一种使用设计特征和工艺参数来估计模具成本的集成框架毕业课程设计外文文献翻译.docx

一种使用设计特征和工艺参数来估计模具成本的集成框架毕业课程设计外文文献翻译.docx

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一种使用设计特征和工艺参数来估计模具成本的集成框架毕业课程设计外文文献翻译

Anintegratedframeworkfordieandmoldcostestimationusingdesignfeaturesandtoolingparameters

Received:

5August2003/Accepted:

6January2004/Publishedonline:

2February2005

Springer-VelaLondonLimited2005

Abstract

Toolingisanessentialelementofnearnetshapemanufacturingprocessessuchasinjectionmoldinganddiecasting,whereitmayaccountforover25%ofthetotalproductcostanddevelopmenttime,especiallywhenorderquantityissmall.Developmentofrapidandlowcosttooling,combinedwithascientistapproachtomoldcostestimationandcontrol,hasthereforebecomeessential.Thispaperpresentsanintegratedmethodologyfordieandmoldcostestimation,basedontheconceptofcostdriversandcostmoodier.Costdriversincludethegeometricfeaturesofcavityandcore,handledbyanalyticalcostestimationapproachtoestimatethebasicmoldcost.Costmoodierincludetoolingparameterssuchaspartingline,presenceofsidecore（s）,surfacetexture,ejectormechanismanddiematerial,contributingtothetotalmoldcost.Themethodologyhasbeenimplementedandtestedusing13industrialexamples.Theaveragedeviationwas0.40%.Themodelisedibleandcanbeeasilyimplementedforestimatingthecostofavarietyofmoldsanddiesbycustomizingthecostmoodierusingqualityfunctiondeploymentapproach,whichisalsodescribedinthispaper.

Keywords：

Costestimation;Diecasting;Injectionmolding;Qualityfunctiondeployment。

1Introduction

Productlifecyclestodayaretypicallylessthanhalfofthoseinthe1980s,owingtothefrequententryofnewproductswithmorefeaturesintothemarket.Manufacturingcompetitivenessismeasuredintermsofshorterlead-timetomarket,withoutscribingqualityandcost.Onewaytoreducethelead-timeisbyemployingnearnetshape（NNS）manufacturingprocesses,suchasinjectionmoldinganddiecasting,whichinvolvefewerstepstoobtainthedesiredshape.However,thetooling（dieormold）,whichisanessentialelementofNNSmanufacturing,consumesconsiderableresourcesintermsofcost,timeandexpertise.

Atypicaldiecastingdieorplasticinjectionmoldismadeintwohalves:

movingandaxedwhichbutttogetherduringmoldlingandmoveapartduringpartejection.TheconstructionofatypicalcoldchamberpressurediecastingdieisshowninFig.1.

Themainfunctionalelementsofthedieandmoldincludethecoreandcavity,whichimpartthedesiredgeometrytotheincomingmelt.Thesemaybemanufacturedassingleblocksorbuilt-upwithanumberofinserts.Thesecondaryelementsincludethefeedingsystem,ejectionsystem,sidecoreactuatorsandfasteners.Thefeedingsystemcomprisingofspreebush,runner,gateandoveraweenablesthetownofmeltfrommachinenozzletomoldcavity.Theejectormechanismisusedforejectingthemoldedpartfromthecoreorcavity.Alltheaboveelementsarehousedinamoldbaseset,comprisingofsupportblocks,guidesandotherelements.Part-specieelements,includingcoreandcavityandfeedingsystemaremanufacturedinatoolroom.Otherelementsareavailableasstandardaccessoriesfromvendors.Moldassemblyandfunctionaltrialsareconductedbyexperiencedtoolmakersinconsultationwithtooldesigners.

Fig.1.Constructionofatypicalpressurediecastingdie

ThetoolingindustryispresentlydominatedbyJapan,Germany,USA,Canada,Korea,Taiwan,China,Malaysia,SingaporeandIndia.Themajorusersoftoolingincludeautomobiles,electronics,consumergoodsandelectricalequipmentsectors.Plasticmoldsaccountforthemajorshareoftoolingindustry.About60%oftoolroomsbelongtosmallandmediumscaleindustriesworldwide[1].ThetoolingrequirementisoverUS$600millionperyearinIndiaalone,withanannualgrowthrateofover10%duringthelastdecade.InIndia,theshareofdifferenttypesofmoldsanddiesis:

plasticmolds33%,sheetmetalpunchesanddies31%,diecastingdies13%,jigs&stores13%,andgauges10%[2].

Thetoolingindustryisincreasinglyfacingthepressuretoreducethetimeandcostofdieandmolddevelopment,offerbetteraccuracyandsurfaceknish,provideedibilitytoaccommodatefuturedesignchangesandmeettherequirementsofshorterproductionruns.Tomeettheserequirements,newtechnologieslikehighspeedmachining,hardenedsteelmachining,processmodeling,toolingdesignautomation,concurrentengineering,rapidprototypingandrapidtoolinghavebeenapplied.Forsuccessfuloperationsandtomaintainthecompetitiveedge,itisnecessarytoestablishquantitativemethodsforcostestimation.

Ourcurrentresearchaimsatdevelopingasystematicandintegratedframeworkfordevelopmentofrapidhardtooling（diesandmolds）forinjectionmoldingandpressuredie-castingapplications.Thenecessityofasystematiccostestimationmodelforcomparativeevaluationofdifferentroutestotoolingdevelopmentmotivatedustoreviewtheexistingmodels,presentedinthenextsection,followedbyourproposedmethodology.

2Previousworks

Thereisconsiderablesimilarityincostestimationapproachesusedforproductandtoolingasreportedintechnicalliterature.Theseapproachescanbeclassedintovetgroups:

intuitive,analogical,analytical,geometricfeaturebasedandparametricbasedmethods,brieryreviewedhere.

Intheintuitivemethod,theaccuracyofcostestimationdependsonthecostappraiser’sexperienceandinterpretations.Theestimationisusuallyperformedinconsultationwiththetooldesigner.Theestimatoracquiresthewisdomandintuitionconcerningthecoststhroughlongassociationwithdiesandmolddevelopment.Thismethodisstillinpracticeinsmallworkshopsandtoolrooms.

Intheanalogicalmethod,thecostofdieandmoldisestimatedbasedonsimilaritycoefficientsofpreviousdiesandmoldsmanufacturedbytherm.Inthistechnique,diesarecodedconsideringfactorssuchasdiesize,diematerial,complexity,ejectorandgatingmechanism.Theappraiserstartsbycomparingthenewdiedesignwiththeclosestmatchamongallpreviousdesigns.Thebasichypothesesare:

similarproblemshavesimilarsolutions,andreuseismorepracticalthanproblemsolvingfromscratch[3].However,thisapproach,alsoreferredtoascasebasedreasoning,requiresacompletecasebaseandanappropriateretrievalsystem,whichhasnotbeenreportedfordieandmoldcostestimationsofar.

Intheanalyticalcostestimation,theentiremanufacturingactivityisdecomposedintoelementarytasks,andeachtaskisassociatedwithanempiricalequationtocalculatetheManufacturingcost.Forexample,acommonequationformachiningcostis：

Machiningcost=（cuttinglength/feedperminute）×Machineoperationcost.

Wilson（quotedin[4,Chap.6,p.121]）suggestedamathematicalmodelforincorporatingageometriccomplexityfactorinturningandmillingoperations,givenby:

di=ithdimensionoffeature

ti=correspondingdimensionaltolerance

N=totalnumberofdimensions.

Thisisexplainedwiththehelpofanexamplelater.

Anothermethodcalledactivitybasedcosting（ABC）involvesapplyingtheanalyticalmethodtoallstepsinmanufacturingagivenproduct,toestimatetheresources（material,laborandenergy）involvedineachstep.Suchadetailedapproachforvariousprocesses,includingcastinghasbeendevelopedbyCrease[5].Intoolrooms,thisapproachisusedinthecaseofdieswithcomplexcavitygeometry.Thesourcesofmoldcostcanbedividedintothreecategories:

moldbasecost,functionalelements（core,cavityinserts）costandsecondaryelementscost.Ineachcategory,thetimeneededtoobtainthedesiredgeometrybymachiningisconsideredasareferenceforcosting[4].Ascanbeexpected,establishingandvalidatingthecostingequation,aswellasusingitinpractice,arecumbersometasks.

Inthefeaturebasedmethod,moldgeometricfeatures（cylinder,slot,hole,rib,etc.）areusedasthecostdrivers.Thediemanufacturingcostisthenestimatedusingeitherempiricalequationsortoolssuchasknowledge-basedsystemsandarterialneuralnetworks.ChenandLiu[6]usedthefeaturerecognitionmethodtoevaluateanewinjectionmoldedproductdesignforitscosteffectiveness.Theyassumedthataproductisanaggregationofasetoffeaturesandfeaturerelationships.Thesefeaturerelationshipsweremappedtoconvertapartfeatureintomoldrelatedcostevaluations.ChinandWong[7]useddecisiontableslinkedtoaknowledgebasetoestimateinjectionmoldcost.

Intheparametriccostestimation,technical,physicalorfunctionalparametersareusedasbasisforcostevaluation.Thismethodallowsonetoproceedfromtechnicalvaluescharacterizingtheproduct（availablewithdesignengineers）toeconomicdata.SandaracandMaslekar[8]usedregressionmodelapproachininjectionmoldcostestimation.LoweandWalshe[9]usedlaborinvolvementininjectionmoldmakingasareference;moldcostwasestimatedusinglinearregressionanalysis.

Tosummarize,costsimilarityandcostfunctions（costfactors）arethetwosetsofmethodsforestimatingthemoldcost.

Intherestset,similaritybetweenanewmoldandapreviousmolddevelopedinthetoolroomsisusedasareference.Intuitiveandanalogicalmethodsfallunderthiscategory.Inthewidelyusedintuitivemethod,thecostappraisermaynotbeinapositiontoidentifyalltheriskfactorsandtoquantifymanyofthem.Theanalogicalmethodcanbesuccessfullyusedforestimatingthecostofdiebasesandothersecondaryelementswheregroupingismucheasier.However,inthecaseoffunctionalelements（coreandcavity）,groupingbecomesadifficulttaskastheirgeometry,machiningsequenceandtolerancegreatlyvarywithprod