外文翻译--计算机辅助设计及制造CADCAM.doc

本科毕业论文（设计）相关中英文翻译资料资料题目：计算机辅助设计与制造学生姓名：所在院系：机电学院所学专业：机电技术教育CADandCAMTheenginelathe,oneoftheoldestmetalremovalmachines,hasanumberofusefulandhighlydesirableattributes.Todaytheselathesareusedprimarilyinsmallshopswheresmallerquantitiesratherthanlargeproductionrunsareencountered.Inthebeginning,CADsystemswerenomorethanagraphicseditorwithsomebuilt-indesignsymbols.Thegeometryavailabletotheuserwaslimitedtolines,circulararcs,andthecombinationofthem.Thedevelopmentoffree-formcurvesandsurfaces,suchasCoonspatch,Bezierspatch,andB-spline,enablesaCADsystemsallowadesignertomoveintothethirddimension.Becauseathree-dimensionalmodelcontainsenoughinformationforNCcutter-pathprogramming,thelinkagebetweenCADandNCcanbedeveloped.SocalledturnkeyCAD/CAMsystemsweredevelopedbasedonthisconceptandbecamepopularinthe1970sand1980s.The1970smarkedthebeginningofanewerainCADtheinventionofthree-dimensionalsolidmodeling.Inthepast,three-dimensional,wire-framemodelsrepresentedanobjectonlybyitsboundingedges.Theyareambiguousinthesensethatseveralinterpretationsmightbepossibleforasinglemodel.Thereisalsonowaytofindthevolumetricinformationofamodel.Solidmodelscontaincompleteinformation；therefore,notonlycantheybeusedtoproduceengineeringdrawing,butengineeringanalysiscanbeperformedonthesamemodelaswell.Later,manycommercialsystemsandresearchsystemsweredeveloped.QuiteafewofthesesystemswerebasedonthePADLandBUILDsystems.Althoughtheyarepowerfulinrepresentation,manydeficienciesstillexist.Forexample,suchsystemshaveextremecomputationandresource(memory)requirements,anunconventionalwayofmodelingobjectsandalackoftolerancecapabilityhaveallhinderedCADapplications.Itwasnotuntilthemid-1980sthatsolidmodelersmadetheirwayintothedesignenvironment.Today,theiruseisascommonasdraftingandwire-framemodelapplication.CADimplementationsonpersonalcomputers(PCs)havebroughtCADtothemasses.ThisdevelopmenthasmadeCADavailableandaffordable.CADoriginallywasatoolusedonlybyaerospaceandothermajorindustrialcorporation.TheintroductionofPCCADpackages,suchasAutoCAD,VersaCAD,CADKEYsystems,madesmallcompanies,evenindividuals,ownanduseCAD.By1988,morethan100,000PCCADPackageshadbeensold.Today,PC-basedsolidmodelersareavailableandarebecomingincreasinglypopular.BecauserapiddevelopmentsinmicrocomputershaveenabledPCstocarrytheheavycomputationalloadnecessaryforsolidmodeling,manysolidgraphicsuserinterface(GUI),CADsystemscanbeportedeasilyfromonecomputertoanother,mostmajorCADsystemsareabletorunonavarietyofplatforms.Thereislittledifferencebetweenmainframe,workstation,andPC-basedCADsystems.Whenadesignhasfrozen,manufacturingcanbegin.Computershaveanimportantroletoplayinmanyaspectsofproduction.Numericallycontrolled(NC)machinetoolsneedapartprogramtodefinethecomponentsbeingmade；computertechniquesexisttoassist,andinsomecasesvirtuallyautomatethegenerationofpartprograms.Modernshipbuildingfabricatesstructuresfromweldedsteelplatesthatarecutfromalargesteelsheet.Computer-controlledflamecuttersareoftenusedforthistaskandthecomputerisusedtocalculatetheoptimumlayoutofthecomponentstominimizewastemetal.Printedcircuitboardassemblycanalsobeimprovedbycomputermethods.Qualityismaintainedbycomputer-controlledautomatictestequipmentthatdiagnosesfaultsinaparticularboardandrejectsdefectiveboardsfromtheassemblyline.ComputersareusedextensivelytoplottheartworkusedtoetchprintedcircuitboardsandalsotoproducepartprogramsforNCdrillingmachines.Oneofthemostimportantmanufacturingfunctionsisstockandproductioncontrol.Iftheoriginaldesignisdoneonacomputer,obtaininglistsofmaterialrequirementsisstraightforward.Standardcomputerdataprocessingmethodsareemployedtoorganizetheworkflowandordercomponentswhenrequired.Partgeometryrequirescalculationofalargenumberoftoolpositions.PartprogrammingsoftwareisusuallyincorporatedintoafamilyofCAM(ComputerAidedManufacturing)software.SomeCAMsoftwareisassociatedwithCAD(ComputerAidedDesign)softwareintoCAD/CAMstations.ThentheCAMsoftwarecanusetheCADfilesasasourceofdata,whichspeedsuptheprogrammingprocess.Partprogrammingsoftwareisuser-friendly,meaningthattheprogrammerdoesnothavetoknowthecomputerprogramminglanguageoritsoperatingsystem.Itusesscreenmenustoleadtheuserthroughtheprogrammingprocess.Datacanbeenteredviathekeyboard,themouse,orthefunctionkeys.Experiencedprogrammerscanusebuilt-inmacrocapabilitiesandadvancedtechniquessuchasafamilyofpartstobecomeevenmoreproductive.Programmingsoftwarehasadynamicgraphicsdatabasetoholdtheactualmachiningsequences.Thesesequencescanbeviewed,edited,chained,ordeleted.TheprogrammingcanbeaccomplishedwhethersinglecutsorCNCmachinecannedcyclewillbeused.Thesoftwarewillalsoautomaticallycalculatetheproperfeedsandspeedstobeusedduringthemachining,createatoolinglist,anddefinethetoolpath.Programmerscanusedifferentlayerstoassociatewitheachprofilebeingcreatedortoconstructclampsandfixturestogetacompletepictureofthepartsetup.Thetoolmotioncanbeseenasitwilloccuratthemachine.Usingpartprogrammingsoftware,theprogrammercaneasilysolvetrigonometryproblemstodefineanaccuratetoolpath.Whentheprogramisdone,theprogrammercansenditfromthePCtothemachineviaacommunicationchannelusingbuilt-insoftwarewithcommunicationscapability.Goodpartprogrammingsoftwareiscapableof:（1）Establishingthemachiningparametersandtoolingforaparticularmachineorjob.（2）Definingthegeometryandtoolpath.（3）Codegeneration,enablingtheprogrammertousestandardcommunicationsprotocolsorcreatehisorherown.