外文翻译--计算机控制程序员与操作员该做什么.doc

英文原文Whatcomputer-controlprogrammersandoperatorsdoComputer-controlprogrammersandoperatorsusecomputerizednumericalcontrol(CNC)machinestocutandshapeprecisionproducts,suchasautomobileparts,machineparts,andcompressors.CNCmachinesincludemachiningtoolssuchaslathes,multiaxisspindles,millingmachines,andelectricaldischargemachines(EDM),butthefunctionsformerlyperformedbyhumanoperatorsareperformedbyacomputer-controlmodule.CNCmachinescutawaymaterialfromasolidblockofmetal,plastic,orglass-knownasaworkpiece-toformafinishedpart.Computer-controlprogrammersandoperatorsnormallyproducelargequantitiesofonepart,althoughtheymayproducesmallbatchesorone-of-a-kinditems.TheyusetheirknowledgeoftheworkingpropertiesofmetalsandtheirskillwithCNCprogrammingtodesignandcarryouttheoperationsneededtomakemachinedproductsthatmeetprecisespecifications.BeforeCNCprogrammers-alsoreferredtoasnumericaltoolandprocesscontrolprogrammers-machineapart,theymustcarefullyplanandpreparetheoperation.First,theseworkersreviewthree-dimensionalcomputeraided/automateddesign(CAD)blueprintsofthepart.Next,theycalculatewheretocutorboreintotheworkpiece,howfasttofeedthemetalintothemachine,andhowmuchmetaltoremove.Theythenselecttoolsandmaterialsforthejobandplanthesequenceofcuttingandfinishingoperations.Next,CNCprogrammersturntheplannedmachiningoperationsintoasetofinstructions,Theseinstructionsaretranslatedintoacomputeraided/automatedmanufacturing(CAM)programcontainingasetofcommandsforthemachinetofollow.Thesecommandsnormallyareaseriesofnumbers(hence,numericalcontrol)thatdescribeswherecutsshouldoccur,whattypeofcutshouldbeused,andthespeedofthecut.CNCprogrammersandoperatorschecknewprogramstoensurethatthemachinerywillfunctionproperlyandthattheoutputwillmeetspecifications.Becauseaproblemwiththeprogramcoulddamagecostlymachineryandcuttingtools,computersimulationsmaybeusedtochecktheprograminsteadofatrialrun.Iferrorsfound,theprogrammustbechangedandresteduntiltheproblemisresolved.Inaddition,growingconnectivitybetweenCAD/CAMsoftwareandCNCmachinetoolsisraisingproductivitybyautomaticallytranslatingdesignsintoinstructionsforthecomputercontrolleronthemachinetool.ThesenewCAMtechnologiesenableprogramstobeeasilymodifiedforuseonotherjobswithsimilarspecifications.Aftertheprogrammingworkiscompleted,CNCoperators-alsoreferredtoascomputer-controlledmachinetooloperators-performthenecessarymachiningoperations.TheCNCoperatorstransferthecommandsfromtheservertotheCNCcontrolmoduleusingacomputernetworklinkorfloppydisk.Manyadvancedcontrolmodulesareconversational,meaningthattheyasktheoperatoraseriesofquestionsaboutthenatureofthetask.CNCoperatorspositionthemetalstockontheCNCmachinetool-lathe,millingmachine,orother-setthecontrols,andletthecomputermakethecuts.Heavierobjectsmaybeloadedwiththeassistanceofotherworkers,autoloaders,acrane,oraforklift.Duringthemachiningprocess,computer-controloperatorsconstantlymonitorthereadoutsfromtheCNCcontrolmodule,checkingtoseeifanyproblemsexist.Machinetoolshaveuniquecharacteristics,whichcanbeproblematic.Duringamachiningoperation,theoperatormodifiesthecuttingprogramtoaccountforanyproblemsencountered.Unique,modifiedCNCprogramsaresavedforeverydifferentmachinethatperformsatask.CNCoperatorsdetectsomeproblemsbylisteningforspecificsounds-forexample,dullcuttingtoolorexcessivevibration.Dullcuttingtoolsareremovedandreplacedandreplaced.Machinetoolsrotateathighspeeds,whichcancreateproblemswithharmonicvibrationsintheworkpiece.vibrationscausethemachinetoolstomakeminorcuttingerrors,hurtingthequalityoftheproduct.Operatorslistenforvibrationsandthenadjustthecuttingspeedtocompensate.inolder,slowermachinetools,thecuttingspeedwouldbereducedtoeliminatethevibrations,buttheamountoftimeneededtofinishtheproductwouldincreaseataresult.innewer,highspeedCNCmachines,increasingthecuttingspeednormallyeliminatesthevibrationsandreducesproductiontime.CNCoperatorsalsoensurethattheworkpieceisbeingproperlylubricatedandcooled,becausethemachiningofmetalproductsgeneratesasignificantamountofheat.Computer-controlprogrammersandoperatorstraininvariousways-inapprenticeshipprograms,informallyonthejop,andinsecondary,vocational,orpostsecondaryschools.Duetoashortageofqualifiedapplicants,manyemployersteachintroductorycourses,whichprovideabasiccomputersandelectronicsalsoishelpful.Experiencewithmachinetoolsisextremelyimportant.Infact,manyentrantstotheseoccupationshavepreviouslyworkedasmachinistsormachinesetters,operators,andtenders.Personsinterestedinbecomingcomputer-controlprogrammersoroperatorsshouldbemechanicallyinclinedandabletoworkindependentlyanddohighlyaccuratework.Highschoolorvocationalschoolcoursesinmathematics(trigonometryandalgebra),blueprintreading,computerprogramming,metalworking,anddraftingarerecommended.Apprenticeshipprogramsconsistofshoptrainingandrelatedclassroominstruction.Inshoptraining,apprenticeslearnfiling,handtapping,anddowelfitting,aswellastheoperationofvariousmachinetools.Classroominstructionincludesmath,physics,programming,blueprintreading,CADsoftware,safely,andshoppractices.Skilledcomputer-controlprogrammersandoperatorsneedanunderstandingofthemachiningprocess,includingthecomplexphysicsthatoccuratthecuttingpoint.Thus,mosttrainingprogramsteachCNCoperatorsandprogrammerstoperformoperationsonmanualmachinespriortooperatingCNCmachine.Agrowingnumberofcomputer-controlprogrammersandoperatorsreceivemostoftheirformaltrainingfromcommunityortechnicalcolleges.LessskilledCNCoperatorsmayneedonlyacoupleofweeksofon-the-jobtraining.Computer-controlprogrammersandoperatorscanadvanceinseveralways.ExperiencedCNCoperatorsmaybecomeCNCprogrammers,andsomearepromotedtosupervisoryoradministrativepositionintheirfirms.Afewopentheirownshops.Computer-controlprogrammersandoperatorsshouldhaveexcellentjobopportunities.Duetothelimitednumberofpeopleenteringtrainingprograms,employersareexpectedtohavecontinuetohavedifficultyfindingworkerswiththenecessaryskillsandknowledge.JobgrowthinbothoccupationswillbedrivenbytheincreasinguseofCNCmachinetools.AdvancesinCNCmachinetoolsandmanufacturingtechnologywillfurtherautomateproduction,boostingCNCoperatorsproductivityandlimitingemploymentgrowth.Thedemandforcomputer-controlprogrammerswillbenegativelyaffectedbytheincreasinguseofsoftwarethatautomaticallytranslatespartandproductdesignsintoCNCmachinetoolinstructions.WhatisCNCCNCstandsforComputerizedNumericalControlandhasbeenaroundsincetheearly1970s.Priortothis,itwascalledNC,fornumericalcontrol.Whilepeopleinmostwalksoflifehaveneverheardofthisterm,CNChastouchedalmosteveryformofmanufacturingprocessinonewayoranother.Ifyoullbeworkingmanufacturing,itslikelythatyoullbedealingwithCNConaregularbasis.BeforeCNCWhilethereareexceptionstothisstatement,CNCmachinesreplace(orworkinconjunctionwith)someexistingmanufacturingprocess.Takeoneofthesimplestmanufacturingprocesses,drillingholes,forexample.Adrillpresscanofcoursebeusedtomachineholes.Apersoncanplaceadrillchuckthatissecuredinthespindleofthedrillpress.Theycanthen(manually)selectthedesiredspeedforrotation(commonlybyswitchingbeltpulleys),andactivatethespindle.Thentheymanuallypullonthequilllevertodrivethedrillintotheworkpiecebeingmachined.Asyoucaneasilysee,thereisalotofmanualinterventionrequiredtouseadrillpresstodrillholes.Apersonisrequiredtodosomethingalmosteverystepalongtheway!Whilethismanualinterventionmaybeacceptableformanufacturingcompaniesifbutasmallnumberofholesorworkpiecesmustbemachined,asquantitiesgrow,sodoesthelikelihoodforfatigueduetothetediousnessoftheoperation.Anddonotethatweveusedoneofthesimplestmachiningoperations(drilling)forourexample.Therearemorecomplicatedmachiningoperationsthatwouldrequireamuchhigherskilllevel(andincreasethepotentialformistakesresultinginscrapworkpieces)ofthepersonrunningtheconventionalmachinetool.(WecommonlyrefertothestyleofmachinethatCNCisreplacingastheconventionalmachine.)Bycomparison,theCNCequivalentforadrillpress(possiblyaCNCmachiningcenterorCNCdrilling&tappingcenter)canbeprogrammedtoperformthisoperationinamuchmoreautomaticfashion.EverythingthatthedrillpressoperatorwasdoingmanuallywillnowbedonebytheCNCmachine,including:placingthedrillinthespindle,activatingthespindle,positioningtheworkpieceunderthedrill,machiningthehole,andturningoffthespindle.HowCNCworksAsyoumightalreadyhaveguessed,everythingthatanoperatorwouldberequiredtodowithconventionalmachinetoolsisprogrammablewithCNCmachines.Oncethemachineissetupandrunning,aCNCmachineisquitesimpletokeeprunning.InfactCNCoperatorstendtogetquiteboredduringlengthyproductionrunsbecausethereissolittletodo.WithsomeCNCmachines,eventheworkpieceloadingprocesshasbeenautomated.Letslookatsomeofthespecificprogrammablefunctions.MotioncontrolAllCNCmachinetypessharethiscommonality:Theyallhavetwoormoreprogrammabledirectionsofmotioncalledaxis.Anaxisofmotioncanbelinear(alongastraightline)orrotary(alongacircularpath).OneofthefirstspecificationsthatimplyaCNCmachinescomplexityishowmanyaxesithas.Generallyspeaking,themoreaxes,themorecomplexthemachine.TheaxesofanyCNCmachinearerequiredforthepurposeofcausingthemotionaneededforthemanufacturingprocess.Inthedrillingexample,these(3)axeswouldpositionthetoolovertheholetobemachined(intwoaxes)andmachinethehole(withthethirdaxis).Axesarenamedwithletters.CommonlinearaxisnamesareX,Y,andZ.CommonrotaryaxisnamesareA,B,andC.Thesearerelatedtothecoordinatesystem.ProgrammableaccessoriesACNCmachinewouldntbeveryhelpfulifallitcouldonlymovetheworkpieceintwoormoreaxes.AlmostallCNCmachinesareprogrammableinseveralotherways.ThespecificCNCmachinetypehasalottodowithitsappropriateprogrammableaccessories.Again,anyrequiredfunctionwillbeprogrammableonfull-blownCNCmachinetools.Herearesomeexamplesforonemachinetype(machiningcenters).AutomatictoolchangerMostmachiningcenterscanholdmanytoolsinatoolmagazine.Whenrequired,therequiredtoolcanbeautomaticallyplacedinthespindleformachining.SpindlespeedandactivationThespindlespeed(inrevolutionsperminute)canbeeasilyspecifiedcanbeturnedoninaforwardorreversedirection.Itcanalso,ofcourse,beturnedoff.CoolantManymachiningoperationsrequirecoolantforlubricationandcoolingpurposes.Coolantcanbeturnedinandofffromwithinthemachinecycle.TheCNCprogramThinkofgivinganyseriesofstep-by-stepinstructions.ACNCprogramisnothingmorethananotherkindofinstructionset.Itswritteninsentence-likeformatandthecontrolwillexecuteitinsequentialorder,stepbystep.AspecialseriesofCNCwordsareusedtocommunicatewhatthemachineisintendedtodo.CNCwordsbeginwithletteraddresses(likeFforfederate,Sforspindlespeed,andX,Y&Zforaxismotion).Whenplacedtogetherinalogicalmethod,agroupofCNCwordsmakeupacommandthatresembleasentence.TheCNCcontrolTheCNCcontrolwillinterpretaCNCprogramandactivatetheseriesofcommandsinsequentialorder.Asitreadstheprogram,theCNCcontrolwillactivatetheappropriatemachinefunctions,causeaxismotion,andingeneral,followtheinstructionsgivenintheprogram.AlongwithinterpretingtheCNCprogram,theCNCcontrolhasseveralotherpurposes.AllcurrentmodelCNCcontrolsallowprogramstobemodified(edited)ifmistakesarefound.TheCNCcontrolallowsspecialverificationfunctions(likedryrun)toconfirmthecorrectnessoftheCNCprogram,TheCNCcontrolallowscertainimportantoperatorinputstobespecifiedseparatefromtheprogram,liketoollengthvalues.Ingeneral,theCNCcontrolallowsallfunctionsofthemachinetobemanipulated.WhatisaCAMsystem?Forsimpleapplications(likedrillingholes),theCNCprogramcanbedevelopedmanually.Thatis,aprogrammerwillsitdowntowritetheprogramarmedonlywithpencil,paper,andcalculator.Again,forsimpleapplications,thismaybetheverybestwaytodevelopCNCprograms.