plc and cnc machines

8/13/2019 plc and cnc machines

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INDUSTRIAL TRAINING REPORT

PLC AND CNC SYSTEMS IN INDUSTRIAL

MACHINE TOOLS

Submitted in partial fulfillment of the

Requirements for the award of

Degree of Bachelor of Technology in Elecronic! an" Co##$nicaion

Engineering

Name: BODDA DURGA TEA

Roll No: !""!"#"$!

SUBMITTED TO%

Department of Electronics and Communication EngineeringS%hool of En&ineerin& and Te%hnolo&'( Sharda Uni)ersit'

Greater Noida( U*+*,-"!#".

/-"!-,-"!#0


2/44

DECLARATION

1 hereb' de%lare that the 1ndustrial Trainin& Report entitled 2+34 and 4N4 s'stems in

industrial ma%hine tools2 is an authenti% re%ord of m' own wor5 as requirements of .,

6ee5s 1ndustrial Trainin& durin& the period from !7,".,-"!# to -8,"8,-"!# for the

award of de&ree of B*Te%h* /Ele%troni%s and 4ommuni%ation En&ineerin&0( S%hool of

En&ineerin& and Te%hnolo&'( Sharda Uni)ersit'( Greater Noida( under the &uidan%e of

9*Ar)ind 5umar*

&Signa$re of !$"en'

Bo""a D$rga Te(a

)**)*+*,)

Dae%

4ertified that the abo)e statement made b' the student is %orre%t to the best of our

5nowled&e and belief*

Signa$re!

E-a#ine" .y%

!* -* #*

Hea" of De/ar#en

&Signa$re an" Seal'


3/44

AC0NO1LEDGEMENT

The su%%ess and final out%ome of this proe%t required a lot of &uidan%e and assistan%e

from man' people and 1 am e;tremel' fortunate to ha)e &ot this all alon& the %ompletion

of m' proe%t wor5* 6hate)er 1 ha)e done is onl' due to su%h &uidan%e and assistan%e

and 1 would not for&et to than5 them*

1 respe%t and than5( for &i)in& me an opportunit' to do the proe%t wor5 in B*


4/44

BHARAT HEA2Y ELECTRICALS LIMITED 3O2ER2IE1

B


5/44

1n all( orders for more than 8"" utilit' sets of thermal( h'dro( &as and nu%lear has

been pla%ed on the %ompan' as on date* The power plant equipment manufa%tured b'

B


6/44

%o,&eneration plants( DG power plants( industrial steam turbines( industrial boilers and

au;iliaries( waste heat re%o)er' boilers( &as turbines( heat e;%han&ers and pressure

)essels %entrifu&al %ompressors( ele%tri%al ma%hines( pumps( )al)es( seam less steel

tubes( ele%trostati% pre%ipitators fabri% filters( rea%tors( fluidiCed bed %ombustion boilers(

%hemi%al re%o)er' boilers and pro%ess %ontrols*

The %ompan' is a maor produ%er of lar&e siCe th'ristor de)i%es* 1t also supplies

di&ital distributed %ontrol s'stems for pro%ess industries and %ontrol and instrumentation

s'stems for power plant and industrial appli%ations* The %ompan' has %ommen%ed

manufa%ture lar&e desalination plants to help au&ment the suppl' of drin5in& water to

people*

Tran!/oraion

B


7/44

Rene4a.le Energy

Te%hnolo&ies that %an be offered b' B


8/44

Ta.le of conen!

!* +ro&rammable lo&i% %ontrollers /+340

i* +34 histor'

ii* 3adder lo&i% and arra's

iii* +34 pro&rammin&

i)* +34 operation

)* 4ase stud'

-* 4N4 s'stems

i* 1ntrodu%tion

ii* Elements of 4N4 ma%hine tool

iii* Output elements

i)* 4onfi&uration of a 4N4 s'stem

)* Elements of 4N4 ma%hine tool

#* Tools and te%hnolo&' used

i* 3adder lo&i%

ii* +ro%ess of Retrofittin&

7* Snapshots

?* 4on%lusion and future s%ope

.* Referen%es


9/44


10/44

Li! of fig$re!

!* A Simple Rela' 3a'outs and S%hemati%s

-* A Simple Rela' 4ontroller

#* A +34 1llustrated with Rela's

7* A Seal in 4ir%uit

?* A Simple 3adder 3o&i% Dia&ram

.* An E;ample of a nemoni% and Equi)alent 3adder 3o&i%

8* An E;ample of a Sequential un%tion 4hart

$* An E;ample of Stru%tured Tree +ro&ram

@* The Separation of 4ontroller and +ro%ess

!"* The S%an 4'%le of a +34


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CHAPTERS

INTRODUCTION TO PLC

4ontrol en&ineerin& has e)ol)ed o)er time* 1n the past humans were the main method for

%ontrollin& a s'stem* ore re%entl' ele%tri%it' has been used for %ontrol and earl'

ele%tri%al %ontrol was based on rela's* These rela's allow power to be swit%hed on and

off without a me%hani%al swit%h* 1t is %ommon to use rela's to ma5e simple lo&i%al

%ontrol de%isions* The de)elopment of low %ost %omputer has brou&ht the most re%ent

re)olution( the +ro&rammable 3o&i% 4ontroller /+340* The ad)ent of the +34 be&an in

the !@8"s( and has be%ome the most %ommon %hoi%e for manufa%turin& %ontrols*

+34s ha)e been &ainin& popularit' on the fa%tor' floor and will probabl' remain

predominant for some time to %ome* ost of this is be%ause of the ad)anta&es the' offer*

!* Reliable %omponents ma5e these li5el' to operate for 'ears before failure*

-* le;ible and %an be re,applied to %ontrol other s'stems qui%5l' and easil'

#* 4omputational abilities allow more sophisti%ated %ontrol*

7* Troubleshootin& aids ma5e pro&rammin& easier and redu%e downtime*

?* Reliable %omponents ma5e these li5el' to operate for 'ears before failure*

)6) LADDER LOGIC

3adder lo&i% is the main pro&rammin& method used for +34s* As mentioned

before( ladder lo&i% has been de)eloped to mimi% rela' lo&i%* The de%ision to use the

rela' lo&i% dia&rams was a strate&i% one* B' sele%tin& ladder lo&i% as the main

pro&rammin& method( the amount of retrainin& needed for en&ineers and tradespeople

was &reatl' redu%ed*

odern %ontrol s'stems still in%lude rela's( but these are rarel' used for lo&i%* A

rela' is a simple de)i%e that uses a ma&neti% field to %ontrol a swit%h( as pi%tured in

i&ure-*!* 6hen a )olta&e is applied to the input %oil( the resultin& %urrent %reates a


12/44

ma&neti% field* The ma&neti% field pulls a metal swit%h /or reed0 towards it and the

%onta%ts tou%h(%losin& the swit%h* The %onta%t that %loses when the %oil is ener&iCed is

%alled normall' open* The normall' %losed %onta%ts tou%h when the input %oil is not

ener&iCed* Rela's are normall' drawn in s%hemati% form usin& a %ir%le to represent the

input %oil* The output %onta%ts are shown with two parallel lines* Normall' open %onta%tsare shown as two lines( and will be open /non,%ondu%tin&0 when the input is not

ener&iCed* Normall' %losed %onta%ts are shown with two lines with a dia&onal line

throu&h them* 6hen the input %oil is not ener&iCed the normall' %losed %onta%ts will be

%losed /%ondu%tin&0*

1nput %oil

Normall'%losed

Normall'opened

or

or

Figure 1*Simple Relay Layouts and Schematics


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Rela's are used to let one power sour%e %lose a swit%h for another /often hi&h %ur,

rent0 power sour%e( while 5eepin& them isolated* An e;ample of a rela' in a simple

%ontrol appli%ation is shown in i&ure -* 1n this s'stem the first rela' on the left is used as

normall' %losed( and will allow %urrent to flow until a )olta&e is applied to the input A*

The se%ond rela' is normall' open and will not allow %urrent to flow until a )olta&e is

applied to the input B* 1f %urrent is flowin& throu&h the first two rela's then %urrent will

flow throu&h the %oil in the third rela'( and %lose the swit%h for output 4* This %ir%uit

would normall' be drawn in the ladder lo&i% form* This %an be read lo&i%all' as 4 will be

on if A is off and B is on*

1nput A

Normall' %losed

1nput BNormall' opened

1nput 4

Normall' open

3adder lo&i%

!!?)a%wall

lu

Figure 2 A simple relay controller


14/44

The e;ample in i&ure - does not show the entire %ontrol s'stem( but onl' the

lo&i%* 6hen we %onsider a +34 there are inputs( outputs( and the lo&i%* i&ure # shows a

more %omplete representation of the +34*


15/44

an' rela's also ha)e multiple outputs /throws0 and this allows an output rela' to

also be an input simultaneousl'* The %ir%uit shown in i&ure 7 is an e;ample of this( it is%alled a seal in %ir%uit* 1n this %ir%uit the %urrent %an flow throu&h either bran%h of the

%ir%uit( throu&h the %onta%ts labelled A or B* The input B will onl' be on when the output

B is on* 1f B is off( and A is ener&iCed( then B will turn on* 1f B turns on then the input B

will turn on( and 5eep output B on e)en if input A &oes off* After B is turned on the

output B will not turn off*

A

B

Note when A is pushed the output B will turn on and the input B alsoturn onand 5eep B on permanentl' until the power is remo)ed

The line on the ri&ht is bein& left off intentionall' and it is implied in

these dia&rams

Figure 4 A seal-in circuit


16/44

)6+ PROGRAMMING

The first +34s were pro&rammed with a te%hnique that was based on rela' lo&i%

wirin& s%hemati%s* This eliminated the need to tea%h the ele%tri%ians( te%hni%ians and en&i,

neers how to pro&ram a %omputer , but( this method has stu%5 and it is the most %ommon

te%hnique for pro&rammin& +34s toda'* An e;ample of ladder lo&i% %an be seen in i&ure

?* To interpret this dia&ram ima&ine that the power is on the )erti%al line on the left hand

side( we %all this the hot rail* On the ri&ht hand side is the neutral rail* 1n the fi&ure there

are two run&s( and on ea%h run& there are %ombinations of inputs /two )erti%al lines0 and

outputs /%ir%les0* 1f the inputs are opened or %losed in the ri&ht %ombination the power %an

flow from the hot rail( throu&h the inputs( to power the outputs( and finall' to the neutral

rail* An input %an %ome from a sensor( swit%h( or an' other t'pe of sensor* An output will

be some de)i%e outside the +34 that is swit%hed on or off( su%h as li&hts or motors* 1n thetop run& the %onta%ts are normall' open and normall' %losed* 6hi%h means if input A is on

and input B is off( then power will flow throu&h the output and a%ti)ate it* An' other %om,

The first +34s were pro&rammed with a te%hnique that was based on rela' lo&i%

wirin& s%hemati%s* This eliminated the need to tea%h the ele%tri%ians( te%hni%ians and en&i,

neers how to pro&ram a %omputer , but( this method has stu%5 and it is the most %ommon

te%hnique for pro&rammin& +34s toda'* An e;ample of ladder lo&i% %an be seen in i&ure

?* To inter ret this dia ram ima ine that the ower is on the )erti%al line on the left hand


17/44

The se%ond run& of i&ure ? is more %omple;( there are a%tuall' multiple %ombi,

nations of inputs that will result in the output K turnin& on* On the left most part of the

run&( power %ould flow throu&h the top if 4 is off and D is on* +ower %ould also /and

simultaneousl'0 flow throu&h the bottom if both E and are true* This would &et power

half wa' a%ross the run&( and then if G or < is true the power will be deli)ered to output

K* 1n later %hapters we will e;amine how to interpret and %onstru%t these dia&rams*

There are other methods for pro&rammin& +34s* One of the earliest te%hniques

in)ol)ed mnemoni% instru%tions* These instru%tions %an be deri)ed dire%tl' from the lad,

der lo&i% dia&rams and entered into the +34 throu&h a simple pro&rammin& terminal* An

e;ample of mnemoni%s is shown in i&ure .* 1n this e;ample the instru%tions are readone line at a time from top to bottom* The first line """"" has the instru%tion 3DN /input

load and not0 for input """"!* This will e;amine the input to the +34 and if it is off it

will remember a ! /or true0( if it is on it will remember a " /or false0* The ne;t line uses

an 3D /input load0 statement to loo5 at the input* 1f the input is off it remembers a "( if

the input is on it remembers a ! /note: this is the re)erse of the 3D0* The AND statement

re%alls the last two numbers remembered and if both are true the result is a !( otherwise

the result is a "* This result now repla%es the two numbers that were re%alled( and there is

onl' one number remembered* The pro%ess is repeated for lines """"# and """"7( but

when these are done there are now three numbers remembered* The oldest number is

from the AND( the newer numbers are from the two 3D instru%tions* The AND in line

""""? %ombines the results from the last 3D instru%tions and now there are two numbers

remembered* The OR instru%tion ta5es the two numbers now remainin& and if either one

is a ! the result is a !( otherwise the result is a "* This result repla%es the two numbers(

and there is now a sin&le number there* The last instru%tion is the ST /store output0 that

will loo5 at the last )alue stored and if it is !( the output will be turned on( if it is " the

output will be turned off*


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"""""

""""!

""""-

""""#

""""7

""""?

"""".

""""8

""""$

end

""""#

""""-

""""7

""!"8

Figure !" An eample o# mnemonic program

3DN

3D

AND

3D

3D

AND

OR

ST

END

""""!

""""-

""""#

""""7

""!"8

""""!


19/44

The ladder lo&i% pro&ram in i&ure .( is equi)alent to the mnemoni% pro&ram*

E)en if 'ou ha)e pro&rammed a +34 with ladder lo&i%( it will be %on)erted to mnemoni%

form before bein& used b' the +34* 1n the past mnemoni% pro&rammin& was the most

%ommon( but now it is un%ommon for users to e)en see mnemoni% pro&rams*

Sequential un%tion 4harts /S4s0 ha)e been de)eloped to a%%ommodate the pro,

&rammin& of more ad)an%ed s'stems* These are similar to flow%harts( but mu%h more

powerful* The e;ample seen in i&ure 8 is doin& two different thin&s* To read the %hart(

start at the top where is sa's start* Below this there is the double horiContal line that sa's

follow both paths* As a result the +34 will start to follow the bran%h on the left and ri&ht

hand sides separatel' and simultaneousl'* On the left there are two fun%tions the first one

is the power up fun%tion* This fun%tion will run until it de%ides it is done( and the power

down fun%tion will %ome after* On the ri&ht hand side is the flash fun%tion( this will run

until it is done* These fun%tions loo5 une;plained( but ea%h fun%tion( su%h as power up

will be a small ladder lo&i% pro&ram* This method is mu%h different from flow%harts

be%ause it does not ha)e to follow a sin&le path throu&h the flow%hart*

#igure $"se%uential #unction chart

E;e%utionfollows

multiple

+ower up

+ower down

Start

end

flash


20/44

Stru%tured Te;t pro&rammin& has been de)eloped as a more modern pro&rammin&

lan&ua&e* 1t is quite similar to lan&ua&es su%h as BAS14* A simple e;ample is shown in

i&ure $* This e;ample uses a +34 memor' lo%ation N8:"* This memor' lo%ation is for

an inte&er( as will be e;plained later in the boo5* The first line of the pro&ram sets the

)alue to "* The ne;t line be&ins a loop( and will be where the loop returns to* The ne;tline re%alls the )alue in lo%ation N8:"( adds ! to it and returns it to the same lo%ation* The

ne;t line %he%5s to see if the loop should quit* 1f N8:" is &reater than or equal to !"( then

the loop will quit( otherwise the %omputer will &o ba%5 up to the RE+EAT statement

%ontinue from there* Ea%h time the pro&ram &oes throu&h this loop N8:" will in%rease b'

! until the )alue rea%hes !"*

N8:" :L "M

RE+EAT

N8:" :L N8:" I !M

UNT13 N8:" L !"

ENDRE+EATM

An e;ample of stru%tured pro&ram

)67 PLC connecion!

6hen a pro%ess is %ontrolled b' a +34 it uses inputs from sensors to ma5e de%i,

sions and update outputs to dri)e a%tuators( as shown in i&ure @* The pro%ess is a real

pro%ess that will %han&e o)er time* A%tuators will dri)e the s'stem to new states /or

modes of operation0* This means that the %ontroller is limited b' the sensors a)ailable( if

an input is not a)ailable( the %ontroller will ha)e no wa' to dete%t a %ondition*

pro%ess

pl%

eedba%5 fromsensors=swit%hes

4onne%tions to a%tuators

#igure &"'he separation o# control and process


21/44

The %ontrol loop is a %ontinuous %'%le of the +34 readin& inputs( sol)in& the lad,

der lo&i%( and then %han&in& the outputs* 3i5e an' %omputer this does not happen

instantl'* i&ure !" shows the basi% operation %'%le of a +34* 6hen power is turned on

initiall' the +34 does a qui%5 sanit' %he%5 to ensure that the hardware is wor5in& prop,

erl'* 1f there is a problem the +34 will halt and indi%ate there is an error* or e;ample( ifthe +34 ba%5up batter' is low and power was lost( the memor' will be %orrupt and this

will result in a fault* 1f the +34 passes the sanit' %he%5 it will then s%an /read0 all the

inputs* After the inputs )alues are stored in memor' the ladder lo&i% will be s%anned

/sol)ed0 usin& the stored )alues , not the %urrent )alues* This is done to pre)ent lo&i%

problems when inputs %han&e durin& the ladder lo&i% s%an* 6hen the ladder lo&i% s%an is

%omplete the outputs will be s%anned /the output )alues will be %han&ed0* After this the

s'stem &oes ba%5 to do a sanit' %he%5( and the loop %ontinues indefinitel'* Unli5e normal

%omputers( the entire pro&ram will be run e)er' s%an* T'pi%al times for ea%h of the sta&es

is in the order of millise%onds*

Figure 1( "'he scan cycle o# plc


22/44

)68 LADDER LOGIC INPUTS

+34 inputs are easil' represented in ladder lo&i%* 1n the below i&ure there are

three t'pes of inputs shown* The first two are normall' open and normall' %losed inputs(

dis%ussed pre)iousl'* The 11T /1mmediate 1npuT0 fun%tion allows inputs to be read after

the input s%an( while the ladder lo&i% is bein& s%anned* This allows ladder lo&i% to

e;amine input )alues more often than on%e e)er' %'%le*

Ladder Logic )nputs

La""er Logic O$/$!

1n ladder lo&i% there are multiple t'pes of outputs( but these are not %onsistentl'

a)ailable on all +34s* Some of the outputs will be e;ternall' %onne%ted to de)i%es


23/44

outside the +34( but it is also possible to use internal memor' lo%ations in the +34*

Three t'pes of outputs are shown in below i&ure* The first is a normal output( when

ener&iCed the output will turn on( and ener&iCe an output* The %ir%le with a dia&onal line

throu&h is a normall' on output* 6hen ener&iCed the output will turn off* This t'pe of

output is not a)ailable on all +34 t'pes* 6hen initiall' ener&iCed the OSR /One ShotRela'0 instru%tion will turn on for one s%an( but then be off for all s%ans after( until it is

turned off* The 3 /lat%h0 and U /unlat%h0 instru%tions %an be used to lo%5 outputs on*

6hen an 3 output is ener&iCed the output will turn on indefinitel'( e)en when the output

%oil is de ener&iCed* The output %an onl' be turned off usin& a output* The last instru%tion

is the 1OT /1mmediate Output0 that will allow outputs to be updated without ha)in& to

wait for the ladder lo&i% s%an to be %ompleted*

Ladder logic outputs


24/44

)69 CASE STUDY%

+roblem: Tr' to de)elop a rela' based %ontroller

that will allow three swit%hes in a room to %ontrol a sin&le li&ht*

Solution: There are two possible approa%hes to this problem* The first assumes that an'

one of the swit%hes on will turn on the li&ht( but all three swit%hes must be off for the

li&ht to be off*

swit%h ! swit%h - swit%h #

li&ht

Swit%h !

li&ht

Swit%h -


25/44

The se%ond solution assumes that ea%h swit%h %an turn the li&ht on or off( re&ardless of

the states of the other swit%hes* This method is more %omple; and in)ol)es thin5in&

throu&h all of the possible %ombinations of swit%h positions* Kou mi&ht re%o&niCe

this problem as an e;%lusi)e or problem*




Swit%h #

Note: 1t is important to &et a %lear understandin& of how the %ontrols are e;pe%ted to

wor5* 1n this e;ample two radi%all' different solutions were obtained based upon a

simple differen%e in the operation*

*

li&ht


26/44

2. CNC Sy!e#!

:6) Inro"$cion

The 4N4 is a %omputer based ele%troni% equipment that re%ei)es %ommands in

di&ital form from perforated tape or other t'pes of input( as well as positional information

of %ertain elements of the ma%hine* The 4N4 interprets %ertain of these di&ital data as

requirements for new positions of the ma%hine elements and &i)es appropriate %ommands

of dire%tion and )elo%it'* The 4N4 also interprets %ertain other additional data as

%ommand of )elo%it'( of dis%rete fun%tions( of a%tions et%*

Numeri%al %ontrol /N40 is a method emplo'ed for %ontrollin& the motions of a

ma%hine tool slide and its au;iliar' fun%tions with an input in the form of numeri%al data*

A %omputer numeri%al %ontrol /4N40 is a mi%ropro%essor based s'stem to store and

pro%ess the data for the %ontrol of slide motions and au;iliar' fun%tions of the ma%hine

tools* The 4N4 s'stem is the heart and brain of a 4N4 ma%hine whi%h enable the

operation of the )arious ma%hine members su%h as a slides( spindles( et%* as per the

sequen%e pro&rammed into it( dependin& on the ma%hinin& operations*

The main ad)anta&e of a 4N4 s'stem lies in the fa%t that the s5ills of the operator

hitherto required in the operation of a %on)entional ma%hine is remo)ed and the part

produ%tion is made automati%*


27/44

The 4N4 s'stems are %onstru%ted with an N4 unit inte&rated with a

pro&rammable lo&i% %ontroller /+340 and sometimes with an additional e;ternal +34

/non,inte&rated0* The N4 %ontrols the spindle mo)ement and the speeds and feeds in

ma%hinin&* 1t %al%ulates the tra)ersin& paths of the a;es as defined b' the inputs* The

+34 %ontrols the peripheral a%tuatin& elements of the ma%hine su%h as solenoids( rela'

%oils( et%* 6or5in& to&ether( the N4 and +34 enable the ma%hine tool to operate

automati%all'*

Ele#en! of a CNC Machine Tool

1n a 4N4 ma%hine tool there are three maor &roups of elements

4ontrol and ele%troni%s

Ele%tri% dri)es /ele%trome%hani%al dri)es0

e%hani%al elements /table( Slide( tool holder( et%*0

1n addition( there %an be h'drauli% and pneumati% s'stems( whi%h are inte&rated with

the 4N4 ma%hine tool*

The primar' fun%tion of the dri)e is to %ause motion of the %ontrolled ma%hine

tool member /spindle( slide( et%*0 to %onform as %losel' as possible to the motion

%ommands issued b' the 4N4 s'stem*


28/44

1n order to maintain a %onstant material remo)al rate( the spindle and the tool

mo)ements ha)e to be %oordinated su%h that the spindle has a %onstant power and the

slide has a %onstant torque*

In/$ Ele#en!

So#e of he co##only e#/loye" in/$ ele#en! are /$!h;.$on< foo !4icher &MCB'

An 4B is a prote%ti)e de)i%e( whi%h will pro)ide both o)erload and short %ir%uit

prote%tion when %onne%ted in a %ir%uit*


30/44

spindle and whene)er this does not mat%h with the pro&rammed )alues( a %orre%ti)e

a%tion is ta5en*

S/ee" Conrol Uni

This unit a%ts in unison with the 4+U for the mo)ement of the ma%hine a;es* The 4+U

sends the %ontrol si&nals &enerated for the mo)ement of the a;is to the ser)o,%ontrol unit

and the ser)o,%ontrol unit %on)erts these si&nals into a suitable di&ital or analo& si&nal to

be fed to a ser)o,dri)er for ma%hine tool a;is mo)ement* This also %he%5s whether

ma%hine tool a;is mo)ement is at the same speed as dire%ted b' the 4+U*

Ser=o Conrol Uni

The de%oded position and )elo%it' %ontrol si&nals( &enerated b' the 4+U for the a;is

mo)ement forms the input to the ser)o,%ontrol unit* This unit in turn &enerates suitable

si&nals as %ommand )alues* The %ommand )alues are %on)erted b' the ser)o,dri)e unit

whi%h are interfa%ed with the a;es and the spindle motors*

The ser)o,%ontrol unit re%ei)es the position feedba%5 si&nals for the a%tual mo)ement of

the ma%hine tool a;es from the feedba%5 de)i%es /li5e linear s%ales( rotar' en%oders(

resol)ers( et%*0* The )elo%it' feedba%5 are &enerall' obtained throu&h ta%ho &enerators*

The feedba%5 si&nals are passed on to the 4+U for further pro%essin&* Thus( the ser)o,

%ontrol unit performs the data %ommuni%ation between the ma%hine tool and the 4+U*

The amount of mo)ement and the rate of mo)ement are %ontrolled b' the 4N4 s'stem*

Clo!e" Loo/ Sy!e#

The %losed loop s'stem is %hara%teriCed b' the presen%e of feedba%5* 1n this s'stem( the

4N4 s'stem sends out %ommands for mo)ement and the result is %ontinuousl' monitored


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b' the s'stem throu&h )arious feedba%5 de)i%es* There are &enerall' two t'pes of

feedba%5 to a 4N4 s'stem,position feedba%5 and )elo%it' feedba%5*

O/en Loo/ Sy!e#

The open loop s'stem la%5s feedba%5* 1n this s'stem( the 4N4 s'stem sends out si&nals

for mo)ement but does not %he%5 whether a%tual mo)ement is ta5in& pla%e or not*

Stepper motors are used for a%tual mo)ement and the ele%troni%s of these stepper motors

is run on di&ital pulses from the 4N4 s'stem*

O/eraor Conrol Panel

The operator %ontrol panel pro)ides the user interfa%e to fa%ilitate a two,wa'

%ommuni%ation between the user( 4N4 s'stem and the ma%hine tool* The %onsists of two

parts:

ideo displa' unit

9e'board

2i"eo Di!/lay Uni &2DU'

The DU displa's the status of the )arious parameters of the 4N4 s'stem and the

ma%hine tool* 1t displa's all %urrent information su%h as:

4omplete information on the blo%5 %urrentl' bein& e;e%uted a%tual position )alues(

set or a%tual differen%e( %urrent feed rate( spindle speed

A%tual position )alue( set or a%tual differen%e( %urrent feed rate( spindle speed*

A%ti)e G fun%tions( mis%ellaneous fun%tions


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ain pro&ram number( subroutine number

Displa' of all entered data( user pro&rams( user data( ma%hine data( et%*

Alarm messa&es in plain te;t

Soft 5e' desi&nations*

0ey.oar"

A 5e'board is pro)ided for the followin& purposes:

Editin& of part pro&rams( tool data( ma%hine parameters*

Sele%tion of different pa&es for )iewin&*

Sele%tion of operatin& modes( e*&*( manual data input( o&( et%*

Sele%tion of feed rate o)erride and spindle speed o)erride

E;e%ution of part pro&rams

E;e%ution of other tool fun%tions

Machine Conrol Panel &MCP'

1t is the dire%t interfa%e between the operator and the N4 s'stem( enablin& the operation

of the ma%hine throu&h the 4N4 s'stem*

Durin& pro&ram e;e%ution( the 4N4 %ontrols the a;is motion( spindle fun%tion or tool

fun%tion on a ma%hine tool( dependin& upon the part pro&ram stored in the memor'* +rior

to the startin& of the ma%hinin& pro%ess( ma%hine should first be prepared with some

spe%ifi% tas5s li5e(

Establishin& a %orre%t referen%e point

3oadin& the s'stem memor' with the required part pro&ram

3oadin& and %he%5in& of tool offsets( Cero offsets( et%*


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Mo"e! of O/eraion

+reset mode

anual data input /D10 mode

Automati% mode

Referen%e point mode

o& mode

1n%remental mode

De!ign of #o"ern CNC M?CS

The desi&n F %onstru%tion of %omputer numeri%all' %ontrolled /4N40 m=%s differs

&reatl' from that of %on)entional m=% tools*

1mportant parts and aspe%ts of 4N4 m=%Hs to be %onsidered in their desi&nin& :

/a0 =4 stru%ture

/b0 Guide wa's

/%0 eed dri)es

/d0 Spindle F spindle bearin&s

/e0 4ontrollers( software F operator interfa%e

/f0 easurin& instruments

/&0 Gau&in&

/h0 Tool monitorin&

(a) M/c Structure:

The =% stru%ture is the load %arr'in& F supportin& member of the =% tool* All themotors( dri)e me%hanism F other fun%tional assemblies of ma%hines tools are


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ali&ned to ea%h other F ri&idl' fi;ed to the =% stru%ture* The =% stru%ture issube%ted to stati% of d'nami% for%es F it is( therefore( essential that the stru%ture

does not deform or )ibrate be'ond the permissible limits under the a%tion of these

for%es*

(b) Guide ways:Guide wa's are used in =% tools to:

i0 4ontrol the dire%tions or lines of a%tion of the %arria&e or the table on whi%h a

tool or a wor5 pie%e is held*

ii0 To absorb all the stati% F d'nami% for%es*

(c) eed Dri!es:

On a 4N4 =% the fun%tion of feed dri)es is to %ause motion of the slides as per the

motion %ommands* Sin%e the de&ree of a%%ura%' requirement is hi&h( the feed dri)eshould ha)e hi&h effi%ien%' F response* The fed dri)e %onsists of /a0 ser)omotor/b0 e%hani%al transmission s'stem*

(d) Spindle / Spindle "earings:

aterial remo)al usin& sin&le point or multi point wor5 pie%e requires rotationalspeeds of the order of #",.""" rpm and e)en hi&her* All wor5 or tool %arr'in&

spindles rotatin& at these speeds are sube%ted torsional and radial defle%tions* The'

are also sube%ted to thrust for%es dependin& on the nature of the metal %uttin&operation bein& performed* To intorsional strain on the spindles the' are desi&ned to

be as stiff as possible with a minimum o)er han&* Also( the final dri)e to the spindleshould be lo%ated as near as possible the bearin&s*

(e) Gauging:

Gau&in& on a =% tool is basi%all' used for wor5 pie%e inspe%tion( for definin& tool

off,sets F for tool brea5in& dete%tion*

(f) #ool monitoring systems:

A tool monitorin& s'stem monitors the tool wear F tool brea5a&e*

(g) Controls$ Software % &ser 'nterface:

4N4 %ontrols are the heart of the 4N4 =4s* The earl' 4N4 %ontrols werede)eloped for simple appli%ations in turnin&( ma%hinin& %entres F &rindin&*

The new &eneration %omputer numeri%al %ontrols allow simulations %ontrol of

more a;es( interpolate positions faster( and use more data points for pre%ise %ontrol*


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These pro%essors perform multi tas5s run one pro&rammin& F simulatin& a se%ond whi%h ma;imiCes the =% use*

() Measuring systems:

On all 4N4 =%( an ele%troni% measurin& s'stem is emplo'ed on ea%h %ontrolled

a;is to monitor the mo)ement F to %ompare the position of the slide F the spindlewith the desired position*

easurin& s'stems are used on 4N4 =%s for:

/i0 onitorin& the positionin& of a slide on a slide wa'*

/ii0 Orientin& the spindle table F measurin& the speed of the spindle*

#urning Centre De!elopments


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3esser floor spa%e

1n%reased operational safet'

a%hinin& of ad)an%ed materials

Elimination of operator errors

le;ibilit' in %han&es of %omponent desi&n

Redu%ed inspe%tion

A%%urate %ostin& and s%hedulin&


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Tool! an" Technology U!e"

La""er Logic

La""er logichas e)ol)ed into a pro&rammin& lan&ua&e that represents a pro&ram b' a

&raphi%al dia&ram based on the %ir%uit dia&rams of rela' lo&i% hardware* 3adder lo&i% is

used to de)elop software for pro&rammable lo&i% %ontrollers /+34s0 used in industrial

%ontrol appli%ations* The name is based on the obser)ation that pro&rams in this lan&ua&e

resemble ladders( with two )erti%al rails and a series of horiContal run&s between them*

3adder lo&i% is widel' used to pro&ram +34s( where sequential %ontrol of a pro%ess or

manufa%turin& operation is required* 3adder lo&i% is useful for simple but %riti%al %ontrol

s'stems or for rewor5in& old hardwired rela' %ir%uits* As pro&rammable lo&i% %ontrollers

be%ame more sophisti%ated it has also been used in )er' %omple; automation s'stems*

Rerofiing

Rerofiingrefers to the addition of new te%hnolo&' or features to older s'stems*

power plant retrofit( impro)in& power plant effi%ien%' = in%reasin& output =

redu%in& emissions

home ener&' retrofit( the impro)in& of e;istin& buildin&s with ener&' effi%ien%'

equipment

seismi% retrofit( the pro%ess of stren&thenin& older buildin&s in order to ma5e

them earthqua5e resistant


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Sna/!ho!

!* 4N4 s'stem After retrofittin&

-* 4N4 s'stem before retrofittin&


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#* 4N4 s'stem

7*+34


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Concl$!ion

This report has dis%ussed the role that pro&rammable lo&i% %ontrollers ha)e in the

effi%ient desi&n and %ontrol of me%hani%al pro%esses* Also dis%ussed about the

understandin& 4N4 S'stems and the operation of it* inall'( the report has dis%ussed

rela' lo&i% and the e)olution that ladder lo&i% made from it*

!* +ro&rammable 3o&i%


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CNC

The ma%hine that we ha)e retrofitted is ust an e;ample of preliminar' retrofittin&

5eepin& in mind the use and the %osts in%urred* There is a hu&e s%ope for further

impro)ements in the ma%hine* These %an be listed as below:

A multi station tool turret %an be in%orporated in the e;istin& 4N4 ma%hine*

Automati% 4lampin& me%hanism %an be installed /Draw bar e%hanism0*

Automati% Tool 4han&in& /AT40 de)i%es usin& Roboti% Arm Te%hnolo&'*

Automati% +allet 4han&er /A+40 for automati% wor5 pie%e %han&in&*

A 4hip 4on)e'or %an be in%orporated for eas' and hassle free disposal of %hips*


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Reference!

!* http:==en*wi5ipedia*or&=wi5i=Retrofittin&

-* http:==en*wi5ipedia*or&=wi5i=3adderlo&i%

#* http:==web*bhelh'd*%o*in


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plc and cnc machines

Documents