外文翻译--艺规程制订与并行工程.doc

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1、英文原文ProcessPlanningandConcurrentEngineeringProcessPlanningProcessplanninginvolvesdeterminingthemostappropriatemanufacturingandassemblyprocessesandthesequenceinwhichtheyshouldbeaccomplishedtoproduceagivenpartorproductaccordingtospecificationssetforthintheproductdesigndocumentation.Thescopeandvarietyo

2、fprocessesthatcanbeplannedaregenerallylimitedbytheavailableprocessingequipmentandtechnologicalcapabilitiesofthecompanyofplant.Partsthatcannotbemadeinternallymustbepurchasedfromoutsidevendors.Itshouldbementionedthatthechoiceofprocessesisalsolimitedbythedetailsoftheproductdesign.Thisisapointwewillretu

3、rntolater.Processplanningisusuallyaccomplishedbymanufacturingengineers.Theprocessplannermustbefamiliarwiththeparticularmanufacturingprocessesavailableinthefactoryandbeabletointerpretengineeringdrawings.Basedontheplannersknowledge,skill,andexperience,theprocessingstepsaredevelopedinthemostlogicalsequ

4、encetomakeeachpart.Followingisalistofthemanydecisionsanddetailsusuallyincludewithinthescopeofprocessplanning.Interpretationofdesigndrawings.Thepartofproductdesignmustbeanalyzed(materials,dimensions,tolerances,surfacefinished,etc.)atthestartoftheprocessplanningprocedure.Processandsequence.Theprocessp

5、lannermustselectwhichprocessesarerequiredandtheirsequence.Abriefdescriptionofprocessingstepsmustbeprepared.Equipmentselection.Ingeneral,processplannersmustdevelopplansthatutilizeexistingequipmentintheplant.Otherwise,thecomponentmustbepurchased,oraninvestmentmustbemadeinnewequipment.Tools,dies,molds,

6、fixtures,andgags.Theprocessmustdecidewhattoolingisrequiredforeachprocessingstep.Theactualdesignandfabricationofthesetoolsisusuallydelegatedtoatooldesigndepartmentandtoolroom,oranoutsidevendorspecializinginthattypeoftooliscontacted.Methodsanalysis.Workplacelayout,smalltools,hoistsforliftingheavyparts

7、,eveninsomecaseshandandbodymotionsmustbespecifiedformanualoperations.Theindustrialengineeringdepartmentisusuallyresponsibleforthisarea.Workstandards.Workmeasurementtechniquesareusedtosettimestandardsforeachoperation.Cuttingtoolsandcuttingconditions.Thesemustbespecifiedformachiningoperations,oftenwit

8、hreferencetostandardhandbookrecommendations.ProcessplanningforpartsForindividualparts,theprocessingsequenceisdocumentedonaformcalledaroutesheet.Justasengineeringdrawingsareusedtospecifytheproductdesign,routesheetsareusedtospecifytheprocessplan.Theyarecounterparts,oneforproductdesign,theotherformanuf

9、acturing.Atypicalprocessingsequencetofabricateanindividualpartconsistsof:(1)abasicprocess,(2)secondaryprocesses,(3)operationstoenhancephysicalproperties,and(4)finishingoperations.Abasicprocessdeterminesthestartinggeometryoftheworkparts.Metalcasting,plasticmolding,androllingofsheetmetalareexamplesofb

10、asicprocesses.Thestartinggeometrymustoftenberefinedbysecondaryprocesses,operationsthattransformthestartinggeometry(orclosetofinalgeometry).Thesecondarygeometryprocessesthatmightbeusedarecloselycorrelatedtothebasicprocessthatprovidesthestartinggeometry.Whensandcastingisthebasicprocesses,machiningoper

11、ationsaregenerallythesecondprocesses.Whenarollingmillproducessheetmetal,stampingoperationssuchaspunchingandbendingarethesecondaryprocesses.Whenplasticinjectionmoldingisthebasicprocess,secondaryoperationsareoftenunnecessary,becausemostofthegeometricfeaturesthatwouldotherwiserequiremachiningcanbecreat

12、edbythemoldingoperation.Plasticmoldingandotheroperationthatrequirenosubsequentsecondaryprocessingarecallednetshapeprocesses.Operationsthatrequiresomebutnotmuchsecondaryprocessing(usuallymachining)arereferredtoasnearnetshapeprocesses.Someimpressiondieforgingsareinthiscategory.Thesepartscanoftenbeshap

13、edintheforgingoperation(basicprocesses)sothatminimalmachining(secondaryprocessing)isrequired.Oncethegeometryhasbeenestablished,thenextstepforsomepartsistoimprovetheirmechanicalandphysicalproperties.Operationstoenhancepropertiesdonotalterthegeometryofthepart；instead,theyalterphysicalproperties.Heattr

14、eatingoperationsonmetalpartsarethemostcommonexamples.Similarheatingtreatmentsareperformedonglasstoproducetemperedglass.Formostmanufacturedparts,theseproperty-enhancingoperationsarenotrequiredintheprocessingsequence.Finallyfinishoperationsusuallyprovideacoatontheworkparts(orassembly)surface.Examplesi

15、ncludedelectroplating,thinfilmdepositiontechniques,andpainting.Thepurposeofthecoatingistoenhanceappearance,changecolor,orprotectthesurfacefromcorrosion,abrasion,andsoforth.Finishingoperationsarenotrequiredonmanyparts；forexample,plasticmoldingrarelyrequirefinishing.Whenfinishingisrequired,itisusually

16、thefinalstepintheprocessingsequence.ProcessingPlanningforAssembliesThetypeofassemblymethodusedforagivenproductdependsonfactorssuchas:(1)theanticipatedproductionquantities；(2)complexityoftheassembledproduct,forexample,thenumberofdistinctcomponents；and(3)assemblyprocessesused,forexample,mechanicalasse

17、mblyversuswelding.Foraproductthatistobemadeinrelativelysmallquantities,assemblyisusuallyperformedonmanualassemblylines.Forsimpleproductsofadozenorsocomponents,tobemadeinlargequantities,automatedassemblysystemsareappropriate.Inanycase,thereisaprecedenceorderinwhichtheworkmustbeaccomplished.Theprecede

18、ncerequirementsaresometimesportrayedgraphicallyonaprecedencediagram.Processplanningforassemblyinvolvesdevelopmentofassemblyinstructions,butinmoredetail.Forlowproductionquantities,theentireassemblyiscompletedatasinglestation.Forhighproductiononanassemblyline,processplanningconsistsofallocatingworkele

19、mentstotheindividualstationsoftheline,aprocedurecalledlinebalancing.Theassemblylineroutestheworkunittoindividualstationsintheproperorderasdeterminedbythelinebalancesolution.Asinprocessplanningforindividualcomponents,anytoolsandfixturesrequiredtoaccomplishanassemblytaskmustbedetermined,designed,built

20、,andtheworkstationarrangementmustbelaidout.MakeorBuyDecisionAnimportantquestionthatarisesinprocessplanningiswhetheragivenpartshouldbeproducedinthecompanysownfactoryorpurchasedfromanoutsidevendor,andtheanswertothisquestionisknownasthemakeorbuydecision.Ifthecompanydoesnotpossessthetechnologicalequipme

21、ntorexpertiseintheparticularmanufacturingprocessesrequiredtomakethepart,thentheanswerisobvious:Thepartmustbepurchasedbecausethereisnointernalalternative.However,inmanycases,thepartcouldeitherbemadeinternallyusingexistingequipment,oritcouldbepurchasedexternallyfromavendorthatprocesssimilarmanufacturingcapability.Inourdiscussionofthemakeorbuydecision,itshouldberecognizedattheoutsetthatnearlyallmanufacturesbuytheirrawmaterialsfromsupplies.Amachineshoppurchasesitsstartingbarstockfromametalsdistributoranditssandcastingsfromafoundry.Aplasticmolding