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CNC

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  1. 1. Computer Numerical Control (CNC) Page(1( Objectives: To(understand(the(working(principle(and(applications(of(CNC(machinesU( To( be( able( to( prepare( CNC( part( programmes( for( machining( 2VD( workpiecesU( Content: Chapter(1( Numerical(Control(Fundamentals( Chapter(2( CNC(Part(Programming( Introduction Computer( Numerical( Control( qCNC'( is( a( specialized( and( versatile( form( of( Soft( Automation( and( its( applications( cover( many( kindsM( although( it( was( initially( developed(to(control(the(motion(and(operation(of(machine(toolsU( Computer( Numerical( Control( may( be( considered( to( be( a( means( of( operating( a( machine(through(the(use(of(discrete(numerical(values(fed(into(the(machineM(where( the(required(,input,(technical(information(is(stored(on(a(kind(of(input(media(such( as( floppy( diskM( hard( diskM( CD( ROMM( DVDM( USB( flash( driveM( or( RAM( card( etcU( The( machine( follows( a( predetermined( sequence( of( machining( operations( at( the( predetermined(speeds(necessary(to(produce(a(workpiece(of(the(right(shape(and( size(and(thus(according(to(completely(predictable(resultsU(A(different(product(can( be( produced( through( reprogramming( and( a( lowVquantity( production( run( of( different(products(is(justifiedU( CCoommppuutteerr(NNuummeerriiccaall( CCoonnttrrooll(qqCCNNCC''(
  2. 2. Computer Numerical Control (CNC) Pagef2f Figk1,1f CNCfMachinefCentreffASPINNERfVC65xw ThefdefinitionfoffCNCfgivenfbyfElectronicfIndustryfAssociationfAEIAwfisfasffollows:f A system in which actions are controlled by the direct insertion of numerical data at some point. The system must automatically interpret at least some portion of this data. InfafsimplefwordpfafCNCfsystemfreceivesfnumericalfdatapfinterpretfthefdatafandf thenfcontrolfthefactionfaccordinglykf Chapter 1. Computer Numerical Control Fundamentals Objectives: TofunderstandfthefworkingfprinciplefoffCNCfmachineskf Tofunderstandfthefcharacteristicsfoffthefdrivingfsystemskf Tofunderstandfthefcharacteristicsfofftheffeedbackfdeviceskf TofunderstandfthefapplicationsfoffCNCfmachineskf 1.1 Control Systems 1.1.1 Open Loop Systems Openfloopfsystemsfhavefnofaccessftofthefrealftimefdatafaboutfthefperformancefoff thefsystemfandfthereforefnofimmediatefcorrectivefactionfcanfbeftakenfinfcasefoff systemf disturbancekf Thisf systemf isf normallyf appliedf onlyf tof thef casef wheref thef outputf isf almostf constantf andf predictablekf Thereforepf anf openf loopf systemf isf unlikelyftofbefusedftofcontrolfmachineftoolsfsincefthefcuttingfforcefandfloadingfoff afmachineftoolfisfneverfafconstantkfThefonlyfexceptionfisfthefwirecutfmachinefforf whichfsomefmachineftoolfbuildersfstillfpreferftofusefanfopenfloopfsystemfbecausef therefisfvirtuallyfnofcuttingfforcefinfwirecutfmachiningkf
  3. 3. Computer Numerical Control (CNC) PageI3I Fig6UA2TajI BlockIDiagramIofIanIOpenILoopISystemI 1.1.2 Close Loop Systems InI aI closeI loopI systemCI feedI backI devicesI closelyI monitorI theI outputI andI anyI disturbanceIwillIbeIcorrectedIinItheIfirstIinstance6IThereforeIhighIsystemIaccuracyI isIachievable6IThisIsystemIisImoreIpowerfulIthanItheIopenIloopIsystemIandIcanIbeI appliedItoItheIcaseIwhereItheIoutputIisIsubjectedItoIfrequentIchange6INowadaysCI almostIallICNCImachinesIuseIthisIcontrolIsystem6I Fig6UA2TbjI BlockIDiagramIofIaICloseILoopISystemI 1.2 Elements of a CNC System AICNCIsystemIconsistsIofItheIfollowingI6ImajorIelements:I a6I InputIDeviceI b6I MachineIControlIUnitI c6I MachineIToolI d6I DrivingISystemI e6I FeedbackIDevicesI f6I DisplayIUnitI
  4. 4. Computer Numerical Control (CNC) Paget4t FigS1U3t WorkingtPrinciplestoftCNCtMachinest 1.2.1 Input Devices aStFloppytDisktDrivet FloppytdisktistatsmalltmagnetictstoragetdevicetfortCNCtdatatinputStItthastbeentthet mostt commont storaget mediat upt tot thet 197Asxt int termst oft datat transfert speedxt reliabilityxt storaget sizext datat handlingt andt thet abilityt tot readt andt writeSt Furthermorextthetdatatwithintatfloppytcouldtbeteasilyteditedtattanytpointtastlongt astyouthavetthetpropertprogramttotreadtitStHoweverxtthistmethodthastproventtotbet quitet problematict int thet longt runt ast floppiest havet at tendencyt tot degradet alarminglytfasttandtaretsensitivettotlargetmagnetictfieldstandtastwelltastthetdustt andtscratchestthattusuallytexistedtontthetshoptfloorSt FigS1U4t FloppytDisktDrivetontatCNCtmachinet bStUSBtFlashtDrivet AtUSBtflashtdrivetistatremovabletandtrewritabletportablethardtdrivetwithtcompactt sizetandtbiggertstoragetsizetthantatfloppytdiskStDatatstoredtinsidetthetflashtdrivet
  5. 5. Computer Numerical Control (CNC) PageC)C areCimperviousCtoCdustCandCscratchesCthatCenableCflashCdrivesCtoCtransferCdataCfromC placeCtoCplace6CInCrecentCyears3CallCcomputersCsupportCUSBCflashCdrivesCtoCreadCandC writeCdataCthatCmakeCitCbecomeCmoreCandCmoreCpopularCinCCNCCmachineCcontrolC unit6C Fig68M)C USBCFlashCDriveConCaCCNCCmachineC c6CSerialCcommunicationC TheC dataC transferC betweenC aC computerC andC aC CNCC machineC toolC isC oftenC accomplishedC throughC aC serialC communicationC port6C InternationalC standardsC forC serialCcommunicationsCareCestablishedCsoCthatCinformationCcanCbeCexchangedCinCanC orderlyCway6CTheCmostCcommonCinterfaceCbetweenCcomputersCandCCNCCmachineC toolsCisCreferredCtoCtheCEIACStandardCRSM0:06C MostCofCtheCpersonalCcomputersCandC CNCCmachineCtoolsChaveCbuiltCinCRS0:0CportCandCaCstandardCRSM0:0CcableCisCusedC toC connectC aC CNCC machineC toC aC computerC whichC enablesC theC dataC transferC inC reliableCway6C PartCprogramsCcanCbeCdownloadedCintoCtheCmemoryCofCaCmachineC toolC orC uploadedC toC theC computerC forC temporaryC storageC byC runningC aC communicationCprogramConCtheCcomputerCandCsettingCupCtheCmachineCcontrolCtoC interactCwithCtheCcommunicationCsoftware6C Fig68M6C SerialCcommunicationCportConCaCCNCCmachineC DirectCNumericalCControlCisCreferredCtoCaCsystemCconnectingCaCsetCofCnumericallyC controlledCmachinesCtoCaCcommonCmemoryCforCpartCprogramCorCmachineCprogramC storageCwithCprovisionCforConMdemandCdistributionCofCdataCtoCtheCmachines6CEISOC 08O6:898OACTheCNCCpartCprogramCisCdownloadedCaCblockCorCaCsectionCatCaCtimeCintoC
  6. 6. Computer Numerical Control (CNC) PageD6D theD controller-D OnceD theD downloadedD sectionD isD executedkD theD sectionD willD beD discardedD toD leaveD roomD forD otherD sections-D ThisD methodD isD commonlyD usedD forD machineDtoolsDthatDdoDnotDhaveDenoughDmemoryDorDstorageDbufferDforDlargeDNCD partDprograms-D DistributedD NumericalD ControlD isD aD hierarchicalD systemD forD distributingD dataD betweenDaDproductionDmanagementDcomputerDandDNCDsystems-D1ISODM876:E99A9D TheD hostD computerD isD linkedD withD aD numberD ofD CNCD machinesD orD computersD connectingD toD theD CNCD machinesD forD downloadingD partD programs-D TheD communicationDprogramDinDtheDhostDcomputerDcanDutilizeDtwozwayDdataDtransferD featuresDforDproductionDdataDcommunicationDincluding:DproductionDschedulekDpartsD producedDandDmachineDutilizationDetc-D Fig-Ez7D SerialDcommunicationDinDaDDistributedDNumericalDControlDsystemD d-DEthernetDcommunicationD DueDtoDtheDadvancementDofDtheDcomputerDtechnologyDandDtheDdrasticDreductionDofD theDcostDofDtheDcomputerkDitDisDbecomingDmoreDpracticalDandDeconomicDtoDtransferD partD programmesD betweenD computersD andD CNCD machinesD viaD anD EthernetD communicationDcable-DThisDmediaDprovidesDaDmoreDefficientDandDreliableDmeansDinD partDprogrammeDtransmissionDandDstorage-DMostDcompaniesDnowDbuiltDaDLocalDAreaD NetworkD1LAN9DasDtheirDinfrastructure-DMoreDandDmoreDCNCDmachineDtoolsDprovideD anDoptionDofDtheDEthernetDCardDforDdirectDcommunicationDwithinDtheDLAN-D
  7. 7. Computer Numerical Control (CNC) Pagel7l Fig.1-8l EthernetlportlonlalCNClmachinel Fig.1-9l EthernetlnetworklinlalDistributedlNumericallControllsysteml e.lConversationallProgrammingl Partl programmesl canl bel inputl tol thel controllerl vial thel keyboard.l Built-inl intelligentlsoftwarelinsidelthelcontrollerlenablesltheloperatorltolenterlthelrequiredl datal stepl byl step.l Thisl isl al veryl efficientl wayl forl preparingl programmesl forl relativelylsimplelworkpieceslinvolvinglupltol2½laxislmachining.l Fig.1-10l ConversationallProgramminglinlalCNClcontrollerl
  8. 8. Computer Numerical Control (CNC) Paged8d 1.2.2 Machine Control Unit (MCU) ThedmachinedcontroldunitdisdthedheartdofdthedCNCdsystem1dTheredaredtwodsub;unitsd indthedmachinedcontroldunit:dthedDatadProcessingdUnitd/DPUFdanddthedControldLoopd Unitd/CLUF1d a1dDatadProcessingdUnitd OndreceivingdadpartdprogrammeEdthedDPUdfirstlydinterpretsdanddencodesdthedpartd programmed intod internald machined codes1d Thed interpolatord ofd thed DPUd thend calculatedthedintermediatedpositionsdofdthedmotiondindtermsdofdBLUd/basicdlengthd unitFdwhichdisdthedsmallestdunitdlengthdthatdcandbedhandleddbydthedcontroller1dThed calculatedddatadaredpasseddtodCLUdfordfurtherdaction1d b1dControldLoopdUnitd TheddatadfromdthedDPUdaredconverteddintodelectricaldsignalsdindthedCLUdtodcontrold thed drivingd systemd tod performd thed requiredd motions1d Otherd functionsd suchd asd machinedspindledONSOFFEdcoolantdONSOFFEdtooldclampdONSOFFdaredalsodcontrolledd bydthisdunitdaccordingdtodthedinternaldmachinedcodes1d 1.2.3 Machine Tool Thisd cand bed anyd typed ofd machined toold ord equipment1d Ind orderd tod obtaind highd accuracyd andd repeatabilityEd thed designd andd maked ofd thed machined slided andd thed drivingdleadscrewdofdadCNCdmachinedisdofdvitaldimportance1dThedslidesdaredusuallyd machineddtodhighdaccuracydanddcoateddwithdanti;frictiondmaterialdsuchdasdPTFEdandd Turcited ind orderd tod reduced thed stickd andd slipd phenomenon1d Larged diameterd recirculatingdballdscrewsdaredemployeddtodeliminatedthedbacklashdanddlostdmotion1d Otherddesigndfeaturesdsuchdasdrigiddanddheavydmachinedstructure;dshortdmachined tabled overhangEd quickd changed toolingd systemEd etcd alsod contributed tod thed highd accuracydanddhighdrepeatabilitydofdCNCdmachines1d Fig11;11/aFd BalldScrewdindadCNCdmachined Fig11;11/bFd Balldscrewdstructured
  9. 9. Computer Numerical Control (CNC) PageS9S 1.2.4 Driving System TheSdrivingSsystemSisSanSimportantScomponentSofSaSCNCSmachineSasStheSaccuracyS andSrepeatabilitySdependSverySmuchSonStheScharacteristicsSandSperformanceSofStheS drivingS system.S TheS requirementS isS thatS theS drivingS systemS hasS toS responseS accuratelyS accordingS toS theS programmedS instructions.S ThisS systemS usuallyS usesS electricSmotorsSalthoughShydraulicSmotorsSareSsometimesSusedSforSlargeSmachineS tools.STheSmotorSisScoupledSeitherSdirectlySorSthroughSaSgearSboxStoStheSmachineS leadscrewS toS movesS theS machineS slideS orS theS spindle.S ThreeS typesS ofS electricalS motorsSareScommonlySused.S a.SDCSServoSMotorS ThisSisStheSmostScommonStypeSofSfeedSmotorsSusedSinSCNCSmachines.STheSprincipleS ofS operationS isS basedSonS theS rotationS ofS anS armatureS windingS inS aS permanentlyS energisedS magneticS field.S TheS armatureS windingS isS connectedS toS aS commutator)S whichSisSaScylinderSofSinsulatedScopperSsegmentsSmountedSonStheSshaft.SDCScurrentS isSpassedStoStheScommutatorSthroughScarbonSbrushes)SwhichSareSconnectedStoStheS machineS terminals.S TheS changeS ofS theS motorS speedS isS byS varyingS theS armatureS voltageS andS theS controlS ofS motorS torqueS isS achievedS byS controllingS theS motor1sS armatureS current.S InS orderS toS achieveS theS necessaryS dynamicS behaviourS itS isS operatedSinSaSclosedSloopSsystemSequippedSwithSsensorsStoSobtainStheSvelocitySandS positionSfeedbackSsignals.S Fig.1312S DCSServoSMotorS-CourtesySofSFlexibleSAutomation2S b.SACSServoSMotorS InS anS ACS servomotor)S theS rotorS isS aS permanentS magnetS whileS theS statorS isS equippedSwithS33phaseSwindings.STheSspeedSofStheSrotorSisSequalStoStheSrotationalS frequencySofStheSmagneticSfieldSofStheSstator)SwhichSisSregulatedSbyStheSfrequencyS converter.S ACSmotorsSareSgraduallySreplacingSDCSservomotors.STheSmainSreasonSisSthatSthereS isSnoScommutatorSorSbrushesSinSACSservomotorSsoSthatSmaintenanceSisSvirtuallySnotS required.SFurthermore)SACSservosShaveSaSsmallerSpower3to3weightSratioSandSfasterS response.S
  10. 10. Computer Numerical Control (CNC) PagecWDc FigXWEWRc ACcServocMotorcHCourtesycofcFlexiblecAutomationwc cXcSteppingcMotorc Ac steppingc motorc isc ac devicec thatc convertsc thec electricalc pulsesc intoc discretec mechanicalcrotationalcmotionscofcthecmotorcshaftXcThisciscthecsimplestcdevicecthatc canc bec appliedc toc CNCc machinesc sincec itc canc convertc digitalc datac intoc actualc mechanicalc displacementXc Itc isc notc necessaryc toc havec anyc analogEtoEdigitalc convertercnorcfeedbackcdevicecforctheccontrolcsystemXcTheycarecideallycsuitedctoc opencloopcsystemsXc Howeverqcsteppingcmotorscarecnotccommonlycusedcincmachinectoolscduectocthec followingc drawbacks:c slowc speedqc lowc torqueqc lowc resolutionc andc easyc toc slipc inc casecofcoverloadXcExamplescofcsteppingcmotorcapplicationcarecthecmagneticcheadc ofcfloppyEdisccdrivecandchardcdisccdrivecofccomputerqcdaisyEwheelctypecprinterqcXEYc tapeccontrolqcandcCNCcEDMcWireEcutcmachineXc FigXWEWLc SteppingcMotorcHCourtesycRealETimecMicrocomputerwc dXcLinearcMotorc AclinearcelectriccmotorciscancACcrotarycmotorclaidcoutcflatXc Thecsamecprinciplecusedc toc producec torquec inc rotaryc motorsc isc usedc toc producec forcec inc linearc motorsXc Throughc thec electromagneticc interactionc betweenc ac coilc assemblyc andc ac permanentc magnetc assemblyqc thec electricalc energyc isc convertedc toc linearc mechanicalcenergyctocgeneratecaclinearcmotionXc Ascthecmotioncofcthecmotorc isc linearcinsteadcofcrotationalqcthereforecitcisccalledclinearcmotorXcLinearcmotorschavec thecadvantagescofchighcspeedsqchighcprecisioncandcfastcresponseXc IncthecW98Dsqc
  11. 11. Computer Numerical Control (CNC) PageR11R machineR toolR buildersR startedR usingR linearR motorsR withR theR commonR motionR controlRservoRdrivesRinRtheRmachineRtoolRdesign.R Fig.1E15R LinearRMotorR3CourtesyRofRRenishawHR AmongR differentR designsR ofR linearR motors6R permanentR magnetR brushlessR motorsR demonstrateRaRhighRforceRdensity6RhighRmaximumRspeed6RandRstableRforceRconstant.R TheR lackR ofR aR brushedR commutatorR assemblyR hasR theR advantagesR ofR fewerR maintenance6RhigherRreliabilityRandRbetterRsmoothness. AnRironRcoreRbrushlessRlinearRmotorRisRsimilarRtoRaRconventionalRbrushlessRrotaryR motorRslitRaxiallyRandRthenRrolledRoutRflat.RTheRunrolledRrotorRisRaRstationaryRplateR consistingR ofR magnetsR tiledR onR anR ironR backR plateR andR theR unrolledR statorR isR aR movingRcoilRassemblyRconsistingRofRcoilsRwoundRaroundRaRlaminatedRsteelRcore.RCoilR windingsR areR typicallyR connectedR inR conventionalR 3R phaseR arrangementR andR commutationRisRoftenRperformedRbyRHallEeffectRsensorsRorRsinusoidal.R ItRhasRhighR efficiencyRandRgoodRforRcontinuousRforce.R AnR ironlessR linearR motorR consistsR ofR aR stationaryR UR shapedR channelR filledR withR permanentR magnetsR tiledR alongR bothR interiorR walls.R AR movingR coilR assemblyR traversesR betweenR twoR opposingR rowsR ofR magnets.R CommutationR isR doneR electronicallyReitherRbyRHallEeffectRsensorsRorRsinusoidal.R TheRironlessRlinearRmotorR hasR theR advantagesR ofR lowerR coreR mass6R lowerR inductanceR andR noR coggingR forR smoothR motionR asR theR ironlessR motorsR haveR noR attractiveR forceR betweenR theR framelessRcomponents.R Fig.1E16R IroncoreRandRIronlessRLinearRMotorR3CourtesyRofRETELHR
  12. 12. Computer Numerical Control (CNC) Pagew12w 1.2.5 Feedback Device InworderwtowhavewawCNCwmachinewoperatingwaccuratelyHwthewpositionalwvalueswandw speedwofwthewaxeswneedwtowbewconstantlywupdatedRw Twowtypeswofwfeedwbackwdevicesw arewnormallywusedHwpositionalwfeedwbackwdevicewandwvelocitywfeedwbackwdeviceRw aRwPositionalwFeedwBackwDevicesw Therewarewtwowtypeswofwpositionalwfeedwbackwdevices:wlinearwtransducerwforwdirectw positionalw measurementw andw rotaryw encoderw forw angularw orw indirectw linearw measurementRw Linearw Transducersw )w Aw linearw transducerw isw aw devicew mountedw onw thew machinewtablewtowmeasurewthewactualwdisplacementwofwthewslidewinwsuchwaw waywthatwbacklashwofwscrews;wmotorsHwetcwwouldwnotwcausewanywerrorwinwthew feedwbackwdataRwThiswdevicewiswconsideredwtowbewofwthewhighestwaccuracywandw alsowmorewexpensivewinwcomparisonwwithwotherwmeasuringwdeviceswmountedw onwscrewsworwmotorsRw FigR1)17w LinearwTransducerwACourtesywofwHeidenhain; RotarywEncodersw)wAwrotarywencoderwiswawdevicewmountedwatwthewendwofwthew motorw shaftw orw screww tow measurew thew angularw displacementRw Thisw devicew cannotwmeasurewlinearwdisplacementwdirectlywsowthatwerrorwmaywoccurwduewtow thew backlashw ofw screww andw motorw etcRw GenerallyHw thisw errorw canw bew compensatedw forw byw thew machinew builderw inw thew machinew calibrationw processRw
  13. 13. Computer Numerical Control (CNC) Pagev13v Fig.1-18v IncrementalvandvAbsolutevRotaryvEncoderv b.vVelocityvFeedbackvDevicev Thev actualv speedv ofv thev motorv canv bev measuredv inv termsv ofv voltagev generatedv fromv av tachometerv mountedv atv thev endv ofv thev motorv shaft.v DCv tachometerv isv essentiallyvavsmallvgeneratorvthatvproducesvanvoutputvvoltagevproportionalvtovthev speed.v Thev voltagev generatedv isv comparedv withv thev commandv voltagev correspondingv tov thev desiredv speed.v Thev differencev ofv thev voltagesv canv isv thenv usedvtovactuatevthevmotorvtoveliminatevtheverror.v Fig.1-19v Tachogeneratorv(CourtesyvofvCallan)v 1.2.6 Display Unit Thev Displayv Unitv servesv asv anv interactivev devicev betweenv thev machinev andv thev operator.v Whenv thev machinev isv running,v thev Displayv Unitv displaysv thev presentv
  14. 14. Computer Numerical Control (CNC) Pagev13v Fig.1-18v IncrementalvandvAbsolutevRotaryvEncoderv b.vVelocityvFeedbackvDevicev Thev actualv speedv ofv thev motorv canv bev measuredv inv termsv ofv voltagev generatedv fromv av tachometerv mountedv atv thev endv ofv thev motorv shaft.v DCv tachometerv isv essentiallyvavsmallvgeneratorvthatvproducesvanvoutputvvoltagevproportionalvtovthev speed.v Thev voltagev generatedv isv comparedv withv thev commandv voltagev correspondingv tov thev desiredv speed.v Thev differencev ofv thev voltagesv canv isv thenv usedvtovactuatevthevmotorvtoveliminatevtheverror.v Fig.1-19v Tachogeneratorv(CourtesyvofvCallan)v 1.2.6 Display Unit Thev Displayv Unitv servesv asv anv interactivev devicev betweenv thev machinev andv thev operator.v Whenv thev machinev isv running,v thev Displayv Unitv displaysv thev presentv
  15. 15. ComputerfNumericalfControlf(CNC)f Pagevq5v Chapterf2.f CNCfPartfProgrammingf Objectives:f TovunderstandvthevDimensionvSystemsvinvCNCvPartvProgramming2v TovunderstandvthevstructurevofvavCNCvPartvProgramme2v Tov understandv thev GFcodesv andv otherv functionsv ofv av CNCv Partv Programme2v 2.1f Axisfoffmotionf InvgenerallyBvallvmotionsvhavev6vdegreesvofvfreedom2vInvothervwordsBvmotionvcanv bevresolvedvintov6vaxesBvnamelyBv3vlinearvaxesvYXBvYvandvZvaxisZvandv3vrotationalv axesvYABvBBvandvCvaxisZ2v Fig22Fqv AxisvofvMotionv 2.2f DimensionfSystemsf 2.2.1f IncrementalfSystemf Thisv typev ofv controlv alwaysv usesv asv av referencev tov thev precedingv pointv inv av sequencevofvpoints2v ThevdisadvantagevofvthisvsystemvisvthatvifvanverrorvoccursBvitv willvbevaccumulated2v X Z
  16. 16. Computer Numerical Control (CNC) PageC16C Fig.2-2C IncrementalCSystem 2.2.2 Absolute System InCanCabsoluteCsystemCallCreferencesCareCmadeCtoCtheCoriginCofCtheCcoCordinateC system.C AllC commandsC ofC motionC areC definedC byC theC absoluteC coordinateC referredCtoCtheCorigin.C Fig.2-3C AbsoluteCSystem 2.3 Definition of Programming NCCprogrammingCisCwhereCallCtheCmachiningCdataCareCcompiledCandCwhereCtheC dataC areC translatedC intoC aC languageC whichC canC beC understoodC byC theC controlC systemCofCtheCmachineCtool.C TheCmachiningCdataCisCasCfollows:C a.C MachiningCsequenceC classificationCofCprocess,CtoolCstartCupCpoint,CcuttingC depth,CtoolCpathCetc.C b.C CuttingCconditionsC spindleCspeed,CfeedCrate,Ccoolant,Cetc.C c.C SelectionCofCcuttingCtools.C
  17. 17. Computer Numerical Control (CNC) PagewqJw 2.4 Programme Structure Program start Block #1 Block #2 Block #30 Block #31 End.of Programme Sequence Number Word. #1 Word #2 N002 G01 X12.0 Address Value G. 01 X. 12.0 FigDyRXw StructurewofwCNCwPartwProgrammew AwCNCwprogrammewconsistswofwblocks)wwordswandwaddressesDw aDw Blockw AwcommandwgivenwtowthewcontrolwunitwiswcalledwawblockDw bDw Wordw AwblockwiswcomposedwofwoneworwmorewwordsDw Awwordwiswcomposedwofwanw identificationwletterwandwawserieswofwnumerals)weDgDwthewcommandwforwawfeedw ratewofwy::mm'minwiswFy::Dw cDw Addressw ThewidentificationwletterwatwthewbeginningwofweachwwordwiswcalledwaddressDw Thew meaningw ofw thew addressw isw inw accordancew withw EIAw TElectronicw IndustrieswAssociationEwstandardwRSRyJXRDDwThewmostwcommonw/addresses/w arewlistedwbelowxw Function Address Sequencewnumberw Nw Preparatorywfunctionw Gw Cowordinatewwordw X)wY)wZw ParameterswforwCircularwInterpolationw I)wJ)wKw Feedwfunctionw Fw Spindlewfunctionw Sw Toolwfunctionw Tw Miscellaneouswfunctionw Mw Anwexamplewofwawprogrammewiswaswfollowsxw Ny:w G:qw Xy:DYw Fy::w Sq:::w M:Gw Nyqw G:yw XG:D:w YX:D:w Iy:DYw JGyD:w
  18. 18. ComputerPNumericalPControlPYCNCZP Pagex9Jx 2.5P ExplanationPofPWordsP 2.5.1P SequencePNumberPYNPAddressZP Ax sequencex numberx isx usedx tox identifyx thex block-x Itx isx alwaysx placedx atx thex beginningx ofx thex blockx andx canx bex regardedx asx thex namex ofx thex block-x Thex sequencex numbersx needx notx bex consecutive-x Thex executionx sequencex ofx thex programmex isx accordingx tox thex actualx sequencex ofx thex blockx andx notx thex sequencex ofx thex number-x Inx factx somex CNCx systemsx dox notx requirex sequencex numbers-x 2.5.2P PreparatoryPFunctionPYGPAddressZP Axpreparatoryxfunctionxdeterminesxhowxthextoolxisxtoxmovextoxthexprogrammedx target-x ThexmostxcommonxGxaddressesxarexlistedxbelowXx Code Function G77x Pointxtoxpointxpositionxatxrapidxfeedx G79x Linearxinterpolationx G7Mx CircularxinterpolationRxclockwisex G7Dx CircularxinterpolationRxantixclockwisex G(7x Cutterxcompensationxcancelx G(9x CutterxcompensationRxLeftx G(Mx CutterxcompensationRxRightx G()x5xG(Jx OtherxcutterxcompensationRxifxusedx GW7x5xGWKx Millingxandxturningxcyclex GJ7x5xGJKx Drillingxandxtappingxcyclex GK7x Absolutexdimensioningx GK9x Incrementalxdimensioningx 2.5.3P CoKordinatePWordPYX/Y/ZPAddressZP Ax co5ordinatex wordx specifiesx thex targetx pointx ofx thex toolx movementx 2absolutex dimensionx system,x orx thex distancex tox bex movedx 2incrementalx dimension,-x Thex wordx isx composedx ofx thex addressx ofx thex axisx tox bex movedx andx thex valuex andx directionxofxthexmovement-x ExampleXx X100 Y-200 representsxthexmovementxtox2977RxM77,-xWhetherxthexdimensionsx arex absolutex orx incrementalx willx havex tox bex definedx previouslyx 2usingxGK7xorxGK9,-x 2.5.4P ParameterPforPCircularPInterpolationPYI/J/KPAddressZP Thesexparametersxspecifyxthexdistancexmeasuredxfromxthexstartxpointxofxthexarcx toxthexcentre-xNumeralsxfollowingxIRxJxandxKxarexthexXRxYxandxZxcomponentsxofxthex distancexrespectively-x
  19. 19. Computer Numerical Control (CNC) Pagex79x 2.5.5 Spindle Function (S Address) ThexspindlexspeedxisxcommandedxunderxanxSxaddressxandxisxalwaysxinxrevolutionx perxminute5x Itxcanxbexcalculatedxbyxthexfollowingxformula:x (mm)meterCutter Dia 1000(m/min)SpeedCuttingSurface =SpeedSpindle × × π Thexfollowingxtablexgivesxthexsurfacexcuttingxspeedsxforxsomexcommonxmaterials:x Example:x S2000 representsxaxspindlexspeedxofx2kkkrpmx 2.5.6 Feed Function (F Address) ThexfeedxisxprogrammedxunderxanxFxaddressxexceptxforxrapidxtraverse5xThexunitx mayx bex inx mmx perx minutex /inx thex casex ofx millingx machineAx orx inx mmx perx revolutionx/inxthexcasexofxturningxmachineA5xThexunitxofxthexfeedratexhasxtoxbex definedxatxthexbeginningxofxthexprogramme5xThexfeedxratexcanxbexcalculatedxbyx thexfollowingxformula:x Feed Rate = Chip Load / tooth No of Tooth Spindle Speed× × Thexfollowingxtablexgivesxthexchipxloadxperxtoothxofxmillingxcuttersxcuttingxsomex commonxmaterials:x MillingxCutterx Chipxloadxperxtoothx /mmWrevAx Materialx Alxalloy Brass CastxIron MildxSteelx HSSx k528x k578x k52kx k573x SinteredxCarbide k525x k575x k525x k525x Example:x F200 representsxaxfeedxratexofx2kkmmWminx 2.5.7 Tool Function (T Address) ThexselectionxofxtoolxisxcommandedxunderxaxTxaddress5x Example:x T02 representsxtoolxnumberx2x Cuttingxtool Workpiecexmaterialx Materialx Alxalloy Brass CastxIron MildxSteelx HSSx 72kx 75x 78x 3kx Carbidex 5kkx 78kx 72kx 2kkx
  20. 20. ComputerhNumericalhControlh(CNC)h Pagekxqk 2.5.8h MiscellaneoushFunctionh(MhAddress)h Thek miscellaneousk functionk isk programmedk tok controlk thek machinek operationk otherk thank fork cok ordinatek movementjk Thek mostk commonk Mk functionsk arek ask follows:k Code Function Mqqk Programmekstopk Mq)k Spindlekrotationk clockwisek MqWk Spindlekrotationk counterclockwisek MqIk SpindlekSTOPk MqEk ChangekofkToolk Mq8k CoolantkONk Mq9k CoolantkOFFk M(qk Clampk M((k Unclampk M)qk Programmekendkandkreadykforkanotherkstartk 2.6h StepshforhCNChProgramminghandhMachiningh Thek followingk isk thek proceduresk tok bek followedk ink CNCk programmingk andk machiningjkThekmostkimportantkpointkisktokverifykthekprogrammekbyktestkrunkitkonk thekmachinekbeforekthekactualkmachiningkinkorderktokensurekthatkthekprogrammek iskfreekofkmistakesjk ajk Studykthekpartkdrawingkcarefullyjk bjk UnlesskthekdrawingkdimensionskarekCNCkadapted,kselectkaksuitablek programmek zerok pointk onk thek workk piecejk Thek toolk willk bek adjustedktokthiskzerokpointkduringkthekmachineksetkupjk cjk Determinekthekmachiningkoperationskandktheirksequencejk djk Determinek thek methodk ofk workk clampingk 1vice,k rotaryk table,k fixturesketcUjk ejk Selectkcuttingktoolskandkdeterminekspindlekspeedskandkfeedsjk fjk Writek programmek 1translatek machiningk stepsk intok programmek blocksUjk Ifkmanyksolutionskarekpossible,ktryktheksimplestksolutionk firstjkItkiskusuallyklonger,kbutkbetterktokproceedkinkthiskwayjk gjk Preparek toolk chartk ork diagram,k measurek toolk geometryk 1lengths,k radiiUkandknotejk hjk Clampkworkkpiecekandksetkupkmachinejk ijk Enterkcompensationkvaluekifknecessaryjk jjk Checkkandktestkprogrammejk Itkiskakgoodkpracticektokdrykrunkthek programmek 1iUk withoutk thek workpiece,k 1iiUk withoutk thek cuttingk tools,kork1iiiUkbykraisingkthektoolktokaksafekheightjk Ifknecessary,kcorrectkandkeditkprogrammekandkcheckkagainjk kjk Startkmachiningjk
  21. 21. Computer9Numerical9Control9(CNC)9 Pagev21v 2.79 G-codes9in9Part9Programming9 2.7.19 Absolute9and9Incremental9Dimensioning9(G90/G91)9 G90vandvG91varevusedvtovcontrolvthevdimensioningvsystemvthatvwillvbevusedvinv thevdatavinput.vInvG90vmode,vthevdimensionsvwillvbevrecognizedvasvabsolutevwhilev invG91vwillvbevincremental.v 2.7.29 Rapid9Positioning9(G00)9 Thisv isv tov commandv thev cutterv tov movev fromv thev existingv pointv tov thev targetv pointvatvthevfastestvspeedvofvthevmachine.v ProgrammevFormatv G00v Xv Yv Zv Fig.2-5v RapidvPositioningv 2.7.39 Linear9Interpolation9(G01)9 Thisv isv tov commandv thev cutterv tov movev fromv thev existingv pointv tov thev targetv pointvalongvavstraightvlinevatvthevspeedvdesignatedvbyvthevFvaddress.v ProgrammevFormatv G01v Xv Yv Zv Fv Xv Y Zv Rapidv Traverse The cutter moves from its current position (starting point) to the programmed target position (end point). The tool moves at the specified feedrate from its current position (starting point) to the programmed target point.
  22. 22. Computer Numerical Control (CNC) Page(SS( FigXSK6( Linear(Interpolation( 2.7.4 Circular Interpolation (G02/G03) This( is( to( command( the( cutter( to( move( from( the( existing( point( to( the( target( point( along( a( circular( arc( in( clockwise( direction( MGZSC( or( counterclockwise( direction(MGZWCX( In(this(caseJ(beside(the(target(pointJ(the(radius(or(the(centre(of(the(arc(is(also( requiredX( Most( of( the( CNC( systems( nowadays( still( require( the( data( of( the( arc( centre(rather(than(the(radiusX( The(parameters(of(the(centre(of(the(circular(arc(is(designated(by(the(IJ(J(and(K( addressesX(I(is(the(distance(along(the(X(axisJ(J(along(the(YJ(and(K(along(the(ZX(This( parameter(is(defined(as(the(vector(Mmagnitude(and(directionC(from(the(starting( point(to(the(centre(of(the(arcX( Programme(Format( MClockwise(DirectionC( GZS( X( Y( I(MXC(K(XSC( J(MYC(K(YSC( Where( XC(and(YC(is(the(coordinate(of(the(centreJ(and( XS(and(YS(is(the(coordinate(of(the(start(point(of(the(arcX( ProgrammingYExample ofYAbsoluteYDimensioning: N.85YG9. N.9.YG..YXh3.YYh3.YZh2 N.95YG.1YZd6 N1..YG.1YXh11.YYh75 ProgrammingYExample forYIncrementalYDimensioning N.85YG..YXh3.YYh3.YZh2 N.9.YG91 N.95YG.1YZd8 N1..YG.1YXh8.YYh45 TheY toolY movesY atY theY specifiedY feedrateY fromY its currentYpositionYcstartingYpoint4YtoYtheYprogrammed targetYposition(
  23. 23. Computer Numerical Control (CNC) PageX23X FigW2y7X CircularXInterpolationXyXClockwise ProgrammeXFormatX xCounterclockwiseXDirectionvX GS3X XX YX IX JX FigW2y8XCircularXInterpolationXyXCounterclockwiseX 2.7.5 Cutter Compensation (G40/G41/G42) InXCNCXmachiningMXifXtheXcutterXaxisXisXmovingXalongXtheXprogrammedXpathMXtheX dimensionXofXtheXworkpieceXobtainedXwillXbeXincorrectXsinceXtheXdiameterXofXtheX cutterXhasXnotXbeXtakenXintoXaccountWX ModernX CNCX systemsX areX capableX ofX doingX thisX typeX ofX calculationX whichX isX knownXasXcutterXcompensationWXWhatXtheXsystemXrequiresXareXtheXprogrammedX pathMX theX cutterX diameterX andX theX positionX ofX theX cutterX withX referenceX toX theX contourWXNormallyMXtheXcutterXdiameterXisXnotXincludedXinXtheXprogrammeWXItXhasX toXbeXinputXtoXtheXCNCXsystemXinXtheXtoolXsettingXprocessWX xXcMXYcv StartXpoint xXsM Ysv EndX X Y IX JX xXcMXYcv StartXpoint xXsM Ysv EndX pointX X Y I JX Programming3Example for3Absolute3Dimensioning: N0853G90 N0903G003X+553Y+353Z+2 N0953G013Z-5 N1003G023X+953Y+753I+303J+10
  24. 24. Computer Numerical Control (CNC) Page1241 Fig.2-91 Comparison1of1Tool1Path1with1and1without1Cutter1Compensation1 If1the1cutter1is1on1the1left1of1the1contour,1G411is1used.1If1the1cutter1is1on1the1right1 of1the1contour,1G421will1be1used.1G401is1to1cancel1the1compensation1calculation.1 Cutter on the Right of the contour, use G42 Fig.2-101 Direction1of1Cutter1Compensation1 Final1contour1does1not1 Match1with1programme1path Final1contour1matches with1programme1path1 Cutter1path1offset1from the1programme1path1 Programme1 Cutter on the Left of the contour, use G41
  25. 25. Computer Numerical Control (CNC) PageZ6fZ ProgrammeZExampleZ/Z Explanation NF/Z GIFZ AbsoluteZDimensioningZ NF6Z GFFZ XcCFZYcCFZZ/FFZ RapidZmoveZtoZUXcCF;ZYcCF;ZZ/FF4Z NFCZ TF/Z UsingZToolZNumberZ/Z NFhZ GFFZ ZfZS/FFFZMFCZRapidZmoveZtoZZf;Z startZspindleZclockwiseZatZ/FFFrpmZ NFfZ GF/Z Zc/FZF/FFZ FeedZtoZZc/FZatZ/FFmmwminZ NF7Z Gh/ZGF/ZXFZY/fZF6FFZCallZupZcompensation;Z cutterZonZtheZleftZfeedZtoZ UXF;ZY/f4ZatZ6FFmmwminZ NF.Z GF/Z Y77kf7hZ FromZNF.ZtoZN/fZisZtheZcontourZcuttingZ NF8Z GF6Z X/7k///ZY87k/8CZ I6FZJFZ NFIZ GF6Z XICk88IZY87k/8CZ IC8k88IZJc/I7k/8CZ N/FZ GF6Z X//FZY77kf7hZ IcCk88IZJc/Ik7/IZ N//Z GF/Z Y67k6h.Z N/6Z GF6Z XI8k886ZY//k.f8Z Ic/fZJFZ N/CZ GF/Z XffZYFZ N/hZ GF/Z X/fZ N/fZ GF6Z XFZY/fZ IFZJ/f N/7ZZZZZGhFZZZZZZXcCFZYcCFZCancelZofZcompensation;Z ZZZZZZZZZZfeedZtoZUXcCF;ZYcCF4Z N/.ZZZZZGFFZZ/FFZMCFZRapidZmoveZtoZZ/FF;ZprogrammeZendZ Programme

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