徐州工程學院畢業設計(論文)1翻譯部分英文部分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.徐州工程學院畢業設計(論文)2ComplexcontouredshapeswereextremelydifficulttoproductpriortoCNCmachining.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.ACNCprogrammerlooksat徐州工程學院畢業設計(論文)3theprintofapartandthenplansthesequenceofmachiningoperationsnecessarytomakeit(FigureO-3).Thisplanincludeseverything,fromtheselectionofpossibleCNCmachinetools,towhichtoolingtouse,tohowthepartisheldwhilemachiningtakesplace.TheCNCprogrammerhastohaveathoroughunderstandingofallthecapacitiesandlimitationsoftheCNCmachinetoolsthataprogramistobemadefor.Machinespecificationssuchashorsepower,maximumspindlespeeds,workpieceweightandsizelimitations,andtoolchangercapacityarejustsomeoftheconsiderationsthataffectprogramming.Anotherareaofmajorimportancetotheprogrammeristheknowledgeofmachiningprocesses.Anexamplewouldbetheselectionofthesurfacefinishrequirementspecifiedinthepartprint.Thesequenceofmachiningprocessesiscriticaltoobtainacceptableresults.Cuttingtoollimitationshavetobeconsideredandthisrequiresknowledgeofcuttingtoolmaterials,tooltypes,andapplicationrecommendations.Agoodprogrammerwillspendaconsiderableamountoftimeinresearchingtherapidlygrowingvolumeofnewandimprovedtoolsandtoolmaterials.Oftenthetoolthatwasonthecuttingedgeoftechnologyjusttwoyearsagoisnowobsolete.Informationonnewtoolscancomefromcatalogsortoolmanufacturerstoolingengineers.Helpintoolselectionoroptimumtoolworkingconditionscanalsobeobtainedfromtoolmanufacturersoftware.ExampleswouldbeKennametalsTOOLPRO,softwaredesignedtohelpselectthebesttoolgrade,speed,andfeedratesfordifferentworkmaterialsinturningapplication.AnotherveryimportantfeatureofTOOLPROisthedisplayofthehorsepowerrequirementforeachmachiningselection.Thisallowtheprogrammertoselectacombinationofcuttingspeed,feedrate,anddepthofcutthatequalsthemachinesmaximumhorsepowerforroughingcuts.Forafinishingcut,thesmallestdiameterofthepartbeingmachinedisselectedandthenthecuttingspeedvarieduntiltheRPMisequaltothemaximumRPMofthemachine.Thishelpsinmaximizingmachiningefficiency.Knowingthehorsepowerrequirementforacutiscriticalifmorethanonetooliscuttingatthesametime.SoftwareforamachiningcenterapplicationwouldbeIngersollToolCompanysActualChipThickness,aprogramusedtocalculatethechipthicknessinrelationtofeed-per-toothforamillingcutter,especiallyduringashallowfinishingcut.IngersollsRigidityAnalysissoftwareealculatestooldeflectionforendmillsasafunctionoftoolstiffnessandtoolforce.Tothispointwelookedatsomegeneralqualificationsthataprogrammershouldpossess.NowweexaminehowaCAMsystemworks.PointControlCompanysSmartCamsystemusesthefollowingapproach.First,theprogrammermakesamentalmodeloftheparttobemachined.Thisincludesthekindofmachiningtobeperformed-turningormilling.Thenthepartprintisstudiedtodevelopamachiningsequence,roughingandfinishingcuts,drilling,tapping,andboringoperations.Whatwork-holdingdeviceistobeused,aviseorfixtureorclamps?Aftertheseconsiderations,computerinputcanbestarted.FirstcomesthecreationofaJOBPLAN.ThisJOBPLANconsistsofentriessuchasinchormetricunits,machinetype,partID,typeofworkpiecematerial,setupnotes,andadescriptionoftherequiredtools.Thislineofinformationdescribesthetoolbynumber,type,andsizeandincludesthe徐州工程學院畢業設計(論文)4appropriatecuttingspeedandfeedrate.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.Differentroughingpatternscanbetriedouttoallowtheprogrammertoselectthemostefllcientonefortheactualmachiningcuts.Sinceeachtoolisrepresentedbyadifferentcolor,itiseasytoobservethetoolpathmadebyeachone.ACAMsystemletstheprogrammerviewthegraphicsmodelfromvaryingangles,suchasatop,front,side,orisometricview.Atoolpaththatlookscorrectfromatopview,mayshowfromafrontviewthatthedepthofthecuttingtoolisincorrect.Changescaneasilybemadeandseenimmediately.Whenthetoolpathandthesequenceofoperationsaresatisfactor