233 Concurrent Engineering and Design for ManufacturingWord文档格式.docx

233 Concurrent Engineering and Design for ManufacturingWord文档格式.docx

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Concurrentengineeringincludesseveralelements:

（1）designformanufacturingandassembly,

（2）designforquality,（3）designforcost,and（4）designforlifecycle.Inaddition,certainenablingtechnologiessuchasrapidprototyping,virtualprototyping,andorganizationalchangesarerequiredtofacilitatetheconcurrentengineeringapproachinacompany.

（1）DesignforManufacturingandAssembly

Ithasbeenestimatedthatabout70%ofthelifecyclecostofaproductisdeterminedbybasicdecisionsmadeduringproductdesign.Thesedesigndecisionsincludethematerialforeachpart,partgeometry,tolerances,surfacefinish,howpartsareorganizedintosub-assemblies,andtheassemblymethodstobeused.Oncethesedecisionsaremade,theabilitytoreducethemanufacturingcostoftheproductislimited.Forexample,iftheproductdesignerdecidesthatapartistobemadeofanaluminumsandcastingbutwhichpossessesfeaturesthatcanbeachievedonlybymachining（suchasthreadedholesandclosetolerances）,themanufacturingengineerhasnoalternativeexcepttoplanaprocesssequencethatstartswithsandcastingfollowedbythesequenceofmachiningoperationsneededtoachievethespecifiedfeatures.Inthisexample,abetterdecisionmightbetouseaplasticmoldedpartthatcanbemadeinasinglestep.Itisimportantforthemanufacturingengineertobegiventheopportunitytoadvisethedesignengineerastheproductdesignisevolving,tofavorablyinfluencethemanufacturabilityoftheproduct.

Termsusedtodescribesuchattemptstofavorablyinfluencethemanufacturabilityofanewproductaredesignformanufacturing（DFM）anddesignforassembly（DFA）,Ofcourse,DFMandDFAareinextricablylinked,soletususethetermdesignformanufacturingandassembly（DFM/A）.Designformanufacturingandassemblyinvolvesthesystematicconsiderationofmanufacturabilityandassemblabilityinthedevelopmentofanewproductdesign.Thisincludes:

（1）organizationalchangesand

（2）designprinciplesandguidelines.

OrganizationalChangesinDFM/A.EffectiveimplementationofDFM/Ainvolvesmakingchangesinacompany’sorganizationalstructure,eitherformallyorinformally,sothatcloserinteractionandbettercommunicationoccursbetweendesignandmanufacturingpersonnel.Thiscanbeaccomplishedinseveralways:

（1）bycreatingprojectteamsconsistingofproductdesigners,manufacturingengineers,andotherspecialties（e.g.,qualityengineers,materialscientists）todevelopthenewproductdesign;

（2）byrequiringdesignengineerstospendsomecareertimeinmanufacturingtowitnessfirst-handhowmanufacturabilityandassemblabilityareimpactedbyaproduct’sdesign;

and（3）byassigningmanufacturingengineerstotheproductdesigndepartmentoneitheratemporaryorfull-!

roebasistoserveasproducibilityconsultants.

DesignPrinciplesandGuidelines.DFM/Aalsoreliesontheuseofdesignprinciplesandguidelinesforhowtodesignagivenproducttomaximizemanufacturabilityandassemblability.Someoftheseareuniversaldesignguidelinesthatcanbeappliedtonear1yanyproductdesign2.3ProcessPlanningandConcurrentEngineering12

situation,suchasthosepresentedinTable25.4.Inothercases,therearedesignprinciplesthatapplytospecificprocesses,forexample,theuseofdraftsortapersincastedandmoldedpartstofacilitateremovalofthepartfromthemold.Weleavethesemoreprocess-specificguidelinestotextsonmanufacturingprocesses.

Theguidelinessometimesconflictwithoneanother.Forexample,oneoftheguidelinesinTable2.3.4isto“simplifypartgeometry;

avoidunnecessaryfeatures.”Butanotherguidelineinthesametablestatesthat“specialgeometricfeaturesmustsometimesbeaddedtocomponents”todesigntheproductforfoolproofassembly.Anditmayalsobedesirabletocombinefeaturesofseveralassembledpartsintoonecomponenttominimizethenumberofpartsintheproduct.Intheseinstances,designforpartmanufactureisinconflictwithdesignforassembly,andasuitablecompromisemustbefoundbetweentheopposingsidesoftheconflict.

TABLE2.3.4GeneralPrinciplesandGuidelinesinDFM/AGuideline

InterpretationandAdvantages

Minimizenumberofcomponents

Reducedassemblycosts.

Greaterreliabilityinfinalproduct.

Easierdisassemblyinmaintenanceandfieldservice.

Automationisofteneasierwithreducedpartcount.

Reducedwork-in-processandinventorycontrolproblems.

Fewerpartstopurchase;

reducedorderingcosts.

Usestandardcommerciallyavailablecomponents

Reduceddesigneffort.

Fewerpartnumbers.

Betterinventorycontrolpossible.

Avoidsdesignofcustom-engineeredcomponents.

Quantitydiscountspossible.

Usecommonpartsacrossproductlines

Grouptechnologycanbeapplied.

Quantitydiscountsarepossible.

Permitsdevelopmentofmanufacturingcells.

Designforeaseofpartfabrication

Usenetshapeandnearnetshapeprocesseswherepossible.

Simplifypartgeometry;

avoidunnecessaryfeatures.

Avoidsurfaceroughnessthatissmootherthannecessarysinceadditionalprocessingmaybeneeded.

Designpartswithtolerancesthatarewithinprocesscapability

Avoidtoleranceslessthanprocesscapability.

Specifybilateraltolerances.

Otherwise,additionalprocessingorsortationandscraparerequired.

Designtheproducttobefoolproofduringassembly

Assemblyshouldbeunambiguous.

Componentsdesignedsotheycanbeassembledonlyoneway.

Specialgeometricfeaturesmustsometimesbeaddedtocomponents.

Minimizeflexiblecomponents

Theseincludecomponentsmadeofrubber,belts,gaskets,electricalcables;

etc.

Flexiblecomponentsaregenerallymoredifficulttohandle.

Designforeaseofassembly.

Includepartfeaturessuchaschamfersandtapersonmatingparts.

Usebaseparttowhichothercomponentsareadded.

Usemodulardesign（seefollowingguideline）.

Designassemblyforadditionofcomponentsfromonedirection,usuallyvertically;

ifmassproduction,thisrulecanbeviolatedbecausefixedautomationcanbedesignedformultipledirectionassembly.

（2）OtherDesignObjectives

Tocompleteourcoverageofconcurrentengineering,letusbrieflydiscusstheotherdesignobjectives:

designforquality,cost,andlifecycle.

DesignforQuality.ItmightbearguedthatDFM/Aisthemostimportantcomponentofconcurrentengineeringbecauseithasthepotentialforthegreatestimpactonproductcostanddevelopmenttime.However,theimportanceofqualityininternationalcompetitioncannotbeminimized.Qualitydoesnotjusthappen.Itmustbeplannedforduringproductdesignandduringproduction.Designforquality（DFQ）isthetermthatreferstotheprinciplesandproceduresemployedtoensurethatthehighestpossiblequalityisdesignedintotheproduct.

DesignforProductCost.Thecostofaproductisamajorfactorindeterminingitscommercialsuccess.Costaffectsthepricechargedfortheproductandtheprofitmadebythecompanyproducingit.Designforproductcost（DFC）referstotheeffortsofacompanytospecificallyidentifyhowdesigndecisionsaffectproductcostsandtodevelopwaystoreducecostthroughdesign.

DesignforLifeCycle.Tothecustomer,thepricepaidfortheproductmaybeasmallportionofitstotalcostwhenlifecyclecostsareconsidered.Designforlifecyclereferstotheproductafterithasbeenmanufacturedandincludesfacto