夹具设计英文文献.docx
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夹具设计英文文献.docx
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夹具设计英文文献
Areviewandanalysisofcurrentcomputer-aidedfixturedesignapproaches
IainBoyle,YimingRong,DavidC.Brown
Keywords:
Computer-aidedfixturedesign
Fixturedesign
Fixtureplanning
Fixtureverification
Setupplanning
Unitdesign
ABSTRACT
Akeycharacteristicofthemodernmarketplaceistheconsumerdemandforvariety.Torespondeffectivelytothisdemand,manufacturersneedtoensurethattheirmanufacturingpracticesaresufficientlyflexibletoallowthemtoachieverapidproductdevelopment.Fixturing,whichinvolvesusingfixturestosecureworkpiecesduringmachiningsothattheycanbetransformedintopartsthatmeetrequireddesignspecifications,isasignificantcontributingfactortowardsachievingmanufacturingflexibility.Toenableflexiblefixturing,considerablelevelsofresearchefforthavebeendevotedtosupportingtheprocessoffixturedesignthroughthedevelopmentofcomputer-aidedfixturedesign(CAFD)toolsandapproaches.Thispapercontainsareviewoftheseresearchefforts.Overseventy-fiveCAFDtoolsandapproachesarereviewedintermsofthefixturedesignphasestheysupportandtheunderlyingtechnologyuponwhichtheyarebased.Theprimaryconclusionofthereviewisthatwhilesignificantadvanceshavebeenmadeinsupportingfixturedesign,thereareprimarilytworesearchissuesthatrequirefurthereffort.ThefirstoftheseisthatcurrentCAFDresearchissegmentedinnatureandthereremainsaneedtoprovidemorecohesivefixturedesignsupport.Secondly,agreaterfocusisrequiredonsupportingthedetaileddesignofafixture’sphysicalstructure.
2010ElsevierLtd.Allrightsreserved.
Contents
1.Introduction………………………………………………………………………………………2
2.Fixturedesign…………………………………………………………………………………….2
3.CurrentCAFDapproaches……………………………………………………………………….4
3.1Setupplanning…………………………………………………………………………….4
3.1.1Approachestosetupplanning……………………………………………………...4
3.2Fixtureplanning…………………………………………………………………………..4
3.2.1Approachestodefiningthefixturingrequirement…………………………………6
3.2.2Approachestonon-optimizedlayoutplanning…………………………………….6
3.2.3Approachestolayoutplanningoptimization………………………………………6
3.3Unitdesign………………………………………………………………………………...7
3.3.1Approachestoconceptualunitdesign……………………………………………..7
3.3.2Approachestodetailedunitdesign………………………………………………...7
3.4Verification………………………………………………………………………………..8
3.4.1Approachestoconstrainingrequirementsverification…………………………….8
3.4.2Approachestotolerancerequirementsverification………………………………..8
3.4.3Approachestocollisiondetectionrequirementsverification………………………8
3.4.4Approachestousabilityandaffordabilityrequirementsverification………………9
3.5Representationoffixturinginformation…………………………………………………..9
4.AnanalysisofCAFDresearch…………………………………………………………………...9
4.1ThesegmentednatureofCAFDresearch………………………………………………...9
4.2Effectivelysupportingunitdesign………………………………………………………10
4.3Comprehensivelyformulatingthefixturingrequirement………………………………..10
4.4ValidatingCAFDresearchoutputs……………………………………………………....10
5.Conclusion…………………………………………………………………………………...…10
References…………………………………………………………………………………………10
1.Introduction
Akeyconcernformanufacturingcompaniesisdevelopingtheabilitytodesignandproduceavarietyofhighqualityproductswithinshorttimeframes.Quickreleaseofanewproductintothemarketplace,aheadofanycompetitors,isacrucialfactorinbeingabletosecureahigherpercentageofthemarketplaceandincreasedprofitmargin.Asaresultoftheconsumerdesireforvariety,batchproductionofproductsisnowmorethenormthanmassproduction,whichhasresultedintheneedformanufacturerstodevelopflexiblemanufacturingpracticestoachievearapidturnaroundinproductdevelopment.
Anumberoffactorscontributetoanorganization’sabilitytoachieveflexiblemanufacturing,oneofwhichistheuseoffixturesduringproductioninwhichworkpiecesgothroughanumberofmachiningoperationstoproduceindividualpartswhicharesubsequentlyassembledintoproducts.Fixturesareusedtorapidly,accurately,andsecurelypositionworkpiecesduringmachiningsuchthatallmachinedpartsfallwithinthedesignspecificationsforthatpart.Thisaccuracyfacilitatestheinterchangeabilityofpartsthatisprevalentinmuchofmodernmanufacturingwheremanydifferentproductsfeaturecommonparts.
Thecostsassociatedwithfixturingcanaccountfor10–20%ofthetotalcostofamanufacturingsystem[1].Thesecostsrelatenotonlytofixturemanufacture,assembly,andoperation,butalsototheirdesign.Hencetherearesignificantbenefitstobereapedbyreducingthedesigncostsassociatedwithfixturingandtwoapproacheshavebeenadoptedinpursuitofthisaim.Onehasconcentratedondevelopingflexiblefixturingsystems,suchastheuseofphase-changingmaterialstoholdworkpiecesinplace[2]andthedevelopmentofcommercialmodularfixturesystems.However,thesignificantlimitationoftheflexiblefixturingmantraisthatitdoesnotaddressthedifficultyofdesigningfixtures.Tocombatthisproblem,asecondresearchapproachhasbeentodevelopcomputer-aidedfixturedesign(CAFD)systemsthatsupportandsimplifythefixturedesignprocessanditisthisresearchthatisreviewedwithinthispaper.
Section2describestheprincipalphasesofandthewidevarietyofrequirementsdrivingthefixturedesignprocess.SubsequentlyinSection3anoverviewofresearcheffortsthathavefocuseduponthedevelopmentoftechniquesandtoolsforsupportingtheseindividualphasesofthedesignprocessisprovided.Section4critiquestheseeffortstoidentifycurrentgapsinCAFDresearch,andfinallythepaperconcludesbyofferingsomepotentialdirectionsforfutureCAFDresearch.Beforeproceeding,itisworthnotingthattherehavebeenpreviousreviewsoffixturingresearch,mostrecentlyBiandZhang[1]andPehlivanandSummers[3].BiandZhang,whileprovidingsomedetailsonCAFDresearch,tendtofocusuponthedevelopmentofflexiblefixturingsystems,andPehlivanandSummersfocusuponinformationintegrationwithinfixturedesign.Thevalueofthispaperisthatitprovidesanin-depthreviewandcritiqueofcurrentCAFDtechniquesandtoolsandhowtheyprovidesupportacrosstheentirefixturedesignprocess.
2.Fixturedesign
ThissectionoutlinesthemainfeaturesoffixturesandmorepertinentlyofthefixturedesignprocessagainstwhichresearcheffortswillbereviewedandcritiquedinSections3and4,respectively.Physicallyafixtureconsistsofdevicesthatsupportandclampaworkpiece[4,5].Fig.1representsatypicalexampleofafixtureinwhichtheworkpiecerestsonlocatorsthataccuratelylocateit.Clampsholdtheworkpieceagainstthelocatorsduringmachiningthussecuringtheworkpiece’slocation.Thelocatingunitsthemselvesconsistofthelocatorsupportingunitandthelocatorthatcontactstheworkpiece.Theclampingunitsconsistofaclampsupportingunitandaclampthatcontactstheworkpieceandexertsaclampingforcetorestrainit.
Typicallythedesignprocessbywhichsuchfixturesarecreatedhasfourphases:
setupplanning,fixtureplanning,unitdesign,andverification,asillustratedinFig.2,whichisadaptedfromKangetal.[6].Duringsetupplanningworkpieceandmachininginformationisanalyzedtodeterminethenumberofsetupsrequiredtoperformallnecessarymachiningoperationsandtheappropriatelocatingdatumsforeachsetup.Asetuprepresentsthecombinationofprocessesthatcanbeperformedonaworkpiecewithouthavingtoalterthepositionororientationoftheworkpiecemanually.Togenerateafixtureforeachsetupthefixtureplanning,unitdesign,andverificationphasesareexecuted.
Duringfixtureplanning,thefixturingrequirementsforasetuparegeneratedandthelayoutplan,whichrepresentsthefirststeptowardsasolutiontotheserequirementsisgenerated.Thislayoutplandetailstheworkpiecesurfaceswithwhichthefixture’slocatingandclampingunitswillestablishcontact,togetherwiththesurfacepositionsofthelocatingandclampingpoints.Thenumberandpositionoflocatingpointsmustbesuchthataworkpiece’ssixdegreesoffreedom(Fig.3)areadequatelyconstrainedduringmachining[7]andthereareavarietyofconceptuallocatingpointlayoutsthatcanfacilitatethis,suchasthe3-2-1locatingprinciple[4].Inthethirdphase,suitableunitdesigns(i.e.,thelocatingandclampingunits)aregeneratedandthefixtureissubsequentlytestedduringtheverificationphasetoensurethatitsatisfiesthefixturingrequirementsdrivingthedesignprocess.Itisworthnotingthatverificationofsetupsandfixtureplanscantakeplaceastheyaregeneratedandpriortounitdesign.
Fixturingrequirements,whichalthoughnotshowninKangetal.[6]aretypicallygeneratedduringthefixtureplanningphase,canbegroupedintosixclasses(Table1).The‘‘physical’’requirementsclassisthemostbasicandrelatestoensuringthefixturecanphysicallysupporttheworkpiece.The‘‘tolerance’’requirementsrelatetoensuringthatthelocatingtolerancesaresufficienttolocatetheworkpieceaccuratelyandsimilarlythe‘‘constraining’’requirementsfocusonmaintainingthisaccuracyastheworkpieceandfixturearesubjectedtomachiningforces.The‘‘affordability’’requirementsrelatetoensuringthefixturerepresentsvalue,forexampleintermsofmaterial,operating,andassembly/disassemblycosts.
The‘‘collisiondetection’’requirementsfocusuponensuringthatthefixturedoesnotcollidewiththemachiningpath,theworkpiece,orindeeditself.The‘‘usability’’requirementsrelatetofixtureergonomicsandi
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