数控生产设备中英文翻译.docx
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数控生产设备中英文翻译.docx
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数控生产设备中英文翻译
九、外文翻译
NUMERICALCONTROLOFPRODUCTIONEQUIPMENTS
Numericalcontrol(NC)isaformofprogrammableautomationinwhichtheprocessingequipmentiscontrolledbymeansofnumbers,letters,andothersymbols.Thenumbers,letters,andsymbolsarecodedinanappropriateformattodefineaprogramofinstructionsforaparticularworkpartorjob.Whenthejobchanges,theprogramofinstructionsischanged.ThecapabilitytochangetheprogramiswhatmakesNCsuitableforlow-andmedium-volumeproduction.Itismucheasiertowritenewprogramsthantomakemajoralterationsoftheprocessingequipment.
BASICCOMPONENTSOFNC
Anumericalcontrolsystemconsistsofthefollowingthreebasiccomponents:
·Programofinstructions
·Machinecontrolunit
·Processingequipment
ThegeneralrelationshipamongthethreecomponentsisillustratedinFig.2.1.Theprogramisfedintothecontrolunit,whichdirectstheprocessingequipmentaccordingly.
Theprogramofinstructionsisthedetailedstep-by-stepcommandsthatdirecttheprocessingequipment.Initsmostcommonform,thecommandsrefertopositionsofamachinetoolspindlewithrespecttotheworktableonwhichthepartisfixtured.Moreadvancedinstructionsincludeselectionofspindlespeeds,cuttingtool,andotherfunction.Themostcommonmediuminuseoverthelastseveraldecadeshasbeen1-in.-widepunchedtape.Becauseofthewidespreaduseofthepunchedtape,NCissometimescalled“tapecontrol”.However,thisisamisnomerinmodernusageofnumericalcontrol.Comingintousemorerecentlyhavebeenmagnetictapecassettesandfloppydiskettes.
Themachinecontrolunit(MCU)consistsoftheelectronicsandcontrolhardwarethatreadandinterprettheprogramofinstructionandconvertitintomechanicalactionsofthemachinetoolorotherprocessingequipment.
TheprocessingequipmentisthethirdbasiccomponentofanNCsystem.Itisthecomponentthatperformsusefulwork.Inthemostcommonexampleofnumericalcontrol,onethatperformsmachiningoperations,theprocessingequipmentconsistsoftheworktableandspindleaswellasthemotorsandcontrolsneededtodrivethem.
TYPESOFCONTROLSYSTEMS
Therearetwobasictypesofcontrolsystemsinnumericalcontrol:
point-to-pointandcontouring.Inthepoint-to-pointsystem,alsocalledpositioning,eachaxisofthemachineisdrivenseparatelybyleadscrewsand,dependingonthetypeofoperation,atdifferentvelocities.Themachinemovesinitiallyatmaximumvelocityinordertoreducenonproductivetimebutdeceleratesasthetoolreachesitsnumericallydefinedposition.Thusinanpotationsuchasdrillingorpunching,thepositioningandcuttingtakeplacesequentially.Aftertheholeisdrilledorpunched,thetoolretracts,movesrapidlytoanotherposition,andrepeatstheoperation.Thepathfollowedfromonepositiontoanotherisimportantinonlyonerespect:
Thetimerequiredshouldbeminimizedforefficiency.Point-to-pointsystemsareusedmainlyindrilling,punching,andstraightmillingoperations.
Inthecontouringsystem,alsoknownasthecontinuouspathsystem,positioningandcuttingoperationsarebothalongcontrolledpathsbutatdifferentvelocities.Becausethetoolcutsasittravelsalongaprescribedpath,accuratecontrolandsynchronizationofvelocitiesandmovementsareimportant.Thecontouringsystemisusedonlathes,millingmachines,grinders,weldingmachinery,andmachiningcenters.
Movementalongthepath,orinterpolation,occursincrementally,byoneofseveralbasicmethods.Inallinterpolations,thepathcontrolledisthatofthecenterofrotationofthetool.Compensationfordifferenttools,differentdiametertools,ortoolwearduringmachining,canbemadeintheNCprogram.
Thereareanumberofinterpolationschemesthathavebeendevelopedtodealwiththevariousproblemsthatareencounteredingeneratingasmoothcontinuouspathwithacontouring-typeNCsystem.Theyinclude:
·Linearinterpolation
·Circularinterpolation
·Helicalinterpolation
·Parabolicinterpolation
·Cubicinterpolation
Eachoftheseinterpolationprocedurespermitstheprogrammer(oroperator)togeneratemachineinstructionsforlinearorcurvilinearpaths,usingarelativelyfewinputparameters.TheinterpolationmoduleintheMCUperformsthecalculationsanddirectsthetoolalongthepath.
Linearinterpolationisthemostbasicandisusedwhenastraight-linepathistobegeneratedincontinuous-pathNC.Two-axisandthree-axislinearinterpolationroutinesaresometimesdistinguishedinpractice,butconceptuallytheyarethesame.Theprogramisrequiredtospecifythebeginningpointandendpointofthestraightline,andthefeedratethatistobefollowedalongthestraightline.Theinterpolatorcomputesthefeedratesforeachofthetwo(orthree)axesinordertoachievethespecifiedfeedrate.
Linearinterpolationforcreatingacircularpathwouldbequiteinappropriatebecausetheprogrammerwouldberequiredtospecifythelinesegmentsandtheirrespectiveendpointsthataretobeusedtoapproximatethecircle.Circularinterpolationschemeshavebeendevelopedthat
permittheprogrammingofapathconsistingofacirculararcbyspecifyingthefollowingparametersofthearc:
thecoordinatesofitsendpoints,thecoordinatesofitscenter,itsradius,andthedirectionofthecutteralongthearc.Thetoolpaththatiscreatedconsistsofaseriesofstraight-linesegments,butthesegmentsarecalculatedbytheinterpolationmoduleratherthantheprogrammer.Thecutterisdirectedtomovealongeachlinesegmentonebyoneinordertogeneratethesmoothcircularpath.AlimitationofcircularinterpolationisthattheplaneinwhichthecirculararcexistsmustbeaplanedefinedbytwoaxesoftheNCsystem.
Helicalinterpolationcombinesthecircularinterpolationschemefortwoaxesdescribedabovewithlinearmovementofathirdaxis.Thispermitsthedefinitionofahelicalpathinthree-dimensionalspace.
Parabolicandcubicinterpolationroutinesareusedtoprovideapproximationsoffree-formcurvesusinghigher-orderequations.Theygenerallyrequireconsiderablecomputationalpowerandarenotascommonaslinearandcircularinterpolation.Theirapplicationsareconcentratedintheautomobileindustryforfabricatingdiesforcarbodypanelsstyledwithfree-formdesignsthatcannotaccuratelyandconvenientlybeapproximatedbycombininglinearandcircularinterpolations.
PROGRAMMINGFORNC
AprogramfornumericalcontrolconsistsofasequenceofdirectionsthatcausesanNCmachinetocarryoutacertainoperation,machiningbeingthemostcommonlyusedprocess.ProgrammingforNCmaybedonebyaninternalprogrammingdepartment,ontheshopfloor,orpurchasedfromanoutsidesource.Also,programmingmaybedonemanuallyorwithcomputerassistance.
Theprogramcontainsinstructionsandcommands.Geometricinstructionspertaintorelativemovementsbetweenthetoolandtheworkpiece.
Processinginstructionspertaintospindlespeeds,feeds,tools,andsoon.Travelinstructionspertaintothetypeofinterpolationandsloworrapidmovementsofthetoolorworktable.Switchingcommandspertaintoon/offpositionforcoolantsupplies,spindlerotation,directionofspindlerotation,toolchanges,workpiecefeeding,clamping,andsoon.
(1)ManualProgramming Manualpartprogrammingconsistsoffirstcalculatingdimensionalrelationshipsofthetool,workpiece,andworktable,basedontheengineeringdrawingsofthepart,andmanufacturingoperationstobeperformedandtheirsequence.Aprogramsheetisthenprepared,whichconsistsofthenecessaryinformationtocarryouttheoperation,suchascuttingtools,spindlespeeds,feeds,depthofcut,cuttingfluids,power,andtoolorworkpieceallyapapertapeisfirstpreparedfortryingoutanddebuggingtheprogram.Dependingonhowoftenitistobeused,thetapemaybemadeofmoredurableMylar.
Manualprogrammingcanbedonebysomeoneknowledgeableabouttheparticularprocessandabletounderstand,read,andchangepartprograms.Becausetheyarefamiliarwithmachinetoolsandprocesscapabilities,skilledmachinistscandomanualprogrammingwithsometraininginprogramming.However,theworkistedious,timeconsuming,anduneconomical-andisusedmostlyinsimplepoint-to-pointapplications.
(2)Computer-AidedProgramming Computer-aidedpartprogramminginvolvesspecialsymbolicprogramminglanguagesthatdeterminethecoordinatepointsofcorners,edges,andsurfacesofthepart.Programminglanguageisthemeansofcommunicatingwiththecomputerandinvolvestheuseofsymboliccharacters.Theprogrammerdescribesthecomponenttobeprocessedinthislanguage,andthecomputerconvertsittocommandsfortheNCmachine.Severallanguageshavingvariousfeaturesandapplicationsarecommerciallyavailable.ThefirstlanguagethatusedEnglish-likestatementswasdevelopedinthelate1950sandiscalledAPT(forAutomaticallyProgrammedTools).Thislanguage,initsvariousexpandedforms,isstillthemostwidelyusedforbothpoint-to-pointandcontinuous-pathprogramming.
Computer-aidedpartprogramminghasthefollowingsignificantadvantagesovermanualmethods:
·Useofrelativelyeasytousesymboliclanguage
·Reducedprogrammingtime.Programmingiscapableofaccommodatingalargeamountofdataconcerningmachinecharacteristicsandprocessvariables,suchaspower,speeds,feed,toolshape,compensationfortoolshapechanges,toolwear,deflections,andcoolantuse.
·Reducedpossibilityofhumanerror,whichcanoccurinmanualprogramming
·Capabilityofsimplechangeoverofmachiningsequenceorfrommachinetomachine.
·Lowercostbecauselesstimeisrequiredforpro
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