1sst sectional test ppt

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Ajay GoyalAssistant Professor

Mechanical Engineering DepartmentGLA University

GLA UNIVERSITY, MATHURA

Module 1: ! MA"#!E$ %MEE&'(1)



METAL CUTTING



HISTORY

1947 JOHN T. PARSONS : Start experimenting for using 3-axis curvature datato control different machine components( to control machine differentdirections :x, y, z) to manufacture air craft components.

1949 JOHN T. PARSONS : Contract aarded to develop first !C machine "y#S $ir force.

1951: #S $ir %orce commissioned &' to develop the first numericallycontrolled machine.

1952: !C machine as developed and it as demonstrated that simultaneous3 axis movement , then 3 axis movement as possi*le using a la*oratory ( *yusing separate type of controllers)

1955: $fter a complete refinement they are a*le to achieve first !C machinelaunched into the industry.



1959: &' start using $+ ( $utomatic program tool) language.

1960: +unch tape eliminates completely and Started using $+language *y using a set of instruction hich are directly send tocontroller unit.

1968: %irst machining centre as developed *y earney andrecer &c tool *uilder.

1970: C!C and !C(istri*uted !umerical Control) came into

existence.

1960 : irect !umerical Control (!C). his eliminates paper tape punchprograms and allos programmers to send files directly to machine tools

HISTORY C!""....



M#$%&!' "(

&achine tool provides:

/or holding

ool holding

0elative motion *eteen tool and orpiece

1. +rimary motion

2. Secondary motion



)%#" &* !+'-&$#( $!"-( NC/

!C is a machine system in hich actions are controlled *y the direct insertion of

numerical data at some points. he system must automatically interpret at least some

portion of this data

NC



NC C!""..

he functions and motions such as

urning the spindle on and off Setting cutting speeds

Setting feed rate

urning coolant on and off

&oving tool ith respect to orpiece are performed *y &achine Control #nit (&C#) in

!C machine tools.

'n general there are three *asic components of an operational !C

1. +rogramme of instruction.

2. $ machine control unit.

3. &achine tool.

P--# 3

&!*"-+$"&!

C!"-( +!&"M#$%&!' "(



NC C!""..

4 he program of instruction is a numerical or sym*olic code that is detailed step-*y-

step to tell the machine tool hat to do.

4 he controller unit is the unit that reads the programme of instructions and converts it

to real movement of a machine tool.

4 he machine tool performs the mechanical or and deals directly ith the part *eing

machined.



NC SYSTEM ELEMENTS



$++5'C$'6!S 6% !C



NC A(&$#"&! C%#-#$"'-&*"&$* M#$%&!&!/

"atch and 7igh 8olume production

0epeat andor 0epetitive orders

Complex part geometries

&undane operations

&any separate operations on one part

$pplications of !C

&achine tool applications:

1. &illing machines.

2. rilling machines.

3. "oring machines.

9. urning machines.

. ;rinding machines.<. Saing machines.

!on- machine tool applications:

=. /elding machines- flame cutting machines.

>. +ress-oring machines- assem*ly machines.

?. 'nspection machines- automatic drafting machines



COSTENEITS O NC

Costs

7igh investment cost

7igh maintenance effort

!eed for silled programmers

7igh utilization re@uired

"enefits

Cycle time reduction

!onproductive time reduction

;reater accuracy and repeata*ility

5oer scrap rates

0educed parts inventory and floor space

6perator sill-level reduced



NC PART PROGRAMMING

1. &anual part programming

2. &anual data input

3. Computer-assisted part programming9. +art programming using C$C$&



M#!+#( P#-" P--#&!

"inary Coded ecimal System

Aach of the ten digits in decimal system (B-?) is coded ith four-digit

*inary num*er

he *inary num*ers are added to give the value

"C is compati*le ith > *its across tape format, the original storage

medium for !C part programs

Aight *its can also *e used for letters and sym*ols



CREATING INSTRUCTIONS OR NC

"it - B or 1 a*sence or presence of hole in the tape

Character - ro of *its across the tape

/ord - se@uence of characters (e.g., y-axis position) "loc - collection of ords to form one complete instruction

+art program - se@uence of instructions (*locs)



($ -#"

6rganization of ords ithin a *loc in !C part program

$lso non as tape format *ecause the original formats ere designed

for punched tape

/ord address format - used on all modern C!C controllers

#ses a letter prefix to identify each type of ord

Spaces to separate ords ithin the *loc

$llos any order of ords in a *loc

/ords can *e omitted if their values do not change from the previous *loc



T'* 3 )-*

! - se@uence num*er prefix

; - preparatory ords

Axample: ;BB ++ rapid traverse move

D, E, F - prefixes for x , y , and z -axes% - feed rate prefix

S - spindle speed

- tool selection

& - miscellaneous command

Axample: &B= turn cutting fluid on



E;#(': )- A-'** -#"

!BB1 ;BB DB=BBB EB3BBB &B3

!BB2 EB<BBB



C+""'- O33*'"

Cutter path must *e offset from actual part outline *y a distancee@ual to the cutter radius



M#!+#( <#"# I!+"

&achine operator does part programming at

machine

6perator enters program *y responding to

prompts and @uestions *y system

&onitor ith graphics verifies tool path

#sually for relatively simple parts

'deal for small shop that cannot afford a part

programming staff

o minimize changeover time, system shouldallo programming of next Go* hile current Go*

is running



C+"'-A**&*"' P#-" P--#&!

/rite machine instructions using natural language type statements

Statements translated into machine code of the &C#

$+ ($utomatically +rogrammed ool) 5anguage



S#(' S"#"''!"*

+art is composed of *asic geometric elements and mathematically defined surfaces

Axamples of statements:

+9 +6'!3,?B,B

51 5'!A+1,+2

C1 C'0C5ACA!A0,+>,0$'#S,3B

ool path is se@uence of points or connected line and arc segments

+oint-to-+oint command: ;66+9

Continuous path command: ;65%51,$!6,C1



NC P#-" P--#&! U*&! CA<=CAM



<NC

irect numerical control (!C) H control of multiple machine tools *y a single

(mainframe) computer through direct connection and in real time

1?<Bs technology

o ay communication

irect !umerical control (!C) can *e defined as a set of !C machines that is connected to a

main computer system to esta*lish a direct interface *eteen the !C computer memory andthe machine tools. he tape is not used in the !C system hence a central time-sharing

computer is used.



<NC C!""..

Multi-machine

controller

Direct axis and

service control

irect !umerical control (!C)



istri*uted numerical control (!C) H netor consisting of central computer

connected to machine tool &C#s, hich are C!C

+resent technology

o ay communication

istri*uted !C is more advanced than !C and is idely used in many current

applications. he distri*uted !C uses a local area netor *ut not lie that in !C. 't

has *een indicated that the main difference *eteen !C and distri*uted !C is that

*ecause modern !C machines have C!C capa*ility, they have memory and

therefore computer programs can *e donloaded into the memory of a C!C localcomputer, rather than one *loc at a time as in !C systems. %igure 9 illustrates the

distri*uted !C system.

<NC C!""..



'S0'"#A !#&A0'C$5 C6!065

<NC C!""..

C'& host data*ase of

processes part

programs controller

5ocal area netor

C!C

controller

C!C

controller

C!C

controller

C!C

controller

C!C

controller

V & N & ( C " ( VNC/



V&$' N+'-&$#( C!"-( VNC/

8oice !umerical Control (8!C) is similar to !C machines *ut the programmer

conveys the information needed to operate the machine *y means of computer

system. he programmer tals into the computer, and the memory receives the

information using a ire. his information can *e taen and used to run the

machines.



CNC

'n C!C (Computer !umerical Control), the instructions are stored as a program in a

micro-computer attached to the machine. he computer ill also handle much of thecontrol logic of the machine, maing it more adapta*le than earlier hard-ired

controllers.

C!C refers to a computer that is Goined to the !C machine to mae the machine

versatile. 'nformation can *e stored in a memory *an. he programme is read from

a storage medium such as the punched tape and retrieved to the memory of the C!C

computer. Some C!C machines have a magnetic medium (tape or dis) for storing

programs. his gives more flexi*ility for editing or saving C!C programs.



M#$%&!' "(

M&*$'((#!'+*

$!"-( '.. (&&"

*>&"$%'*, $(#!",

*&!(', '"$.

A;&* -&?' #!

$!"-(

;,,@,#,,>/

*&!(' *''

CNC $!"-(('-

>&"% '#

#! &*(#

M#!'"&$ "#'

- &* - #'-

"#' -'#'-

P#'-

"#' +!$%



CNC SYSTEM ELEMENTS

$ typical C!C system consists of the folloing six elements:

+art program

+rogram input device

&achine control unit

rive system

&achine tool

%eed*ac system



OPERATIONAL EATURES O CNC MACHINES



CNC TERMINOLOGY

LU: #*&$ ('!"% +!&"

*#(('*" --##(' ?' 3 '#$% #;&*.

C!"-(('-: M#$%&!' C!"-( U!&", MCU/

E('$"-!&$ #! $+"'-&@' &!"'-3#$' '">''! '-#"- #! =$

C!"-(('- $!'!"*:

1. <#"# P-$'**&! U!&" <PU/

2. C!"-(L* U!&" CLU/



CONTROLLER COMPONENTS

<#"# P-$'**&! U!&":I!+" '?&$' BRS22 -"= T#' R'#'-= P+!$%' T#' R'#'-D

<#"# R'#&! C&-$+&"* #! P#-&" C%'$&! C&-$+&"*

<'$'-* " &*"-&+"' #"# " "%' #;'* $!"-(('-*.

C!"-( L* U!&":

I!"'-(#"- " *+( #$%&!'"&! $#!* '">''! #"# &!"*

P*&"&! $!"-( ( %#->#-' 3- '#$% #;&* 3 "&!



ypes of C!C machines

#*' ! M"&! T':

P&!""P&!" - C!"&!++* #"%

#*' ! C!"-( L*:

O'! ( - C(*' (

#*' ! P>'- S+(:

E('$"-&$ - H-#+(&$ - P!'+#"&$

#*' ! P*&"&!&! S*"'

I!$-''!"#( - A*(+"'



OPENLOOP CONTROL SYSTEM

'n open-loop control system step motors are used

Step motors are driven *y electric pulses

Avery pulse rotates the motor spindle through a certain amount

"y counting the pulses, the amount of motion can *e controlled !o feed*ac signal for error correction

5oer positioning accuracy



CLOSE<LOOP CONTROL SYSTEMS

'nclosed-loop control systems C or $C motors are used

+osition transducers are used to generate position feed*ac signals for errorcorrection

"etter accuracy can *e achieved &ore expensive

Suita*le for large size machine tools



O'! L ?*. C(*' L $!"-(*



EATURES O CNC SYSTEM



%eatures of C!C System

Control System %eatures &emory %eatures

+rogramming %eatures iagnostic %eatures

A CNC S*"' &* 3&""' " # #$%&!' "( " $!"-( ?'-

*'?'-#( #$%&!' 3+!$"&!*. I! -'- " '-3- "%'*' 3+!$"&!*

CNC **"' &* $%#-#$"'-&@' # !+'- 3 3'#"+-'*.

CONTROL SYSTEM EATURES



CONTROL SYSTEM EATURES

hese features provide information a*out characteristics and capa*ilities of C!C system . 't

includes

o T'$%!( 3 S*"' : Currently to types of architectures are *eing used

Single &icroprocessor $rchitecture : 't uses 1<,32 or <9 *it microprocessor

&ultiprocessor $rchitecture : he control functions are carried out *y set of microprocessors ,

each doing an assigned tas.

o E;'$+"&?' P--# : 't contains intelligence needed to carry out different tass. 't is resident

usually in A+06&"u**le &emory.

o A;&* C#(&-#"&! : 't ensures higher positioning accuracy as it compensates errors.

o R'?'-*#( E---#$(#*%/ C'!*#"&! : Comes into action hen slides are reversed .his

system ensures automatic compensation of *aclash *eteen scre and nut or *all scres



o +itch error compensation : +ositioning error that might arise due to error in pitch are

compensated.

o ool nose compensation : 't compensates contouring errors arising due to radius of

tool.

&achine Setup ata (&S) : 't indicates the machine tool characteristics, specifications

and parameters. hey are entered in machine *y :

o Setting through perimeter C-06&o Setting data through &'

o Setting data in A+06&Is

6ther System %eatures :

o C0 display and alphanumeric ey*oardo &anual data input and operator programming

o System resolution

o %eed and rapid traverse rates

o Spindle Speeds

MEMORY EATURES



<'*&! A(&$#"&! '#"+-'*

Axecutive Storage A+06& !on-volatile and idely

used.

+art program storage 4 ynamic 0$&4 C&6S 0$&4 "u**le memory

4Semi conductor memory4%ast access and volatile4!on volatile , sloer thansemiconductor memory

&achine constant A+06& !onvolatile and can *e fieldprogrammed . !eeds*attery *ac up.

&emory (+arameter) C&6S 0$& 'ntermediate oring

Scratch pad 0$&Static 0$& area

&6S 0$&

6ffline data storage &agnetic digitalCassette, &agnetic disc%loppy disc , 7ard discC-06&

MEMORY EATURES

PROGRAMMING EATURES



PROGRAMMING EATURES

S+-+"&!' P--#&!= M#$- P--#&! : 0epetitive operations can *e ritten

as su*routines and main program can call these su*routines , it saves memory space.

P#-#'"-&$ P--#&! : +arameters are freely assigned *y the control for purpose of

arithmetic calculation in a part program.

C#!!' C$('* : 't shortens the length of program as they are single *loc multipassfixed cycles.

P--##(' L&$ C!"-(('- : 't is a softare oriented machine interface *eteen

the C!C system and machine tool functions .hey are microprocessor *ased units

hich are integrated to C!C system . %eatures of +5C :

&emory capacity 9,> etc

7igh speed microprocessors

Softare timers and counters

<IAGNOSTIC EATURES



<IAGNOSTIC EATURES

he C!C system have diagnostic features for error and fault finding . iagnostics

are in form of softare programs, hich chec the functioning of C!C system at

various levels. 't follos :

R'#( T&' <&#!*"&$* : C poer supply voltages , lo voltage are monitored .'n

case of failure, control system assumes emergency stop.

O!L&!' <&#!*"&$* : 't is active during machine operation and diagnostic

messages are either reada*le from C0 screen or from 5A indicators.

O33L&!' <&#!*"&$* : 't is provided in the form of C-06& or 06& *oard (+C").

'n case of malfunction offline programs are loaded on C!C hich checdifferent areas of system and respond ith errors on C0 display.

R'"' <&#!*"&$* : 't is no possi*le to send diagnostic programs through

internet to chec errors in C!C machines. &anufacturers can locate faults even

if machine is located in other country.

SOME EATURES O MO<ERN CNC SYSTEMS



SOME EATURES O MO<ERN CNC SYSTEMS

o $dvanced 7ardare architecture: 8ery large scale integrated circuits (85S') are

provided hich can handle several functions in a single chip.

o Softare &odularity : Aach function is ritten as discrete modules and additional

softare features can *e added any time to upgrade the control.

o $daptive Control: 0educes the production time *y maximizing the utilization of

machine tool. 't acts on measurements taen from external sensors and modifies the

cutting conditions suita*ly.

o +rogramming %lexi*ility : 't introduces high level commands lie '%-7A!,;6-

6,A5SA-/7'5A hich extends program poer .

o Colour ;raphics : his provides visual interface *eteen operator and C!C

.6perating instructions and arning display can *e colour coded for more clarity.



o M#$%&!' I!"'-3#$': $ high level language lie C is used for

programming the machine logic in +C e.g. ;A 2BBB &C

o A+"#"&$ *'('$"&! 3 $+""&! *''* : 'f e specify the toolmaterial , it selects cutting speed and feed from cutting condition

technology data*ase.

o A+"#"&$ *'('$"&! 3 "(* #! *'+'!$&! 3 "(* : 'f operation

is specified , system selects corresponding tools and se@uence oftools. Systems lie &aza %usion <9B provides this feature.

o O"&&@#"&! 3 #$%&!' --# : 't is useful for components ith

large no. of drilling , tapping , operations or repetitive end milling tool

paths.

o <&*(# 3 3&!&*%' $!'!" : oday C!C systems offers this

feature to display the finished component along ith its dimensions.

Sectioning and rotation of model is also possi*le.



o #$-+! P--#&! : he user can edit and simulate

other program hile one program is already running.

o <&&"#( CNC :he ne *reed of C!C uses digital technology.'t

incorporates features lie acceleration ith Ger limitation , use of

high level languages , execution of large programs.

o L #%'# 3'#"+-' : he control system scans 1B or more

*locs ahead of the *loc that is *eing executed and carries out

necessary optimizations to generate re@uired tool path . 't helps

to produce accurate profiles in high speed machining

C " 3 S " " (( CNC



C!'!"* 3 S'-?"- $!"-((' CNC

M"- *'' $!"-(

T> "'* 3 '!$'- $!3&+-#"&!*

M"- ('# *$-'> -"#"&! "#(' ?'*

*&"&! *'!*' '!$'- 3''#$



CNC M#$%&!' C!'!"*

Cutting ool Collet 8ery common to

have 1BB or more diverse cutting toolsloaded into a collet caddy

hey are num*ered for ease of

identification

he operator must no the common

tools *y simple visual o*servation

CNC % V&



CNC '!$% V&*'

!otice the smooth machined surfaces *e careful not to

dama e surfaces



CAM F #;&* T#(' A(&!'!"

o machine a part ith C!C,

the end of the tool must *enon relative to the *ench

vise, x-axis ta*le, or some

other fixed distance



#;&* A--

Jeep the lands clean and oiled

$ slight tilt ill cause noticea*le

cut deformations

$lign the protrusions ith slots in

the cutting tool @uic change

adapter *ody



A&- N@@('

#sed for:

Jeeping cutting area free of

excessive cutting de*ris

Kuic cleaning

/hen supplied ith misting,

provides cutting tool cooling



E! M&(( = #$&! C+""'-

7ogs off large amounts of

material 0adius of cut very large

+rovides a non surface from

hich to measure from

0e@uires orpiece to *e ro*ustlysupported due to high tor@ue

created



UIC CHANGE EN< MILL A<APTER

7elps provide @uic changing

of cutting tools ithout havingto use complex setup

procedures



P>'- P#!'(

5oca*le 6n-6ff Sitch

Circuit "reaers

+oer Cord



C!"-( P#!'(



C!"-( P#!'(

1. EE< HOL<

$cts as an interrupt control to the program hen pressed, preventing anyfurther tool movement until canceled. uring an $utomatic cycle, aftercanceling CEC5A S$0 must *e pressed to resume the cycle.

2. SINGLE LOC

/ith machine running in automatic mode controlled from the +C, thisallos the operation of only a single *loc (line) of the program at a time to*e toggled onoff. +ress CEC5A S$0 to proceed.

. CYCLE START

his sets the machine in automatic mode and starts the machining fromthe +C program. $lso used to resume an $utomatic cycle after a %AA765 is canceled and to action the next line if Single "loc is active.

C!"-( P#!'( C!""



C!"-( P#!'( C!""..

4. EE< SPEE< CONTROL

+rovides stepless control of tool feed speed in the D, E and F axes from B to 1BBL in 1BLincrements.

5. JOG TALE AIS CONTROLS

hese four *uttons control manual movement of the ta*le in the D and E axes.

&ove the ta*le in the D axis hile held pressed.

&ove the ta*le in the E-axis hile held pressed.

6. JOG HEA< AIS CONTROLS

&ove the head in the F axis hile held pressed.

+ressing this *utton together ith any of the other six axis control *uttons provides rapid

movement of the axes in the indicated direction.

C!"-( P#!'( C!""



C!"-( P#!'( C!""..

7. MANUAL

/hen lit, machine is operated from control panel (&anual mode). +ressing &$! puts light out andmachine is controlled *y computer ($utomatic mode). +ress &$! again to revert to manual mode

operation.

8. AIR MIST CONTROL

Sitches on or off the optional air mist coolant hen fitted.

9. <ATUM M=C PROGRAM AORT

$fter initially poering up the machine and pressing the +oer 0eset *utton (23), ith the machine

in &anual mode (&anual mode *utton lit) press to datum the machine axes.

• /ith the machine in &anual mode, the machine can *e re-datumed at any point. his should

alays *e done if a physical stall of the axes has occurred.

• uring an $utomatic Cycle ith a %eed 7old (1) active, pressing ill $*ort the current Go*.

C!"-( P#!'( C!""



C!"-( P#!'( C!""..

10. TOOL CHANGE

/ith auto tool changer fitted, press to change to next tool automatically.

11. TOOL RELEASE

0eleases the tool holder from the spindle if fitted ith the auto tool changer. ;uard door

must *e open and tool holder held.

12. )OR HOL<ING UNCLAMP

Controls un-clamping of orpiece in pneumatic or holder vice, hen fitted.

1. )OR HOL<ING CLAMP

Controls clamping of orpiece in pneumatic or holder vice, hen fitted.

14. <OOR OPEN

Controls opening of the automatic doors hen fitted.

C!"-( P#!'( C!""



C!"-( P#!'( C!""..

15. <OOR CLOSE

Controls closing of the automatic doors hen fitted.

16. SPIN<LE CONTROLS

hese control the speed and direction of rotation of the spindle.

S&!(' ->#- - +ressing this *utton starts the spindle rotating forard. 7olding

it don increases forard speed. +ressing and holding the MSpindle 0everseM *utton

reduces speed in the forard direction.

S&!(' R'?'-*' - +ressing this *utton starts the spindle rotating in reverse

direction. 7olding it don increases spindle speed in reverse direction. +ressing and

holding the MSpindle %orardM *utton reduces speed in the reverse direction.

S&!(' S" - +ressing this *utton stops spindle rotation.

C!"-( P#!'( C!""



C!"-( P#!'( C!""..

17. EMERGENCY STOP

+ressing this push*utton stops all machine movement and sitches off the electronics,and the *utton locs in the depressed position.

'f the machine is in production, an appropriate message is displayed on the +C screen.

he *utton must *e turned to release it and the 7ard 0eset *utton (23) pressed to

ena*le the machine to *e started. he machine must *e datumed using the atum &C

ey (?).'f the machine as performing a production cycle, the cycle must *e repeated from the

*eginning.

PROGRAM INPUT <EVICE



PROGRAM INPUT <EVICE

he program input device is the mechanism for part programs to *e entered into theC!C control. he most commonly used program input devices are ey*oards,

punched tape reader, disette drivers, throgh 0S 232 serial ports and netors.

MACHINE CONTROL UNIT



MACHINE CONTROL UNIT

he machine control unit (&C#) is the heart of a C!C system. 't is used toperform the folloing functions:

0ead coded instructions

ecode coded instructions

'mplement interpolations (linear, circular, and helical) to generate axismotion commands

%eed axis motion commands to the amplifier circuits for driving the axismechanisms

0eceive the feed*ac signals of position and speed for each drive axis

'mplement auxiliary control functions such as coolant or spindle onoff, andtool change

TYPES 3 CNC CONTROL SYSTEMS



TYPES 3 CNC CONTROL SYSTEMS

6pen-loop control

Closed-loop control

<RIVE SYSTEM



<RIVE SYSTEM

$ drive system consists of amplifier circuits, stepping motors or servomotors and *alllead-scres. he &C# feeds control signals (position and speed) of each axis to theamplifier circuits. he control signals are augmented to actuate stepping motorshich in turn rotate the *all lead-scres to position the machine ta*le.

STEPPING MOTORS



STEPPING MOTORS

$ stepping motor provides open-loop, digital control of the position of a orpiece in

a numerical control machine. he drive unit receives a direction input (c or cc) andpulse inputs. %or each pulse it receives, the drive unit manipulates the motor voltage

and current, causing the motor shaft to rotate *ya fixed angle (one step). he lead

scre converts the rotary motion of the motor shaft into linear motion of the

orpiece .

STEPPING MOTORS



STEPPING MOTORS

RECIRCULATING ALL SCRE)S




ransform rotational motion of the motor into

translational motion of the nut attached to the machineta*le.





$ccuracy of C!C machines depends on their

rigid construction, care in manufacturing, andthe use of *all scres to almost eliminate slopin the scres used to move portions of themachine.



POSITIONING



he positioning resolution of a *all scre drive mechanism is directly

proportional to the smallest angle that the motor can turn. he smallest angle is controlled *y the motor step size.

&icrosteps can *e used to decrease the motor step size.

C!C machines typically have resolutions of B.BB2 mm or *etter.

MACHINE TOOL



C!C controls are used to control various types of machine tools. 0egardless of hich

type of machine tool is controlled, it alays has a slide ta*le and a spindle to controlof position and speed. he machine ta*le is controlled in the D and E axes, hile the

spindle runs along the F axis.

EE<AC SYSTEM



he feed*ac system is also referred to as the measuring system. 't uses position

and speed transducers to continuously monitor the position at hich the cutting toolis located at any particular time. he &C# uses the difference *eteen referencesignals and feed*ac signals to generate the control signals for correcting positionand speed errors.



CNC MACHINES EE<AC <EVICES

POTENTIOMETERS



POTENTIOMETERS C!""..



ENCO<ERS



$ device used to convert linear or rotational position information into an electrical

output signal.

ENCO<ERS C!""



IN<USTRIAL APPLICATIONS 3 ENCO<ERS



RESOLVERS



SO S

$ resolver is a rotary transformer that

produces an output signal that is a

function of the rotor position.

SERVOMOTOR >&"% RESOLVER



VELOCITY EE<AC



achometers:

Alectrical output is proportional to rate of angular rotation.

Ancoders, 0esolvers, +otentiometers: !um*er of pulses per time is proportional to rate change of position.

CNC CUTTERS



urning center cutters

&achining center cutters

TURNING CENTER CUTTERS



ypes of cutters used on C!C turning centers

Car*ides (and other hard materials) insert turning and *oring tools Ceramics

7igh Speed Steel (7SS) drills and taps

STAN<ART INSERT SHAPES



8 H used for profiling, eaest insert, 2 edgesper side.

H somehat stronger, used for profiling henthe angle allos it, 2 edges per side.

H commonly used for turning *ecause it has 3edges per side.

C H popular insert *ecause the same holder can*e used for turning and facing. 2 edges per side.

/ H neest shape. Can turn and face lie the C,*ut 3 edges per side.

S H 8ery strong, *ut mostly used for chamfering*ecause it onIt cut a s@uare shoulder. 9 edges

per side. 0 H strongest insert *ut least commonly used.

TYPICAL TURNING,THREA<ING #! PARTING TOOLS



MACHINING CENTER CUTTING TOOLS



&ost machining centers use some form

of 7SS or car*ide insert endmill as the

*asic cutting tool.

'nsert endmills cut many times fasterthan 7SS, *ut the

7SS endmills leave a *etter finish

hen side cutting.

MACHINING CENTER CUTTING TOOLS $!"K/



%acemills flatten large surfaces @uicly

and ith an excellent finish. !otice the

engine *loc *eing finished in one pass

ith a large cutter.




/

"all endmills (*oth 7SS and insert) areused for a variety of profiling operationssuch as the mold shon in the picture.

Slitting and side cutters are used hendeep, narro slots must *e cut.




rills, aps, and 0eamers

Common 7SS tools such as drills, taps, andreamers are commonly used on C!Cmachining centers. !ote that a spot drill is usedinstead of a centerdrill. $lso, spiral point or guntaps are used for through holes and spiral flutefor *lind holes. 0arely are hand taps used on amachining center.

TOOL HOL<ERS



$ll cutting tools must *e held in a holder that fits in thespindle. hese include end mill holders (shon), colletholders, face mill adapters, etc. &ost machines in the#S$ use a C$ taper hich is a modified !S 3B, 9B,or B taper that uses a pull stud and a groove in theflange. he machine pulls on the pull stud to hold theholder in the spindle, and the groove in the flange givesthe automatic tool changer something to hold onto.7SJ tool holders ere designed a num*er of years agoas an improvement to C$ tapers, *ut they are gainingacceptance sloly.

CNC APPLICATIONS



&achining

2. 3 urning N 5athes, urning Centre

&illing N &achining Centres

%orming

2

+lasma and 5aser Cutting

"laning, ni**ling and punching

3

0apid +rototyping

CNC MACHINES EAMPLES



C!C #0!'!; C!C &'55'!;

C6!OOOO

C!C 5$SA0 C#'!; C!C +5$S&$ C#'!;



C!C +0ASS C!C 0$+' +066E+'!;

IN<USTRIES MOST AECTE< Y CNC



$erospace

&achinery

Alectrical

%a*rication

$utomotive

'nstrumentation

&old maing

SAMPLES PRO<UCT O CNC MACHINES



A<VANTAGES O CNC



PRO<UCTIVITY

&achine utilization is increased *ecause more time is spent cutting and less time is

taen *y positioning. 0educed setup time increases utilization too.

K#$5'E

+arts are more accurate.

+arts are more repeata*le.

5ess aste due to scrap

0A#CA '!8A!60E

0educed setup time permits smaller economic *atch @uantities.

5oer lead time allos loer stoc levels.

5oer stoc levels reduce interest charges and oring capital re@uirements.

A<VANTAGES O CNC



M#$%&!&! C('; *%#'*

Slide movements under computer control.

Computer controller can calculate steps.

%irst !C machine *uilt 1?1 at &' for aircraft sin milling.

M#!#''!" C!"-(

C!C leads to C$

+rocess planning

+roduction planning

<RA)ACS O CNC



7igh capital cost : &achine tools cost.

0etraining and recruitment of staff

!e support facilities

7igh maintenance re@uirements

!ot cost-effective for lo-level production on simple parts

&aintenance personnel must have *oth mechanical and electronics expertise



THANS

1sst sectional test ppt

Documents