Cnc Turing m1 Presentation

8/10/2019 Cnc Turing m1 Presentation

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CNC Turning

Module 1: Introduction to CNC

Turning


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Watch the following video, and answer the

following questions:


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Module Objectives

1 !efine the ter" CNC

# $ecogni%e the advantages and disadvantages of CNC

& !ifferentiate between Cartesian and 'olar coordinate

s(ste"s used in CNC )rogra""ing* $ecogni%e the turning "achine a+es

Identif( the )ositive and negative "ove"ent directions on

the turning CNC "achines

- !escribe the difference between absolute and incre"ental

di"ensioning "ethods


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Introduction


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Introduction

CNC stands for Computer Numerical Control.

It is the technology of controlling a "achining

o)eration using a co")uter )rogra", which iscalled Nu"erical Control .NC/ 'rogra"

In other words, a co")uter rather than a )ersonwill directl( control the "achine tool


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Introduction

The "ost i")ortant co")uteri%ed "achine tools

that are used e+tensivel( in the industr( are:

CNC Turning

.0athe/ "achineCNC Milling

"achine


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Advantages of CNC

Increased s)eed at which )arts are

)roduced .)roductivit(/

'roducing the sa"e qualit( for all wor)arts

2etter di"ensional accurac( which gives

e+act and correct di"ensions

Increased abilit( to )roduce difficult )arts

0ess scra)


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Disadvantages of CNC

3igh initial cost

Need high qualified o)erator


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Coordinate Systems


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Coordinate Systems

In order to sha)e "etal b( "achine tools,

the cutting tool should "ove in contact with

the wor)iece at certain s)ecific )oints,

while the wor)iece or cutting tool is

rotating

Coordinate s(ste" is required to define the

"ove"ent on the "achine


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Coordinate Systems

Basically there are two common

coordinate systems:

Cartesian

coordinate

system

Polar

coordinate

system


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4+a")les


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4+a")le 1

0ocate )oints '1 through '* on the

coordinate s(ste" shown in 5ig 1*

'1 6 7 89 7 -9

'# 6 7 ;89 7 #9

'& 6 7 ;9 7 ;-9

'* 6 7 -9 7 ;


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4+a")le #

3ow can (ou

describe the linegiven in the figure

using )olar

coordinate s(ste"=


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CNC athe !turning" #achine$s

coordinate system


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coordinate system:

To ensure that the control s(ste" of the

"achine will read the s)ecified

coordinates correctl( to indicate the

)osition of the wor)iece> the "achine tool

has its own ?coordinate s(ste"@


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coordinate system:

The following )oints are )art of this

s(ste"

;Machine Aero )oint

.M/

;Wor)iece Aero

'oint .W/


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coordinate system:

The following )oints are )art of this

s(ste"

Wor)iece

Aero )ointMachine Aero

)oint


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%urning #achine a&es:


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%urning #achine a&es

CNC Turning "achine has at least #

controllable feed a+es, "ared as 6 and A>

5ig 18


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When the cutting tool "oves toward and

bacward the "achine s)indle, this is called

"ove"ent along A a+is

When the cutting tool "oves in cross

direction to the longitudinal a+is of thewor)iece, this is called "ove"ent along 6

a+is


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'ositive A direction

is when the tool "oves

awa( fro" the

wor)iece in A a+is

'ositive 6 direction

is when the tool "oves

awa( fro" the wor

)art in 6 a+is


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Dimensioning


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Dimensioning

To "achine a wor)iece we need a

technical drawing on which we should

illustrate the required di"ensions to "ae

the required sha)e


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Dimensioning

To di"ension the wor)iece we need to

s)ecif( a certain )oint on it, fro" which we

should tae the "easure"ent This )oint is

the origin )oint

The origin )oint on the wor)iece is called

'or(piece )ero point !'".


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Dimensioning

There are two t()es of !i"ensioning

Incremental

Dimensioning

A*solute

Dimensioning


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Cutting Speeds and +eeds


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The cutting s)eed is the

s)eed at which thecircu"ference of the

wor )art "oves along

the cutter, see 5ig119


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The "agnitude of cutting s)eed is

deter"ined b( the:

1 Material of the wor )art

# Material of the cutting tool

& Infeed .surface qualit( roughing,finishing/


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The cutting s)eed is chosen fro" ta*ulated values.


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$otational B)eed


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$otational B)eed

Once the cutting s)eed is chosen, the rotational

s)eed has to be calculated


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$otational B)eed

The following for"ula can be used to calculate the

rotational s)eed:

Where,

CS: the cutting speed in !m,min".

d: the wor( part diameter in !m".

n: the rotational speed in revolution per minute

!-P#".

: Constant / 0.12


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4+a")les


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4+a")le 1

Calculate the rotational s)eed .n/ if 1#

"" dia"eter wor)iece "ade of

alu"inu" is to be "achined .finishingcut/ The cutting tool is "ade of 3BB=


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4+a")le 1 Bolution

5ro" table 11 the cutting s)eed

for alu"inu" under finishing cut 7 & "D"in

The dia"eter 7 1#D1999 7 991# "

n 7 &D .&1* E991#/$otational s)eed 7 #*-8 $'M


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4+a")le #

Calculate the rotational s)eed .n/ if *9 ""

dia"eter wor)iece "ade of bron%e is to be

"achined .finishing cut/ The cutting tool is

"ade of 3BB=


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5eed


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5eed

The feed of a lathe may be defined as the

distance the cutting tool advances along the

length of the wor for ever( revolution of the

s)indle


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5eed

5or e+a")le, if the lathe is set for a 9* ""

feed, the cutting tool will travel along the

length of the wor 9* "" for ever(

co")lete turn that the wor "aes Bo theunit of feed .5/ is ""Drev


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!e)th of Cut


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!e)th of Cut

Depth of cut is the

difference in height

*etween machined

surface and thewor surface

Bee 5ig11#


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!onFt forget to solve (our

ho"ewor

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Cnc Turing m1 Presentation