专业英语翻译.docx

专业英语翻译.docx

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专业英语翻译

翻译资料：

Computer-aideddesign

Computer-aideddesignistheuseofcomputersystemstofacilitatethecreation,modification,analySIS,andoptimizationofadesign.Inthiscontextthetermcomputersystemmeansacombinationofhardwareandsoftware.Computer-aidedmanufacturingistheuseofacomputersystemtoplan,manage,andcontroltheopemtionofamanufacturingplant.AnappreciationofthescopeofCAD/CAMcanbeobtainedbyconsideringthestagesthatmustbecompletedinthedesignandmanufactureofaproduct,asillustmtedbytheproductcycleshowninFig.5.8.Theinnerloopofthisfigurein~ludesthevariousstepsintheproductcycleandtheouterloopshowssomeofthefunctionsofCAD/CAMsuperimposedontheproductcycle.

Basedonmarketandcustomerrequirements,aproductisconceived,whichmaywellbeamodificationofpreviousproducts.Thisproductisthendesignedindetail,includinganyrequireddesignanalysis,anddrawingsandpartslistsareprepared.Subsequently,thevariouscomponentsandassembliesareplannedforproduction,whichinvolvestheselectionofsequencesofprocessesandmachinetoolsandtheestimationofcycletimes,togetherwiththedeterminationofprocessparameters,suchasfeedsandspeedsCJJ.Whentheproductisinproduction,schedulingandcontrolofmanufacturetakeplace,andtheorderandtimingofeachmanufacturingstepforeachcomponentandassemblyisdetemnnedtomeetanoverallmanufacturingschedule.Theactualmanufacturingandcontrolofproductqualitythentakesplaceaccordingtothescheduleandthefinalproductsaredeliveredtothecustomers.

Computer-basedprocedureshavebeenorarebeingdevelopedtofacilitateeachofthesestagesintheproductcycle,andtheseareshownintheouterloopofFig.5.8.Computer-aideddesignanddraftingtechniqueshavebeendeveloped.Theseallowageometricmodeloftheproductanditscomponentstobecreatedinthecomputer.ThismodelcantlIenbeanalyzedusingspecializedsoftwarepackages,suchasthoseforfiniteelementstressanalysis,mechanismsdesign,andsoon.Subsequently,dmwingsandpartslistscanbeproducedwithcomputer-aideddraftingsoftwareandplotters.Computer-aidedprocess-planningsystems,includingtheprepamtionofNCprograms,areavailablethatproduceworkplans,estimates,andmanufacturinginstructionsautomaticallyfromgeometricdescriptionsofthecomponentsandassembliesCll•

r'orschedulingandproductioncontrol,largeamountsofdataandnumerousrelativelysimplecalculationsmustbecarriedout.Oneexampleisthedeterminationoforderquantitiesbysubtmctingstocklevelsfromforecastsofthenumberofitemsrequiredduringaparticularmanufacturingperiod®.Manycommercialsoftwarepackagesareavailableforscheduling,inventorycontrol,andshopfloorcontrol,includingmaterialsrequirementsplanning（MRP）systems.Attheshop-floorlevelcomputersareusedextensivelyforthecontrolandmonitoringofindividualmachines.

Thereisadifferenceinthetimescalerequiredforprocessingdataandtheissuingofinstructionsforthesevariousapplicationsofcomputersintheproductcycle.Forexample,designandprocess-planningfunctionsarecarriedoutonceforeachnewproductandthetimescalerequiredisontheorderofweekstoyearsforthecompetionofthetask.Schedulingandproductionperiodcusuallyoneweek,throughouttheyear.atthemachine-controllevelin-structionsmustbeissuedcontinuallywithatimescaleofmicro-ornanosecondsinmanycases.

OneofthemajorobjectivesofCAMistheintegrationofthevariousactivitiesintheproductcycleintooneunifiedsystem,inwhichdataistransfenedfromonefunctiontoanotherautomatically.Thisleadstothe

conceptofcomputer-integratedmanufacture（CIM）,withthefinalobjectivebeingthe"paperless"factory.Severaldevelopmentshavetakenplace,butnototallyintegratedCIMsystemshaveyetbeenachieved.Sincethedesignandprocess-planningfunctionsarecarnedoutonceintheproductcycle,thesearethemostsuitablefunctionsforintegration.Thisintegrationisparticularlydesirablebecausethegeometricdatageneratedduringthedesignprocessisoneofthebasicinputsusedbyprocessplannipgwhendeterminingappropriatemanufacturingsequencesandworkplans®.Consequently,variousactivitiesindesilSllandprocessplanningcanshareacommondesignandmanufacturingdatabase,asillustratedinFig.5.9.Withsuchasystem,geometricmodelsoftheproductsandcomponentsarecreatedduringthedesignprocess.Thisdataisthenaccessedbyvariousdownstreamactivities,includingNCprogramming,processplanning,androbotprogramming.Theprogramsandworkplansgeneratedbytheseactivitiesarealsoaddedtothedatabase.Productioncontrolandinventorycontrolprogramscanthenaccesstheworkplans,timeestimates,andpartslists（billofmaterialsfile）,inpreparingthemanufacturingschedules,forexample.

1Computer-AidedDesign

Computer-aideddesign,orCADasitismorecommonlyknown,hasgrownfromanarrowactivityandconceI;>ttoamethodologyofdesignactivitiesthatincludeacomputerorgroupofcomputersusedtoassistintheanalysis,development,anddraw-ingofproductcomponents.TheoriginalCADsystemsdevelopedandusedinindustrycouldmorerealisticallybeclassifiedascomputer-aideddraftingsystems.However,thebenefits,ofusingbasicgeometricinformationforstructuralanalysisandplanningformanufacturingwerequicklyrecognizedandincludedinmanyCADsystems.Today,asinthepast,thebasisforCADisstillthedraftingfeaturesorinteractivecomputergraphics（ICG）thatthesesystemswereoriginallydesignedtoperform.However,thescopeofthesesystemshastakenonanewmeaning.

Ingeneral,therearefourbasicreasonsforimplementingCADsystems.

1.Areductionindesigntime.Thetotaltimerequiredfrominceptionofanideatoitscompletespecificationcanbereducedbyanorderofmagnitudebyusingeasilyalterablegeometricmodels.Designperturbations/changescanbecompletedinminimaltime.Wholescenariosofdesignpossibilitiescanbeconstructedquickly.

2.Improvedproductdesign.BecauseCADsystemsallowthedesignertoaltertheproductwithoutmajorredrav-ringwithconsiderabletimecommitment,manyfinaldesignscanbeconstructedinareasonableperiodoftime.Similarly,thesedesignscanbeautomaticallyanalyzedforstlUCturalcharacteristicsbyusingcomputer-aidedengineering（CAE）softwaresuchasfinite-elementmodeling（FEM）.

3.Improvedinformationaccess.BecauseCADdrawingsarestoredinalargecomputerdatabase,theycanbeaccessedquicklyandeasily.Partscanbecodedonthebasisofgeometricshape,andsimilarpartscanbecalleduptoassistinthedesignandspecificationofnewparts."Standardparts"canbeemployedwheneverpossible,ratherthanhavingtore-inventthewheeloverandagain.

4.Manufacturing,datacreation.Withtheadventofnumericalcontrol（NC）carnetheneedtoautomaticallygeneratethetoolpathrequiredformachining.Sincethepartgeometrydictatesthemachiningrequired,kno,,-ingthepartshapecanallowfor（semi-）automaticpart-prograrnpreparation.CADdatacanalsobeusedforautomatedprocessplanning.

Itisinterestingtonotethattwentyyearsagoifapartofreasonablegeometricandmanufacturingsophisticationwascreated,hundredsofdesignanddraftinghourswouldberequired.Afterthepartwasspecified,marlufacturewouldbegin.ll1isplanningwouldnormallyrequiresomeminordesignchanges（backtothedesigneranddraftsman）,andmighttakeaslongastheoriginaldesignprocess.Specialtooling,fixturing,etc.,mightalsobespecifiedduringtheplarmingformanufacture.Inall,theentireprocessofproductandprocessdesigncouldtakeseveralweeksormonths.Withtoday'sCADsystems,designing（againgarea.'\onablysophisticatedcomponent）andgeneratingmanufacturingplans,preparing

paItprogramsandproducingthepmispossibleindaysratherthanweeks.Ingeneral,thetatalen!

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ineeringaI1dmanufacturingtimehasbeenmarkedlyusingintegratedCAD/CAMmethodalogies.

2Computer-AidedlVIanufacturing

Thescientificstudyofmetal-cuttingandautamatiantechniquesarepnxluctsafthetwentiethcentury.Two.pianeersofthesetechniqueswereFrederickTaylarandHenryFord.Duringtl1eearly1900s,theimprovingU.S.standardaflivingbroughtanewhighinpenlOnalwealth.'Illemajarresultwa<;theincreaseddemandfardurablegoods.Thisincreaseddemandmeantthatmanufacturingcauldno.longerbetreatedasablacksmithtrade,aIldtheuseafscientificstudywasemplayedinmanufacturinganalysis.Taylarpianeeredstudiesin"scientificITlaI1agement"inwhichmethodsfarproductianbybothmenandmachineswerestudied.Taylaralsoconduetedmeatal-cuttingexperimentsattheMidvaleSteelCampai1ythatlasted26yeaI"Sandproduced400tansafmetalchips.TheresultafTaylar'smetal-cuttingexperimentswasthedevelapmentaftheTaylartool-lifeequationthatisstillusedinindustrytoday.Thistoollifeequatianisstillthebasisafdetenniningecanamicmetalcuttingandhasbeenusedinadaptivecanhulledmachining.

HenryFord'scontributionstookadifferentturnfromTaylor's.Fordrefinedanddevelopedtheuseofassemblylinesforthemajorcomponentmanufacturerofhisautomobile.FordfeltthateveryAmericanfamilysh~dhaveanautomobile,andiftheycouldbemanufacturedinexpensivelyenoughtheneveryfamilywouldbuyone.SeveralmechanismsweredevelopedatFordtoaccommodateassemblylines.TheautomationthatForddevelopedwasbuiltintothehardware,andFordrealizedthatsignificantdemandwasnecessarytooffs