233 Concurrent Engineering and Design for Manufacturing.docx
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233 Concurrent Engineering and Design for Manufacturing.docx
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233ConcurrentEngineeringandDesignforManufacturing
2.3.3ConcurrentEngineeringandDesignforManufacturing
Concurrentengineeringreferstoanapproachusedinproductdevelopmentinwhichthefunctionsofdesignengineering,manufacturingengineering,andotherfunctionsareintegratedtoreducetheelapsedtimerequiredtobringanewproducttomarket.Alsocalledsimultaneousengineering,itmightbethoughtofastheorganizationalcounterparttoCAD/CAMtechnology.Inthetraditionalapproachtolaunchinganewproduct,thetwofunctionsofdesignengineeringandmanufacturingengineeringtendtobeseparatedandsequential,asillustratedinFigure2.3.5(a).Theproductdesigndepartmentdevelopsthenewdesign,sometimeswithoutmuchconsiderationgiventothemanufacturingcapabilitiesofthecompany.Thereislittleopportunityformanufacturingengineerstoofferadviceonhowthedesignmightbealteredtomakeitmoremanufacturable.Itisasifawallexistsbetweendesignandmanufacturing.Whenthedesignengineeringdepartmentcompletesthedesign,ittossesthedrawingsandspecificationsoverthewall,andonlythendoesprocessplanningbegin.
Bycontrast,inacompanythatpracticesconcurrentengineering,themanufacturingengineeringdepartmentbecomesinvolvedintheproductdevelopmentcycleearlyon,providingadviceonhowtheproductanditscomponentscanbedesignedtofacilitatemanufactureand
assembly.Italsoproceedswiththeearlystagesofmanufacturingplanningfortheproduct.ThisconcurrentengineeringapproachispicturedinFigure2.3.5(b).Inadditiontomanufacturingengineering,otherfunctionsarealsoinvolvedintheproductdevelopmentcycle,suchasqualityengineering,themanufacturingdepartments,fieldservice,vendorssupplyingcriticalcomponents,andinsomecasesthecustomerswhowillusetheproduct.Allofthesefunctionscanmakecontributionsduringproductdevelopmenttoimprovenotonlythenewproduct'sfunctionandperformance,butalsoitsproduceability,inspectability,testability,serviceability,andmaintainability.Throughearlyinvolvement,asopposedtoreviewingthefinalproductdesignafteritistoolatetoconvenientlymakeanychangesinthedesign,thedurationoftheproductdevelopmentcycleissubstantiallyreduced.
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
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