1GENERAL1.1TOOLMOVEMENTALONGWORKPIECEPARTS

FIGURE-INTERPOLATION1.2FEEDFUNCTION1.3PARTDRAWINGANDTOOLMOVEMENT1.4CUTTINGSPEED-SPINDLESPEEDFUNCTION1.5SELECTIONOFTOOLUSEDFORVARIOUS

MACHINING-TOOLFUNCTION1.6COMMANDFORMACHINEOPERATIONS-

MISCELLANEOUSFUNCTION1.7PROGRAMCONFIGURATION1.8TOOLFIGUREANDTOOLMOTIONBYPROGRAM1.9TOOLMOVEMENTRANGE-STROKE1.1TOOLMOVEMENTALONGWORKPIECEPARTSFIGURE-INTERPOLATION

Thetoolmovesalongstraightlinesandarcsconstitutingtheworkpiecepartsfigure.Explanations

Thefunctionofmovingthetoolalongstraightlinesandarcsiscalledtheinterpolation.·ToolmovementalongastraightlineFig.1.1(a)Toolmovementalongastraightline·

ToolmovementalonganarcFig.1.1(b)Toolmovementalonganarc

SymbolsoftheprogrammedcommandsG01,G02,…arecalledthepreparatoryfunctionandspecifythetypeofinterpolationconductedinthecontrolunit.Fig.1.1(c)InterpolationfunctionNOTE

Somemachinesmovetablesinsteadoftoolsbutthisbookassumesthattoolsaremovedagainstworkpieces.

1.2FEEDFUNCTION

Movementofthetoolataspecifiedspeedforcuttingaworkpieceiscalledthefeed.Fig.1.2Feedfunction

Feedratescanbespecifiedbyusingactualnumerics.Forexample,tofeedthetoolatarateof150mm/min,specifythefollowingintheprogram:

F150.0

Thefunctionofdecidingthefeedrateiscalledthefeedfunction.1.3PARTDRAWINGANDTOOLMOVEMENT1.3.1ReferencePosition(Machine-SpecificPosition)

ACNCmachinetoolisprovidedwithafixedposition.Normally,toolchangeandprogrammingofabsolutezeropointasdescribedlaterareperformedatthisposition.Thispositioniscalledthereferenceposition.Fig.1.3(a)Referenceposition

Explanations

Thetoolcanbemovedtothereferencepositionintwoways:

(i)Manualreferencepositionreturn.

Referencepositionreturnisperformedbymanualbuttonoperation.

(ii)Automaticreferencepositionreturn.

Ingeneral,manualreferencepositionreturnisperformedfirstafterthepoweristurnedon.Inordertomovethetooltothereferencepositionfortoolchangethereafter,thefunctionofautomaticreferencepositionreturnisused.1.3.2

CoordinateSystemonPartDrawing

andCoordinate

SystemSpecified

byCNC-CoordinateSystemFig.1.3(b)CoordinatesystemExplanations

·Coordinatesystem

Thefollowingtwocoordinatesystemsarespecifiedatdifferentlocations:

(i)Coordinatesystemonpartdrawing.

Thecoordinatesystemiswrittenonthepartdrawing.Astheprogramdata,thecoordinatevaluesonthiscoordinatesystemareused.

(ii)CoordinatesystemspecifiedbytheCNC.

Thecoordinatesystemispreparedontheactualmachinetooltable.

Thiscanbeachievedbyprogrammingthedistancefromthecurrentpositionofthetooltothezeropointofthecoordinatesystemtobeset.Fig.1.3(c)CoordinatesystemspecifiedbytheCNC

Thepositionalrelationbetweenthesetwocoordinatesystemsisdeterminedwhenaworkpieceissetonthetable.Fig.1.3(d)CoordinatesystemspecifiedbyCNCandcoordinatesystemonpartdrawing

ThetoolmovesonthecoordinatesystemspecifiedbytheCNCinaccordancewiththecommandprogramgeneratedwithrespecttothecoordinatesystemonthepartdrawing,andcutsaworkpieceintoashapeonthedrawing.

Therefore,inordertocorrectlycuttheworkpieceasspecifiedonthedrawing,thetwocoordinatesystemsmustbesetatthesameposition.

·Methodsofsettingthetwocoordinatesystemsinthesameposition

Tosetthetwocoordinatesystemsatthesameposition,simplemethodsshallbeusedaccordingtoworkpieceshape,thenumberofmachinings.

(i)Usingastandardplaneandpointoftheworkpiece.Fig.1.3(e)Setthecoordinatesystemsbyusingastandardplane(ii)Mountingaworkpiecedirectlyagainstthejig.Fig.1.3(f)Mountingaworkpiecedirectlyagainstthejig

(iii)Mountingaworkpieceonapallet,thenmountingtheworkpieceandpalletonthejig.Fig.1.3(g)Mountingaworkpiece1.3.3HowtoIndicateCommandDimensionsforMovingthe

Tool-Absolute,IncrementalCommands

Explanations

Commandformovingthetoolcanbeindicatedbyabsolutecommandorincrementalcommand.

·Absolutecommand

Thetoolmovestoapointat“thedistancefromzeropointofthecoordinatesystem”thatistothepositionoftheoordinatevalues.Fig.1.3(h)Absolutecommand·Incrementalcommand

Specifythedistancefromtheprevioustoolpositiontothenexttoolposition.Fig.1.3(i)Incrementalcommand1.4CUTTINGSPEED-SPINDLESPEEDFUNCTION

Thespeedofthetoolwithrespecttotheworkpiecewhentheworkpieceiscutiscalledthecuttingspeed.

AsfortheCNC,thecuttingspeedcanbespecifiedbythespindlespeedinrpmunit.Fig.1.4Thecuttingspeed

Examples

Whenaworkpieceshouldbemachinedwithatoolof100mmindiameteratacuttingspeedof80m/min,thespindlespeedisapproximately250rpm,whichisobtainedfromN=1000V/πD.Hencethefollowingcommandisrequired:

S250;

Commandsrelatedtothespindlespeedarecalledthespindlespeedfunction.1.5

SELECTIONOFTOOLUSEDFORVARIOUSMACHINING-TOOLFUNCTION

Whendrilling,tapping,boring,millingorthelike,isperformed,itisnecessarytoselectasuitabletool.Whenanumberisassignedtoeachtoolandthenumberisspecifiedintheprogram,thecorrespondingtoolisselected.Fig.1.5TheATCmagazine

Examples

WhenNo.01isassignedtoadrillingtool.

Whenthetoolisstoredatlocation01intheATCmagazine,thetoolcanbeselectedbyspecifyingT01.Thisiscalledthetoolfunction.1.6

COMMANDFORMACHINEOPERATIONS-MISCELLANEOUSFUNCTION

Whenmachiningisactuallystarted,itisnecessarytorotatethespindle,andfeedcoolant.Forthispurpose,onoffoperationsofspindlemotorandcoolantvalveshouldbecontrolled.Fig.1.6Themiscellaneousfunction

Thefunctionofspecifyingtheonoffoperationsofthecomponentsofthemachineiscalledthemiscellaneousfunction.Ingeneral,thefunctionisspecifiedbyanMcode.

Forexample,whenM03isspecified,thespindleisrotatedclockwiseatthespecifiedspindlespeed.1.7PROGRAMCONFIGURATION

AgroupofcommandsgiventotheCNCforoperatingthemachineiscalledtheprogram.Byspecifyingthecommands,thetoolismovedalongastraightlineoranarc,orthespindlemotoristurnedonandoff.

IntheprograminFig.1.7(a),itsfunctionistospecifythecommandsinthesequenceofactualtoolmovements.Fig.1.7(a)Programconfiguration

Agroupofcommandsateachstepofthesequenceiscalledtheblock.

Theprogramconsistsofagroupofblocksforaseriesofmachining.Thenumberfordiscriminatingeachblockiscalledthesequencenumber,andthenumberfordiscriminatingeachprogramiscalledtheprogramnumber.Explanations

Theblockandtheprogramhavethefollowingconfigurations.·BlockFig.1.7(b)Blockconfiguration

Ablockstartswithasequencenumbertoidentifytheblockandendswithanendofblockcode.

ThismanualindicatestheendofblockcodebyLFintheISOcodeandCRintheEIAcode.·ProgramFig.1.7(c)Programconfiguration

Normally,aprogramnumberisspecifiedaftertheendofblock(;)codeatthebeginningoftheprogram,andaprogramendcode(M02orM30)isspecifiedattheendoftheprogram.·Mainprogramandsubprogram

Whenmachiningofthesamepatternappearsatmanyportionsofaprogram,aprogramforthepatterniscreated.Thisiscalledthesubprogram.Ontheotherhand,theoriginalprogramiscalledthemainprogram.Whenasubprogramexecutioncommandappearsduringexecutionofthemainprogram,commandsofthesubprogramareexecuted.Whenexecutionofthesubprogramisfinished,thesequencereturnstothemainprogram.Fig.1.7(d)MainprogramandsubprogramFig.1.7(e)Thesamepatternappears1.8TOOLFIGUREANDTOOL

MOTIONBYPROGRAM

Explanations·Machiningusingtheendofcutter-Toollengthcompensationfunction

Usually,severaltoolsareusedformachiningoneworkpiece.Thetoolshavedifferenttoollength.Itisverytroublesometochangetheprograminaccordancewiththetools.

Therefore,thelengthofeachtoolusedshouldbemeasuredinadvance.BysettingthedifferencebetweenthelengthofthestandardtoolandthelengthofeachtoolintheCNC(DataDisplayandSetting:seeoperation),machiningcanbeperformedwithoutalteringtheprogramevenwhenthetoolischanged.Thisfunctioniscalledtoollengthcompensation.Fig.1.8(a)Toollengthcompensationfunction·Machiningusingthesideofcutter-Cuttercompensationfunction

Becauseacutter