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英文原文COMPUTERNUMERICALCONTROLUNITTODAY,COMPUTERNUMERICALCONTROLCNCMACHINESAREFOUNDALMOSTEVERYWHERE,FROMSMALLJOBSHOPSINRURALCOMMUNITIESTOFORTUNE500COMPANIESINLARGEURBANAREASTRULY,THEREISHARDLYAFACETOFMANUFACTURINGTHATISNOTINSOMEWAYTOUCHEDBYWHATTHESEINNOVATIVEMACHINETOOLSCANDOEVERYONEINVOLVEDINTHEMANUFACTURINGENVIRONMENTSHOULDBEWELLAWAREOFWHATISPOSSIBLEWITHTHESESOPHISTICATEDMACHINETOOLSINTHISCHAPTER,WEWILLEXPLORETHEBASICSOFTHECOREOFCNCMACHINETOOLCNCUNIT,SHOWINGYOUMUCHOFWHATISINVOLVEDWITHITSFUNCTION,WORKINGPRINCIPLES,HARDWARECONFIGURATIONANDSOFTWARESTRUCTUREWITHSOMANYTYPESOFCNCMACHINETOOLSANDCNCUNITSINEXISTENCE,ITISNEXTTOIMPOSSIBLEFORTHISCHAPTERTOBEEXTREMELYSPECIFICABOUTANYONEPARTICULARTYPETHEKEYCONCEPTSALLOWUSTOVIEWTHEMAINFEATURESOFCNCUNITINMOREGENERALTERMS,STRESSINGWHYTHINGSAREHANDLEDTHEWAYTHEYAREEVENMORETHANTHESPECIFICTECHNIQUESUSEDWITHANYONEPARTICULARCNCMACHINETOOLWITHTHISBROADBACKGROUND,YOUSHOULDBEABLETOEASILYZEROINONANYKINDOFCNCMACHINETOOLYOUWILLBEWORKINGWITH1．1INTRODUCTIONMACHINECONTROLSAREDIVIDEDINTOTWOTYPESNUMERICALCONTROLNCANDCOMPUTERNUMERICALCONTROLCNC．NCCONTROLSHAVETOREADTHEPROGRAMEACHTIMEAPARTISRUN；THEYHAVENOMEANSOFEDITINGEXISTINGPROGRAMS．CNCCONTROLSCANSTOREANDALLOWEDITINGOFLOADEDPROGRAMS．ALLMACHINESBUILTTODAYARECNCMACHINES．CNCUNITISTHEHEARTOFCNCMACHINENEVERTHELESS，INORDERTOAIDTOUNDERSTANDTHEWORKINGPRINCIPLESOFCNCUNIT，ITISNECESSARYTHATTHEPRINCIPLESOFNCSYSTEMBEINTRODUCEDFIRSTLY．1．1．1NCSYSTEMTHENCMACHINECANBEDIVIDEDINTOTHREEBASICAREASTHEFIRSTAREAISTHECONTROLUNIT,WHICHPROCESSESTHECOMMANDSFROMTHEINPUTMEDIATHESECONDAREAISTHEDRIVEMECHANISMS,ANDTHELASTAREAISTHEMACHINEITSELF．THEMOSTBASICFUNCTIONOFANYNCMACHINEISAUTOMATIC，PRECISE，ANDCONSISTENTMOTIONCONTROL．A11FORMSOFNCEQUIPMENTHAVETWOORMOREDIRECTIONSOFMOTION，CALLEDAXES．THESEAXESCANBEPRECISELYANDAUTOMATICALLYPOSITIONEDALONGTHEIRLENGTHSOFTRAVEL．THETWOMOSTCOMMONAXISTYPESARELINEARDRIVENALONGASTRAIGHTPATHANDROTARYDRIVENALONGACIRCULARPATH．INSTEADOFCAUSINGMOTIONBYMANUALLYTURNINGCRANKSANDHANDWHEELSASISREQUIREDONCONVENTIONALMACHINETOOLS，NCMACHINESALLOWMOTIONSTOBEACTUATEDBYSERVOMOTORSUNDERCONTROLOFTHENC，ANDGUIDEDBYTHEPARTPROGRAM．GENERALLYSPEAKING，THEMOTIONTYPERAPID,LINEAR，ANDCIRCULAR，THEAXESTOMOVE，THEAMOUNTOFMOTIONANDTHEMOTIONRATEFEEDRATEAREPROGRAMMABLEWITHALMOSTALLNCMACHINETOOLS．FIGURE1．1SHOWSTHEMAKEUPOFALINEARAXISOFANNCMACHINE．FIGURE1．1THEMAKEUPOFALINEARAXISOFALLNCMACHINEANNCCOMMANDEXECUTEDWITHINTHECONTROLCOMMONLYTHROUGHAPROGRAMTELLSTHEDRIVEMOTORTOROTATEAPRECISEAMOUNTOFANGLE．THEROTATIONOFTHEDRIVEMOTORINTURNROTATESTHEBALLSCREW．ANDTHEBALLSCREWDRIVESTHELINEARAXIS．AFEEDBACKDEVICEATTHEOPPOSITEENDOFTHEBALLSCREWALLOWSTHECONTROLTOCONFIRMTHATTHECOMMANDEDNUMBEROFROTATIONSHASTAKENPLACE．ALLNCMACHINETOOLSNEEDNUMERICALDATAFORCONTROLLINGTHERELATIVEMOTIONBETWEENCUTTINGTOOLANDPIECEPART,THECOMPONENTDIMENSIONSNORMALLYEMANATINGDIRECTLYFROMENGINEERINGDRAWINGSTHEGEOMETRICDATA．OTHERDIGITIZEDNUMERICALDATADEFINEFEEDRATES，SPINDLESPEEDS，TOOLIDENTIFICATIONNUMBERS，ANDMISCELLANEOUSFUNCTIONSTOPERFORMSUCHOPERATIONSASTOOLORWORKCHANGING，ORCOOLANTCONTROLTHETECHNOLOGICALDATA．THECOMBINATIONOFALLTHISNUMERICALINFORMATIONINASEQUENCEUNDERSTOODBYTHEMACHINETOOL’SCONTROLLERISCALLEDAPARTPROGRAM，ANDTHEPROCESSOFCREATINGTHEDATAINACORRECTLYSTRUCTUREDFORMATISCALLEDPROGRAMMING．NUMERICALCONTROLSUSESTANDARDMICROELECTRONICMODULESTHATHAVEBEENDEVELOPEDFORCOMPUTERHARDWARE。EXCEPTFORSPECIALMODULESNEEDEDINSERVOCONTROLCIRCUITS，NOINDIVIDUALMODULESARENECESSARY，INCONTRASTTOTRADITIONALCONTROLS，WHICHEMPLOYONLYCOMPONENTSTAILOREDTOSUITONESPECIFICCONTROLFUNCTION．INMODERNNCCONTROLLERSEXTENSIVECONTROLANDCALCULATIONTASKSAREPERFORMEDBYONEORMOREINTEGRALMICROPROCESSORS。THESEARETERMEDCOMPUTERNUMERICALCONTROLSYSTEMCNCS．1．1．2CNCSYSTEMANDFUNCTIONSOFCNCUNITCONTROLSYSTEMSBASEDONINDUSTRIALPCABBREVIATIONFORPERSONALCOMPUTERAREINCREASINGLYUSEDINAUTOMATIONTECHNOLOGY．MACHINECONTROLSHAVECHANGEDGREATLYWITHTHE“AGEOFTHECOMPUTER”．CONTROLSTODAYARE“SOFTWIRED”,WHICHALLOWSGREATERFLEXIBILITYINCHANGINGANDUPGRADINGTHECOMPUTERCONTROL．INFACT，MANYOFMACHINE’SOPERATINGCHARACTERISTICSCANBECHANGEDBYTHEOPERATOR，SOTHATTHEMACHINEOPERATESTHEWAYHE／SHEWANTSITTOPARAMETERTABLESINCNCMACHINESTODAYALLOWEACHMACHINETOBEPERSONALIZEDTOTHENEEDSOFTHEJOBTOBERUN．THEMODERNCNCMACHINETOOLISSOFTWAREDRIVEN．SIMPLYSPEAKING，COMPUTERCONTROLSAREPROGRAMMEDINSTEADOFHARDWIRED．DEFINITIONACCORDINGTOELECTRONICINDUSTRIESASSOCIATIONEIA，CNCSYSTEMISASPECIALCOMPUTERSYSTEMTHATISEQUIPPEDWITHCERTAININTERFACECIRCUITSANDSERVODRIVERS，ANDCANDOPARTORA11THEWORKSANNCSYSTEMDOBYRUNNINGTHESOFTWARESTOREDINITSMEMORIES．CNCSHAVEEXPANDABLEMEMORIESTHATCANSTORELARGENUMBERSOFPROGRAMS，PLUSSUBROUTINESANDCORRECTIONDATA。SOPHISTICATEDGRAPHICDISPLAYSANDDYNAMICSIMULATIONHAVEALSONOWBECOMEAVAILABLEASARESULTOFTHEEXTENSIVEMEMORYCAPACITYBEINGBUILTINTOCURRENTCNCS．WITHINONLYFEWYEARS，THECAPABILITYANDEFFICIENCYOFMACHINECONTROLLERSHASINCREASEDTOSUCHANEXTENTTHATTHENAME“NUMERICALCONTROL”ISNOLONGERAPPROPRIATE；“COMPUTERNUMERICALCONTROL”ISMOREACCURATELYDESCRIPTIVE．GENERALLY，CNCSCOMPRISESCNCUNIT，FEEDMOTIONSERVOSUBSYSTEM，SPINDLESERVOSUBSYSTEMANDSOMEAUXILIARYCONTROLCELLS,ASSHOWNINFIGURE12，CNCUNITISTHECOREOFTHEWHOLECNCSYSTEM．ITISCOMPOSEDOFHARDWAREANDSOFTWARE。THEHARDWARECOMPRISINGACNCUNITISMADEUPOFMICROPROCESSORS，ELECTRONICMEMORYMODULES，I／0INTERFACES，ANDPOSITIONCONTROLMODULES，ETC．CNCSOFTWARECONTROLSALLFUNCTIONSOFTHEMACHINEANDITSEFFICIENCYOFOPERATION，ANDMANAGESALLLOCALPROGRAMMINGATTHEMACHINETOOLANDGRAPHICSIMULATIONOFTHECUTTINGPROCESSIFAVAILABLE．THEHARDWAREANDTHESOFTWAREWORKTOGETHERTODOALLFUNCTIONSOFCNCUNIT，WHICHANORDINARYNCSYSTEMCANNEVERDO，SUCHASGRAPHICDISPLAYHMIHUMANMACHINEINTERFACE，SYSTEMDIAGNOSIS，IMPLEMENTINGOFVARIOUSCOMPLEXTOOLPATHCONTROLLINGANDCOMPENSATIONALGORITHMS，INTELLIGENTCONTROLLING，ONLINEPROGRAMMING，ANDWEBCOMMUNICATIONS，ETC．THEMAINFUNCTIONSANDFEATURESOFCNCUNITAREDESCRIBEDASFOLLOWSFIGURE1．2CNCMACHININGSYSTEM1CONTROLLINGFUNCTIONTHENUMBEROFCONTROLAXESANDSYNCHRONOUSLYCONTROLAXESCONTROLLINGFUNCTIONINDICATESTHEMAXIMUMAXISNUMBERTHECNCUNITCANCONTROLANDTHENUMBEROFAXESTHECNCUNITCANCONTROLSYNCHRONOUSLY．ITISALSOTHEMAREFEATURESOFCNCMACHINE．AXESTOBECONTROLLEDBYCNCUNITHAVELINEARAXESANDROTATEAXES,BASICAXESANDAUXILIARYAXES．GENERALLY，CNCMACHINENEEDSONLY2AXESTOBECONTROLLEDSYNCHRONOUSLY．INCASEOFDOUBLETOOLSLIDES，FOURAXESARENEEDED．CNCMILLINGMACHINE，BORINGMACHINE,ANDCNCMACHINECENTERNEED3ORMORECONTROLLEDAXES．THEMORETHENUMBEROFCONTROLLEDAXES,ESPECIALLYTHENUMBEROFAXESBEINGCONTROLLEDSYNCHRONOUSLY,THEMOREPOWERFULFUNCTIONSOFTHECNCUNIT,ANDTHEMORECOMPLEXSTRUCTUREOFTHECNCUNIT，THEMOREDIFFICULTYOFPROGRAMMING．2PREPARATORYFUNCTIONPREPARATORYFUNCTION，ALSOCALLEDGFUNCTION，DESCRIBESTHEMOTIONMODESOFCNCMACHINE．THEMOTIONMODESCOMPRISEINSTRUCTIONSOFBASICMOTIONS，DWELL，PLANESELECTIONS，COORDINATESYSTEMSETTINGS，TOOLCOMPENSATIONS，REFERENCEPOINTRETURN，FIXEDOPERATIONCIRCLES，ANDMETRIC／INCHUNITTRANSFER，ETC．ACCORDINGTOISOSTANDARD，THEREARE100TYPESOFGCODESFROMG00TOG99USEDINCNCUNIT，WHICHCANBEDIVIDEDINTOTWOCLASSESNONMODALCODESWHICHFUNCTIONSAREVALIDONLYINTHECODESEGMENTINCLUDINGTHECODESTHEMSELVESANDMODALCODESWHICHCANKEEPEFFECTIVEBEFORETHECOMINGOFNEXTGCODEOFTHESAMEGROUP．FORTHEEXACTFUNCTIONOFEACHGCODEUSEDINYOURMACHINETOOLS，YOUMUSTREFERENCEYOURCONTROLMANUFACTURER’SMANUALTOFINDTHELISTOFFUNCTIONSFORYOURMACHINE．3INTERPOLATIONFUNCTIONCNCUNITDOESINTERPOLATIONBYUSINGSOFTWAREREALTIMECALCULATIONS．LINEARINTERPOLATION，CIRCULARINTERPOLATION，HELICALINTERPOLATION，ANDPOLARCOORDINATEINTERPOLATIONWILLDOTHEIRBESTTOHELPCNCUNITGENERATETOOLTRACKASCLOSETOVARIOUSPATHSASPOSSIBLE．4FEEDFUNCTIONFEEDFUNCTIONUSESFFEEDRATEDESIGNATIONTODESIGNATETHEFEEDRATETOAXIS．THEMETHODBYWHICHFEEDRATEISPROGRAMMEDVARIESFROMONEMACHINETYPETOTHENEXT．GENERALLYSPEAKING，MACHININGCENTERSONLYALLOWTHEFEEDRATETOBESPECIFICINPERMINUTEFORMATINCHESORMILLIMETERSPERMINUTE，SUCHAS，F15000MEANSTHEFEDERATEIS15000MILLIMETERSPERMINUTE．TURNINGCENTERS，WHICHHAVEPOSITIONENCODERSINTHEIRSPINDLES，ALSOALLOWFEEDRATETOBESPECIFIEDINPERREVOLUTIONFORMATINCHESORMILLIMETERSPER．REVOLUTIONTHATISNAMEDSYNCHRONOUSFEEDRATE．5SPINDLEFUNCTIONAN“S”WORDISUSEDTOSPECIFYTHESPINDLESPEEDINRPMFORMACHININGCENTERSANM03ISUSEDTOTURNTHESPINDLEONINACLOCKWISEFORWARDD1A11NER．M04TURNSTHESPINDLEONINACOUNTERCLOCKWISEMANNER．M05TURNSTHESPINDLEOFF．NOTETHATTURNINGCENTERSALSOHAVEAFEATURECALLEDCONSTANTSURFACESPEED，WHICHALLOWSSPINDLESPEEDTOBESPECIFIEDINSURFACEFEETPERMINUTEORMETERSPERMINUTE．ONOPERATIONPANEL，THEREISABUTTONTOTURNTHESPINDLEONANDOFF，ASWELLASARHEOSTATTOCONTROLSPINDLESPEED．ALLOFTHESEFUNCTIONSAREACTIVATEDMANUALLY，THROUGHTHEMANUALORJOGMODE．6MISCELLANEOUSFUNCTIONLIKEPREPARATORYFUNCTIONS，MISCELLANEOUSFUNCTIONSMWORDS，FROMM00TOM99ALLOWAVARIETYOFSPECIALFUNCTIONS．MISCELLANEOUSFUNCTIONSARETYPICALLYUSEDASPROGRAMMABLESWITCHES1IKESPINDLEON／OFF，COOLANTON／OFF，ANDSOON7COMPENSATIONFUNCTIONALLTYPESOFCNCMACHINETOOLSREQUIRESOMEFORMSOFCOMPENSATION．THOUGHAPPLIEDFORDIFFERENTREASONSONDIFFERENTMACHINETYPES，ALLFORMSOFCOMPENSATIONALLOWTHECNCUSERTOALLOWFORUNPREDICTABLECONDITIONSRELATEDTOTOOLING．8ENHANCEDGRAPHICDISPLAYFUNCTION
