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外文翻译--艺规程制订与并行工程.doc

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外文翻译--艺规程制订与并行工程.doc

英文原文ProcessPlanningandConcurrentEngineeringProcessPlanningProcessplanninginvolvesdeterminingthemostappropriatemanufacturingandassemblyprocessesandthesequenceinwhichtheyshouldbeaccomplishedtoproduceagivenpartorproductaccordingtospecificationssetforthintheproductdesigndocumentation.Thescopeandvarietyofprocessesthatcanbeplannedaregenerallylimitedbytheavailableprocessingequipmentandtechnologicalcapabilitiesofthecompanyofplant.Partsthatcannotbemadeinternallymustbepurchasedfromoutsidevendors.Itshouldbementionedthatthechoiceofprocessesisalsolimitedbythedetailsoftheproductdesign.Thisisapointwewillreturntolater.Processplanningisusuallyaccomplishedbymanufacturingengineers.Theprocessplannermustbefamiliarwiththeparticularmanufacturingprocessesavailableinthefactoryandbeabletointerpretengineeringdrawings.Basedontheplannersknowledge,skill,andexperience,theprocessingstepsaredevelopedinthemostlogicalsequencetomakeeachpart.Followingisalistofthemanydecisionsanddetailsusuallyincludewithinthescopeofprocessplanning..Interpretationofdesigndrawings.Thepartofproductdesignmustbeanalyzedmaterials,dimensions,tolerances,surfacefinished,etc.atthestartoftheprocessplanningprocedure..Processandsequence.Theprocessplannermustselectwhichprocessesarerequiredandtheirsequence.Abriefdescriptionofprocessingstepsmustbeprepared..Equipmentselection.Ingeneral,processplannersmustdevelopplansthatutilizeexistingequipmentintheplant.Otherwise,thecomponentmustbepurchased,oraninvestmentmustbemadeinnewequipment..Tools,dies,molds,fixtures,andgags.Theprocessmustdecidewhattoolingisrequiredforeachprocessingstep.Theactualdesignandfabricationofthesetoolsisusuallydelegatedtoatooldesigndepartmentandtoolroom,oranoutsidevendorspecializinginthattypeoftooliscontacted..Methodsanalysis.Workplacelayout,smalltools,hoistsforliftingheavyparts,eveninsomecaseshandandbodymotionsmustbespecifiedformanualoperations.Theindustrialengineeringdepartmentisusuallyresponsibleforthisarea..Workstandards.Workmeasurementtechniquesareusedtosettimestandardsforeachoperation.Cuttingtoolsandcuttingconditions.Thesemustbespecifiedformachiningoperations,oftenwithreferencetostandardhandbookrecommendations.ProcessplanningforpartsForindividualparts,theprocessingsequenceisdocumentedonaformcalledaroutesheet.Justasengineeringdrawingsareusedtospecifytheproductdesign,routesheetsareusedtospecifytheprocessplan.Theyarecounterparts,oneforproductdesign,theotherformanufacturing.Atypicalprocessingsequencetofabricateanindividualpartconsistsof1abasicprocess,2secondaryprocesses,3operationstoenhancephysicalproperties,and4finishingoperations.Abasicprocessdeterminesthestartinggeometryoftheworkparts.Metalcasting,plasticmolding,androllingofsheetmetalareexamplesofbasicprocesses.Thestartinggeometrymustoftenberefinedbysecondaryprocesses,operationsthattransformthestartinggeometryorclosetofinalgeometry.Thesecondarygeometryprocessesthatmightbeusedarecloselycorrelatedtothebasicprocessthatprovidesthestartinggeometry.Whensandcastingisthebasicprocesses,machiningoperationsaregenerallythesecondprocesses.Whenarollingmillproducessheetmetal,stampingoperationssuchaspunchingandbendingarethesecondaryprocesses.Whenplasticinjectionmoldingisthebasicprocess,secondaryoperationsareoftenunnecessary,becausemostofthegeometricfeaturesthatwouldotherwiserequiremachiningcanbecreatedbythemoldingoperation.Plasticmoldingandotheroperationthatrequirenosubsequentsecondaryprocessingarecallednetshapeprocesses.Operationsthatrequiresomebutnotmuchsecondaryprocessingusuallymachiningarereferredtoasnearnetshapeprocesses.Someimpressiondieforgingsareinthiscategory.Thesepartscanoftenbeshapedintheforgingoperationbasicprocessessothatminimalmachiningsecondaryprocessingisrequired.Oncethegeometryhasbeenestablished,thenextstepforsomepartsistoimprovetheirmechanicalandphysicalproperties.Operationstoenhancepropertiesdonotalterthegeometryofthepartinstead,theyalterphysicalproperties.Heattreatingoperationsonmetalpartsarethemostcommonexamples.Similarheatingtreatmentsareperformedonglasstoproducetemperedglass.Formostmanufacturedparts,thesepropertyenhancingoperationsarenotrequiredintheprocessingsequence.Finallyfinishoperationsusuallyprovideacoatontheworkpartsorassemblysurface.Examplesincludedelectroplating,thinfilmdepositiontechniques,andpainting.Thepurposeofthecoatingistoenhanceappearance,changecolor,orprotectthesurfacefromcorrosion,abrasion,andsoforth.Finishingoperationsarenotrequiredonmanypartsforexample,plasticmoldingrarelyrequirefinishing.Whenfinishingisrequired,itisusuallythefinalstepintheprocessingsequence.ProcessingPlanningforAssembliesThetypeofassemblymethodusedforagivenproductdependsonfactorssuchas1theanticipatedproductionquantities2complexityoftheassembledproduct,forexample,thenumberofdistinctcomponentsand3assemblyprocessesused,forexample,mechanicalassemblyversuswelding.Foraproductthatistobemadeinrelativelysmallquantities,assemblyisusuallyperformedonmanualassemblylines.Forsimpleproductsofadozenorsocomponents,tobemadeinlargequantities,automatedassemblysystemsareappropriate.Inanycase,thereisaprecedenceorderinwhichtheworkmustbeaccomplished.Theprecedencerequirementsaresometimesportrayedgraphicallyonaprecedencediagram.Processplanningforassemblyinvolvesdevelopmentofassemblyinstructions,butinmoredetail.Forlowproductionquantities,theentireassemblyiscompletedatasinglestation.Forhighproductiononanassemblyline,processplanningconsistsofallocatingworkelementstotheindividualstationsoftheline,aprocedurecalledlinebalancing.Theassemblylineroutestheworkunittoindividualstationsintheproperorderasdeterminedbythelinebalancesolution.Asinprocessplanningforindividualcomponents,anytoolsandfixturesrequiredtoaccomplishanassemblytaskmustbedetermined,designed,built,andtheworkstationarrangementmustbelaidout.MakeorBuyDecisionAnimportantquestionthatarisesinprocessplanningiswhetheragivenpartshouldbeproducedinthecompanysownfactoryorpurchasedfromanoutsidevendor,andtheanswertothisquestionisknownasthemakeorbuydecision.Ifthecompanydoesnotpossessthetechnologicalequipmentorexpertiseintheparticularmanufacturingprocessesrequiredtomakethepart,thentheanswerisobviousThepartmustbepurchasedbecausethereisnointernalalternative.However,inmanycases,thepartcouldeitherbemadeinternallyusingexistingequipment,oritcouldbepurchasedexternallyfromavendorthatprocesssimilarmanufacturingcapability.Inourdiscussionofthemakeorbuydecision,itshouldberecognizedattheoutsetthatnearlyallmanufacturesbuytheirrawmaterialsfromsupplies.Amachineshoppurchasesitsstartingbarstockfromametalsdistributoranditssandcastingsfromafoundry.Aplasticmolding

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