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COURSE: ADVANCED MANUFACTURING PROCESSES

Module No. 1: INTRODUCTION

Lecture No-1

Manufacturing and Manufacturing Systems

Manufacturing covers wide areas of inputs, processes and products. It reaches out to the

demands in production for thousands of different varieties and types of goods. These

demands range from large ships to hand drilling equipment, and from micro circuits to

automobiles. The number and complexity of processes involved in the production of

these goods varies drastically. The extent of alterations involved in these processes form

the very basis for getting a bird’s eye view of the manufacturing activity. Some aresimple primary product and some are simply transformed products such as basic metallic

shapes, paint and utensils. The next are moderately transformed products such as wires,

rods, metal pipes and tubes, while others are elaborately transformed products such as

prefabricated metal shapes, wire products, glassware and ceramic products. The

mechanization and extent to which it is involved in the process of production gives

another view of manufacturing. Manufacturing covers a very wide range of situations

right from robot controlled highly mechanized lines of production to some simple day

to day use equipments with mechanical activities.

Thus, manufacturing industries, today, encompasses a dimension scale of more than

fifteen orders of magnitudes. The design and manufacture of huge machinery, ship and

spacecrafts on one side while nano and pico technology on the other side of the

dimension scale, highlights the challenges ahead for engineers and technologists. With

the advancement of technology newer materials, energy sources, manufacturing

technology, decision-making and management techniques are being developed. These

unfold lot of opportunities for the scientific and academic fraternity. At the same time,

newer challenges in the form of environmental and other issues put stringent

requirements on the technology. Global competition, the thrust on quality and demand for

higher productivity are some of the challenges before the present industrial and

manufacturing units. To survive and to succeed further, the competitors have a unique

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option, which is understanding of the dynamic changes that are taking place in the

business environment. In view of the above, a nation should develop and update its

infrastructure, such that the new and advanced technology gets into hand in hand, with

the ongoing time.

What is manufacturing?

There are many ways and definitions available to explain the concept of

manufacturing. Some of these definitions are listed below:

A. The process of converting raw materials into finished products

B. Manufacturing is defined in the Macquarie Dictionary as the making of goods

or wares by manual labor and / or by the use of machinery, especially on a large

scale

C. Manufacturing is a very broad activity, encompassing many functions –

everything from purchasing to quality control of the final product

D. Chemical or Physical transformation of the materials, substances or

components into some new products

E. Manufacturing is a value addition activity to the raw materials, substances or

componentsF. Manufacturing is a process through which products are made through various

production activities

G. Manufacturing may be considered as a system, wherein there is an integration of

people, equipment, policies and procedures to accomplish

the objectives of an organization i.e. production of the required product.

H. Manufacturing is the use of machines, tools and labor to make things for use or

sale

I. Manufacturing is an application of different resources such as machinery and

people used for converting the materials into finished goods


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Fig.1.1.2 Manufacturing System Boundary

Customer feed back (Existing product) or

New Innovative idea (New Product)

Product Design

Translating the voice of customer intoQuality oriented design

Purchasing/ vendor managementProcuring the quality raw material and

Components in right quantity

Engineering and Manufacturing

Right planning of processing the raw materials and

Right selection of manufacturing processes

Reliability and Quality Checks

Inspection report of 100 % quality product

Field Service and Report ofPerformance of the product

Energy

Resources:Financial, Material or

Labor

WasteManagement

Feed back


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Lecture No-2

Facts Trends and Challenges in Manufacturing

Some Facts about Manufacturing

The proof of the following dates and products is available in literature related to

manufacturing

5000-4000 BC Manufacturing started during 5000 – 4000 BC (Wood

work, ceramics, stones, metal works, earth wares)

2500 BC Sculptures produced by lost wax casting, jewelry

Production, earth wares, glass beads

600-800 AD Steel production 800-1200 AD Sand casting of cast iron 1750 AD Machine tools run by the power of steam engine, resulting

in growth of production and abundant availability of goods

1920-1940 Automation, mass production, interchangeable parts, die-

casting and lost wax methods for engineering parts

1940-1960 Computers development, Ceramic mold, nodular iron,

semiconductors, continuous castings

1960-1990 NC, CNC machines, group technology, robotics and control,

CAD / CAM, adaptive controls etc, squeeze casting, single

crystal turbine blades, vacuum casting, organically bonded

sand, compacted graphite, automation of molding and

pouring, large aluminum castings for aircraft structures for

rapid solidification technology, advanced manufacturing

processes

(advanced, casting, joining, machining, finishing processes)

1990-date Hybrid processes, micro-machining processes, nano

materials, hard machining, lean manufacturing, agile

manufacturing, etc


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Manufacturing Trends

In 1960s, the success of a manufacturing company depended on cost In 1980s, the success of a manufacturing company depended on quality Present day, the success of manufacturing company depends on cost, quality and lead

time (lead time is time between placing the order and receiving it, alternatively, it is

also known as time to market)

Manufacturing Challenges

The emerging economies, the social and political transitions taking place and the new

ways of doing business are changing the world dramatically. It is visualized through these

trends that manufacturing environment of the future would be extremely competitive and

significantly different from what it is today. In-order to remain successful in such an

environment, the manufacturers needs to be updated with the latest trends and should

possess dynamic capabilities, which need to be distinctly different. The main challenge

for the future entrepreneurs is the attainment of such capabilities, some of which are as

discussed below:

The ability to innovate ideas and to develop a creative environment for such innovations

in manufacturing

Development of effective and efficient training and education programs for the

manufacturing workforce, as more skilled workforce is required

The use and implementation of information technology in various areas of the

manufacturing industries and their sub-functions

Sustainability of small and medium scale enterprises to provide support to the largescale manufacturing organizations

Focusing on clean and green manufacturing technologies, the environment and the

society issues. The responsibility for the production process thus goes hand-in-hand


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with responsibility for the final disposal of products i.e. recycling in line with

environmental policies.

Need of Advance Manufacturing Technology

Manufacturing is the basis for all economic activities and future growth of a country At the beginning of 20th century, mass production using efficient machine tools

emerged in USA (Ford motors)

After the second world war, new / advanced manufacturing processes came into

existence

Since 1950s, new technologies have been emerged – computerized numerical control,

flexible manufacturing systems, lean manufacturing, green manufacturing, computer

integrated manufacturing are some of those.

Newer materials have been developed and their processing requires special machine

tools or special manufacturing process

Therefore, there is a vital need to have more efforts to continuously advance

manufacturing technology for a better-off and more stable future


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Lecture No-3

Manufacturing Aspects, Selection and Classification

Three Aspects of Manufacturing:

The three aspects of manufacturing and their linkages with each other have been

depicted in the figure 1.3.1 below:

Fig. 1.3.1 (Click here)

Design: Consumer’s Perspective

The product must be designed to meet the requirement of the end-customer. It must be

designed ‘right’ the first time and ‘every time’ and while designing all aspects of

customer expectations must be incorporated into the product.

Manufacturing: Manufacturer’s Perspective

The product must be manufactured exactly as designed. The activities involved at thisstage include: defect finding, defect prevention, defect analysis, and rectification. The

difficulties encountered at the manufacturing stage must be conveyed to the designers for

modification in design, if any. The two-way communication between design and

manufacturing can help to improve the quality of the product to a great extent, as

different issues such as practical difficulties, achievable tolerances and process

capabilities will be addressed.

Performance of the manufactured product

The product must function as per the expectations of the end customer. The two way

communication between designers and customer is the key to have a high quality product.

Manufacturing Process Selection Criteria


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The following points need to be considered before the actual manufacturing of a

product.

Material selection including and considering all the environmental and recycling

aspects Selection of processing methods such as metal casting, metal forming, sheet metal

working, powder metallurgy, machining, joining, finishing etc.

Shape and appearance of the final product Dimensional tolerance and surface finish aspects of the final product Economics of tooling Design requirements

Functional requirements of the product Production quantity required Safety and environmental concerns Cost

Product design is the most important parameter amongst all the parameters of the

manufacturing system. As quality is imbibed at each stage in the product, if the product

has not been designed right at the first stage, no subsequent operation or steps can bring

back the quality into the product. Hence, the material and manufacturing process

selection and all associated concerns such as availability, environmental considerations,

recycling etc must be taken care of right at the product design and development stage. As

far as the manufacturing process is concerned, it must be economical and capable of

producing the geometric surfaces and other features which are embodied in the design of

the product.

Manufacturing Processes Classification

There are six basic / fundamental classifications of manufacturing processes.

1. Metal casting or Molding: expendable mold and permanent mold

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2. Metal Forming and Shearing: rolling, forging, extrusion, drawing, sheet

forming, powder metallurgy

3. Material Removal Processes / Machining Processes: turning, boring,

drilling, milling, planing, shaping, broaching, grinding, ultrasonic machining,

chemical machining, electrical discharge machining (EDM), Abrasive flow

machining (AFM), abrasive jet machining (AJM), electrochemical

machining, high-energy beam machining, laser beam machining (LBM) etc.

4. Joining: welding, brazing, soldering, diffusion bonding, adhesive bonding,

mechanical joining, plasma arc, plasma MIG, projection welding, ultrasonic,

electron beam welding, laser welding etc.

5. Finishing (painting, anti-corrosion coatings, etc.)

6. Rapid Manufacturing: stereo-lithography, selective laser sintering, fuseddeposition modeling, three dimensional printing, laminated object

manufacturing, laser engineered net shaping

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Hot compression molding Transfer molding Injection molding Extrusion molding Laminating Vacuum forming Expandable bead molding Blow Moulding

Metal Forming (Net Shape Processes)

Metal forming is a process which involves the shaping of materials in a solid form. It can

be defined as a bulk deformation process that induces change in shape under the applied

force. Metal forming is of two basic types; namely hot forming and cold forming. Hot

forming is performed by heating the metal above the re-crystalline temperature. Hot

forming reduces its yield stress, so that its shape can be easily changed / formed by

applying the force. Cold forming is performed by heating the metal below its re-

crystalline temperature. The major metal forming processes are as given below:

Smith Forging Drop Forge Press, Extrusion Cold and Hot Rolling Sheet Metal Embossing Blanking, Shearing

Notching Perforating, Nibbling Electroforming Explosive Forming

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Joining (Additive Processes)

There are three basic methods of joining material together:

1. Joining using fasteners (rivets, screws, bolts and nuts etc.)

2. Joining by adding gluing material in-between the two components

(brazing, soldering)

3. Joining by fusing the material together with an aim to have the joint which

have same metallic properties of the parts to be joined (welding)

Out of the above three, the most popular method (though applications may bind us to use

other methods too) is welding. Welding is defined as the process of joining two similar or

dissimilar metallic/ material components through the application of heat. Filler metal can be used and pressure may also be applied as per the necessity.

ARC welding, GAS welding Thermit welding Soldering, Brazing Submerged ARC welding Plasma ARC welding Plasma-MIG welding Projection welding Seam welding Solid State; Ultrasonic, Explosive welding: Friction welding Electron beam welding Laser welding

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Rapid Manufacturing (Additive Processes)

Rapid manufacturing is an emerging additive fabrication technique. It is made use in

manufacturing mainly the solid objects. Using an additive approach by sequential

delivery of energy and/or materials, layer by layer the RM machines fabricate plastic,

wood, ceramic and metal powders to form physical objects. In-order to control the

process, computerized programs through mathematical modeling are made used in

manufacturing.

The major rapid manufacturing processes are as given below:

Stereo-lithography Selective laser sintering Fused deposition modeling Three dimensional printing Laminated object manufacturing Laser engineered net shaping

Taxonomy of the Manufacturing Processes

The classification of the manufacturing processes descried above is summarized in Fig.

1.4.1. The processes which are relatively new and advanced have been shown below in a

different color/ shade. These processes and their details will be discussed in the following

lectures.

Fig. 1.4.1 Taxonomy of the Manufacturing Processes (Click here)

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Module-3: ADVANCED MATERIAL REMOVAL PROCESSES

Lecture No-1

Need For Advanced Material Removal Processes and Abrasive Flow Machining

Advanced Material Removal Processes represent one of the technologies, which emerged

after the second world war to cope up with the demands of sophisticated, more durable

and cost competitive products. With the advent of new materials such as metal-matrix

composites, super-alloys, ceramics, aluminates and high performance polymers etc. and

the stringent requirements to machine complex geometrical shapes with high precision

and accuracy, a strong need existed for the development of advanced material removal

processes. The processes in this category differ from conventional processes in either

utilization of energy in an innovative way or, in using forms of energy that were unused

for the purpose of manufacturing. The conventional machining processes normally

involve the use of energy from electric motors, hydraulics, gravity, etc. and rely on the

physical contact between tools and work components. On the contrary, advanced material

removal processes utilize energy from sources such as electrochemical reactions, high

temperature plasma, high velocity jets and loose abrasives mixed in various carriers etc.

Although these processes were originally developed to handle unique problems in

aerospace industry (machining of very hard and tough alloys), today wide range of

industries have adopted this technology in numerous manufacturing operations.

Why are Advanced Machining / Material Removal Processes Needed?

With the advent of new materials and the requirements of complex features on them,

there was a necessity to develop new processes. Some of these features are:

1. Related to material properties:

High hardness High strength High brittleness

2. Related to workpiece structure:

Complex shapes


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Typical thin and delicate geometries Parts which are difficult in fixturing

3. Related to requirements in high surface finish and tight tolerances.

4. Related to controlling of temperature rise and residual stresses.

Classification of Advanced Machining / Material Removal Processes:

These processes are referred to a typical group of advanced machining processes in

which the excess material is removed by non-traditional source of energy arising from

electrical, mechanical, thermal or chemical source. Most of these processes don’t use a sharp

cutting tool, as in the conventional case. Advanced material removal processes are generally

classified according to the type of energy used to remove material. The classification of these

processes based on the energy is given as below:

The processes based on use of Electrochemical Energy are:

Electro-Chemical Machining (ECM), Electro-Chemical Grinding (ECG),

The processes based on the use of Thermal Energy are:

Electric- Discharge Machining (EDM), Wire-Cut Electric Discharge Machining (WEDM) Laser Beam Machining (LBM), Electron Beam Machining (EBM).

The processes based on the use of Mechanical Energy are:

Abrasive Flow Machining (AFM)

Abrasive Jet Machining (AJM), Water Jet Machining (WJM), Abrasive Water Jet Machining Ultrasonic Machining (USM),

Abrasive Flow Machining (AFM)


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It is a process of polishing and smoothening internal surfaces and thereby producing

controlled radii. The abrasive media is flown across the surface to be super-finished

either in a single direction or two-way and this extrudes through the workpiece thereby

finishing and smoothening the surfaces. In case of one-way systems, the media is flown/

passed through the work piece and it returns from the other end. Whereas in a two-way

process, two vertically opposite hydraulic cylinders, push the abrasive mixed media to

and fro. This process was first patented by the Extrude Hone Corporation in 1970. The

process is particularly used in contours which are difficult to polish and such internal

passages, cavities, edges and bends.

The AFM process is widely used in a range of different finishing operations. At a given

time, it can process a number of parts or different areas of the same work piece. The areas

which are not accessible and such complex internal passages can also be very effectively

finished. The atomized AFM systems are capable of handling thousands of parts per day,

thereby considerably reducing the labor costs and eliminating tedious handwork. Through

proper knowledge and control of the process parameters, this process can be effectively

used for variety of super-finishing operations thereby achieving very uniform and precise

results. Practical applications of this process could be in any of the situations wherein the

media could be flown across.

Abrasive Flow Machining (AFM) Principle

In the AFM process, a semi-solid media is used which comprises of a carrier in the form

of a polymer base containing abrasive powders in a desired proportion, which is extruded

under the given pressure across the surface, which is to be machined. The media acts as a

flexible tool whenever it is subjected to some restrictions due to the uneven surface.

The special deformable ability of media is responsible for its movement through any

shape of the passage. Restricted media flow passages are necessary at the surfaces to be

processed by AFM, wherein the media behaves somewhat like flexible grinding stone,

abrades the material, and provides a good surface finish over the surface. Generally, a

fixture is required to offer restriction or to direct and focus the media to desired locations

in the work piece. Fig. 3.1.1 illustrates the principle and basic operation of AFM process.

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hydraulic systems, which force the abrasive laden media through the fixture work piece at

a selected pressure and flow rate. Standard units operate within 10 bar to 200 bars and

with flow rates up to 400 liters/min. AFM systems are essentially provided with controls

on hydraulic system pressure, clamping and unclamping of fixtures, volume flow rate of

media, and advance and retract of media pistons. The accessories such as automatic flow

timers, cycle counters, volumetric displacement systems, pressure and temperature

compensated flow control valves, media heat exchangers are integrated to conventional

AFM systems for production applications.

The most essential component of the process is the media, which is considered a

proprietary item by machine manufacturers. It consists of base material or carrier,

abrasive grains and proprietary additives. Most widely used carrier is a high viscosityrheopetic fluid (at any constant rate of shear, its apparent viscosity increases with time to

some maximum value). The base material has enough degree of cohesion and tenacity to

drag the abrasive grains along with it through various passages/regions. Aluminum oxide

and silicon carbide are most suitable abrasives for many applications but boron carbide

and diamond are specifically used for special applications. Abrasive grain to base

material ratio can vary from 2 to 12. The additives are mainly used to modify the base

material properties to get desired flow-ability and rheological characteristics of the

media. Hydrocarbon gels are frequently used lubricants in the media. All additives are

carefully blended in predetermined quantities to obtain consistent formulations.

The primary function of a fixture is to hold the work piece in proper position

between two opposite cylinders and direct the media by restricting it to the areas to be

worked during the process cycle. When necessary, the fixture can protect edges or surfaces

from abrasion by acting as mechanical mask. Steel, urethane, and nylon are the main

materials used for manufacturing fixtures. The fixture design may be straight forward orvery complex depending upon the work piece configuration.

AFM Advantages

Inaccessible areas can be easily finished The finishing rate is much faster than manual methods of finishing

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The polishing and de-burring operations can be combined in one stage. High surface finish with tight tolerances are possible

AFM Disadvantages

Costly Process: Requires high capital investment. The cost of media is very high and is unusable after the process. The work-holding fixture is at times expensive Processing of blind holes is difficult.

AFM Applications

The process was initially developed for effective de-burring of hydraulic control blocks.

Later on, the field of applications got rapidly diversified into defense, medical andmanufacturing units. The inaccessible areas in components that are very difficult to finish

with traditional methods, can be easily finish machined by AFM process with up to 90 %

improvement in it with respect to the original accuracy. The typical applications of AFM

are in improving airfoil surfaces of compressor and turbine components, edge finishing of

holes and attachment features, improvement in fatigue strength of blades, disks, hubs and

shafts with uniform polishing on its edges. The adjustment of air flow resistance in

blades, vanes, combustion liners, nozzles and diffusers, finishing of fuel spray nozzles,

fuel control bodies, bearing components, reworking the components to remove coke and

carbon deposits and to improve its surface integrity.

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Lecture No-2

Mechanism and Process Parameters in AFM

The mechanism of material removal in AFM is as follows:

1. Initially, the material is ploughed by the fine abrasives that come in contact with

the work material as they rub over the metal surface with high pressure. The

material flow occurs in the direction of motion of abrasive particles as well as in

lateral direction, resulting into the formation of lips.

2. At the lips, work hardening is noticed due to the rubbing action of the continuous

flowing abrasive particles which are also responsible for intense plastic flow with

considerable stress concentration.

3. The further flow of abrasive particle causes continued work hardening which

results in embrittlement and fragmentation of the lips into microchips.

AFM Process Parameters

The AFM Process Parameters are classified as given below:

Parameters controllable by the machine: extrusion pressure, flow volume, media flow

speed and number of process cycles.

Parameters controllable by the media: media viscosity, media rheology, abrasive type

(aluminum oxide, silicon carbide, boron carbide, diamond etc.), abrasive grain size,

shape and concentration.

Parameters controllable by the work piece configuration and tooling: type of passage

(cylindrical, rectangular or complex), cross sectional area, length of the passage,

initial surface roughness.

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Media Flow Rate

The literature on AFM strongly recommends that the affect of flow rate of media is not

significant.

Media Viscosity

Viscosity of media is the significant parameter affecting the quality of surface finish and

amount of material removal in AFM process. Media viscosity is affected by type of

abrasives, its concentration and size of grains. It is also strongly affected by the working

temperatures. In general, increase in temperature causes appreciable decrease in media

viscosity, which may result in ‘settling’ of grains thereby influencing the flow properties

and overall abrasion process. Table 3.2.1 gives general guidelines to select viscosity ofmedia for various passageways with 2:1 length to width ratio.

Table 3.2.1 The Guidelines for Media Selection

Passage

size* (mm)

Media Viscosity

Low Low/Medium Medium High/Medium High

Minimum

Maximum

0.4

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50.8

* Passage sizes are widths or diameters of the cavity and assume that the passage length

is two times the width.

Number of Cycles

The travel of media from lower cylinder to upper cylinder and then back to lower

cylinder is termed as a cycle. Several cycles are required to get a particular amount of

material removal and final surface finish on a component. Various researchers have

reported that the improvement in surface finish and required amount of material removal

occurs in some of the initial cycles and then it stabilizes.

Abrasive Grain Size and Its Concentration

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Abrasive grain sizes range used in AFM varies from #500 grit (tiny hole applications) to

#8 grit (roughing and stock removal applications). Larger abrasives cut faster, while

smaller size gives better finish and can reach into complex and narrow passages.

AFM Process Capabilities

The surface finish improvement by AFM process is 10 times than that of the original

surface finish, provided the surface finish is in the range of 28-280 m. Holes diameter

must be at least 0.2 mm and dimensional tolerances achievable must be up to ± 0.005

mm.

Recent Developments in AFM Technology

Ultrasonic Flow Polishing

Ultrasonic Flow Polishing (UFP) is the combination of AFM and USM. In this process,

the abrasive/polymer mixture is pumped down the centre of the ultrasonically energized

tool. On its exit, the flow is constrained by the tool and the work piece, the mixture flows

radially relative to the axis of the tool. While it is constrained, the vibrating tool

ultrasonically energizes the mixture. The combination of flow and vibration results in the

effective abrasion of the workpiece surface. The process is reported to have the capacity

to produce micro/nano level finish on closed cavity surfaces without causing muchdeterioration to its profile or dimensional accuracy. The improvement in surface finish of

upto 10:1 is been reported by this process. The Ultrasonic flow polishing process is very

much suitable for applications in machining blind cavities that are not easily polishable

by normal AFM.

Orbital AFM

Orbital AFM combines abrasive flow machining and orbital grinding. An additional

mechanical motion is given to the medium to enable it polish three dimensional forms

that are not possible with conventional AFM. The motion is typically a planetary

oscillation that creates relative displacement between tooling and the work piece. The

oscillations can be in the vertical or horizontal or combination of both the planes,

yielding an elliptical or gyratory polishing action. Orbital Polishing is made used in

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polishing the edges and surfaces in complex shapes and cavities such as bottle molds,

coining dies and aluminum wheels along with high precision and accuracy.

Magneto Abrasive Flow Machining

Magneto Abrasive Flow machining process has been developed by providing a magnetic

assistance to the flowing abrasives. Through this additional assistance, modification of

the distribution pattern of abrasive particles near to the inner surface of the hollow work

piece has been observed. Therefore, more number of abrasive particles could take part in

the abrasion process. In addition, some of the axially flowing abrasive particles get

deflected and strike on the work piece surface a slight incidence angle. On an average,

20-30 % enhancement in the material removal rate along with considerable

improvements in the finish has been recorded depending upon the material of the work piece particularly at low flow rates of the media.

Centrifugal Force Assisted AFM

A controlled rotation of a centrally placed rod in flow passage generates the centrifugal

forces in the flowing media. This force increases the media contact force to the work

piece as the media flows through the work piece cavity due to the extrusion pressure. It is

compounded upon by the centrifugal force. The combined effect of these two forces

improves the contact of the abrasive particles with the work piece surface. In this process,

a special type of nylon fixture is used to hold the work piece that is placed in between the

two media cylinders in-order to create an artificial dead zone and increase the pressure

required for extruding the media

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AJM process is a highly flexible process wherein the abrasive media is carried by

a flexible hose, which can reach out to some difficult areas and internal regions. AJM process creates localized forces and generates lesser heat than the

conventional machining processes. There is no damage to the workpiece surface and also the process does not havetool-workpiece contact, hence lesser amount of heat is generated.

The power consumption in AJM process is low.

Disadvantages

The material removal rate is low The process is limited to brittle and hard materials

The wear rate of nozzle is very high The process results in poor machining accuracy The process can cause environmental pollution

Applications:

Metal working:

De-burring of some critical zones in the machined parts.

Drilling and cutting of the thin and hardened metal sections. Removing the machining marks, flaws, chrome and anodizing marks.

Glass:

Cutting of the optical fibers without altering its wavelength. Cutting, drilling and frosting precision optical lenses. Cutting extremely thin sections of glass and intricate curved patterns. Cutting and etching normally inaccessible areas and internal surfaces. Cleaning and dressing the grinding wheels used for glass.

Grinding:

Cleaning the residues from diamond wheels, dressing wheels of any shape andsize.

Principle of AJM

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Lecture No-4

Components and Process Parameters in Abrasive Jet Machining

Abrasive jet cutting machines are used in cutting sheet materials or in removing materialsfrom the surface by generating a focused stream of fluid mixed with the abrasive

particles. They make use of compressed air as the driving fluid in-order to propel theabrasive particles. Abrasive jet cutting machines are available as complete systems withall of the components required for blasting or jet machining applications such as pressuregeneration / intensification, cabinets, nozzles or wheels and dust collectors. They aresometimes purchased in component-form to either build a complete customized system orto replace the worn out parts from an existing system. Abrasive jet cutting machinesincludes the following types of devices:

Gas propulsion device Nozzle for delivery of abrasive mix Abrasive Collection device

The gas propulsion system provides the supply of clean, dry gas or air to propel the

abrasives particles to the workpiece. In this system care must be taken to have the filtersattached in so that moisture content or any oil or grease contents can be filtered out at thefirst stage itself. Also, in this system there must be some arrangement to regulate the flowof air or gas and the mixture of abrasive particles. The vibrating system is generallyattached to the system so that the abrasive is properly and uniformly mixed with the gasor air stream. The nozzle used to deliver the mixture at the workpiece should bemanufactured from such materials which can withstand the erosive action of the abrasive

particles and should be wear resistant. The size of the nozzle opening depends upon theflow rate requirement of abrasive mix on the surface of the workpiece. The abrasive dust

collection system is essential for the safety of the operator. Vacuum based dust collectorsystem is the most preferred choice. A typical nozzle used in the AJM machines is asshown in Figure 3.4.1.

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Lecture No-5

Water Jet and Abrasive Water Jet Machining (WJM and AWJM)

In this process a water jet cutter is used, which acts as a tool in the form of a water-saw.This water-jet at a high velocity and pressure is able to slice materials and some metalsusing some abrasive particles mixed in it. This process resembles the water erosion

phenomenon existing in nature whereas herein it is greatly accelerated and furtherconcentrated. Some examples of this process are in fabrication and in manufacturing ofmachinery parts and some other devices. As most of the metal cutting techniquesgenerate high heat-affected zones, this method being environmental friendly is more

preferred. There are diverse applications of this process ranging from mining industries tothe aerospace industries, wherein primarily it is used for cutting, carving and shapingapplications.

Water Jet Machining and Abrasive Water Jet Machining have potential for cost reductionand speeding up the process through considerable reduction in secondary processes ofmachining. The cut edges are clean with fewer burrs as there is no heat application. Inthis process the subsequent problems faced in other processes such as crystallization,edge defects, hardening, reduction in weldability and machinability are considerablyreduced.

The term water jet is made used for describing equipment which uses a high pressurewater stream for cleaning and cutting applications. In some applications no abrasives areused, therein the process is termed as Pure-Water Jet machining. The block diagram ofwater jet machine is schematically shown in Fig. 3.5.1 along with a typical pure water jetmachining nozzle in Fig. 3.5.2

Abrasive Water Jet Machining (AWJM) is a subcategory of water jet machining in whichabrasive is introduced in the water to accelerate the process. In AWJM processes, which

is considered as an extension of water jet cutting, abrasive particles such as aluminiumoxide or silicon carbide are added, which increases the material removal rate further. Theabrasive water jet cutting process is suitable for machining different types of materialsranging from hard, brittle ceramics and glass to soft metals such as rubber and foam.

The abrasives are separately mixed in the nozzle with the water-stream, making it distinctfrom water jet machining process.

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The process traces back to 1950s, when an early form of water jet cutter was made usedin forests for lumber cuttings. It took around 20 more years for the technology toadvance, after which in 1970’s the abrasive water jet machining was introduced.

Nowadays the process has matured and has changed the manufacturing methods of many products. It is further available in variety of different modes such as plain water jets,abrasive water jets, cavitation jets, percussive water jets and hybrid water jets.

The aviation and space industries were first to adopt this technology for cutting highstrength metals such as stainless steel, titanium and inconel along with some light weightcomposite materials which were used in military aircrafts and later on in commercialairplanes.

The chronological evolution of WJM is as given below:

Year Usage/ applications

1930s: Used in mining industries for removing stone and coal1960s: Necessity arose in aerospace industries for cutting advanced materials.1970s: The earliest attempt was made in aerospace applications for advanced

composites using Water Jet Process.1980s: The first commercial AWJ machines were started

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Lecture No-6

Theory, Advantages and Applications of Water Jet and Abrasive Jet Machining

The theory of water jet and abrasive jet machining can be described as follows:

1. Water is forced at a sufficiently high pressure, 180-420 MPa through a small

orifice in a nozzle (generally of 0.2- 0.4 mm diameter), causing high acceleration

of water.

2. The potential energy of water gets further converted into kinetic energy which

yields a very high jet velocity of around 1000 m/s.

3. The steam impact and high pressure of the accelerating water particles develop

fine cracks on the material.

4. These fine cracks propagate further under the impact of high pressure and

abrasives to the extent that the material gets cut.

5. The extended version of WJM is AWJM. In AWJM process the particles of

abrasives such as sand (SiO 2) or beads of glass are added in the water jet in-order

to enhance its ability of cutting by many folds.

6. The AWJM are mainly of two types – entrained and suspended type. In theentrained type of AWJM, the particles are allowed to draw in the water jet

thereby forming an enhanced abrasive water jet with significantly higher

velocities of around 800 m/s. Almost any material can be machined at such a high

velocity of the abrasive jet.

Advantages of WJM and AWJM

In cases where the excessive heat generated can cause changes in the material properties, AWJM and WJM are very useful processes for hard metals like cutting

tool steels.

The water jet cutting process does not produce any dust or such particles which

are harmful if inhaled like in the case of machining and grinding operations.

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No further secondary or finishing operations are required in most cases. In AWJM process, the cutting forces generated on work pieces are typically low. The tooling requirements are limited Typical surface finish achieved is in the range of 125-250 microns Ra. The material wastages are reduced due to smaller kerf sizes. There is no heat affected zone. There is no cutter induced metallic contamination Eliminates thermal distortion There is no tool re-sharpening cost It can cut metals, plastics, stones, composites, glass, ceramics and rubber

Disadvantages of WJM and AWJM

Cannot cut materials which degrades quickly with moisture Higher cutting speeds are frequently used for rough cutting purposes which

degrade the surface finish.

There is a strong possibility of cracking in brittle materials and only few varieties

of materials could be cut economically.

With WJM process, thick parts cannot be cut accurately and economically. In thicker materials the taper generated is also a problem. The equipment used are quite expensive There are safely concerns due to noise and high pressures

Applications of WJM and AWJM

The Water Jet Cutting (WJC) process is mainly made used in cutting low strength

materials like plastics, wood and aluminium. With the addition of abrasives, the AWJM

process can be used for stronger materials like tool steels.

Equipment

The major components of Jet equipment (WJ or AWJ) are:

Pump Nozzle

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Orifice Control System

A pump is used to create pressure in the liquid in the range of 1500-4000 bars. In

achieving this purpose, an electric motor of 50-100 HP rating is used. Nozzles are used to

convert the high pressure liquid to a high velocity jet. As there is a possibility of erosion

in the orifice of the nozzle due to the high pressure of liquid in WJM and that of abrasives

in AWJM, a high wear resistant material is used for nozzles. Control system in the

equipment helps in optimum settings for various parameters.

Process Parameters

The process parameters of WJM and AWJM have been grouped in the categories asshown in the Ishikawa cause and effect diagram (Fig.3.6.1). This depicts the effect of

various parameters affecting the accuracy and quality of the machining operations by

water jet and abrasive water jet machines.

1. Hydraulic parameters: Size of the orifice and required pressures.

2. Abrasive Used: Type; Grit size and the flow rate required

3. Target material: Composition of workpiece and mechanical properties such as

hardness etc.

4. Mixing: Inlet angle; tube length, bore diameter;

5. Cutting: Angle of Attack; Stand of Distance (SOD); Traverse Speed

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Historic l Develop ent of US

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The historical development of Ultrasonic Machining (USM) started through the research works

in 1927. During investigating the ultrasonic grinding of abrasive powders, it was found that the

surface of a container which was holding the suspended abrasives disintegrated as soon as the tip

of an ultrasonically vibrating transducer was placed close to it. Interestingly, the shape of the

cavity, thus produced accurately reproduced the tip of the transducer. In the early 1950’s

industries started realizing its benefits and the production of ultrasonic machines began

thereafter. A wide range of brittle materials, including glass, ceramics and diamond can be

effectively machined through this process.

USM Process

The USM process is performed using a desirable tool along-with abrasives slurry as a

media. The cutting tool oscillates at high frequencies (typically 20-40 kHz)

The shape of tool corresponds to the shape requirements in the workpiece. The abrasive grains are driven by the high speed reciprocations across the small gap, in-

between the tool and the workpiece.

Uniform force is used to gradually feed the tool. The impact of abrasives is the energy source which is mainly responsible in removal of

material, through the form of small wear particles which are carried away by the abrasive

slurry.

Due to the abrasive action of particles, gradually wear of the tool occurs, thereby requiring the

tool to be made of tough materials.

Mechanism of Material Removal

Although the USM process is commercially used since many decades the exact details of

mechanism leading to the removal of fine materials is still to be understood. The research

works done till date in understanding the process parameters have thrown light on some

possible mechanisms. Through the investigations and the corresponding literatures, the main

mechanisms responsible for the material removal in USM are as listed below:

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Mechanical abrasion: Occurs due to the hammering effect of abrasive particles on work

piece through the tool.

Impact: The freely moving particles impact with a certain velocity on the work piece

resulting in micro chipping.

Erosion: Due to cavitation effect of the abrasive slurry, erosion of the work surface occurs. Chemical: Due to fluid employed, chemical effect can come into consideration.

It has been reported in the literature that among the above mentioned mechanisms, the first two

are primarily responsible for major stock removal. The literature reveals that erosion plays a

lesser role in the removal of material for normal materials, however for the porous materials; it

is observed that erosion due to cavitations is a significant factor.

Advantages of USM

In USM process, there are no physical, chemical or thermal changes. The

microstructures reveal that there are also no structural changes as the stresses induced

are too less. The cutting forces being low, workpiece is unstressed, undistorted and free

from heat effects.

There is no direct contact of the tool and workpiece due to the slurry used, it makes it a

wet cutting process. The surfaces produced are free from stress and damages.

The process is free from burrs and distortions. The process is suitable for any materials, irrespective of electrical conductivity The process is very much suitable for machining brittle materials The process offers good surface finish and structural integrity.

Disadvantages / Limitations of USM

Soft materials like lead and plastics are not suitable for machining by the USM process,

since they tend to absorb the abrasive particles rather than to chip under their impact.

The USM process consumes higher power and has lower material-removal rates

compared to traditional fabrication processes.

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The tool wear rate in USM process is fast. The areas of machining and higher depths are the constraints in USM. As the USM process continuous, the lateral wear of the tool increases gradually and it

tends to make the holes tapered. The sharp corners of the tool get rounded off thereby

requiring tool replacement essential for producing accurate blind holes.

The accuracy of the machined surface gets lost due to setting up of strong lateral

vibrations. This occurs if the axis of the tool and horn, which are brazed together, are not

properly aligned with the transducer axis. In such a case, the tool needs to be redesigned.

The holes produced in USM have a tendency to break out at the bottom owing to the

static load and high amplitudes.

While producing deeper holes through USM method, there is ineffective slurry

circulation leading to presence of a fewer active grains under the tool face. Due to this,

the bottom surfaces of blind holes tend to become slightly concave.

Applications of USM

USM process is used in machining hard and brittle metallic alloys, semiconductors, glass,

ceramics, carbides etc.

In machining of advanced ceramics for applications in auto-engine components.

In machining, wire drawing, punching or blanking of small dies Machining ceramic substrates for drilling holes in borosilicate glass for the sensors used

in electronic industries

Drilling small holes in helicopter power transmission shafts and gears.

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Lecture No-8

Ultrasonic Machine and its Process Parameters

The basic ultrasonic equipment consists of the following elements:

A generator for high frequency oscillations (Ultrasonic generator) An acoustic head consisting of transducer and trunk (shank) Tool and abrasive slurry elements

The High Frequency Oscillating Current (OC) Generator

The purpose of the OC generator is to produce high frequency oscillating currents. Thisgenerator transmits electrical power to the transducer which creates energy impulses in

the ultrasonic range i.e. 18-20 KHz and converts them into mechanical vibrations. The

primary function of the transducer is to convert electrical impulses into vertical and two-

dimensional strokes.

The Acoustic Head

This is the ‘heart’ of the whole equipment and consists of two parts,(a) The transducer, which converts the high frequency output of the generator

into linear vibrations and

(b) The trunk, which mechanically amplifies the linear vibrations.

Ultrasonic transducer

The ultrasonic vibrations are produced by a transducer that is driven by the signal

generator which gets further powered by an amplifier. The USM transducer works on the

following principle:

Piezo-electric effect Magneto-strictive effect Electro-strictive effect

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The function of ultrasonic transducer is to converts high frequency electrical impulses

from the oscillator into mechanical vibrations. The periodicity of these vibrations

periodically shortens and lengthens. For low power applications piezo-electric

transducers are used, whereas for high power applications magneto-strictive transducers

are commonly used.

The trunk

It is a critical link in the ultrasonic machining system. It is known by several names such

as shank, horn, concentrator and amplifier. The trunk amplifies and focuses vibrations of

the transducer to the required intensity necessary enough for driving the tool. The

increase in amplitude of vibrations at the tool end is obtained by reducing the cross

section of the trunk.

The Tool

The tool is designed to provide the maximum amplitude of vibration at the free end. The

selection of tool material is very important as the tool tip is subjected to vibration and it

must not fail due to wear. The commonly used tool materials are brass, high speed steel,

mild-steel, silver, stainless steel, tungsten carbide and monel. The tool is attached to the

trunk (horn) by silver brazing or by hard soldering. At times it is fastened (screwed) withthe trunk.

The Abrasive Slurry

The recommended slurry to be used in this process is a mixture of abrasive particles and

liquid (water or kerosene). The slurry is pumped across the tool face. Slurry pump is a

part of the machine-system. The properties required from the transport medium of

abrasives include low viscosity, good wetting and high thermal conductivity. Water is arecommended medium for abrasive transportation which generally meets most of the

process requirement.

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Process Parameters in USM

The determination of accurate process parameters which affect performance of ultrasonic

machining is hard to determine as it works under multiple factors. The geometry and

material properties of the work piece and tool make the system further complex toascertain its performance characteristics. However, the performance of ultrasonic

machining, to some extent is decided by the machining rate, machining accuracy, surface

finish and tool wear. The process parameters which can affect the performance of USM

are arranged into the following four major groups. In order to identify the process

parameters in USM affecting the qualities of the machined surface, an Ishikawa cause –

effect diagram as shown in Fig. 3.8.1 is constructed.

Machine Parameters

These are those parameters which can be set on the machine. They include frequency and

amplitude of the ultrasonic vibrations, the static load, work piece rotation and tool-head

rotation.

Abrasive Slurry Characteristics

The type and size of the abrasives particles, its hardness, type of the fluid used as a

carrier to form the abrasive slurry and the concentration of abrasive particles in the slurry.

Work piece properties

The hardness, fracture characteristics, strength, work hardening tendency and fatigue

properties of the work material also affect the process performance.

Tool Material Properties and Tool Geometry

The shape of the tool (solid or hollow), mechanical properties of the material used in

tool-making are some of the other parameters that may affect the USM process

performance.

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Lecture No-9

Electrical Discharge Machining (EDM)

It is an advanced machining process primarily used for hard and difficult metals which

are difficult to machine with the traditional techniques. Only electrically conducting

materials are machined by this process. The EDM process is best suited for making

intricate cavities and contours which would be difficult to produce with normal machines

like grinders, end-mills or other cutting tools. Metals such as hardened tool-steels,

carbides, titanium, inconel and kovar are easily machined through EDM.

EDM is a thermal process which makes use of spark discharges to erode the material

from workpiece surface. The cavity formed in EDM is a replica of the tool shape used as

the erosions occur in the confined area. Since spark discharges occur in EDM, it is also

called as "spark machining". The material removal takes place in EDM through a rapid

series of electrical discharges. These discharges pass between the electrode and the

workpiece being machined. The fine chips of material removed from the workpiece gets

flushed away by the continuous flowing di-electric fluid. The repetitive discharge createsa set of successively deeper craters in the work piece until the final shape is produced.

History

In 1770, Joseph Priestly a british scientist first discovered the erosive effects of electrical

discharges. In 1943, soviet scientists B. Lazarenko and N. Lazarenko had exploited the

destructive effect of an electrical discharge and developed a controlled process for

machining materials that are conductors of electricity.

EDM Principle

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Hard die materials with complicated shapes can be easily finished with good

surface finish and accuracy through EDM process.

Due to the presence of dielectric fluid, there is very little heating of the bulk

material.

Limitations of EDM

Material removal rates are low, making the process economical only for very hard

and difficult to machine materials.

Re-cast layers and micro-cracks are inherent features of the EDM process, thereby

making the surface quality poor.

The EDM process is not suitable for non-conductors. Rapid electrode wear makes the process more costly. The surfaces produced by EDM generally have a matt type appearance, requiring

further polishing to attain a glossy finish.

Applications of EDM

Hardened steel dies, stamping tools, wire drawing and extrusion dies, header dies,

forging dies, intricate mould cavities and such parts are made by the EDM

process.

The process is widely used for machining of exotic materials that are used in

aerospace and automatic industries.

EDM being a non-contact type of machining process, it is very well suited for

making fragile parts which cannot take the stress of machining. The parts that fit

such profiles include washing machine agitators; electronic components, printer

parts and difficult to machine features such as the honeycomb shapes.

Deep cavities, slots and ribs can be easily made by EDM as the cutting forces areless and longer electrodes can be used to make such collets, jet engine blade slots,

mould cooling slots etc.

Micro-EDM process can successfully produce micro-pins, micro-nozzles and

micro-cavities.

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Mechanism of Material Removal in EDM

In EDM, for a particular machining condition there are numerous phenomena involved,

i.e., heat conduction and radiation, phase changes, electrical forces, bubble formation and

collapse, rapid solidification etc. Thermo-electric phenomenon is the most appropriate

theory for the explanation of the electrical discharge machining process. The removal of

material in EDM is associated with the erosive effects produced when discrete and spatial

discharge occurs between the tool and workpiece electrodes. Short duration sparks are

generated between these two electrodes. The generator releases electrical energy, which

is responsible for melting a small quantity of material from both the electrodes. At the

end of the pulse duration, a pause time begins. The forces that may be of electric,

hydrodynamic and thermodynamic in nature remove the melted pools. The material

removal process by a single spark is as follows:

An intense electric field develops in the gap between electrode and workpiece. There are some contaminants inside the dielectric fluid which build a high-

conductivity bridge between the electrode and workpiece.

When the voltage increases, the bridge and dielectric fluid between the electrode and

workpiece heat up. The dielectric is ionized to form a spark channel. The temperature

and pressure rapidly increase and a spark is generated. A small amount of material isevaporated on the electrode and workpiece at the spark contact point.

Bubbles rapidly expand and explode during sparking until the voltage is turned off.

Next the heating channel collapses and the dielectric fluid enters into the gap in-order

to flush away the molten metal particles.

The material removal rate depends on the following factors:

Peak amperage or intensity of the spark Length of the ON time OFF time influences the speed and stability Duty cycle: percentage of on-time relative to total cycle time Gap distance: Smaller the gap better is the accuracy and slower is the material

removal rate.

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Th

material re

ypes of ED 1. Die S

2. Wire

3. Powd

moval phen

M Processe

nker EDM

ut EDM

er Mixed E

omena in E

s

M

M are sho n schematically in the ig. 3.9.3

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E

d

a

p

t

d

a

o

T

Modul

ie-Sinker E

DM and pl

ie-sinker E

s oil or oth

ower suppl

rough the

own starts t

d sparks ju

orkpiece. T

f die-sinker

he main co

Powe Diele

Elect Servo

-3: ADV

Di

DM is kno

nge EDM.

M, the elec

r dielectric

. An electr

ower suppl

king place

mp from the

he principle

EDM proce

ponents of

supply.

tric system.

ode

system.

ANCED

Le

-Sinker E

n by differ

The proce

trode and

fluids. The

cal potenti

y. As the e

n the fluid.

electrode t

of die-sink

ss is shown

Die-sinker

.

ATERI

ture No-10

M and its

ent names s

s is general

orkpiece ar

electrode a

l is genera

ectrode ap

Due to this

the workpi

ing EDM is

in Fig. 3.10.

DM are:

L REM

Systems

uch as Ram

ly used for

e submerge

d workpiec

ed betwee

roaches w

activity, a p

ece leading

shown in

.2

VAL PR

EDM, sink

producing

in an insul

e are conne

the tool a

rkpiece, th

lasma chan

to material

ig. 3.10.1 a

OCESSE

er EDM, ve

blind caviti

ating liquid

ted to a su

d the work

dielectric

el starts fo

emoval fro

nd the sche

S

rtical

s. In

such

table

piece

break

ming

the

atic

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T

d t

a

(

ower Supp

he power s

Curre

Pulse Pulse Duty Elect Pulse

ielectric a

he dielectri

ielectric fluansformer

ppropriate

such as flas

he dielectri

y

pply provid

nt

voltageduration

ycle

ode polarit

frequency

d its Circul

c fluids use

ids are hyd il, paraffin

ielectric fl

point, diel

system pe

es a series o

ation Syste

d in EDM

ocarbon oiloil; silicon

id depend

ctric streng

forms the f

f DC electri

m

operations

(kerosene based oil,

upon its

h, viscosity

llowing tas

cal discharg

re of differ

in particular de-ionize

arious che

, specific gr

s:

es and cont

ent types.

). The othed water. Th

ical and

avity and co

ols:

he most po

r fluids usee selection

luidic prop

lor)

pular

d areof an

erties

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It induces clean dielectric into the cutting zone Flushes away debris Cools the workpiece and electrodes

In order to provide circulation of the dielectric fluid to the work piece, the EDM machine

tool is equipped with a well-designed dielectric circulation system. It consists of

following two parts:

1. Pump : Its main purpose is to circulate the dielectric fluid on-to the workpiece

2. Filter and suction unit : This unit filters out the material debris and any other

foreign parts from the dielectric.

Servo System

The servo system is commanded by signals from gap voltage sensor system in the power

supply and it controls the in-feed of the electrode to precisely match the required rate of

material removal. At times stepper motor can be used instead of a servomotor. As soon as

the gap voltage sensor system determines bridging of some pieces of electrically

conductive materials between the electrode and work-piece, the servo system

immediately reacts and reverses the direction. The process is restored when the gap is

flushed by the dielectric fluid. When the gap becomes clear, the in-feed resumes and

cutting process continues.

Electrodes

The electrodes for EDM process are usually made of brass, copper, graphite and copper-

tungsten alloys.

Design considerations for EDM process

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In EDM process, fine openings and deeper slots need to be avoided. Very fine surface finish values should not be specified. As the MRR of EDM process is low, the rough cutting should be done by some

other machining process and EDM machine should me made used for the

finishing operations only.

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T

g

e

T

u

f

u

I

r

he WEDM

enerally us

ergy/powe

echanical p

aterials wh

he selectio

ndergoes si

rm recast

ndesired.

rocess of

the WEDaterial is

aterials are

moval take

orkpiece i

process re

ed when l

per pulse i

roperties of

ch are not s

of proces

nificant th

layers and

aterial Re

process, tut/ remov

cut by the

s place by

the presen

quires less

wer residu

s relatively

the material

tress-reliev

parameter

rmal cycle

induce resi

oval in Wi

e motion od from th

WEDM pr

a series of

ce of a di-

r cutting f

al stresses

low (as in f

are expect

d earlier ca

s is very c

that can b

dual tensile

re-Cut ED

f wire is sle workpiec

ocess by th

discrete dis

lectric flui

orces in m

in the wo

nishing op

d due to th

n get distor

ucial, as i

very seve

stresses o

w. It is fede accordin

e electro-th

harges bet

. The di-

terial rem

rkpiece are

rations), litt

se low resi

ed in the m

some cas

e. These th

n the work

in the progly. Electri

ermal mech

een the w

lectric flui

val; hence

desired. I

le changes i

ual stresses

chining pr

s the work

ermal cycle

piece whic

ammed patally cond

anisms. Ma

re electrod

gets ioniz

it is

f the

n the

. The

cess.

piece

s can

are

andctive

terial

and

ed in

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between the tool-electrode gap thereby creating a path for each discharge. The area

wherein discharge takes place gets heated to very high temperatures such that the surface

gets melted and removed. The cut particles (debris) get flushed away by the continuously

flowing dielectric fluid.

WEDM is a non-conventional process and is very widely used in tool steels for pattern

and die making industries. The process is also used for cutting intricate shapes in

components used for the electric and aerospace industries.

Applications of Wire-Cut EDM

Wire EDM is used for cutting aluminium, brass, copper, carbides, graphite, steels and

titanium. A schematic of the cutting through wire EDM is shown in Fig. 3.11.2. The wire

material varies with the application requirements. Example: for quicker cutting action,

zinc-coated brass wires are used while for more accurate applications, molybdenum wires

are used.

The process is used in the following areas:

Aerospace, Medical, Electronics and Semiconductor applications

Tool & Die making industries. For cutting the hard Extrusion Dies In making Fixtures, Gauges & Cams Cutting of Gears, Strippers, Punches and Dies Manufacturing hard Electrodes. Manufacturing micro-tooling for Micro-EDM, Micro-USM and such other micro-

machining applications.

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T

c

I

i

T

c

i

r

p

p

he Subsyst

Powe Diele Wire

Positi

he power s

onventional

wire cut E

the requir

he drive sy

ontinuously

sue in WE

llers which

ower to the

rocess. The

ms of Wir

supply.

tric system.

eeding syst

oning syste

pply and d

EDM. The

M, a movi

d workpiec

tem contin

exposed to

M process.

direct the

wire and g

other parts

EDM

.

em.

.

i-electric s

ain differe

ng wire elec

. The wire

ously deliv

the workpie

The wire

ire through

ides it furt

are the pi

stem used

nce lies onl

trode is use

is wound o

ers the fres

ce hence th

eeding syst

the machin

er in-order

ch rollers

n WEDM i

in the type

to cut co

a spool an

wire on-t

wear of th

m consists

. The prese

to keep it st

hich provi

s very simi

of dielectri

plex outlin

d is kept in

the work a

e wire (tool

of a large s

ce of metal

raight throu

e drive an

lar to that

used.

s and fine d

constant te

rea. New w

is not the

pool of wir

contact pro

ghout the c

wire tensi

f the

etails

sion.

ire is

ajor

e and

vides

tting

on, a

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s

t

T

fi

stem to thr

e wire runs

rocess Par

he process

EDM pro

g.3.11.3. T

Elect

volta

Non-

rate o Elect Diele

ead the wir

out or brea

meters in

arameters

ess are sh

e major par

ical parame

e and polari

lectrical pa

flushing.

ode based p

tric System

from the u

s.

EDM

hat can aff

wn throug

meters are

ers: Peak c

ty.

ameters: W

arameters:

: Type, visc

pper to the

ct the quali

an Ishik

as follows:

rrent, pulse

ire speed; w

aterial and

osity, and o

lower guide

ty of machi

wa cause-

on time, pu

ork feed rat

size of the

her flow ch

and a sens

ning or cutt

ffect diagr

lse off time

e, machinin

ire.

aracteristics

r to detect

ing or drilli

m as sho

and supply

time, gain

when

ng in

n in

and

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Lecture No-12

Laser Beam Machining (LBM)

Laser machining is a technology that uses a laser beam (narrow beam of intense

monochromatic light) to cut required shapes or profile or pattern in almost all types of

materials. Some of the examples include metals, ceramics, food products, leather etc. In

this process, the output of a high power laser beam is directed in a programmed manner

towards the material required to be cut. The high amount of heat thus generated either

melts, burns, or vaporizes away the material at the focused region. The process can be

used to make precise holes in thin sheets and materials. The laser beam cutting finds itsapplications in a variety of fields. The fields where laser beam has been successfully used

are cloth and plastic cutting, laser marking, laser welding, laser drilling, cleaning and

surface treatments.

Principle of Laser

The word laser is an acronym for Light Amplification by the Stimulated Emission of

Radiation. When an atom absorbs a quantum of energy from a light source, the orbitalelectron of an atom jumps to a higher energy level. The electron later drops to its original

orbit and emits the absorbed energy. If the electron, which is already at high energy level,

absorbs the second quantum of energy, it emits two quanta of energy and after emitting

the energy it returns back to its original orbit. The energy that is radiated has the same

wave length as the simulating energy. The laser material when placed in an optical cavity

and exposed to light energy keeps storing the energy. The energy initially builds up in the

laser material and finally gets emitted in the form of a highly amplified light beam. The

basic mechanism of energy transfer in laser beam is shown in Fig. 3.12.1 and laser beam

generation is schematically shown in Fig.3.12.2

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T

ttributes o

he attribute

It is c

This

sourccoher

are at

It is

perfe

It is

Diffe

each

Laser Bea

of laser lig

oherent i.e.

ptical prop

is ‘coher ent light sou

best only p

ighly colli

tly parallel

monochrom

ent media u

ype of laser

t are as fol

all photons

rty of light

nce’. Therce. Other li

rtially cohe

ated; i.e.

atic means

sed to stim

has a speci

ows:

that make u

that mostl

laser is reght sources

ent.

parallel b

the light i

late the ph

ic wavelen

p the beam

distinguis

arded, quit, such as the

am is pro

s of one c

tons gener

th.

are in phase

es the laser

correctlysun or a ga

uced. Ligh

lor, or of

te different

with each

from other

s the firsts discharge

rays are a

one wavele

wavelength

ther.

light

trulyamp,

most

ngth.

s, but

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Classific Laser be

c

a

The rep

T

state

the a

ation of La

ms can be

ontinuous

ontoured pa

ulse mode:

d intricate

resentation

ypes of La

here are tw

Neodymiu

ove two ty

Co 2 Lase

• Wave• Powe• Pulse

ser Beams

lassified in

mode: This

hs (the cutti

This mode

etails to be

of continuo

er

types of la

-doped Ytt

es of laser

s: these las

lengths: 10.

up to 100

and contin

two ways a

mode is g

ng is fastest

is preferred

cut without

s and pulse

ers used fo

ium Alumi

re given be

rs can be o

m

W

uous wave

Continuou

nerally pre

).

for cutting

exces

Documents

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