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外文翻译机床,CNC,CAM.doc外文翻译机床,CNC,CAM.doc

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编号:201311171424416550    类型:共享资源    大小:85.50KB    格式:DOC    上传时间:2013-11-17
  
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附录2外文翻译(外文部分)ADVANCEDMACHININGPROCESSESAsthehardwareofanadvancedtechnologybecomesmorecomplex,newandvisionaryapproachestotheprocessingofmaterialsintousefulproductscomeintocommonuse.Thishasbeenthetrendinmachiningprocessesinrecentyears..Advancedmethodsofmachinecontrolaswellascompletelydifferentmethodsofshapingmaterialshavepermittedthemechanicaldesignertoproceedindirectionsthatwouldhavebeentotallyimpossibleonlyafewyearsago.Paralleldevelopmentinothertechnologiessuchaselectronicsandcomputershavemadeavailabletothemachinetooldesignermethodsandprocessesthatcanpermitamachinetooltofarexceedthecapabilitiesofthemostexperiencedmachinist.InthissectionwewilllookatCNCmachiningusingchip-makingcuttingtools.CNCcontrollersareusedtodriveandcontrolagreatvarietyofmachinesandmechanisms,Someexampleswouldberoutersinwoodworking;lasers,plasma-arc,flamecutting,andwaterjetsforcuttingofsteelplate;andcontrollingofrobotsinmanufacturingandassembly.Thissectionisonlyanoverviewandcannottaketheplaceofaprogrammingmanualforaspecificmachinetool.Becauseofthetremendousgrowthinnumbersandcapabilityofcomputers,changesinmachinecontrolsarerapidlyandconstantlytakingplace.Theexcitingpartofthisevolutioninmachinecontrolsisthatprogrammingbecomeseasierwitheachnewadvancedinthistechnology.AdvantagesofNumericalControlAmanuallyoperatedmachinetoolmayhavethesamephysicalcharacteristicsasaCNCmachine,suchassizeandhorsepower.Theprinciplesofmetalremovalarethesame.Thebiggaincomesfromthecomputercontrollingthemachiningaxesmovements.CNC-controlledmachinetoolscanbeassimpleasa2-axisdrillingmachiningcenter(FigureO-1).Withadualspindlemachiningcenter,thelowRPM,highhorsepowerspindlegiveshighmetalremovalrates.ThehighRPMspindleallowstheefficientuseofhighcuttingspeedtoolssuchasdiamondsandsmalldiametercutters(FigureO-2).Thecuttingtoolsthatremovematerialsarestandardtoolssuchasmillingcutters,drills,boringtools,orlathetoolsdependingonthetypeofmachineused.Cuttingspeedsandfeedsneedtobecorrectasinanyothermachiningoperation.ThegreatestadvantageinCNCmachiningcomesfromtheunerringandrapidpositioningmovementspossible.ACNCmachinedoesdotstopattheendofacuttoplanitsnextmove;itdoesnotgetfatigued;itiscapableofuninterruptedmachiningerrorfree,hourafterhour.Amachinetoolisproductiveonlywhileitismakingchips.Sincethechip-makingprocessiscontrolledbytheproperfeedsandspeeds,timesavingscanbeachievedbyfasterrapidfeedrates.Rapidfeedshaveincreasedfrom60to200to400andarenowoftenapproaching1000inchesperminute(IPM).Thesehighfeedratescanposeasafetyhazardtoanyonewithintheworkingenvelopeofthemachinetool.ComplexcontouredshapeswereextremelydifficulttoproductpriortoCNCmachining.CNChasmadethemachiningoftheseshapeseconomicallyfeasible.Designchangesonapartarerelativelyeasytomakebychangingtheprogramthatdirectsthemachinetool.ACNCmachineproducespartswithhighdimensionalaccuracyandclosetoleranceswithouttakingextratimeorspecialprecautions,CNCmachinesgenerallyneedlesscomplexwork-holdingfixtures,whichsavestimebygettingthepartsmachinedsooner.Onceaprogramisreadyandproductionparts,eachpartwilltakeexactlythesameamountoftimeasthepreviousone.Thisrepeatabilityallowsforaveryprecisecontrolofproductioncosts.AnotheradvantageofCNCmachiningistheeliminationoflargeinventories;partscanbemachinedasneeds.Inconventionalproductionoftenagreatnumberofpartsmustbemadeatthesametimetobecosteffective.WithCNCevenonepiececanbemachinedeconomically.Inmanyinstances,aCNCmachinecanperforminonesetupthesameoperationsthatwouldrequireseveralconventionalmachines.WithmodernCNCmachinetoolsatrainedmachinistcanprogramandproductevenasingleparteconomically.CNCmachinetoolsareusedinsmallandlargemachiningfacilitiesandrangeinsizefromtabletopmodelstohugemachiningcenters.InafacilitywithmanyCNCtools,programmingisusuallydonebyCNCprogrammersawayfromtheCNCtools.Themachinecontrolunit(MCU)onthemachineisthenusedmostlyforsmallprogramchangesorcorrections.ManufacturingwithCNCtoolsusuallyrequiresthreecategoriesofpersons.Thefirstistheprogrammer,whoisresponsiblefordevelopingmachine-readycode.Thenextpersoninvolvedisthesetupperson,wholoadstherawstorkintotheMCU,checksthatthecorrecttoolsareloaded,andmakesthefirstpart.Thethirdpersonisthemachineandunloadsthefinishedparts.Inasmallcompany,onepersonisexpectedtoperformallthreeofthesetasks.CNCcontrolsaregenerallydividedintotwobasiccategories.OneusesawardaddressformatwithcodedinputssuchasGandMcodes.Theotherusersaconversationalinput;conversationalinputisalsocalleduser-friendlyorpromptedinput.Laterinthissectionexamplesofeachoftheseprogrammingformatsinmachiningapplicationswillbedescribes.CAMandCNCCAMsystemshavechangedthejoboftheCNCprogrammerfromonemanuallyproducingCNCcodetoonemaximizingtheoutputofCNCmachines.SinceCNCmachinetoolsaremadebyagreatnumberofmanufacturers,manydifferentCNCcontrolunitsareinuse.Controlunitsfromdifferentmanufacturersuseavarietyofprogramformatsandcodes.ManyCNCcodewordsareidenticalfordifferentcontrollers,butagreatnumbervaryfromonetoanother.ToproduceanidenticalpartonCNCmachinetoolswithdifferentcontrollerssuchasonebyFANCU,OKUMAorDYNAPATH,wouldrequirecompletelydifferentCNCcodes.EachmanufacturerisconstantlyimprovingandupdatingitsCNCcontrollers.Theseimprovementsoftenincludeadditionalcodewordspluschangesinhowtheexistingcodeworks.ACAMsystemsallowstheCNCprogrammertoconcentrateonthecreationofanefficientmachiningprocess,ratherthenrelearningchangedcodeformats.ACNCprogrammerlooksattheprintofapartandthenplansthesequenceofmachiningoperationsnecessarytomakeit(FigureO-3).Thisplanincludeseverything,fromtheselectionofpossibleCNCmachinetools,towhichtoolingtouse,tohowthepartisheldwhilemachiningtakesplace.TheCNCprogrammerhastohaveathoroughunderstandingofallthecapacitiesandlimitationsoftheCNCmachinetoolsthataprogramistobemadefor.Machinespecificationssuchashorsepower,maximumspindlespeeds,workpieceweightandsizelimitations,andtoolchangercapacityarejustsomeoftheconsiderationsthataffectprogramming.Anotherareaofmajorimportancetotheprogrammeristheknowledgeofmachiningprocesses.Anexamplewouldbetheselectionofthesurfacefinishrequirementspecifiedinthepartprint.Thesequenceofmachiningprocessesiscriticaltoobtainacceptableresults.Cuttingtoollimitationshavetobeconsideredandthisrequiresknowledgeofcuttingtoolmaterials,tooltypes,andapplicationrecommendations.Agoodprogrammerwillspendaconsiderableamountoftimeinresearchingtherapidlygrowingvolumeofnewandimprovedtoolsandtoolmaterials.Oftenthetoolthatwasonthecuttingedgeoftechnologyjusttwoyearsagoisnowobsolete.Informationonnewtoolscancomefromcatalogsortoolmanufacturers'toolingengineers.Helpintoolselectionoroptimumtoolworkingconditionscanalsobeobtainedfromtoolmanufacturersoftware.ExampleswouldbeKennametal's"TOOLPRO",softwaredesignedtohelpselectthebesttoolgrade,speed,andfeedratesfordifferentworkmaterialsinturningapplication.Anotherveryimportantfeatureof"TOOLPRO"isthedisplayofthehorsepowerrequirementforeachmachiningselection.Thisallowtheprogrammertoselectacombinationofcuttingspeed,feedrate,anddepthofcutthatequalsthemachine'smaximumhorsepowerforroughingcuts.Forafinishingcut,thesmallestdiameterofthepartbeingmachinedisselectedandthenthecuttingspeedvarieduntiltheRPMisequaltothemaximumRPMofthemachine.Thishelpsinmaximizingmachiningefficiency.Knowingthehorsepowerrequirementforacutiscriticalifmorethanonetooliscuttingatthesametime.SoftwareforamachiningcenterapplicationwouldbeIngersollToolCompany's"ActualChipThickness",aprogramusedtocalculatethechipthicknessinrelationtofeed-per-toothforamillingcutter,especiallyduringashallowfinishingcut.Ingersoll's"RigidityAnalysis"softwareealculatestooldeflectionforendmillsasafunctionoftoolstiffnessandtoolforce.Tothispointwelookedatsomegeneralqualificationsthataprogrammershouldpossess.NowweexaminehowaCAMsystemworks.PointControlCompany'sSmartCamsystemusesthefollowingapproach.First,theprogrammermakesamentalmodeloftheparttobemachined.Thisincludesthekindofmachiningtobeperformed-turningormilling.Thenthepartprintisstudiedtodevelopamachiningsequence,roughingandfinishingcuts,drilling,tapping,andboringoperations.Whatwork-holdingdeviceistobeused,aviseorfixtureorclamps?Aftertheseconsiderations,computerinputcanbestarted.FirstcomesthecreationofaJOBPLAN.ThisJOBPLANconsistsofentriessuchasinchormetricunits,machinetype,partID,typeofworkpiecematerial,setupnotes,andadescriptionoftherequiredtools.Thislineofinformationdescribesthetoolbynumber,type,andsizeandincludestheappropriatecuttingspeedandfeedrate.Afteralltheselectedtoolsareentered,thefileissaved.Thesecondprogrammingstepisthemakingofthepart.Thisrepresentsagraphicmodelingoftheprojectedmachiningoperation.AfterselectingatoolfromthepreparedJOBPLAN,parametersforthecuttingoperationareentered.Foradrill,oncethecoordinatelocationoftheholeandthedeptharegiven,acircleappearsonthatspot.Ifthelocationisincorrect,theUNDOcommanderasesthisentryandallowsyoutogivenewvaluesforthisoperation.Whenanendmillisbeingused,cuttingmovements(toolpath)areusuallydefinedaslinesandarcs.Asalineisprogrammed,thetoolpathisgraphicallydisplayedanderrorscanbecorrectedinstantly.Atanytimeduringprogramming,thecommandSHOWPATHwillshowtheactualtoolpathforeachoftheprogrammedtools.Thetoolswillbedisplayedinthesequenceinwhichtheywillbeusedduringactualmachining.Ifthesequenceofatoolmovementneedstobechanged,afewkeystrokeswilltothat.SometimesinCAMtheprogrammingsequenceisdifferentfromtheactualmachiningorder.Anexamplewouldbethemachiningofapocketinapart.WithCAM,thefinishedpocketoutlineisprogrammedfirst,thenthisoutlineisusedtodefinetheroughingcutstomachinethepocket.Theroughingcutsarecomputergeneratedfrominputssuchasdepthandwidthofcutandhowmuchmaterialtoleaveforthefinishcut.Differentroughingpatternscanbetriedouttoallowtheprogrammertoselectthe
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