外文翻译机床实践.docx
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外文翻译机床实践.docx
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外文翻译机床实践
附录2外文翻译(外文部分)
ADVANCEDMACHININGPROCESSES
Asthehardwareofanadvancedtechnologybecomesmorecomplex,newandvisionaryapproachestotheprocessingofmaterialsintousefulproductscomeintocommonuse.Thishasbeenthetrendinmachiningprocessesinrecentyears..Advancedmethodsofmachinecontrolaswellascompletelydifferentmethodsofshapingmaterialshavepermittedthemechanicaldesignertoproceedindirectionsthatwouldhavebeentotallyimpossibleonlyafewyearsago.
Paralleldevelopmentinothertechnologiessuchaselectronicsandcomputershavemadeavailabletothemachinetooldesignermethodsandprocessesthatcanpermitamachinetooltofarexceedthecapabilitiesofthemostexperiencedmachinist.
InthissectionwewilllookatCNCmachiningusingchip-makingcuttingtools.CNCcontrollersareusedtodriveandcontrolagreatvarietyofmachinesandmechanisms,Someexampleswouldberoutersinwoodworking;lasers,plasma-arc,flamecutting,andwaterjetsforcuttingofsteelplate;andcontrollingofrobotsinmanufacturingandassembly.Thissectionisonlyanoverviewandcannottaketheplaceofaprogrammingmanualforaspecificmachinetool.Becauseofthetremendousgrowthinnumbersandcapabilityofcomputers,changesinmachinecontrolsarerapidlyandconstantlytakingplace.Theexcitingpartofthisevolutioninmachinecontrolsisthatprogrammingbecomeseasierwitheachnewadvancedinthistechnology.
AdvantagesofNumericalControl
AmanuallyoperatedmachinetoolmayhavethesamephysicalcharacteristicsasaCNCmachine,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.
CAMandCNC
CAMsystemshavechangedthejoboftheCNCprogrammerfromonemanuallyproducingCNCcodetoonemaximizingtheoutputofCNCmachines.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.Afteralltheselectedtoolsa
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