 1,000 spindles operating at 15,000 revolutions per minute and 90% 15,000 revolutions per minute and 90% efficiency. If the mill works 120 hours efficiency. If the mill works 120 hours perweek, calculate the weight of yarn perweek, calculate the weight of yarn produced per week. produced per week.

Note that:Note that:

So we need to know the production per spindle firsSo we need to know the production per spindle firs

t. This requires the yarn twist level.t. This requires the yarn twist level. We know from the first module of this unit We know from the first module of this unit

that:that:

efficiency Machinex spindlesof No. x production Spindle=production Machine

Tex

factorTwisttpmTwist )(

In this example, we know the In this example, we know the twist factortwist factor 捻系捻系数数 and and yarn countyarn count 纱线号数纱线号数 . So the twist level . So the twist level in the yarn is: in the yarn is:

Using equation 1.1 we have:Using equation 1.1 we have:

TThis is the production rate per spindle running at 10his is the production rate per spindle running at 100% efficiency. Since there are 1,000 spindles runnin0% efficiency. Since there are 1,000 spindles running at 90% efficiency, the total production of the ring fg at 90% efficiency, the total production of the ring frame will be:rame will be:

Machine production = 30 m/min x 1,000 x 90% = 27,0Machine production = 30 m/min x 1,000 x 90% = 27,000 m/min.00 m/min.

)(50049

3500tpmtwistYarn

min)/(30500

15000min)/( m

twist

rpmSpindlemspeeddeliveryYarn

Now the machine operates 120 hours a week, so tNow the machine operates 120 hours a week, so the weekly machine production will be:he weekly machine production will be:

Weekly machine production = 27,000 m/min x (120 Weekly machine production = 27,000 m/min x (120 x 60 min) = 194,400,000 m = 194,400 km.x 60 min) = 194,400,000 m = 194,400 km.

For a 49 tex yarn, each kilo meter of yarn weighs 49 For a 49 tex yarn, each kilo meter of yarn weighs 49 grams. So a total of 194,400 km of yarn would weiggrams. So a total of 194,400 km of yarn would weigh about 9525600 grams or 9525.6 kg. In other wordh about 9525600 grams or 9525.6 kg. In other words, the average production per spindle is about 9.5 s, the average production per spindle is about 9.5 kg per 120 hour week. kg per 120 hour week.

If finer yarns are produced, the weight will be even If finer yarns are produced, the weight will be even less. This gives you an idea of the production rate less. This gives you an idea of the production rate of ring frames.of ring frames.

Winding and folding after spinningWinding and folding after spinning

It is convenient here to discuss some of It is convenient here to discuss some of the key processes immediately after ring the key processes immediately after ring spinning - winding and folding. spinning - winding and folding.

► WindingWinding We already know that ring spun yarns are wound onto We already know that ring spun yarns are wound onto

small bobbins or cops during spinning. Each bobbin small bobbins or cops during spinning. Each bobbin contains only a few grams of yarn. For transport, storage contains only a few grams of yarn. For transport, storage and further processing, the small cops of yarn must be and further processing, the small cops of yarn must be rewound onto large yarn packages of the right density and rewound onto large yarn packages of the right density and structure. If the yarns are to be dyed, then regular yarn structure. If the yarns are to be dyed, then regular yarn packages of a low density are necessary for even and packages of a low density are necessary for even and good penetration of the dye liquor. For weavinggood penetration of the dye liquor. For weaving 机织 机织 and and knittingknitting 针织针织 , fault free yarns should be prepared on a , fault free yarns should be prepared on a large package of high density. So the first process after large package of high density. So the first process after ring spinning is yarn winding (or rewinding). Today ring spinning is yarn winding (or rewinding). Today automatic winding machines perform a number of automatic winding machines perform a number of important functions. These include automatic change of important functions. These include automatic change of the small yarn cops, the small yarn cops, automatic yarn piecingautomatic yarn piecing 自动接头自动接头 , , and yarn and yarn clearingclearing 清纱清纱 . During yarn clearing, . During yarn clearing, yarn faultsyarn faults 纱线疵点纱线疵点 such as very such as very thick and very thin placesthick and very thin places 纱线粗纱线粗节和纱线细节节和纱线细节 are removed. Otherwise these faults may are removed. Otherwise these faults may cause problems in weaving or show up in the final fabrics cause problems in weaving or show up in the final fabrics as defects. as defects.

The two basic winding mechanisms are: (a) a The two basic winding mechanisms are: (a) a package rotation mechanismpackage rotation mechanism 卷装回转机构，卷卷装回转机构，卷装回转装置装回转装置 to form coils of yarn on the package; to form coils of yarn on the package; and (b) a and (b) a yarn traverse mechanismyarn traverse mechanism 纱线横动装纱线横动装置置 to vary the position of wind. Two important to vary the position of wind. Two important parameters about winding are the parameters about winding are the wind ratiowind ratio 卷卷绕比绕比 and and wind anglewind angle 卷绕角卷绕角 (or angle of wind). (or angle of wind). The wind ratio is defined as the number of yarn The wind ratio is defined as the number of yarn coils wound on a package while the traverse coils wound on a package while the traverse mechanism completes a mechanism completes a full strokefull stroke 全程全程 in one in one direction. In other words, the wind ratio is the direction. In other words, the wind ratio is the number of revolutions of yarn package per number of revolutions of yarn package per traverse stroke. The wind angle is defined as the traverse stroke. The wind angle is defined as the angle contained between a coil of yarn on the angle contained between a coil of yarn on the surface of a package and the diametrical plane of surface of a package and the diametrical plane of the package as indicated in figure 1.10. the package as indicated in figure 1.10. Increasing the wind angle will increase package Increasing the wind angle will increase package stability but reduce the package density.stability but reduce the package density.

Figure 1.10 Angle of wind and angle of crossingFigure 1.10 Angle of wind and angle of crossing

► Figure 1.11shows the principle of Figure 1.11shows the principle of random cross random cross windingwinding 交叉卷绕 交叉卷绕 oror drum winding drum winding 槽筒卷绕，鼓盘式卷槽筒卷绕，鼓盘式卷绕绕 . A . A grooved drumgrooved drum 沟槽鼓盘即槽筒沟槽鼓盘即槽筒 is used as both is used as both package rotation mechanism and yarn traverse package rotation mechanism and yarn traverse mechanism. During winding, the yarn package rotates mechanism. During winding, the yarn package rotates via frictional contact with the surface of the grooved via frictional contact with the surface of the grooved drum, which is driven at a constant speed. Because the drum, which is driven at a constant speed. Because the grooved drum rotates at a constant speed, the linear grooved drum rotates at a constant speed, the linear speed at which the yarn is wound onto the package is speed at which the yarn is wound onto the package is also constant. As winding continues, the package also constant. As winding continues, the package diameter grows, and the rotational speed (rpm) of the diameter grows, and the rotational speed (rpm) of the package decreases to maintain a constant yarn linear package decreases to maintain a constant yarn linear speed (linear speed = package rpm x package speed (linear speed = package rpm x package circumference). As a result, the wind ratio changes as the circumference). As a result, the wind ratio changes as the package builds up, but the angle of wind remains package builds up, but the angle of wind remains constant (i.e. package density is constant). When the constant (i.e. package density is constant). When the wind ratio becomes an integer or half integer, each wind ratio becomes an integer or half integer, each succeeding wrap of yarn is laid exactly on top of the succeeding wrap of yarn is laid exactly on top of the preceding wrap, and a ribbon forms until the wind ratio preceding wrap, and a ribbon forms until the wind ratio assumes a value that is sufficiently different from the assumes a value that is sufficiently different from the integer or half integer. This is the so called integer or half integer. This is the so called ribboning ribboning effecteffect 重叠效应重叠效应 in random cross winding.in random cross winding.

Figure 1.12 shows a Figure 1.12 shows a cone packagecone package 锥形卷装锥形卷装with ribbons. Ribbonswith ribbons. Ribbons 指重叠的纱线条带 指重叠的纱线条带 are a are a serious problem because they interfere with serious problem because they interfere with smooth unwinding of the package, cause smooth unwinding of the package, cause localised abrasion of yarns in the ribbon, and localised abrasion of yarns in the ribbon, and change the density of the package (ribbons are change the density of the package (ribbons are much denser than the rest of the package). For much denser than the rest of the package). For this reason, many random cross winders are this reason, many random cross winders are fitted with ribbon breaking devices to prevent fitted with ribbon breaking devices to prevent ribbon formation. These devices may oscillate ribbon formation. These devices may oscillate the yarn package or the grooved drum the yarn package or the grooved drum sideways in a random manner, or introduce sideways in a random manner, or introduce rational speed variations to the yarn package.rational speed variations to the yarn package.

Figure 1.11 Random cross winding (Lord 1981, p.557)

Figure 1.12 A cross wound cone package with ribbons

Another form of winding is precision cross winding, iAnother form of winding is precision cross winding, in which the wind ratio is constant but the angle of wn which the wind ratio is constant but the angle of wind decreases as the package builds up. The mechanind decreases as the package builds up. The mechanisms of precision winding are shown in figure 1.13. Inisms of precision winding are shown in figure 1.13. Instead of using a groove drum to drive the package vistead of using a groove drum to drive the package via frictional contact, the package a frictional contact, the package mandrelmandrel 辊筒铁芯辊筒铁芯子，心轴子，心轴 is driven positively by a motor, and a recipris driven positively by a motor, and a reciprocating yarn guide is used as the traversing mechaniocating yarn guide is used as the traversing mechanism. Ribbon formation is avoided by setting the packsm. Ribbon formation is avoided by setting the package rpm so that the wind ratio is not an integer or haage rpm so that the wind ratio is not an integer or half integer. As the package builds up, the angle of winlf integer. As the package builds up, the angle of wind decreases so the package density increases. Precisd decreases so the package density increases. Precision winding can be used to build a very dense packaion winding can be used to build a very dense package.ge.

Figure 1.13 Precision cross winding (Lord 1981, p.557)

Assembly windingAssembly winding 并线络筒并线络筒 is the winding of is the winding of two or more yarns on to a single package side two or more yarns on to a single package side by side, without adding any twist. This is by side, without adding any twist. This is usually done in preparation for the subsequent usually done in preparation for the subsequent folding or twisting operation.folding or twisting operation.

► Folding or twistingFolding or twisting 并纱或捻线并纱或捻线 Folding is a process of combining two or more Folding is a process of combining two or more

single yarns by twisting. It is also known as single yarns by twisting. It is also known as twistingtwisting, , plyingplying and and doublingdoubling. The resultant . The resultant yarn is a yarn is a folded yarnfolded yarn 股线股线 , also known as plied , also known as plied yarn or doubled yarn. Two-folding is a typical yarn or doubled yarn. Two-folding is a typical process in the worsted industry.process in the worsted industry.

You may wonder why it is necessary to twist You may wonder why it is necessary to twist together two single yarns to make a two-fold together two single yarns to make a two-fold yarn. This is because a two-fold yarn has a yarn. This is because a two-fold yarn has a number of distinct advantages over its single number of distinct advantages over its single components, including:components, including:

(1)A balanced yarn can be produced(1)A balanced yarn can be produced

Single yarns are twist lively. In other words, Single yarns are twist lively. In other words, they always untwist when there is an they always untwist when there is an opportunity. The twist liveliness may lead to opportunity. The twist liveliness may lead to snarlingsnarling 纱线扭结，缠结纱线扭结，缠结 when the tension in when the tension in the yarn is insufficient. Twist liveliness may the yarn is insufficient. Twist liveliness may also need to distortion of the resultant fabrics, also need to distortion of the resultant fabrics, knitted fabrics in particular. However, if two knitted fabrics in particular. However, if two single yarns are combined and twisted single yarns are combined and twisted together in reverse direction, a together in reverse direction, a balanced balanced folded yarnfolded yarn 指不扭结的股线指不扭结的股线 can be obtained.can be obtained.

(2)Improved abrasion resistance(2)Improved abrasion resistance

As we have discussed already, ring spun As we have discussed already, ring spun yarns are relatively hairy. The hair fibres often yarns are relatively hairy. The hair fibres often cause problems in subsequent processes such cause problems in subsequent processes such as weaving. Also in weaving, warp yarns are as weaving. Also in weaving, warp yarns are subject to repeated abrasion and fibres may be subject to repeated abrasion and fibres may be gradually rubbed away, leading to yarn gradually rubbed away, leading to yarn breakage. When two single yarns are twisted breakage. When two single yarns are twisted together, their surface fibres are trapped together, their surface fibres are trapped between the two single yarns. This improves between the two single yarns. This improves the abrasion resistance.the abrasion resistance.

(3)Increased strength(3)Increased strength

The two fold yarn is stronger than its single The two fold yarn is stronger than its single components.components.

(4)Reduced irregularity(4)Reduced irregularity

The doubling reduces the irregularity The doubling reduces the irregularity according to the law of doubling discussed according to the law of doubling discussed in the module on yarn evenne in the module on yarn evenne

Two-for-one twistingTwo-for-one twisting 倍捻倍捻 has been the has been the common method of producing a folded yarn. common method of producing a folded yarn. Figure 1.14 shows a schematic of the two-for-one Figure 1.14 shows a schematic of the two-for-one twisting process. An twisting process. An assembly wound packageassembly wound package并线筒子并线筒子 (i.e. two yarns assembled onto one (i.e. two yarns assembled onto one package without any twist) is usually used as the package without any twist) is usually used as the stationary supply package. The supply yarn is stationary supply package. The supply yarn is threaded through a guide mounted on a freely threaded through a guide mounted on a freely rotating flyer and then passes through the hollow rotating flyer and then passes through the hollow rotating spindle. At the base of the spindle, the rotating spindle. At the base of the spindle, the yarn comes out forming a balloon, and then goes yarn comes out forming a balloon, and then goes onto the winding head via the yarn guide. Each onto the winding head via the yarn guide. Each rotation of the spindle will insert one turn of twist rotation of the spindle will insert one turn of twist in the length of yarn within the spindle, plus in the length of yarn within the spindle, plus another turn of twist in the yarn balloon. As a another turn of twist in the yarn balloon. As a result, two turns of twist are inserted into the result, two turns of twist are inserted into the yarn for each rotation of the spindle, hence the yarn for each rotation of the spindle, hence the name two-for-one twisting.name two-for-one twisting.Figure 1.14 Two-for-one twisting (Grosberg and Iype 1999, p.20)

Review questionsReview questions

11. . Based on the discussion in this topic, sketch the appearance of a Based on the discussion in this topic, sketch the appearance of a typical ring spun yarn. typical ring spun yarn.

22. . Rovings of 500 tex are used to feed a ring frame with 1000 Rovings of 500 tex are used to feed a ring frame with 1000 spindles running at 20,000 rpm and 90% efficiency. A spinning spindles running at 20,000 rpm and 90% efficiency. A spinning draft of 20 is used to produce the ring spun yarn. If 54 draft of 20 is used to produce the ring spun yarn. If 54 kilograms of yarn are produced each hour on the machine, kilograms of yarn are produced each hour on the machine, calculate the twist level in the yarn (t.p.m) and its twist factor calculate the twist level in the yarn (t.p.m) and its twist factor (t.p.m.). Include details of your calculation. (t.p.m.). Include details of your calculation.

33. . One of the limitations of ring spinning is the relatively small One of the limitations of ring spinning is the relatively small amount of yarn on a full bobbin. Explain why we can not simply amount of yarn on a full bobbin. Explain why we can not simply increase the ring radius and use a small empty bobbin to allow increase the ring radius and use a small empty bobbin to allow for a large quantity of yarn to be wound onto the bobbin before for a large quantity of yarn to be wound onto the bobbin before the full bobbin is doffed.the full bobbin is doffed.

44. . Explain, with the help of sketch, the principle of Sirospun and 2-Explain, with the help of sketch, the principle of Sirospun and 2-for-1 twisting.for-1 twisting.

Rotor spinningRotor spinning 转杯纺转杯纺 IntroductionIntroduction Rotor spinning belongs to the family of Rotor spinning belongs to the family of open-open-

end (OE) spinningend (OE) spinning 自由端纺纱自由端纺纱 . Open-end . Open-end spinning systems are designed to overcome spinning systems are designed to overcome some of the problems associated with ring some of the problems associated with ring spinning. As discussed in the previous topic, spinning. As discussed in the previous topic, twist insertion in ring spinning requires the twist insertion in ring spinning requires the rotation of the whole yarn package. In open-end rotation of the whole yarn package. In open-end spinning, only an end of the yarn is rotated to spinning, only an end of the yarn is rotated to insert twist, which consumes much less energy insert twist, which consumes much less energy than rotating a yarn package. The most than rotating a yarn package. The most successful examples of the open-end spinning successful examples of the open-end spinning concept are the rotor spinning and friction concept are the rotor spinning and friction spinning systems. This topic discusses rotor spinning systems. This topic discusses rotor spinning. Friction spinning will be discussed in spinning. Friction spinning will be discussed in the next topic.the next topic.

ObjectivesObjectives

At the end of this topic you should be able to:At the end of this topic you should be able to:► Understand the basic concept of open-end Understand the basic concept of open-end

(OE) spinning(OE) spinning► Know the principle of rotor spinningKnow the principle of rotor spinning► Understand the differences between ring Understand the differences between ring

spinning and rotor spinningspinning and rotor spinning

General concept of open-end General concept of open-end spinningspinning

Open-end spinning is a relatively new Open-end spinning is a relatively new concept of spinning. The basic principle concept of spinning. The basic principle of open-end spinning is illustrated in of open-end spinning is illustrated in figure 2.1 (Lord 1981, p.96). figure 2.1 (Lord 1981, p.96).

Figure 2.1 The principle of open-end spinning (Lord Figure 2.1 The principle of open-end spinning (Lord 1981, p.96)1981, p.96)

Like ring spinning, open-end spinning Like ring spinning, open-end spinning involves the three basic steps of involves the three basic steps of drafting, twisting and winding-on.drafting, twisting and winding-on.

► DraftingDrafting

Very high draft is used to Very high draft is used to attenuateattenuate 拉细拉细 the the feed sliver (not roving) into individual fibres. feed sliver (not roving) into individual fibres. Such a high draft is usually by means of pinned Such a high draft is usually by means of pinned drafting (with toothed rollers) rather than by drafting (with toothed rollers) rather than by roller drafting. roller drafting.

Because of the direct sliver feed, there is no Because of the direct sliver feed, there is no need to convert the sliver into roving first before need to convert the sliver into roving first before spinning, which is necessary in conventional spinning, which is necessary in conventional ring spinning. ring spinning.

► TwistingTwisting The individual fibres are collected at the yarn The individual fibres are collected at the yarn

open-end and twist is then inserted at the yarn open-end and twist is then inserted at the yarn open-end.open-end.

Since only the yarn opne-end is rotated to Since only the yarn opne-end is rotated to insert twist, open-end spinning is much more insert twist, open-end spinning is much more energy efficient than ring spinning, which energy efficient than ring spinning, which requires the rotation of a massive yarn requires the rotation of a massive yarn package to insert twist. In addition, the twist package to insert twist. In addition, the twist insertion rate in open-end spinning can be very insertion rate in open-end spinning can be very fast. For a given yarn twist level, this translates fast. For a given yarn twist level, this translates into fast yarn delivery speed or high production into fast yarn delivery speed or high production rate. rate.

► Winding-onWinding-on

In open-end spinning, twisting and winding are In open-end spinning, twisting and winding are separate operations so that yarns can be separate operations so that yarns can be wound onto a large yarn package.wound onto a large yarn package.

In ring spinning, the In ring spinning, the package sizepackage size 卷装尺寸卷装尺寸 is is restricted and the yarns from the many small restricted and the yarns from the many small packages need to be joined up to make up a packages need to be joined up to make up a large package.large package.

In summary, open-end spinning has the following In summary, open-end spinning has the following major advantages compared to ring spinning:major advantages compared to ring spinning:

►elimination of roving stageelimination of roving stage►high productivity and low energy consumptionhigh productivity and low energy consumption►large package sizelarge package size

Now that we know the basic principle of open-end Now that we know the basic principle of open-end spinning and its advantages, we can proceed to spinning and its advantages, we can proceed to discuss the details of rotor spinning. As mentioned discuss the details of rotor spinning. As mentioned in the introduction, rotor spinning is a successful in the introduction, rotor spinning is a successful example of the open-end spinning concept. example of the open-end spinning concept.

We start with a brief account of the history of rotor We start with a brief account of the history of rotor spinning.spinning.

Historical perspectives of rotor spinningHistorical perspectives of rotor spinning Compared with ring spinning, rotor spinning is a Compared with ring spinning, rotor spinning is a

relatively new spinning technology that has not relatively new spinning technology that has not yet reached its maturity. A brief chronology of yet reached its maturity. A brief chronology of rotor spinning developments is listed below:rotor spinning developments is listed below:

► 1937 The first idea and basic rotor patented by 1937 The first idea and basic rotor patented by Berthelsen (Denmark). Berthelsen (Denmark).

► 1951 Meimberg (Germany) developed the 1951 Meimberg (Germany) developed the invention further and built the first spinning invention further and built the first spinning models.models.

► 1965 Rohlena and his group (Czechoslovakia) 1965 Rohlena and his group (Czechoslovakia) found the correct combination of spinning found the correct combination of spinning elements and showed the first commercially elements and showed the first commercially functional units in Brunn.functional units in Brunn.

► 19671967 The Czech firm ELITEX exhibited its rotor The Czech firm ELITEX exhibited its rotor spinning machine (BD200) near the spinning machine (BD200) near the international textile machinery exhibition (ITMA) international textile machinery exhibition (ITMA) in Basel, Switzerland. The machine had a rotor in Basel, Switzerland. The machine had a rotor diameter of 75 mm, a rotating speed of 25,000 diameter of 75 mm, a rotating speed of 25,000 rpm, and a high twist multiplier (TM=6, or a rpm, and a high twist multiplier (TM=6, or a twist factor of about 5740 tpm.).twist factor of about 5740 tpm.).

► 1970 First sale of BD200 in the West1970 First sale of BD200 in the West► 1971 Invention of the twin disk rotor drive 1971 Invention of the twin disk rotor drive

allowing higher rotor speed (Suessen). With allowing higher rotor speed (Suessen). With smaller rotors (60 mm), the rotor speed smaller rotors (60 mm), the rotor speed increased to 35,000 rpm.increased to 35,000 rpm.

► 1978 Introduction of 40-50 mm diameter rotors, 1978 Introduction of 40-50 mm diameter rotors, improved spinbox geometries, lower yarn twist improved spinbox geometries, lower yarn twist possible, first automatic yarn piecer and package possible, first automatic yarn piecer and package doffer fitted on the rotor spinner.doffer fitted on the rotor spinner.

► 1989 Smaller rotors with speeds of 100,000 rpm.1989 Smaller rotors with speeds of 100,000 rpm.► 1992 Quality yarns as fine as 13-15 tex produced 1992 Quality yarns as fine as 13-15 tex produced

commercially at rotor speeds up to 120,000 rpm.commercially at rotor speeds up to 120,000 rpm.► 1999 Rotor speeds up to 150,000 rpm possible.1999 Rotor speeds up to 150,000 rpm possible.

The development of rotor spinning technology The development of rotor spinning technology continues today. The ultimate aim is to produce continues today. The ultimate aim is to produce rotor spun yarns that match the quality of rotor spun yarns that match the quality of comparable ring spun yarns, but at a fraction of comparable ring spun yarns, but at a fraction of the cost of ring spinning.the cost of ring spinning.

Rotor spinning principleRotor spinning principle Figure 2.2 shows the key elements inside the Figure 2.2 shows the key elements inside the

‘spin-box’ ‘spin-box’ 纺纱器纺纱器 of a rotor spinning system. Like of a rotor spinning system. Like any other staple spinning system, the principle any other staple spinning system, the principle of rotor spinning entails three basic steps of of rotor spinning entails three basic steps of drafting, twisting and winding-on. drafting, twisting and winding-on.

Figure 2.2 Key elements inside the 'spin-box' of a rotor spinner

► Drafting Drafting

When the feed sliver enters the ‘spin-box’, it is When the feed sliver enters the ‘spin-box’, it is presented to a presented to a toothed combing rolltoothed combing roll 锯齿分梳锯齿分梳辊辊 (or comber roll) by a feed roller and feed (or comber roll) by a feed roller and feed plate assembly. The teethplate assembly. The teeth 锯齿 锯齿 on the comber on the comber roll comb the fibres in the sliver and because roll comb the fibres in the sliver and because the surface speed of the comber roll is much the surface speed of the comber roll is much higher than the feed roller, the density of fibres higher than the feed roller, the density of fibres on the surface of the comber roll is much less on the surface of the comber roll is much less than the density of the sliver. In other words, than the density of the sliver. In other words, drafting is performed by the comber roll on the drafting is performed by the comber roll on the incoming sliver. The amount of draft exercised incoming sliver. The amount of draft exercised by the comber roll is very high, and can be by the comber roll is very high, and can be calculated using the equation below:calculated using the equation below:

min)/(

min)/(

mspeedfeedSliver

mrollcomberofspeedSurfacerollcomberofDraft

The The housinghousing 外壳外壳 of the comber roll has an of the comber roll has an opening. Because trash and other impurities have opening. Because trash and other impurities have a higher density than fibres, they are ejected a higher density than fibres, they are ejected through the opening by centrifugal forces, while through the opening by centrifugal forces, while the flexible fibres can bend their way around the the flexible fibres can bend their way around the comber roll until they are sucked into the rotor via comber roll until they are sucked into the rotor via a transport tube. The a transport tube. The transport tubetransport tube输纤管 输纤管 is is tapered to allow acceleration of fibre flow through tapered to allow acceleration of fibre flow through it. This acceleration helps with fibre straightening. it. This acceleration helps with fibre straightening. This acceleration also means some fibre drafting This acceleration also means some fibre drafting is performed by the transport tube. This draft is is performed by the transport tube. This draft is usually quite small. usually quite small.

For a uniform flow of individual fibres into the For a uniform flow of individual fibres into the rotor, the feed sliver should have good uniformity rotor, the feed sliver should have good uniformity in linear density (e.g. a Uster CV% between 2.5 in linear density (e.g. a Uster CV% between 2.5 and 3.5), and the comber roll should be in good and 3.5), and the comber roll should be in good condition.condition.

► TwistingTwisting

Once inside the gyrating rotor, the individual fibres Once inside the gyrating rotor, the individual fibres are thrown against the inner wall of the are thrown against the inner wall of the rotorrotor 转杯，转杯，纺纱杯纺纱杯 by the centrifugal force. The fibres slide by the centrifugal force. The fibres slide down the wall into the vee-shaped rotor groove as down the wall into the vee-shaped rotor groove as shown in figure 2.3. As the rotor rotates, many shown in figure 2.3. As the rotor rotates, many layers of fibre are collected around the rotor layers of fibre are collected around the rotor groove to make up sufficient linear density for the groove to make up sufficient linear density for the final yarn. This is the important final yarn. This is the important doublingdoubling effect effect并并合效应 合效应 in rotor spinning. The doubling or layering in rotor spinning. The doubling or layering of fibres tends to even out any short term of fibres tends to even out any short term irregularities in the yarn, which makes the rotor irregularities in the yarn, which makes the rotor spun yarn surprisingly even. In contrast, there is spun yarn surprisingly even. In contrast, there is no doubling in ring spinning, the roving is no doubling in ring spinning, the roving is attenuated to yarn linear density during ring attenuated to yarn linear density during ring spinning.spinning.

Once a sufficient number of fibres is collected in the rotor Once a sufficient number of fibres is collected in the rotor groove, the fibres need to be taken out continuously groove, the fibres need to be taken out continuously otherwise they will soon clog the rotor groove. To do this, otherwise they will soon clog the rotor groove. To do this, a a ‘seed yarn‘seed yarn’’引头纱 引头纱 is first introduced into the rotor is first introduced into the rotor through the navel (figure 2.3). Again, the centrifugal force through the navel (figure 2.3). Again, the centrifugal force throws the seed yarn into the rotor groove. As the rotor is throws the seed yarn into the rotor groove. As the rotor is rotating rapidly, the seed yarn rotates with it. This rotating rapidly, the seed yarn rotates with it. This rotation traps the loose fibres at the end of the seed yarn. rotation traps the loose fibres at the end of the seed yarn. At this point, the seed yarn is pulled out, the fibres At this point, the seed yarn is pulled out, the fibres trapped to the yarn end are peeled off the rotor groove by trapped to the yarn end are peeled off the rotor groove by the outgoing yarn. Since the the outgoing yarn. Since the peel-off pointpeel-off point 剥离点剥离点 is is rotating with the rotor, twist is inserted into the out-going rotating with the rotor, twist is inserted into the out-going fibres. Furthermore, the twist at the fibres. Furthermore, the twist at the peeling pointpeeling point 剥离点剥离点 extends a distance inside the groove to form the binding extends a distance inside the groove to form the binding zone or twist zone as shown in figure 2.4. Within this zone or twist zone as shown in figure 2.4. Within this zone, new yarn is formed. The stability of rotor spinning is zone, new yarn is formed. The stability of rotor spinning is affected by the length of this twist zone, which is in turn a affected by the length of this twist zone, which is in turn a function of the amount of twist at a given rotor speed and function of the amount of twist at a given rotor speed and the additional the additional false twistfalse twist 假捻假捻 induced by the induced by the navelnavel 阻捻阻捻盘盘 . Before we talk about the false twist, let us see how . Before we talk about the false twist, let us see how the actual (real) twist in a rotor spun yarn is calculated.the actual (real) twist in a rotor spun yarn is calculated.

► Figure 2.3 A look inside the rotorFigure 2.3 A look inside the rotor

Figure 2.4 Formation of a twist zone inside the rotor groove (Deussen1993, p.24)

We now know that the rotation of the peeling-off We now know that the rotation of the peeling-off point inside the rotor groove inserts twist into the point inside the rotor groove inserts twist into the fibres to form a rotor spun yarn. The peeling-off fibres to form a rotor spun yarn. The peeling-off point rotates with the rotor at a very high point rotates with the rotor at a very high rotational speed (i.e. over 100,000 rpm). In rotational speed (i.e. over 100,000 rpm). In addition, by continuously withdrawing the newly addition, by continuously withdrawing the newly formed yarn from the rotor at the yarn delivery formed yarn from the rotor at the yarn delivery speed, the peeling-off point also moves relative speed, the peeling-off point also moves relative to and in the same direction as the rotor, at the to and in the same direction as the rotor, at the same speed as the yarn withdrawal or delivery same speed as the yarn withdrawal or delivery speed. In other words, the real speed of the speed. In other words, the real speed of the peeling-off point is actually slightly faster than peeling-off point is actually slightly faster than the rotor speed, by an amount equal to the yarn the rotor speed, by an amount equal to the yarn delivery speed. But the additional twist from this delivery speed. But the additional twist from this will be very small compared with the twist from will be very small compared with the twist from the rotor rotation. The following example will the rotor rotation. The following example will demonstrate this point. demonstrate this point.

Suppose a rotor yarn is produced at 150 m/min Suppose a rotor yarn is produced at 150 m/min by a rotor at 120,000 rpm, and the diameter of by a rotor at 120,000 rpm, and the diameter of inner groove of the rotor is 30 mm. We wish to inner groove of the rotor is 30 mm. We wish to find out the actual twist put into the yarn by the find out the actual twist put into the yarn by the peeling-off point inside the rotor groove.peeling-off point inside the rotor groove.

Relative to the rotor, the peeling-off point travels Relative to the rotor, the peeling-off point travels at the yarn delivery speed of 150 m/min. The at the yarn delivery speed of 150 m/min. The circumference of the rotor groove is 30 x circumference of the rotor groove is 30 x = = 94.2 mm (or 0.0942 m). Therefore, the rotational 94.2 mm (or 0.0942 m). Therefore, the rotational speed of the peeling-off point (POP) relative to speed of the peeling-off point (POP) relative to the rotor is: the rotor is:

This rpm is about 1.3% of the rotor RPM, and the This rpm is about 1.3% of the rotor RPM, and the

twist put into the yarn from this additional source twist put into the yarn from this additional source will be about 1.3% of the twist due to rotor will be about 1.3% of the twist due to rotor rotation.rotation.

)(15920942.0

150)( rpm

grooverotorofnceCircumfere

POPofspeedLinearrotortorelativePOPofrpm

This example shows that for practical purpose, This example shows that for practical purpose, the twist in a rotor spun yarn can be calculated the twist in a rotor spun yarn can be calculated from the rotor rpm and yarn delivery speed, from the rotor rpm and yarn delivery speed, using the equation below.using the equation below.

This will be the real theoretical twist in the This will be the real theoretical twist in the rotor spun yarn. What about the false twist we rotor spun yarn. What about the false twist we mentioned a little earlier? This is briefly mentioned a little earlier? This is briefly discussed in the following paragraph.discussed in the following paragraph.

min)/()(

mspeeddeliveryYarn

rpmRotortpmtwistYarn

The The trumpet shaped naveltrumpet shaped navel 嗽叭形状的阻捻盘嗽叭形状的阻捻盘 is usually is usually made of wear-resistant ceramic material. The newly made of wear-resistant ceramic material. The newly formed rotor yarn is withdrawn through the stationary formed rotor yarn is withdrawn through the stationary navel to the winding mechanism. As indicated in figure navel to the winding mechanism. As indicated in figure 2.3, the yarn path is deflected 902.3, the yarn path is deflected 90OO at the navel. The at the navel. The tension in the yarn pushes the yarn against the navel tension in the yarn pushes the yarn against the navel inner surface. Because of the friction between the inner surface. Because of the friction between the rotating yarn and the navel inner surface, the yarn rolls rotating yarn and the navel inner surface, the yarn rolls on the navel surface. This rolling action produces a on the navel surface. This rolling action produces a false twist in the section of the yarn inside the rotor and false twist in the section of the yarn inside the rotor and this false twist is in addition to the real twist from the this false twist is in addition to the real twist from the rotor rotation. Because of this additional twist, the rotor rotation. Because of this additional twist, the length of the binding zone or twist zone (figure 2.4) is length of the binding zone or twist zone (figure 2.4) is increased, which increases the stability of spinning. The increased, which increases the stability of spinning. The yarn (inside the rotor) is also stronger due to the yarn (inside the rotor) is also stronger due to the additional twist, which reduces the ends-down. additional twist, which reduces the ends-down. Therefore, the navel induced false twist plays an Therefore, the navel induced false twist plays an important role in rotor spinning. It should be noted that important role in rotor spinning. It should be noted that the false twist does not show up in the final yarn, which the false twist does not show up in the final yarn, which has real twist only. Also, rolling of the yarn against the has real twist only. Also, rolling of the yarn against the navel surface tends to increase yarn hairiness. navel surface tends to increase yarn hairiness.

► WindingWinding

The yarn withdrawn from the rotor is wound The yarn withdrawn from the rotor is wound onto a large yarn package, ready for use. Unlike onto a large yarn package, ready for use. Unlike in ring spinning, twisting and winding functions in ring spinning, twisting and winding functions are divorced and this permits the use of large are divorced and this permits the use of large package size. Figure 2.5 shows the key package size. Figure 2.5 shows the key elements of the winding mechanism. The yarn elements of the winding mechanism. The yarn package sits on a winding drum. The winding package sits on a winding drum. The winding drum is positively driven and friction contact drum is positively driven and friction contact between the yarn package and the winding between the yarn package and the winding drum drives the yarn package. A reciprocation drum drives the yarn package. A reciprocation yarn guide ensures that the yarn is laid across yarn guide ensures that the yarn is laid across the package traverse. the package traverse.

Figure 2.5 Yarn winding mechanism Figure 2.5 Yarn winding mechanism (Deussen 1993, p.12)(Deussen 1993, p.12)

Figure 2.6 shows the whole process of rotor Figure 2.6 shows the whole process of rotor spinning from sliver feed to yarn package.spinning from sliver feed to yarn package.

Figure 2.6 Rotor spinning process (Deussen Figure 2.6 Rotor spinning process (Deussen 1993, p. 6)1993, p. 6)

► Characteristics of rotor yarnCharacteristics of rotor yarn

Ideally, fibres should be incorporated by twist Ideally, fibres should be incorporated by twist into the yarn in a helical configuration. In rotor into the yarn in a helical configuration. In rotor spinning, this is only possible if the fibres are laid spinning, this is only possible if the fibres are laid parallel inside the rotor groove away from the parallel inside the rotor groove away from the twist zone and the peeling-off point (figure 2.4). twist zone and the peeling-off point (figure 2.4). However, during the course of spinning, it is However, during the course of spinning, it is unavoidable that some fibres actually land in the unavoidable that some fibres actually land in the twist zone or on the yarn catenary between the twist zone or on the yarn catenary between the peeling-off point and the navel. When this peeling-off point and the navel. When this happens, the fibres get wrapped tightly around happens, the fibres get wrapped tightly around the already formed yarn and become the the already formed yarn and become the characteristic characteristic wrapper fibreswrapper fibres 包缠纤维包缠纤维 on the on the yarn surface. The formation of a wrapper from a yarn surface. The formation of a wrapper from a fibre landing in the twist zone is depicted in fibre landing in the twist zone is depicted in figure 2.7.figure 2.7.

Figure 2.7 Formation of wrapper fibres in rotor spinning (Deussen 1993, p.24)

While a longer twist zone makes spinning more While a longer twist zone makes spinning more stable, it also increases the chance of wrapper stable, it also increases the chance of wrapper formation. The percentage of wrapper formation. The percentage of wrapper formation can be approximated by the formula formation can be approximated by the formula below.below.

100)(

)(

mmdiameterrotor

mmlengthfibreMeanwrappersofPercentage

From this formula, it is clear that long fibres and From this formula, it is clear that long fibres and small rotors will increase the chance of wrapper small rotors will increase the chance of wrapper formation. For this reason, rotor spinning has formation. For this reason, rotor spinning has been primarily used for short staple fibres such been primarily used for short staple fibres such as cotton and cotton blends. With long staple as cotton and cotton blends. With long staple fibres, a large rotor is necessary to reduce the fibres, a large rotor is necessary to reduce the wrapper fibres and a slow rotor rpm has to be wrapper fibres and a slow rotor rpm has to be used, this makes spinning uneconomical. This is used, this makes spinning uneconomical. This is one of the reasons why rotor spinning has not one of the reasons why rotor spinning has not been successful in the long staple spinning been successful in the long staple spinning sector. In recent years, rotor technology has sector. In recent years, rotor technology has been used to spin fine and short wool fibres.been used to spin fine and short wool fibres.

Increasing the twist will also increase the Increasing the twist will also increase the number of wrapper fibres. This is because an number of wrapper fibres. This is because an increase in yarn twist will increase the length of increase in yarn twist will increase the length of twist zone inside the rotor groove, causing the twist zone inside the rotor groove, causing the newly arrived fibres to be held on the otherside newly arrived fibres to be held on the otherside of the already twisted section and thereby of the already twisted section and thereby increasing the number of wrapper fibres. increasing the number of wrapper fibres.

Because the wrapper fibres simply wrap around Because the wrapper fibres simply wrap around the yarn surface, they contribute little to yarn the yarn surface, they contribute little to yarn strength. However, wrapper fibres tend to strength. However, wrapper fibres tend to increase the abrasion resistance and reduce increase the abrasion resistance and reduce the hairiness of rotor spun yarns.the hairiness of rotor spun yarns.

Sometimes, the middle section of a fibre gets caught by Sometimes, the middle section of a fibre gets caught by the rotating yarn arm inside the rotor, as indicated in the rotating yarn arm inside the rotor, as indicated in figure 2.8. When this fibre gets wrapped around the figure 2.8. When this fibre gets wrapped around the yarn, its two ends are twisted in opposite directions. So yarn, its two ends are twisted in opposite directions. So it is possible to have both S-twist and Z-twist in the it is possible to have both S-twist and Z-twist in the wrapper fibres, even though rotor spun yarn is usually wrapper fibres, even though rotor spun yarn is usually spun with Z-twist only. Because of the presence of both spun with Z-twist only. Because of the presence of both S-twist and Z-twist, it is difficult to completely untwist a S-twist and Z-twist, it is difficult to completely untwist a rotor spun yarn. The wrapper fibres, and difficulty to rotor spun yarn. The wrapper fibres, and difficulty to completely untwist the yarn have been used to completely untwist the yarn have been used to differentiate between ring and rotor spun yarns. The differentiate between ring and rotor spun yarns. The presence of S and Z twists in wrappers also explains the presence of S and Z twists in wrappers also explains the fact that the measured twist of rotor spun yarns is lower fact that the measured twist of rotor spun yarns is lower than the nominal machine twist calculated from the than the nominal machine twist calculated from the rotor rpm and yarn delivery speed. The so-called the rotor rpm and yarn delivery speed. The so-called the TT% value has been used to reflect the degree of this % value has been used to reflect the degree of this difference, as indicated below.difference, as indicated below. %100%

twistMachine

twistmachinetwistMeasuredT

The lower the The lower the T% value, the more orderly T% value, the more orderly and ring-yarn-like the fibre orientation is in the and ring-yarn-like the fibre orientation is in the rotor yarn. High rotor yarn. High T% values indicate a more T% values indicate a more disorderly rotor yarn structure and the disorderly rotor yarn structure and the presence of wrapper fibres. Rotor yarns of presence of wrapper fibres. Rotor yarns of 100% cotton exhibit 100% cotton exhibit T% values between near T% values between near 0 and -20%, while polyester/cotton blends 0 and -20%, while polyester/cotton blends measure between -10 and -45% (Deussen measure between -10 and -45% (Deussen 1993, p.27).1993, p.27).

Figure 2.8 Formation of a wrapper with two ends twisted in opposite direction (Nield 1975, p.34)

In ring spinning, fibre alignment is carried out In ring spinning, fibre alignment is carried out right up to the point of twist insertion, and fibres right up to the point of twist insertion, and fibres are straight and parallel to each other when twist are straight and parallel to each other when twist is inserted. In rotor spinning, fibre alignment is is inserted. In rotor spinning, fibre alignment is achieved to a less extent than in ring spinning. achieved to a less extent than in ring spinning. Poor fibre alignment may occur as fibres impinge Poor fibre alignment may occur as fibres impinge on the sliding wale of the rotor, as they lie in the on the sliding wale of the rotor, as they lie in the rotor groove (unlike in ring spinning, fibres are not rotor groove (unlike in ring spinning, fibres are not under tension in the twist zone in the rotor under tension in the twist zone in the rotor groove). This, together with the formation of groove). This, together with the formation of wrapper fibres, means that rotor spun yarns are wrapper fibres, means that rotor spun yarns are usually weaker than comparable ring spun yarns, usually weaker than comparable ring spun yarns, and a higher twist plus more fibres in yarn cross and a higher twist plus more fibres in yarn cross section is necessary to increase the strength of section is necessary to increase the strength of rotor spun yarns. A minimum of 90 fibres is rotor spun yarns. A minimum of 90 fibres is necessary in rotor spun yarns, compared with a necessary in rotor spun yarns, compared with a minimum of 40 for ring yarns. So in the fine yarn minimum of 40 for ring yarns. So in the fine yarn market, rotor spinning can not compete with ring market, rotor spinning can not compete with ring spinning.spinning.

Another important feature of rotor spun yarns Another important feature of rotor spun yarns is their good evenness. As mentioned before, is their good evenness. As mentioned before, fibres are deposited in the rotor groove in fibres are deposited in the rotor groove in layers. The number of doublings is quite large, layers. The number of doublings is quite large, which tends to even out the short-term which tends to even out the short-term irregularities and improve the evenness of the irregularities and improve the evenness of the resultant yarn. The number of doublings can be resultant yarn. The number of doublings can be calculated using the equation below:calculated using the equation below:

1000

)()()(.

mmncecircumfererotortpmtwistYarngrooverotorindoublingsofNo

Table 2.1 summaries the characteristics of rotor Table 2.1 summaries the characteristics of rotor spun yarns in comparison with ring spun yarns.spun yarns in comparison with ring spun yarns.

Table 2.1 A comparison of rotor and ring yarnsTable 2.1 A comparison of rotor and ring yarnsRotor YarnRotor Yarn Compared to Ring YarnCompared to Ring Yarn ReasonReason__________________________________________________________________________________________________________________Production rateProduction rate much highermuch higher Higher twist rateHigher twist ratePackage sizePackage size 20 times greater20 times greater No ringNo ringTwist levelTwist level 10-15% higher10-15% higher StructureStructureStrengthStrength 15-20% weaker15-20% weaker Fibre orientationFibre orientationExtensibilityExtensibility 10% higher10% higher Fibre orientationFibre orientationRegularityRegularity 10-20% better10-20% better Doubling Doubling

in rotorin rotorHandleHandle harsherharsher Wrapper Wrapper

fibres,fibres,Higher twistHigher twist

AbrasionAbrasion 20-30% better20-30% better Wrapper fibresWrapper fibresYarn countYarn count coarsercoarser WeakerWeakerFibre typeFibre type short staple mainlyshort staple mainly Wrapper fibresWrapper fibresHairinessHairiness LowerLower Higher twist,Higher twist,

Wrapper fibresWrapper fibres________________________________________________________________________________________________________________________________________

This comparison highlights differences made by This comparison highlights differences made by the presence of wrapper fibres. The fewer the the presence of wrapper fibres. The fewer the number of wrapper fibres in a rotor spun yarn, number of wrapper fibres in a rotor spun yarn, the more closely the rotor spun yarn resembles the more closely the rotor spun yarn resembles the structure of ring spun yarns. This has been the structure of ring spun yarns. This has been the aim that drives further developments in the aim that drives further developments in rotor spinning technology. rotor spinning technology.

► Selection or spinning components and Selection or spinning components and parametersparameters

The key components for rotor spinning are the The key components for rotor spinning are the combing roll, the rotor, and the navel. The combing roll, the rotor, and the navel. The combing roll (or comber roll) opens the feed combing roll (or comber roll) opens the feed sliver and individualises the fibres. The rotor is sliver and individualises the fibres. The rotor is the twist insertion element, while the navel the twist insertion element, while the navel adds additional twist inside the rotor and adds additional twist inside the rotor and changes the surface texture of the resultant changes the surface texture of the resultant yarn.yarn.

► Figure 2.9 shows the tooth profiles of combing Figure 2.9 shows the tooth profiles of combing rolls used for different fibre materials, and the rolls used for different fibre materials, and the corresponding speed range.corresponding speed range.

► Figure 2.10 shows the yarn count ranges in Figure 2.10 shows the yarn count ranges in relation to rotor diameters and speeds. Small relation to rotor diameters and speeds. Small rotors of 30 mm diameter (K-230) and 31 mm rotors of 30 mm diameter (K-230) and 31 mm diameter (G-231) are used primarily for finer diameter (G-231) are used primarily for finer yarns and higher rotor speed than large rotors.yarns and higher rotor speed than large rotors.

► In figure 2.11, the typical twist multipliers (TM) In figure 2.11, the typical twist multipliers (TM) used for knitting and weaving yarns of different used for knitting and weaving yarns of different fibre compositions are given (note that twist fibre compositions are given (note that twist factor = 956.7 x TM). factor = 956.7 x TM).

► Finally, an explanation of different navels and Finally, an explanation of different navels and their applications is given in figure 2.12. their applications is given in figure 2.12.

►

► Figure 2.9 Tooth profiles and speed ranges of Figure 2.9 Tooth profiles and speed ranges of combing rolls (Deussen 1993, p.55)combing rolls (Deussen 1993, p.55)

► Figure 2.10 Yarn count ranges for rotor diameters Figure 2.10 Yarn count ranges for rotor diameters and speeds (Deussen 1993, p.57)and speeds (Deussen 1993, p.57)

► Figure 2.11 Twist multipliers (TM) for weaving and Figure 2.11 Twist multipliers (TM) for weaving and knitting rotor yarns (Deussen 1993, p.60)knitting rotor yarns (Deussen 1993, p.60)

► Figure 2.12 Different navels and their applications Figure 2.12 Different navels and their applications (Deussen 1993, p.62)(Deussen 1993, p.62)

► Review questionsReview questions ► 1.Based on the discussion of the 1.Based on the discussion of the

characteristics of rotor spun yarns, draw a characteristics of rotor spun yarns, draw a sketch depicting the key features of a typical sketch depicting the key features of a typical rotor spun yarn.rotor spun yarn.

► 2.This question relates to a yarn being spun on 2.This question relates to a yarn being spun on a rotor spinner under the following conditions:a rotor spinner under the following conditions:

input sliverinput sliver 5.0 kTex5.0 kTex output yarnoutput yarn 50 tex50 tex diameter of combing rolldiameter of combing roll 70 mm70 mm speedspeed of combing rollof combing roll 7,000 r.p.m.7,000 r.p.m. rotor diameterrotor diameter 45 mm45 mm rotor speedrotor speed 100,000 r.p. 100,000 r.p. yarn delivery rateyarn delivery rate 200 m/min.200 m/min.

(a)Calculate the yarn twist level (t.p.m) and the twist factor of the rotor (a)Calculate the yarn twist level (t.p.m) and the twist factor of the rotor yarn, ignoring the small additional twist due to rotation of the yarn yarn, ignoring the small additional twist due to rotation of the yarn "peeling-off-point"."peeling-off-point".

(b)If the above yarn is made from fibres all of the same length of 25 mm, (b)If the above yarn is made from fibres all of the same length of 25 mm, what proportion of fibres will end up with some portion of their length in a what proportion of fibres will end up with some portion of their length in a wrapper configuration?wrapper configuration?

(c)In order to reduce the number of wrapper fibres, would it be more (c)In order to reduce the number of wrapper fibres, would it be more effective to use fibres which are 5 mm shorter, or use a rotor of 5 mm effective to use fibres which are 5 mm shorter, or use a rotor of 5 mm greater in diameter? Show your reasoning.greater in diameter? Show your reasoning.

(d)Sliver for the above yarn received 2 drawframe passages between (d)Sliver for the above yarn received 2 drawframe passages between carding and spinning, with 6 doublings at each passage. Calculate the carding and spinning, with 6 doublings at each passage. Calculate the number of doublings provided during spinning and the total doublings the number of doublings provided during spinning and the total doublings the fibre assembly has received since carding.fibre assembly has received since carding.

(e)The fibre transport chute (between beater and rotor) has been (e)The fibre transport chute (between beater and rotor) has been designed so that fibres enter the chute at the speed of the beater surface, designed so that fibres enter the chute at the speed of the beater surface, and are accelerated by air so that they leave the chute travelling 50% and are accelerated by air so that they leave the chute travelling 50% faster. Calculate the average number of fibres lying across the chute inlet faster. Calculate the average number of fibres lying across the chute inlet at any one time and the corresponding value at chute outlet. (Take the at any one time and the corresponding value at chute outlet. (Take the linear density of the fibres to be 0.25 tex.)linear density of the fibres to be 0.25 tex.)

(f)What are the finest yarns (expressed in Tex and English cotton count) (f)What are the finest yarns (expressed in Tex and English cotton count) that could be economically spun that could be economically spun from fibres of linear density 0.25 from fibres of linear density 0.25 tex on the rotor spinner. (Hint: consider the minimum nunber of fibres tex on the rotor spinner. (Hint: consider the minimum nunber of fibres required for a rotor spun yarn).required for a rotor spun yarn).

5 5 、、 In about 1,000 words, compare and contrast the In about 1,000 words, compare and contrast the technology of ring spinning and rotor spinning, technology of ring spinning and rotor spinning, with reference to the economics and yarn quality with reference to the economics and yarn quality of each spinning system.of each spinning system.

Friction spinning Friction spinning 摩擦纺纱摩擦纺纱IntroductionIntroduction Friction spinning belongs to the family of open-end Friction spinning belongs to the family of open-end

spinning. Most patents related to friction spinning spinning. Most patents related to friction spinning were filed in the 1970s and 1980s, many of which were filed in the 1970s and 1980s, many of which were from Dr Ernst Fehrer in Austria. Today friction were from Dr Ernst Fehrer in Austria. Today friction spinning is almost synonymous with the term spinning is almost synonymous with the term DREF(DREF(DrDr EErnst rnst FFehrer). It has been used to produce ehrer). It has been used to produce yarns usually much coarser than ring and rotor spun yarns usually much coarser than ring and rotor spun yarns at much higher production rate, and the yarns yarns at much higher production rate, and the yarns have been largely used for domestic and industrial have been largely used for domestic and industrial applications.applications.

This topic discusses the principle of friction spinning This topic discusses the principle of friction spinning in general, followed by a discussion of the DREF 2 in general, followed by a discussion of the DREF 2 and DREF 3 friction spinning systems.and DREF 3 friction spinning systems.

ObjectivesObjectives At the end of this topic you should be able to:At the end of this topic you should be able to:

► Explain the principle of friction spinningExplain the principle of friction spinning► Understand the features of friction spun yarnsUnderstand the features of friction spun yarns► Know the differences between DREF 2 and Know the differences between DREF 2 and

DREF 3 friction spinning systemsDREF 3 friction spinning systems

Principle of friction spinningPrinciple of friction spinning Friction spinning uses two friction surfaces to Friction spinning uses two friction surfaces to

roll up fibres into a yarn. A simplified sketch of roll up fibres into a yarn. A simplified sketch of friction spinning is shown in figure 3.1. The friction spinning is shown in figure 3.1. The fibres flow freely to two rotating friction drums fibres flow freely to two rotating friction drums (spinning drums, friction rollers, torque rollers). (spinning drums, friction rollers, torque rollers). The surfaces at the nip of the two drums move The surfaces at the nip of the two drums move in opposite direction to twist the fibres collected in opposite direction to twist the fibres collected in the nip. The yarn is formed from inside in the nip. The yarn is formed from inside outwards, by the superimposition of twisting of outwards, by the superimposition of twisting of individual fibres. The yarn is then withdrawn individual fibres. The yarn is then withdrawn from the nip to take-up package. from the nip to take-up package.

Figure 3.1 A sketch of friction spinning

IIn friction spinning, the yarn end in the nip of n friction spinning, the yarn end in the nip of the friction drums is tapered, just as the yarn the friction drums is tapered, just as the yarn tail inside the rotor groove is tapered in rotor tail inside the rotor groove is tapered in rotor spinning. Fibres are added continuously to the spinning. Fibres are added continuously to the tapered yarn end as the newly formed yarn is tapered yarn end as the newly formed yarn is withdrawn. This is illustrated in figure 3.2. withdrawn. This is illustrated in figure 3.2.

Figure 3.2 A tapered yarn end in the nip of the spinning drums

It can be envisaged that fibres deposited at It can be envisaged that fibres deposited at the thin end of the taper will end up in the the thin end of the taper will end up in the interior of the final yarn, while fibre deposited interior of the final yarn, while fibre deposited at the thin end will stay on the surface.at the thin end will stay on the surface.

The twisting rate in friction spinning is related The twisting rate in friction spinning is related to the drum rpm, drum diameter and yarn to the drum rpm, drum diameter and yarn diameter as indicated below.diameter as indicated below.

efficiencyTwistingdiameterYarn

diameterDrumrpmDrumtpmTwist )(

Because of the very large ratio between the drum Because of the very large ratio between the drum and yarn diameters, the rotational speed of the and yarn diameters, the rotational speed of the drums need not be high, provided adequate twist drums need not be high, provided adequate twist efficiency is achieved. The twist efficiency is efficiency is achieved. The twist efficiency is reduced due to the slippage between the yarn in the reduced due to the slippage between the yarn in the nip and the drum surfaces. It is possible to have a nip and the drum surfaces. It is possible to have a twist efficiency as low as 40%. But even allowing for twist efficiency as low as 40%. But even allowing for this, friction spinning is still the most efficient way of this, friction spinning is still the most efficient way of inserting twist to fibres, because twist is directly inserting twist to fibres, because twist is directly applied to yarn end.applied to yarn end.

Unlike ring spinning and rotor spinning, friction Unlike ring spinning and rotor spinning, friction

spinning imposes very little tension to the yarn. So spinning imposes very little tension to the yarn. So the ends-down rate in friction spinning is very low the ends-down rate in friction spinning is very low and the yarn can be withdrawn from the nip of the and the yarn can be withdrawn from the nip of the drums at a very high speed, say 250 m/min. This drums at a very high speed, say 250 m/min. This makes friction spinning more productive than ring makes friction spinning more productive than ring and rotor spinning.and rotor spinning.

Similar to rotor spinning, friction spinning uses sliver feed Similar to rotor spinning, friction spinning uses sliver feed and tooth drafting. Fibres opened by a toothed roller are and tooth drafting. Fibres opened by a toothed roller are directed towards the nip of the friction drums, at a very high directed towards the nip of the friction drums, at a very high speed. The fibres should then impinge on the friction surface speed. The fibres should then impinge on the friction surface that is entering the nip or the rotating mass of fibres in the that is entering the nip or the rotating mass of fibres in the nip. Because the velocity of the entering fibres is much nip. Because the velocity of the entering fibres is much higher than the surface velocity of the drum surface and the higher than the surface velocity of the drum surface and the rotating mass of fibres in the nip, fibres are decelerated as rotating mass of fibres in the nip, fibres are decelerated as they impinge on the drum surface or the rotating fibres in they impinge on the drum surface or the rotating fibres in the nip. This deceleration causes considerable fibre buckling the nip. This deceleration causes considerable fibre buckling just before the fibres are incorporated into the yarn just before the fibres are incorporated into the yarn structure. As a result, the fibre alignment in friction spun structure. As a result, the fibre alignment in friction spun yarns is poor, leading to poor strength of friction spun yarns. yarns is poor, leading to poor strength of friction spun yarns. Having long fibres does not help yarn strength much in Having long fibres does not help yarn strength much in friction spinning, because the long fibres buckle more readily friction spinning, because the long fibres buckle more readily than short ones, so their configurations within the yarn than short ones, so their configurations within the yarn structure may not be as good as shorter fibres. The poor structure may not be as good as shorter fibres. The poor yarn strength also means that friction spinning can only yarn strength also means that friction spinning can only produce relatively coarse yarns. produce relatively coarse yarns.

With friction spinning, a core component can With friction spinning, a core component can be easily introduced in the nip to make a be easily introduced in the nip to make a composite yarn of a sheath/core composition. composite yarn of a sheath/core composition. Examples of this will be discussed in the Examples of this will be discussed in the following section on DREF friction spinning following section on DREF friction spinning systems.systems.

In this section, we have discussed the basic In this section, we have discussed the basic principle of friction spinning, and the key principle of friction spinning, and the key features of friction spun yarns. Next, we will features of friction spun yarns. Next, we will discuss the DREF 2 and DREF 3 friction discuss the DREF 2 and DREF 3 friction spinning systems developed by the Fehrer spinning systems developed by the Fehrer company located in Linz, Austria. company located in Linz, Austria.

DREF 2 friction spinning systemDREF 2 friction spinning system

The DREF 2 friction spinning system was The DREF 2 friction spinning system was introduced into the world market in 1977. It is introduced into the world market in 1977. It is designed for coarse yarn counts in the 100 tex designed for coarse yarn counts in the 100 tex to 4,000 tex range. The DREF 2 system is to 4,000 tex range. The DREF 2 system is primarily used for the recycling of all types of primarily used for the recycling of all types of textile waste fibres and mixtures with 10 -120 textile waste fibres and mixtures with 10 -120 mm fibre lengths, and the spinning of technical mm fibre lengths, and the spinning of technical and other yarns for specialised applications, and other yarns for specialised applications, such as blankets, cleaning rags and mops, such as blankets, cleaning rags and mops, yarns for secondary carpet backings etc. yarns for secondary carpet backings etc.

A diagram of the DREF 2 friction spinning A diagram of the DREF 2 friction spinning system is shown in figure 3.3.system is shown in figure 3.3.

Figure 3.3 DREF 2 friction spinning system (Fehrer Figure 3.3 DREF 2 friction spinning system (Fehrer AG)AG)

As mentioned in the previous section, toothed As mentioned in the previous section, toothed drafting is used in friction spinning. With the drafting is used in friction spinning. With the DREF 2 system, the feed slivers are opened DREF 2 system, the feed slivers are opened and drafted by the teeth of a carding drum. and drafted by the teeth of a carding drum. The individualised fibres are then stripped from The individualised fibres are then stripped from the carding drum by centrifugal force, the carding drum by centrifugal force, supported by an air flow. Gravity and air flow supported by an air flow. Gravity and air flow then carry the fibres into the nip of two then carry the fibres into the nip of two perforated spinning drums. Assisted by air perforated spinning drums. Assisted by air suction through the spinning drums, the fibres suction through the spinning drums, the fibres in the nip are twisted by friction on the two in the nip are twisted by friction on the two drum surfaces to form the yarn. The yarn is drum surfaces to form the yarn. The yarn is then withdrawn by the take-up rollers at then withdrawn by the take-up rollers at delivery speeds of up to 250 m/min, and wound delivery speeds of up to 250 m/min, and wound onto a large yarn package.onto a large yarn package.

A filament core can be easily introduced into A filament core can be easily introduced into the nip of the spinning drums via the core the nip of the spinning drums via the core feeding (figure 3.3), to make a composite yarn feeding (figure 3.3), to make a composite yarn of a sheath/core structure. During spinning, the of a sheath/core structure. During spinning, the filament core gets false twisted by the spinning filament core gets false twisted by the spinning drums, while the staple fibres are deposited on drums, while the staple fibres are deposited on the false twisted filament to make a sheath. the false twisted filament to make a sheath. The staple fibres are twisted as usual. But as The staple fibres are twisted as usual. But as the filament core emerges from the nip of the the filament core emerges from the nip of the spinning drums, the false twist in it is removed spinning drums, the false twist in it is removed automatically, and the sheath fibres receive a automatically, and the sheath fibres receive a reserve twist in the process. The resultant reserve twist in the process. The resultant composite yarn has the characteristics of a composite yarn has the characteristics of a twistless filament core surrounded by a sheath twistless filament core surrounded by a sheath of helical wound fibres of varying helix angles.of helical wound fibres of varying helix angles.

The core/sheath effect can also be achieved The core/sheath effect can also be achieved without the filament component. As indicated without the filament component. As indicated in the previous section, the yarn in the nip of in the previous section, the yarn in the nip of the spinning drums has a tapered end, and the spinning drums has a tapered end, and fibres deposited in the thin end of the taper are fibres deposited in the thin end of the taper are likely to end up in the core position of the likely to end up in the core position of the resultant yarn. For example, fibres in the left-resultant yarn. For example, fibres in the left-most card sliver in figure 3.3 are likely to stay most card sliver in figure 3.3 are likely to stay as core fibres in the yarn, surrounded by as core fibres in the yarn, surrounded by sheath fibres from the remaining two card sheath fibres from the remaining two card slivers. This preferential fibre arrangement slivers. This preferential fibre arrangement facilitates an economic use of a variety of raw facilitates an economic use of a variety of raw materials. A 'core' sliver of waste fibres may be materials. A 'core' sliver of waste fibres may be used with other 'sheath' slivers of high quality used with other 'sheath' slivers of high quality virgin fibres to make a quality yarn with virgin fibres to make a quality yarn with reduced raw material cost. reduced raw material cost.

It is worth mentioning that even if a It is worth mentioning that even if a filament core is not to be used as part of filament core is not to be used as part of the final yarn, a filament is often used to the final yarn, a filament is often used to help start the spinning process. Once help start the spinning process. Once started, the filament is then cut to allow started, the filament is then cut to allow the process to continue without it. This the process to continue without it. This also applies to the DREF 3 friction also applies to the DREF 3 friction spinning system that is discussed next.spinning system that is discussed next.

DREF 3 friction spinning systemDREF 3 friction spinning system After the introduction of DREF 2 into the world After the introduction of DREF 2 into the world

market in 1977, Dr Ernst Fehrer began work on market in 1977, Dr Ernst Fehrer began work on the development of the DREF 3 friction the development of the DREF 3 friction spinning system, which was first presented to spinning system, which was first presented to the public at the 1979 international textile the public at the 1979 international textile machinery exhibition (ITMA'79) in Hanover. In machinery exhibition (ITMA'79) in Hanover. In 1981, DREF 3 entered the global textile 1981, DREF 3 entered the global textile machinery market. DREF 3 is designed for the machinery market. DREF 3 is designed for the manufacture of multi-component yarns in the manufacture of multi-component yarns in the medium count range (25 - 667 tex). The yarns medium count range (25 - 667 tex). The yarns have been used in a wide range of industrial have been used in a wide range of industrial applications, including fire-resistant protective applications, including fire-resistant protective clothing, aircraft and contract carpeting, clothing, aircraft and contract carpeting, conveyor and transport belts, composites for conveyor and transport belts, composites for aviation and automotive industries etc.aviation and automotive industries etc.

Figure 3.4 shows a diagram of the DREF 3 friction spinning system.Figure 3.4 DREF 3 friction spinning system (Fehrer AG)

There are a number differences between DREF There are a number differences between DREF 2 and DREF 3. First of all, toothed drafted is 2 and DREF 3. First of all, toothed drafted is achieved by two toothed drums in DREF 3 achieved by two toothed drums in DREF 3 rather than just one carding drum in DREF 2. rather than just one carding drum in DREF 2. Second, another roller drafting unit (Drafting Second, another roller drafting unit (Drafting unit I in figure 3.4) is now added in DREF 3. unit I in figure 3.4) is now added in DREF 3. This drafting unit will deliver parallel fibres that This drafting unit will deliver parallel fibres that will form a will form a core of parallel fibrescore of parallel fibres in the final in the final yarn, surrounded by the sheath fibres from yarn, surrounded by the sheath fibres from drafting unit II (figure 3.4). There is also the drafting unit II (figure 3.4). There is also the option for the introduction of a filament core as option for the introduction of a filament core as in DREF 2. Therefore, composite yarns of three in DREF 2. Therefore, composite yarns of three different components can be engineered on different components can be engineered on the DREF 3 system. the DREF 3 system.

Figure 3.5 shows a side view of the DREF 3 Figure 3.5 shows a side view of the DREF 3 system.system.

► Figure 3.5 A side view showing the principle of DREF 3Figure 3.5 A side view showing the principle of DREF 3

For good For good doubling effectdoubling effect 并合效应并合效应 , fibres , fibres slivers are used as feed slivers. The overall slivers are used as feed slivers. The overall density of the feed slivers is very high, which density of the feed slivers is very high, which means they have to be fed to the toothed means they have to be fed to the toothed drafting rollers (carding drums) at a very slow drafting rollers (carding drums) at a very slow speed. To minimise fibre damage, the distance speed. To minimise fibre damage, the distance between the clamping line of the last pair of between the clamping line of the last pair of feed rollers and the line of the narrowest feed rollers and the line of the narrowest clearance between the two toothed drafting clearance between the two toothed drafting rollers is set at about one fibre length. In rollers is set at about one fibre length. In addition, this distance is adjustable to cater addition, this distance is adjustable to cater for raw materials of different fibre length.for raw materials of different fibre length.

As with DREF 2, As with DREF 2, fibre bucklingfibre buckling 纤维弯曲纤维弯曲 occurs occurs as the individual fibres impinge upon the surface as the individual fibres impinge upon the surface of the spinning drum and the mass of fibres of the spinning drum and the mass of fibres already in the nip of the two spinning drums. already in the nip of the two spinning drums. This leads to poor fibre orientation in the yarn, This leads to poor fibre orientation in the yarn, which reduces yarn strength. But in DREF 3, the which reduces yarn strength. But in DREF 3, the core fibres are of parallel configuration. So DREF core fibres are of parallel configuration. So DREF 3 yarns should have higher tenacity than DREF 2 3 yarns should have higher tenacity than DREF 2 yarns under similar conditions.yarns under similar conditions.

The percentage of core/sheath components can The percentage of core/sheath components can be easily adjusted with the DREF friction be easily adjusted with the DREF friction spinning systems.spinning systems.

►Review questionsReview questions

1.1.Describe in your own words the principle of Describe in your own words the principle of friction spinning.friction spinning.

2.2.Friction spun yarns do not have wrapper Friction spun yarns do not have wrapper fibres on the yarn surface. Why are friction fibres on the yarn surface. Why are friction spun yarns weaker than comparable rotor spun yarns weaker than comparable rotor spun yarns?spun yarns?

3.3.Compare and contrast the differences and Compare and contrast the differences and similarities between DREF 2 and DREF 3 similarities between DREF 2 and DREF 3 friction spinning systems.friction spinning systems.

Air jet spinningAir jet spinning 喷气纺纱喷气纺纱IntroductionIntroduction In the early 1960s, the DuPont company (USA) In the early 1960s, the DuPont company (USA)

patented a method for producing what was called a patented a method for producing what was called a fasciatedfasciated yarn yarn 包缠纱包缠纱 , which is composed of a , which is composed of a core of more or less parallel fibres, wrapped around core of more or less parallel fibres, wrapped around by a small proportion of surface fibres. A false twist by a small proportion of surface fibres. A false twist air jet was used as the twister, hence the name air air jet was used as the twister, hence the name air jet spinning or air vortex spinning. Because the jet spinning or air vortex spinning. Because the speed of air vortex can be extremely high, the speed of air vortex can be extremely high, the twisting rate is very high with air jet spinning, twisting rate is very high with air jet spinning, which then leads to high yarn delivery speed or which then leads to high yarn delivery speed or high production rate. Today, air jet spinning is high production rate. Today, air jet spinning is almost the most productive staple spinning almost the most productive staple spinning technologies.technologies.

DuPont did not pursue its patented method to DuPont did not pursue its patented method to commercialisation. Instead, further research commercialisation. Instead, further research and development on air jet spinning were and development on air jet spinning were carried by other companies. Since the 1980s, carried by other companies. Since the 1980s, the name most widely associated with air jet the name most widely associated with air jet spinning has been Murata, Japan.spinning has been Murata, Japan.

This topic discusses DuPont's basic idea of air This topic discusses DuPont's basic idea of air jet spinning to make fasciated yarns. This is jet spinning to make fasciated yarns. This is followed by a discussion of Murata Jet Spinning followed by a discussion of Murata Jet Spinning (MJS) and the associated development(MJS) and the associated development

ObjectivesObjectives At the end of this topic you should be able to:At the end of this topic you should be able to:

► Understand the basic principle of the Murata Understand the basic principle of the Murata Jet Spinning systemJet Spinning system

► Appreciate the characteristics of air jet spun Appreciate the characteristics of air jet spun yarnsyarns

► Know the developments in air jet spinningKnow the developments in air jet spinning

Principle of air jet spinningPrinciple of air jet spinning

As mentioned in the introduction, air jet As mentioned in the introduction, air jet spinning makes a fasciated yarn with a parallel spinning makes a fasciated yarn with a parallel core wrapped around by some surface fibres. core wrapped around by some surface fibres. The original DuPont process uses one air jet The original DuPont process uses one air jet only. Figure 4.1 shows the principle of the only. Figure 4.1 shows the principle of the DuPont method, together with a comparison of DuPont method, together with a comparison of fasciated yarn versus conventional ring spun fasciated yarn versus conventional ring spun yarn.yarn.

Figure 4.1 Schematic diagram of the fasciated yarn spinning system (Hunter 1978, p.16).

The feed sliver is drafted by a roller drafting unit (now The feed sliver is drafted by a roller drafting unit (now shown in full). The drafted fibres are presented as a flat shown in full). The drafted fibres are presented as a flat bundle to the aspirator and then pass the air jet twister bundle to the aspirator and then pass the air jet twister (torque jet). Because the fibre strand is nipped (torque jet). Because the fibre strand is nipped between the delivery rollers (on the right) and the front between the delivery rollers (on the right) and the front drafting rollers (on the left), only false twist is inserted drafting rollers (on the left), only false twist is inserted into the fibre strand by the air jet twister. At the air jet into the fibre strand by the air jet twister. At the air jet twister, the main bundle of fibres are false twisted, but twister, the main bundle of fibres are false twisted, but some fibres at the edges of the fibre ribbon will escape some fibres at the edges of the fibre ribbon will escape the twisting effect to some extent. the twisting effect to some extent.

As soon as the fibres emerge from the air As soon as the fibres emerge from the air jet, the main bundle of fibres will untwist to jet, the main bundle of fibres will untwist to cancel out the false twist in the bundle. cancel out the false twist in the bundle. Because of the increased fibre contact with Because of the increased fibre contact with the main bundle, the edge fibres will also the main bundle, the edge fibres will also 'untwist' with the main bundle, and the 'untwist' with the main bundle, and the amount of untwisting is greater than the amount of untwisting is greater than the initial false twist these edge fibres received initial false twist these edge fibres received from the air jet. As a result, the net result is from the air jet. As a result, the net result is that the edge fibres will be given a real twist that the edge fibres will be given a real twist in the opposite direction to that of the in the opposite direction to that of the original false twist. This difference in twist original false twist. This difference in twist direction is also depicted in figure 4.1. direction is also depicted in figure 4.1.

An important feature of this process the high An important feature of this process the high rate of twist, leading to much higher rate of rate of twist, leading to much higher rate of yarn delivery than the ring and rotor spinning yarn delivery than the ring and rotor spinning systems. Roving stage is also eliminated systems. Roving stage is also eliminated because the jet spinning systems can spin because the jet spinning systems can spin directly from slivers. Jet spun yarns are usually directly from slivers. Jet spun yarns are usually weaker than comparable ring spun yarns.weaker than comparable ring spun yarns.

The jet spinning process relies heavily on the The jet spinning process relies heavily on the clever manipulation of the edge fibres which clever manipulation of the edge fibres which refuse to receive the full initial false twist. This refuse to receive the full initial false twist. This aspect is further developed by Murata in its aspect is further developed by Murata in its own jet spinning systems. The Murata Jet own jet spinning systems. The Murata Jet Spinning concept is discussed next.Spinning concept is discussed next.

Murata jet spinning (MJS)Murata jet spinning (MJS) The Murata jet spinning (MJS) system uses two The Murata jet spinning (MJS) system uses two

air jets rather than one. The direction of air air jets rather than one. The direction of air vortex of the two jets is opposite. The first jet is vortex of the two jets is opposite. The first jet is employed specifically to manipulate the edge employed specifically to manipulate the edge fibres while the second jet (main jet) is used as fibres while the second jet (main jet) is used as the false twist jet. Figure 4.2 shows a schematic the false twist jet. Figure 4.2 shows a schematic of the Murata jet spinning system.of the Murata jet spinning system.

Figure 4.2 Schematic of Murata jet spinning (MJS) process (Murata).

A drawframe sliver is fed from can (1) to a A drawframe sliver is fed from can (1) to a roller drafting unit (2). A high draft in the roller drafting unit (2). A high draft in the range 100-200 is used to attenuate the range 100-200 is used to attenuate the sliver to a thin strand of fibres. The fibre sliver to a thin strand of fibres. The fibre strand then proceeds to the two air jets (3 strand then proceeds to the two air jets (3 and 4). The direction of air vortex in these and 4). The direction of air vortex in these two jets is opposite to each other. The two jets is opposite to each other. The intensity of air vortex in these jet is also intensity of air vortex in these jet is also quite different, with the second jet (4) quite different, with the second jet (4) having an air vortex of much higher having an air vortex of much higher intensity. The angular velocity of the air intensity. The angular velocity of the air vortex inside the 2vortex inside the 2nd nd jet (4) is more than 1 jet (4) is more than 1 million rpm. Owing to the intensity of its air million rpm. Owing to the intensity of its air vortex, the 2vortex, the 2nd nd jet (4) is the actual false jet (4) is the actual false twist jet and will affect the main bundle of twist jet and will affect the main bundle of fibres from the drafting unit. fibres from the drafting unit.

The first jet (3), on the other hand, will affect the small The first jet (3), on the other hand, will affect the small number of edge fibres. Because the air vortex inside number of edge fibres. Because the air vortex inside the 1st jet (3) rotates in the opposite direction to that the 1st jet (3) rotates in the opposite direction to that of the 2of the 2ndnd jet, the edge fibres are twisted by the 1 jet, the edge fibres are twisted by the 1stst jet jet in the opposite direction to the main fibre bundle. As in the opposite direction to the main fibre bundle. As soon as the main fibre bundle and the edge fibres soon as the main fibre bundle and the edge fibres emerge from the 2emerge from the 2ndnd jet (4), the main bundle untwists jet (4), the main bundle untwists to cancel out the false twist it received from the 2to cancel out the false twist it received from the 2ndnd jet. jet. In the same process, the edge fibres also 'untwist' with In the same process, the edge fibres also 'untwist' with the main bundle. Because the direction of 'untwisting' the main bundle. Because the direction of 'untwisting' is the same as the direction of the twist these edge is the same as the direction of the twist these edge fibres received from the 1st jet, the edge fibres fibres received from the 1st jet, the edge fibres actually receive a boost of real twist, allowing them to actually receive a boost of real twist, allowing them to wrap tightly around the now parallel main fibre bundle. wrap tightly around the now parallel main fibre bundle. The distribution of twist in the fibre strand is depicted The distribution of twist in the fibre strand is depicted in figure 4.3.in figure 4.3.

Figure 4.3 Distribution of twist in the whole fibre strand (Klein 1993, p.14)

Since the installation of the 1st Murata jet Since the installation of the 1st Murata jet spinner in USA, this technology has achieved spinner in USA, this technology has achieved considerable market penetration. Today, it is considerable market penetration. Today, it is used to spin yarns in the count range Ne 10 to used to spin yarns in the count range Ne 10 to Ne 80 (7.5 to 59 tex), at a yarn delivery speed Ne 80 (7.5 to 59 tex), at a yarn delivery speed of about 200 m/min. Fibres used include 100% of about 200 m/min. Fibres used include 100% cotton, synthetics, and their blends (fibre cotton, synthetics, and their blends (fibre length up to 2 inches). length up to 2 inches).

Compared with ring spun yarns, the Murata air Compared with ring spun yarns, the Murata air jet spun yarns are usually weaker, stiffer and jet spun yarns are usually weaker, stiffer and harder, but they have a lower tendency to harder, but they have a lower tendency to pilling and snarling. pilling and snarling.

Developments in air jet spinningDevelopments in air jet spinning

Two major developments in this field are from Two major developments in this field are from Murata - the Murata Twin Spinner (MTS) and Murata - the Murata Twin Spinner (MTS) and the Roller Jet Spinner (RJS).the Roller Jet Spinner (RJS).

► Murata Twin Spinner (MTS)Murata Twin Spinner (MTS) The Murata twin spinner produces an The Murata twin spinner produces an

assembly wound air jet spun yarns directly on assembly wound air jet spun yarns directly on the the spinning framespinning frame 环锭细纱机环锭细纱机 ..

Figure 4.4 shows the process of Murata twin Figure 4.4 shows the process of Murata twin spinner. The principle of yarn formation is spinner. The principle of yarn formation is exactly the same the Murata jet spinning exactly the same the Murata jet spinning discussed in the previous section. Rather than discussed in the previous section. Rather than making one air jet spun yarn, two single air jet making one air jet spun yarn, two single air jet spun yarns are produced from two feed slivers. spun yarns are produced from two feed slivers. Upon emerging from the air jets, these two Upon emerging from the air jets, these two single yarns are brought together, cleared if single yarns are brought together, cleared if necessary by a yarn clearing device, and necessary by a yarn clearing device, and assembly wound onto a large package. The assembly wound onto a large package. The assembly wound package is usually twisted assembly wound package is usually twisted with a two-for-one twister to form a quality 2-with a two-for-one twister to form a quality 2-folded yarn or doubled yarn.folded yarn or doubled yarn.Figure 4.4 Murata Twin Spinner (Murata)

► Roller Jet Spinner (RJS)Roller Jet Spinner (RJS)

This is a relatively new development. Again This is a relatively new development. Again the basic principle is similar to Murata jet the basic principle is similar to Murata jet spinning. But only one jet is used, the 2nd false spinning. But only one jet is used, the 2nd false twist jet is replaced by a pair of twisting rollers, twist jet is replaced by a pair of twisting rollers, called the balloon rollers. The rotation of the called the balloon rollers. The rotation of the balloon rollers not only inserts false twist to the balloon rollers not only inserts false twist to the main fibre bundle, they also drive forward the main fibre bundle, they also drive forward the yarn at a predetermined delivery speed. A yarn at a predetermined delivery speed. A schematic diagram of the balloon rollers is schematic diagram of the balloon rollers is shown in figure 4.5.shown in figure 4.5.

Figure 4.5 The balloon rollers used in RJSFigure 4.5 The balloon rollers used in RJS

The roller jet spinner (RJS) can achieve a yarn The roller jet spinner (RJS) can achieve a yarn delivery speed of bout 400 m/min, making it delivery speed of bout 400 m/min, making it the most productive staple spinning system in the most productive staple spinning system in commercial production. A notable feature of commercial production. A notable feature of the roller jet spun yarns is the very low yarn the roller jet spun yarns is the very low yarn hairiness level. This is because of the rolling of hairiness level. This is because of the rolling of surface fibres on the yarn by the surfaces of surface fibres on the yarn by the surfaces of the balloon rollers. the balloon rollers.

The reading material "Murata: RJS Spinning for The reading material "Murata: RJS Spinning for Coarse Counts" by Murata Machinery Ltd briefs Coarse Counts" by Murata Machinery Ltd briefs explains the principle of roller jet spinning, and explains the principle of roller jet spinning, and compares the relevant yarn and fabric compares the relevant yarn and fabric performances.performances.

► Review questionsReview questions

1.1.Rotor spun yarns have wrapper fibres and Rotor spun yarns have wrapper fibres and Murata jet spun yarns also have wrapping Murata jet spun yarns also have wrapping fibres binding the yarn together. What is the fibres binding the yarn together. What is the main difference between the structures of main difference between the structures of yarns produced by these two spinning yarns produced by these two spinning systems? systems?

2.2.The following diagrams show the process The following diagrams show the process flow-chart for making two-folded (two-plied) flow-chart for making two-folded (two-plied) ring and rotor spun yarns from cotton fibres. ring and rotor spun yarns from cotton fibres. Please sketch the processing flow-charts for Please sketch the processing flow-charts for making two-folded cotton yarns from Murata making two-folded cotton yarns from Murata Jet Spinner (MJS) and Murata Twin Spinner Jet Spinner (MJS) and Murata Twin Spinner (MTS). (MTS).

33 、、 There are a number of spinning systems There are a number of spinning systems that are not discussed in this module. that are not discussed in this module. These spinning systems, while not as These spinning systems, while not as commonly used as the ones discussed in commonly used as the ones discussed in this module, are nevertheless worth this module, are nevertheless worth knowing. Please consult the relevant knowing. Please consult the relevant library resources at Deakin and class library resources at Deakin and class handouts, explain (with the help of handouts, explain (with the help of sketches) the working principle of each sketches) the working principle of each of the following spinning systems:of the following spinning systems:

(1)Wrap spinning(1)Wrap spinning 包缠纺纱包缠纺纱 (2)Self-twist spinning(2)Self-twist spinning 自捻纺纱自捻纺纱 (3)Mule spinning(3)Mule spinning 走锭纺纱走锭纺纱 (4)Woollen ring spinning(4)Woollen ring spinning 粗梳毛纺粗梳毛纺

Filament Yarn TexturingFilament Yarn Texturing

IntroductionIntroduction Manufactured fibres have been used Manufactured fibres have been used

increasingly, often at the expenses of a declining increasingly, often at the expenses of a declining share of natural fibres. Manufactured fibres can share of natural fibres. Manufactured fibres can be produced in various forms - tape, mono-be produced in various forms - tape, mono-filament, multi-filament, and tow. Figure 5.1 filament, multi-filament, and tow. Figure 5.1 shows an overview of the production and shows an overview of the production and subsequent processing of manufactured fibres subsequent processing of manufactured fibres

Figure 5.1: An overview of manufactured fibre production and processing

Different dies or spinnerets are used to extrude the various forms of Different dies or spinnerets are used to extrude the various forms of manufactured fibres. For example, to make a tape yarn, the polymer manufactured fibres. For example, to make a tape yarn, the polymer material is extruded as a thin sheet first, which is then slit into flat and material is extruded as a thin sheet first, which is then slit into flat and narrow tape yarns for applications such as carpet backing, sacks and narrow tape yarns for applications such as carpet backing, sacks and packing bags. Manufactured fibres can also be extruded as a think bundle packing bags. Manufactured fibres can also be extruded as a think bundle of continuous filaments known as a of continuous filaments known as a towtow, which is subsequently cut or , which is subsequently cut or stretch broken into staple fibres for processing on their own or in blends stretch broken into staple fibres for processing on their own or in blends with other fibres on conventional short staple or long staple processing with other fibres on conventional short staple or long staple processing systems. But most commonly, manufactured fibres are extruded as systems. But most commonly, manufactured fibres are extruded as continuously multi-filament yarns. The majority of multi-filament yarns that continuously multi-filament yarns. The majority of multi-filament yarns that we use today are polyester and nylon. In making these yarns, the polymer we use today are polyester and nylon. In making these yarns, the polymer chip is melt by heat and extruded through a series of tiny holes in a chip is melt by heat and extruded through a series of tiny holes in a spinneret. The filaments are then brought together and drawn to align the spinneret. The filaments are then brought together and drawn to align the molecular chains in each filament to improve the strength of the resultant molecular chains in each filament to improve the strength of the resultant multi-filament yarn. Depending on the level of drawing, the resultant multi-multi-filament yarn. Depending on the level of drawing, the resultant multi-filament can be a partially oriented yarn (filament can be a partially oriented yarn (POYPOY) or a fully oriented yarn ) or a fully oriented yarn ((FOYFOY). Up to this stage, the yarn is often referred to as producer filament ). Up to this stage, the yarn is often referred to as producer filament yarn, smooth filament yarn, and flat filament yarn. Such a yarn is generally yarn, smooth filament yarn, and flat filament yarn. Such a yarn is generally unsuitable for apparel applications. Owing to the smooth surface of unsuitable for apparel applications. Owing to the smooth surface of individual filaments, the filaments are closely packed together, with little individual filaments, the filaments are closely packed together, with little bulk and extension. Fabrics made from these yarns are slippery, have poor bulk and extension. Fabrics made from these yarns are slippery, have poor breathability and handle. To overcome these drawbacks, the filaments are breathability and handle. To overcome these drawbacks, the filaments are either converted into staple fibres first for processing on conventional wool either converted into staple fibres first for processing on conventional wool or cotton processing machinery, or are textured through a filament yarn or cotton processing machinery, or are textured through a filament yarn texturing process.texturing process.

For information on converting continuous filaments to For information on converting continuous filaments to staple fibres, please raed the reading "Tow-to-sliver staple fibres, please raed the reading "Tow-to-sliver conversion and bulked acrylic yarn production" by Oxtoby conversion and bulked acrylic yarn production" by Oxtoby (1987, p.232). Please note that "tow-to-sliver" conversion (1987, p.232). Please note that "tow-to-sliver" conversion is also known as "tow-to-top" conversion. Furthermore, a is also known as "tow-to-top" conversion. Furthermore, a similar technique to bulked acrylic yarn production has similar technique to bulked acrylic yarn production has also been used to produce bulky yarns from wool fibres.also been used to produce bulky yarns from wool fibres.

This topic focuses on the texturing of continuous filament This topic focuses on the texturing of continuous filament yarns.yarns.

Textured yarns in comparison with the original smooth Textured yarns in comparison with the original smooth filament yarn show increased bulkiness, porosity, filament yarn show increased bulkiness, porosity, softness, and some of them also possess high elasticity. softness, and some of them also possess high elasticity. Garments made from textured yarns are comfortable to Garments made from textured yarns are comfortable to wear. They are noted for good draping qualities. They wear. They are noted for good draping qualities. They have good air permeability and thermal insulation have good air permeability and thermal insulation properties. They are more absorbent and allow less static properties. They are more absorbent and allow less static build-up than the original smooth filament yarn. Textured build-up than the original smooth filament yarn. Textured yarns may be in different forms, depending on the yarns may be in different forms, depending on the texturing process used. texturing process used.

The basic principle of texturing is to introduce The basic principle of texturing is to introduce arcs, crimps, or loops into the smooth arcs, crimps, or loops into the smooth structure of continuous filament yarns. structure of continuous filament yarns. Different processes have been developed for Different processes have been developed for this purpose. The two commonly used this purpose. The two commonly used processes are false-twist texturing and air-jet processes are false-twist texturing and air-jet texturing.texturing.

ObjectivesObjectives At the end of this topic you should be able to:At the end of this topic you should be able to:

► Understand the process of 'tow-to-top' Understand the process of 'tow-to-top' conversion and the production of bulked acrylic conversion and the production of bulked acrylic yarnsyarns

► Understand the objectives of filament yarn Understand the objectives of filament yarn texturingtexturing

► Know the principle and process false twist Know the principle and process false twist texturingtexturing

► Know the principle and process of air jet Know the principle and process of air jet texturingtexturing

False-twist TexturingFalse-twist Texturing

► Principle and processPrinciple and process Filament yarns like polyester and nylon and thermoplastic. They Filament yarns like polyester and nylon and thermoplastic. They

soften and can be easily deformed with the application of heat; soften and can be easily deformed with the application of heat; and upon cooling, the filaments remain in their deformed state and upon cooling, the filaments remain in their deformed state (i.e. the filaments become heat-set). Normally if filaments are (i.e. the filaments become heat-set). Normally if filaments are twisted, torsional stress develops in the filaments and the twisted, torsional stress develops in the filaments and the filaments will want to untwist to release the stress. However, if filaments will want to untwist to release the stress. However, if such filaments are twisted and heat-set (i.e. heated above their such filaments are twisted and heat-set (i.e. heated above their glass transition temperature and then cooled below their glass glass transition temperature and then cooled below their glass transition temperature), their torsional stress will be relaxed and transition temperature), their torsional stress will be relaxed and the filaments will remain twisted even though the external force is the filaments will remain twisted even though the external force is removed. If these filaments are then untwisted, stress will develop removed. If these filaments are then untwisted, stress will develop again in the individual filaments. If these stressed filaments are again in the individual filaments. If these stressed filaments are allowed to relax, they will seek the allowed to relax, they will seek the minimum-energy-stateminimum-energy-state (or (or least stressed state!) by forming adjacent helices and snarls. least stressed state!) by forming adjacent helices and snarls. These helices and snarls prevent the individual filaments from These helices and snarls prevent the individual filaments from staying as closely packed as before and the filaments will occupy staying as closely packed as before and the filaments will occupy a much greater volume than before. In other words, the filaments a much greater volume than before. In other words, the filaments become bulky and textured. This process is illustrated in Figure become bulky and textured. This process is illustrated in Figure 5.25.2

Fig. 5.2 Principle of filament texturing by twisting, heat-setting and Fig. 5.2 Principle of filament texturing by twisting, heat-setting and untwistinguntwisting

In the early days of filament yarn texturing, the In the early days of filament yarn texturing, the three steps of twisting, heat-setting, and untwisting three steps of twisting, heat-setting, and untwisting are carried out in separate stages as indicated in are carried out in separate stages as indicated in figure 5.3. This traditional process has now become figure 5.3. This traditional process has now become obsolete. But the principle has been used in modern obsolete. But the principle has been used in modern continuous false twist (FT) texturing processes.continuous false twist (FT) texturing processes.

Figure 5.3: Traditional filament yarn texturing with separate twisting, Figure 5.3: Traditional filament yarn texturing with separate twisting, heat-setting, and untwisting stagesheat-setting, and untwisting stages

In principle, continuous false-twist (FT) texturing is In principle, continuous false-twist (FT) texturing is very similar to a dynamic false-twisting process, as very similar to a dynamic false-twisting process, as indicated in figure 5.4. The main difference is that indicated in figure 5.4. The main difference is that in FT texturing, heating setting is involved. This is in FT texturing, heating setting is involved. This is also why FT texturing can only work on also why FT texturing can only work on thermoplastic filaments. Non-thermoplastic thermoplastic filaments. Non-thermoplastic filaments, such as glass filaments, can not be false-filaments, such as glass filaments, can not be false-

twist texturedtwist textured..

Fig. 5.4 Difference between stationary false twisting, dynamic false Fig. 5.4 Difference between stationary false twisting, dynamic false twisting, and false-twist texturingtwisting, and false-twist texturing

A typical false-twist texturing process is shown in Figure 5.5.A typical false-twist texturing process is shown in Figure 5.5.

Without the second heating process, the Without the second heating process, the textured yarn is called a stretch yarn, which textured yarn is called a stretch yarn, which is bulky and stretchy. The stretch yarn is is bulky and stretchy. The stretch yarn is suitable for hosiery and sportswear (track-suitable for hosiery and sportswear (track-suiting, stretch pants, and swimwear etc). If suiting, stretch pants, and swimwear etc). If less stretch is required, the yarn can pass less stretch is required, the yarn can pass through a 2nd heater under controlled through a 2nd heater under controlled tension. This results in a modified stretch (or tension. This results in a modified stretch (or set) yarn, which retains certain bulk, but with set) yarn, which retains certain bulk, but with much reduced extensibility, suitable for much reduced extensibility, suitable for outwear applications.outwear applications.

Figure 5.6 shows the possible processing routes from filament Figure 5.6 shows the possible processing routes from filament extrusion (spinning) to textured yarn.extrusion (spinning) to textured yarn.

1 - spinning,1 - spinning, 2 - drawing,2 - drawing, 3 - texturing3 - texturing

Route A: 3-step process (Spin undrawn yarn conventionally + Draw Route A: 3-step process (Spin undrawn yarn conventionally + Draw + Texture)+ Texture)

Route B: Spin-Draw + Texture Route B: Spin-Draw + Texture

Route C: Spin + Sequential Draw TextureRoute C: Spin + Sequential Draw Texture

Route D: Spin + Simultaneous Draw TextureRoute D: Spin + Simultaneous Draw Texture

Route E: Spin-Draw-Texture (under development)Route E: Spin-Draw-Texture (under development)

Figure 5.6 Possible processing routes from extrusion (spinning) to Figure 5.6 Possible processing routes from extrusion (spinning) to textured yarn (Hes and Ursiny 1994, p.24) textured yarn (Hes and Ursiny 1994, p.24)

►False twist devicesFalse twist devices

A key element of a false-twist texturing A key element of a false-twist texturing system is the actual false-twister. The false system is the actual false-twister. The false twister should satisfy the following twister should satisfy the following requirements:requirements:

► Grip yarn well to rotate itGrip yarn well to rotate it► Allow yarn to travel throughAllow yarn to travel through► Insert twist at high speed, and Insert twist at high speed, and ► Easy to thread upEasy to thread up

(A) Pin-spindle false twister(A) Pin-spindle false twister

This is a hollow spindle with a horizontal pin This is a hollow spindle with a horizontal pin made of ceramic or sapphire. The filament is made of ceramic or sapphire. The filament is threaded across the pin. The hollow spindle is threaded across the pin. The hollow spindle is driven via frictional contact with large rolls at driven via frictional contact with large rolls at speeds up to 1,000,000 rpm, and each speeds up to 1,000,000 rpm, and each rotation of the spindle (and the pin) will insert rotation of the spindle (and the pin) will insert one turn of twist into the filament. Figure 5.7 one turn of twist into the filament. Figure 5.7 shows a pin false-twist spindle.shows a pin false-twist spindle.

Figure 5.7: Pin spindle false twister (McIntyre Figure 5.7: Pin spindle false twister (McIntyre and Daniels 1995, p. 247)and Daniels 1995, p. 247)

(B) Stacked disk type false twister(B) Stacked disk type false twister

This is the most widely used false twister in This is the most widely used false twister in filament yarn texturing. It consists of three sets filament yarn texturing. It consists of three sets of stacked disks mounted on three shafts of stacked disks mounted on three shafts (figure 5.8), through which the filament yarn (figure 5.8), through which the filament yarn runs. The rotation of the disks not only inserts runs. The rotation of the disks not only inserts twist into the filament, but also drives the twist into the filament, but also drives the filament through the disks. By setting the filament through the disks. By setting the surface speed ratio between the disk and the surface speed ratio between the disk and the yarn (the yarn (the D/Y ratioD/Y ratio) correctly, equal yarn ) correctly, equal yarn tension can be achieved at both sides of the tension can be achieved at both sides of the false twister. For easy threading of the false twister. For easy threading of the filament, one disk shaft is movable while the filament, one disk shaft is movable while the other two are fixed.other two are fixed.

Figure 5.8 Stacked disc type false twister (McIntyre Figure 5.8 Stacked disc type false twister (McIntyre and Daniels 1995, p. 144)and Daniels 1995, p. 144)

(c) Crossed-belts false twister(c) Crossed-belts false twister

As shown in figure 5.9, this false twister has As shown in figure 5.9, this false twister has two belts crossed at a specific angle. The two belts crossed at a specific angle. The filament yarn is twisted and driven between filament yarn is twisted and driven between two belt surfaces by the rotation of the belts. two belt surfaces by the rotation of the belts. It is said to give a soft yarn texturing with It is said to give a soft yarn texturing with little yarn damage. This type of false twister is little yarn damage. This type of false twister is difficult to work with fine denier filaments (eg. difficult to work with fine denier filaments (eg. <78 dtex).<78 dtex).

Fig. 5.9: A crossed-belts type false twisterFig. 5.9: A crossed-belts type false twister

(D)Ring false twister (disk-sandwich twister)(D)Ring false twister (disk-sandwich twister)

This false twister consists of two off-setting This false twister consists of two off-setting rings or disks rotating in opposite direction, rings or disks rotating in opposite direction, with the filament yarn running between the with the filament yarn running between the rings. One of the rings is rigid while the other rings. One of the rings is rigid while the other is flexible. At the yarn input end, a presser is flexible. At the yarn input end, a presser presses on the flexible ring so that the yarn presses on the flexible ring so that the yarn can be twisted as the rings rotate. Similar to can be twisted as the rings rotate. Similar to the crossed-belts, the rotation of the rings the crossed-belts, the rotation of the rings also provides a 'driving force' that drives the also provides a 'driving force' that drives the yarn through the rings. Figure 5.10 shows yarn through the rings. Figure 5.10 shows two diagrams of a ring false twister.two diagrams of a ring false twister.

Figure 5.10: A ring false twister (Demir and Behery Figure 5.10: A ring false twister (Demir and Behery 1997, p.90)1997, p.90)

(E) SZ simultaneous texturing twister(E) SZ simultaneous texturing twister

This is a new development, released by This is a new development, released by Muratec (Japan) at the 1995 international Muratec (Japan) at the 1995 international textile machinery exhibition (ITMA'95) held in textile machinery exhibition (ITMA'95) held in Milan.Milan.

It works on two filaments simultaneously, It works on two filaments simultaneously, inserting S twist in one filament and Z twist in inserting S twist in one filament and Z twist in the other. The two filaments are then the other. The two filaments are then combined and wound onto the same package. combined and wound onto the same package. The resultant textured yarn is claimed to have The resultant textured yarn is claimed to have high bulkiness, and is torque-free (balanced). high bulkiness, and is torque-free (balanced). Figure 5.11 shows the SZ twister and the actual texturing process using this type of

twister. Figure 5.11 A SZ simultaneous twister (a) and the texturing process (b) (Courtesy of Muratec, Japan)

Air-jet Texturing Air-jet Texturing ►Principle and processPrinciple and process Air-jet texturing is a versatile process. It works Air-jet texturing is a versatile process. It works

with both thermo-plastic (eg. Polyester and with both thermo-plastic (eg. Polyester and nylon) and non-thermoplastic (e.g. rayon, glass nylon) and non-thermoplastic (e.g. rayon, glass filament) filaments. In air-jet texturing, yarn filament) filaments. In air-jet texturing, yarn morphology is modified without disturbing the morphology is modified without disturbing the internal structure of individual filaments. This is internal structure of individual filaments. This is achieved by achieved by creating loops and air pockets in creating loops and air pockets in the yarn by opening up the yarn structure, the yarn by opening up the yarn structure, buckling the filaments, and locking up the buckling the filaments, and locking up the structure again.structure again.

The principle of loop formation in air jet The principle of loop formation in air jet texturing can be described as:texturing can be described as:

► Overfeed the filament yarn into an air nozzleOverfeed the filament yarn into an air nozzle► Open the feed yarn (or parent yarn) in a Open the feed yarn (or parent yarn) in a

turbulent air streamturbulent air stream► The air stream displaces the filaments, and The air stream displaces the filaments, and

convert the excess length into loopsconvert the excess length into loops► interlace filaments to stabilise the loop interlace filaments to stabilise the loop

structurestructure

Figure 5.12 depicts the principle of air-jet Figure 5.12 depicts the principle of air-jet texturing. texturing.

Fig. 5.12: Sketch of an air jet texturing processFig. 5.12: Sketch of an air jet texturing process

Wetting of the filaments before the air nozzle Wetting of the filaments before the air nozzle is used for the following reasons:is used for the following reasons:

► to reduce between-filament frictionto reduce between-filament friction► to reduce friction between filaments and to reduce friction between filaments and

nozzle wallnozzle wall► to improve separation of filamentsto improve separation of filaments► to get better texturing effect with smaller and to get better texturing effect with smaller and

more even and frequent loopsmore even and frequent loops A yarn with good textured effect is shown in A yarn with good textured effect is shown in

figure 5.13 below.figure 5.13 below.

Figure 5.13: An air jet textured yarn with good texturing effect

Figure 5.14 shows example photos of dry and wet textured Figure 5.14 shows example photos of dry and wet textured yarns, while figure yarns, while figure

5.15 shows a series of high-speed still photograph of yarn 5.15 shows a series of high-speed still photograph of yarn being textured under wet conditions.being textured under wet conditions.

Fig. 5.14: Photos of dry and wet textured yarns (Demir & Fig. 5.14: Photos of dry and wet textured yarns (Demir & Behery, 1997, p.276)Behery, 1997, p.276)

Figure 5.15: High-speed still photograph of yarn being Figure 5.15: High-speed still photograph of yarn being textured under wet conditions textured under wet conditions (Demir & Behery, 1997, p.249)(Demir & Behery, 1997, p.249)

As can be seen from figure 5.13, air jet As can be seen from figure 5.13, air jet textured yarn closely resembles a spun yarn, textured yarn closely resembles a spun yarn, with the protruding loops mimicking surface with the protruding loops mimicking surface hairs of a spun yarn. For this reason, air jet hairs of a spun yarn. For this reason, air jet textured yarns have found applications in a textured yarns have found applications in a wide range of products, such as jackets, shirts, wide range of products, such as jackets, shirts, blouses, suits, outwear, furnishing fabrics etc.blouses, suits, outwear, furnishing fabrics etc.

► Air nozzlesAir nozzles Many different air jet texturing nozzles have Many different air jet texturing nozzles have

been developed and the development is been developed and the development is continuing. continuing.

The reading material "Air-jet texturing: Effect The reading material "Air-jet texturing: Effect of jet type and some process parameters on of jet type and some process parameters on properties of air-jet textured yarns" by Kothari properties of air-jet textured yarns" by Kothari and Timble (1991, p.29) gives a good account and Timble (1991, p.29) gives a good account on the history of air-jet development, as well on the history of air-jet development, as well as on the test of air-jet textured yarns.as on the test of air-jet textured yarns.

►Other possibilities with air-jet Other possibilities with air-jet texturingtexturing

Apart from being a versatile texturing process, Apart from being a versatile texturing process, air-jet texturing also offers considerable scope air-jet texturing also offers considerable scope for engineering quite different yarns.for engineering quite different yarns.

First of all, the linear density of air jet textured First of all, the linear density of air jet textured yarns can be easily changed by changing the yarns can be easily changed by changing the level of overfeed into the air nozzle. A higher level of overfeed into the air nozzle. A higher overfeed will lead to a heavier textured yarn.overfeed will lead to a heavier textured yarn.

Secondly, co-texturing is possible by feeding Secondly, co-texturing is possible by feeding two or more filaments yarns together. By two or more filaments yarns together. By having different overfeeds for the different having different overfeeds for the different yarns, a core-and-effect yarn can be produced. yarns, a core-and-effect yarn can be produced. The yarn with a lower overfeed will stay in the The yarn with a lower overfeed will stay in the centre as the core while that with a higher centre as the core while that with a higher overfeed will stay predominantly on the overfeed will stay predominantly on the surface. Figure 5.16 shows the process of surface. Figure 5.16 shows the process of producing a core-effect yarn using three feed producing a core-effect yarn using three feed yarns.yarns.

Figure 5.16: Core-effect textured yarn production (Demir & Behery, 1997, p.214)

The loops of air-jet textured yarn can also be The loops of air-jet textured yarn can also be broken after textured with a loop breaker as broken after textured with a loop breaker as shown in figure 5.17. In this process, the air shown in figure 5.17. In this process, the air textured yarn wraps around several rolls in textured yarn wraps around several rolls in succession so that protruding loops of the succession so that protruding loops of the incoming yarn are rubbed by the outgoing incoming yarn are rubbed by the outgoing yarn and thereby broken up. The resultant yarn and thereby broken up. The resultant yarn is called a yarn is called a TexspunTexspun yarn yarn （变形纱）（变形纱） , , because the free fibre ends of this textured because the free fibre ends of this textured yarn give the yarn a very spun-like yarn give the yarn a very spun-like appearance.appearance.

Figure 5.17: A Texspun processFigure 5.17: A Texspun process

►Intermingling/InterlacingIntermingling/Interlacing （（交络交络纱）纱）

In staple spun yarns, twist is used to hold the In staple spun yarns, twist is used to hold the fibres together in the yarn. In multi-filament fibres together in the yarn. In multi-filament continuous yarns, there is very little cohesion continuous yarns, there is very little cohesion between individual filaments in the yarn, and between individual filaments in the yarn, and filaments separate easily. Even after texturing, filaments separate easily. Even after texturing, the yarns still lack inter-filament cohesion. the yarns still lack inter-filament cohesion. Consequently, the tendency for individual Consequently, the tendency for individual filaments to separate has caused problems in filaments to separate has caused problems in subsequent winding and weaving processes. subsequent winding and weaving processes. While twist can be used to impart inter-While twist can be used to impart inter-filament cohesion, it is not a very efficient and filament cohesion, it is not a very efficient and is costly. The favoured approach in the is costly. The favoured approach in the synthetic fibre industry is the intermingling or synthetic fibre industry is the intermingling or interlacing process.interlacing process.

So what is the intermingling process then? So what is the intermingling process then? Intermingling is a process of imparting inter-Intermingling is a process of imparting inter-filament cohesion by entwining the filaments filament cohesion by entwining the filaments instead of or in addition to inserting twist. The instead of or in addition to inserting twist. The entwining is usually achieved by passing the entwining is usually achieved by passing the yarn under light tension through the turbulent yarn under light tension through the turbulent zone of an intermingling or interlacing jet zone of an intermingling or interlacing jet (nozzle). (nozzle).

A simple intermingling nozzle is shown in A simple intermingling nozzle is shown in figure 5.18. It consists of a yarn channel, and figure 5.18. It consists of a yarn channel, and an air inlet in the centre of the channel. The an air inlet in the centre of the channel. The compressed air impinges on the traversing compressed air impinges on the traversing yarn vertically and entwining the yarn at yarn vertically and entwining the yarn at regular intervals.regular intervals.

Figure 5.18: Simplified representation of the intermingling processFigure 5.18: Simplified representation of the intermingling process

Intermingling has become a very efficient and Intermingling has become a very efficient and low-cost way of imparting cohesion to multi-low-cost way of imparting cohesion to multi-filaments. It has been used in many fields filaments. It has been used in many fields where inter-filament cohesion is required. where inter-filament cohesion is required. Figure 5.11(b) shows the use of an interlacing Figure 5.11(b) shows the use of an interlacing nozzle in false-twist texturing. The use of nozzle in false-twist texturing. The use of intermingling in other processes is depicted intermingling in other processes is depicted in figure 5.19.in figure 5.19.

Figure 5.19: Applications of the intermingling Figure 5.19: Applications of the intermingling process (Demir and Behery 1997, p.310)process (Demir and Behery 1997, p.310)

REVIEW QUESTIONSREVIEW QUESTIONS1.1.Compare and contrast false twisting Compare and contrast false twisting

texturing with air-jet texturing. You should texturing with air-jet texturing. You should make reference to differences in filament make reference to differences in filament input, the texturing process, and the input, the texturing process, and the resultant yarn. You can use sketches to help resultant yarn. You can use sketches to help explain the points.explain the points.

2.2.Briefly describe the objective, principle, and procBriefly describe the objective, principle, and process of filament intermingling. ess of filament intermingling.