汽车专业毕业设计 翻译 中英文全lean remanufacture of an automobile clutch.docx
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汽车专业毕业设计 翻译 中英文全lean remanufacture of an automobile clutch.docx
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汽车专业毕业设计翻译中英文全leanremanufactureofanautomobileclutch
LeanRemanufactureofanAutomobileClutch
TonyAmezquita*andBertBras**
SaturnCorporationSystemsRealizationLaboratory
SpringHill,TennesseeWoodruffSchoolofMechanicalEngineering
GeorgiaInstituteofTechnology
Atlanta,Georgia30332-0405
Abstract
Inthehistoryofmanufacturingtherehavebeenthreeproductionsystems,namely,craftproduction,massproduction,andleanproduction.Inmanyautomotiveremanufacturingoperations,craftproductionandmassproductionsystemsareusedasthebasisforremanufacturingprocesses.Theleanproductionsystemhasproventobemoreeffectiveinthemanufactureofautomotivepartsandithasallowedmanufacturerswhouseittoproduceinmuchgreatervarieties,withhigherqualitylevels,andwithlowercosts.Hence,ifusedinremanufacturing,itwouldgreatlyenhanceit.Inthispaper,acurrentremanufacturingprocessofanautomobileclutchisanalyzed,andaleanremanufacturingprocessisdevelopedandcomparedtotheasisprocess.Ourfindingsindicatethattheleanremanufacturingprocessprovidesamorerobustprocesswithlowercostswhencomparedwiththecurrentclutchremanufacturingprocessthatutilizecraftandmassproductionpractices.
1OurFrameofReference–RemanufactureintheAutomotiveIndustry
Remanufacturingisthemosteconomicallysustainableformofreuseandrecyclingofmanufacturedgoods,anditcanbedefinedastheindustrialprocesswherewornoutproductsreferredtoascores,arebroughtbacktooriginalspecificationsandcondition.Insomecases,especiallyintheremanufactureofOEMautomotiveparts,remanufacturedproductsexceedoriginalspecifications.Thereasonisthatthelatestengineeringdesignandspecifications,coupledwithfailuremodecountermeasuresderivedfromfailureanalysis,areusedinsteadoftheoriginalspecifications.Thebenefitsofremanufacturingaremany,butthemostsalientare:
1)Remanufacturingsalvagesthematerial,energy,capital,labor,andemissionsthatwentintothemanufactureandmaterialprocessingofproducts.
2)Theresultingproductioncostscanoftenbelowerthanmanufacturing,allowingremanufacturerstoselltheirunitsfor25to50%lessthanmanufacturedunitswithequivalentorbetterqualitylevels.
Thesetwobenefitsaretheresultofthefactthatpartsarereusedandtheembeddedutilityinthepartsaremaintained.Hencetheresultingproductioncosts,whichshouldbeconsiderablylessthaninmanufacturing,allowremanufacturerstopassthesavingsontoconsumers.
Remanufacturingintheautomotiveindustrycanbedividedintotwogroups;independentremanufacturersandOriginalEquipmentManufacturer(OEM)remanufacturers.BothoftheseactivitiesinthedomainofautomotiveproductsconstitutethelargestremanufacturingconsumermarketsegmentintheUnitedStatesandEurope.
In1978,KuttaandLunddocumentedasurveycapturingsomeoftheissuesimportanttoremanufacturers(KuttaandLund,1978).However,wediscoveredinsurveysandinterviewswithremanufacturersthatmanychangeshaveoccurredintheindustrysincethen(Hammond,etal.,1996,Hammond,1996).Majorchangeshavebeentherestructuringofautomotivecompaniesintoplatformsandthetrendtowardsmasscustomizationofproducts.Especiallythelatterhasresultedinwhatremanufacturershavetermed“PartsProliferation”,whichreferstothepracticeofmakingmanyvariationsofthesameproduct-differingonlyinoneortwominorareas.However,thesedifferences(suchaselectricalconnectors)aredistinctenoughtopreventinterchangingthesesimilarproducts.
Thefocusinthispaperisonindependentautomotiveremanufacturers,becausetheyremanufacturecomponentpartsfrommostoftheautomobilemanufacturersintheworld,andforaverylargenumberofmodelyears.Thisbeingthecase,independentremanufacturersarefacedwithapartsproliferationproblemwhichcannotbesuccessfullyhandledwiththeircurrentproductionpractices,thatconsistofamixtureofmassproductionandcraftproductionpractices.Asdescribedbelowcraftproductionpracticesmaintainproductioncostshighregardlessofvolume,andmassproductionpracticesarenotcompatiblewithlargeproductvarieties.Consequentlyindependentpartsremanufacturersareloosingmarketsharetoaftermarketpartsmanufacturers,andinsomecases,remanufacturersarebeingforcedoutofthemarket,asinthecaseofclutchremanufacturing.Forexample,in1989thepricedifferencebetweenremanufacturedandmanufacturedclutcheswas50%.In1994thedifferencedroppedto20%,andnowalargenumberofclutchremanufacturersaregettingoutofclutchremanufacturingaltogether.
Itisourbeliefthatthetrendsinmasscustomizationandpartsproliferationwillnotdecreaseandthesmalltomediumsizedindependentremanufacturersseemtosuffermostfromthesetrends.Oursurveysalsopointoutthedifferencesandsometimeshard“usversusthem”attitudebetweenindependentremanufacturersandOriginalEquipmentManufacturers(OEMs),leadingustobelievethatthesharingofdesigninformationbetweenOEMandremanufacturerisnotafeasiblesolutionand/oroptioninmanycases.Hence,theonlywaywecanhelpincreasetheremanufacturabilityofthoseproductsisbyimprovingtheremanufacturingprocesses.
Inthispaper,wepresentsomeofourfindingswhich,interestinglyenough,indicatethattheintroductionofleanproductiontechniques(whichareoneofthemaincausesofpartproliferationandproductdiversity)intheremanufacturingindustry,andhencecreatingleanremanufacturingprocesses,canleadtosignificantprocessimprovementsandsavingscomparedtothecurrentremanufacturingprocesseswhichareheavilybatchoriented.Inthispaper,asolutiontothepartsproliferationproblemofindependentautomobilepartsremanufacturersisdevelopedbytransformingacurrentremanufacturingprocessofanautomobileclutchintoaleanremanufacturingprocess.Thisleanclutchremanufacturingprocesshasbeendevelopedingreatdetailin(Amezquita,1996).Inthispaper,wewilldiscusstheas-isprocess,followedbyadiscussiononhowtoconvertthisprocessintoaleanremanufacturingprocess.Itshouldbestatedup-frontthatalthoughtheproposedleanprocessofferssubstantialsavings,ithasnotbeenimplementedbythecompanywhosupportedthiscasestudy.First,however,wewillprovidethenecessarybackgroundoncraft,mass,andleanproductionsystems.
2Craft,Mass,andLeanProduction
Inthe1800s,automobilemanufacturingwasthedomainoftheskilledcraftsmenwhocontrolledmostoftheactivitiesonthemanufacturingfloor.Theseskilledcraftsmendesignedandbuiltcustomizedvehiclesbymakingandfittingeachpartbyfilingitdownuntilitmatedwiththeothervehicleparts.Evenifcraftproducerscouldmake10,000identicalcars,thepricepercarwouldnothavedroppedbymuch,becauseeachcarwasessentiallyaprototype.Thebiggestbenefitsofthiscraftproductionsystemintheautomotiveindustrywerethat:
•customerswereabletoobtainproductswhichspecificallymettheirneeds,and
•workersweresatisfied,proud,andfulfilled,andtheirgoalwastohoneandperfecttheirskillsandonedaybecomeindependentowners.
Attheturnofthecentury,FrederickTaylorremovedthecontrolofthemanufacturingoperationsfromthehandsoftheskilledcraftsmenbycreatingdivisionsoflabor.Thiswasthefirststeptowardsthedevelopmentofmassproduction,whichwasfullyimplementedbyHenryFord.TakingthedevelopmentsofTaylor,Fordaddedthestandardizationoftheproductionofparts,whichledtocompletepartsinterchangeability,whichinturnledtothesimplificationofpartsassembly.In1908,anassemblerwasspending514minutes(8.56hours)assemblingalargeportionofthecarbeforemovingtothenextcar(Womack,etal.,1991).Toreducethecycletimeofassemblers(periodoftimespentwitheachvehiclebyeachemployee),Fordhadeachassemblerperformasingletaskandmovefromvehicletovehicleintheassemblyhall.Thecycletimepervehiclewasreducedfrom8.56hoursto2.3minutes(Womack,etal.,1991)!
Finally,thesimplificationofassemblytasksallowedFordtoutilizethemovingassemblylinetobringthecarstotheassemblersandeliminateallthewalkingpreviouslydone.Inaddition,themovingassemblylineenforcedafasterandevenworkpace.Ford’simplementationofthemovingassemblyline,whichbroughtthecarpastthestationaryworker,cutcycletimeevenfurtherfrom2.3minutesto1.19minutes(Womack,etal.,1991).
Forddiscoveredthathisnewsystemreducedtheamountofhumaneffortneededtoassembleavehicle,andwiththesamenumberofpeople,equipment,etc.,themorestandardizedvehiclesheproduced,themorethecostpervehicledropped(economiesofscale).BythetimeFordreachedvolumesoftwomillionidenticalvehiclesperyear,hehadslashedtherealcosttotheconsumerbyanadditionaltwothirdsfromthetimehestartedproductionoftheModelTin1908.
Consequently,aproductionsystemwhichmostcloselyresemblesthemassproductionsystemcanbringsubstantialsavingstoaremanufacturer,andisoftenadvocated.However,thissystemrunsagroundwhenconfrontedwithalargevarietyofparts,whichisthecurrentsituationmanyindependentautomotiveremanufacturersarefacing.Mostautomotivepartsremanufacturers(andotherremanufacturers)stillrelyoncraftproductionsystemstohandlethevariabilityinthenumberofpartstoberemanufacturedandthevariabilityinherentinrefurbishingoperationsduetoweardifferences.However,asnotedalreadybyHenryFord,craftproductionsystemhastwomaindr
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