外文翻译原文：计算机辅助夹具设计发展趋势.pdf

Computer-AidedDesign42(2010)10851094 ContentslistsavailableatScienceDirect Computer-AidedDesign journalhomepage:/locate/cad Computeraidedfixturedesign:Recentresearchandtrends HuiWang a, ,Yiming(Kevin)Rong a,b ,HuaLi b ,PriceShaun b a DepartmentofPrecisionInstrumentsandMechanology,TsinghuaUniversity,Beijing,100084,China b ComputerAidedManufacturingLaboratory,WorcesterPolytechnicInstitute,MA,01609,USA a r t i c l e i n f o Articlehistory: Received7April2009 Accepted15July2010 Keywords: Computeraidedfixturedesign Literaturesurvey Trend a b s t r a c t Widelyusedinmanufacturing,fixtureshaveadirectimpactuponproductmanufacturingquality,pro- ductivityandcost,somuchattentionhasalreadybeenpaidtotheresearchofcomputeraidedfixture design(CAFD)andmanyachievementsinthisfieldhavebeenreported. Inthispaper,aliteraturesurveyofcomputeraidedfixturedesignandautomationoverthepastdecade isproposed.First,anintroductionisgivenonthefixtureapplicationsinindustry.Then,significantworks doneintheCAFDfield,includingtheirapproaches,requirementsandworkingprinciplesarediscussed. Finally,someprospectiveresearchtrendsarealsodiscussed. 2010ElsevierLtd.Allrightsreserved. 1. Introduction Afixtureisamechanismusedinmanufacturingtoholdawork- piece,positionitcorrectlywithrespecttoamachinetool,andsup- portitduringmachining.Widelyusedinmanufacturing,fixtures haveadirectimpactuponproductquality,productivityandcost. Generally,thecostsassociatedwithfixturedesignandmanufac- turecanaccountfor10%20%ofthetotalcostofamanufactur- ingsystem1.Approximately40%ofrejectedpartsaredueto dimensioningerrorsthatareattributedtopoorfixturingdesign2. Fixturedesignworkisalsotediousandtime-consuming.Itoften heavilyreliesonfixturedesignengineersexperience/knowledge andusuallyrequiresover10yearsmanufacturingpracticetode- signqualityfixtures3.Traditionally,thedesignandmanufacture ofafixturecantakeseveraldaysorevenlongertocompletewhen humanexperienceinfixturedesignisutilized.Andagoodfixture designisoftenbasedonthedesignersexperience,hisunderstand- ingoftheproducts,andatry-and-errorprocess. Therefore, with the increasingly intense global competition whichpusheseverymanufacturerinindustrytomakethebest efforttosharpenitscompetitivenessbyenhancingtheproducts quality,squeezingtheproductioncostsandreducingtheleadtime tobringnewproductstothemarket,thereisanstrongdesire fortheupgradingoffixturedesignmethodologywiththehope ofmakingsoundfixturedesignmoreefficientlyandatalower cost.Thedevelopmentofcomputer-aidedfixturedesign(CAFD) technologyoverthepastdecadescanbeattributedtothefulfilling ofthisgoal. Correspondingauthor. E-mailaddress:(H.Wang). Asanimportantfieldinmanufacturing,researchandapplica- tionsoffixturedesignhasbeenpaidmuchattentionoverpast decades4,5.Manyacademicandapplicationspapershavebeen publishedinthisarea.Inthispaper,wewillfocusonaninvestiga- tionofcomputeraidedfixturedesignresearchinthepastdecade. Thefollowingsectionswillgiveasurveyonthestateoftheartof theseresearches.Someconclusionsonresearchtrendsarealsodis- cussed. 2. Fixturesinmanufacturing Afixtureisdesignedtopositionandholdoneormorework- piece(s) within some specifications. It is widely used in man- ufacturing,e.g.machining(includingturning,milling,grinding, drilling,etc),welding,assembly,inspectionandtesting.Thefol- lowingFigs.19,aresomerealfixturedesigncasesinmanufactur- ing.Fixturescanbeclassifiedwithdifferentprinciples.However, comparedwiththepublicationsofCAFDresearchinmachiningfix- turefield,onlyafew616havebeenfocusedonotherimportant manufacturingfields,forinstance,assemblyfixturesandwelding fixtures. 2.1.Weldingfixtures Weldingisessentialtoahighdollarvolumeofmanufactur- ingprocesses,includingnationaldefenseindustries.Accordingto EconomicImpactandProductivityofWelding,HeavyManufacturing IndustriesReport,byAmericanWeldingSocietyandEdisonWeld- ingInstituteonJune2001,ThecontributionofweldingtotheUS economyin1999viatheseindustrieswasnolessthan$7.85bil- lion.Thisfigurerepresented7%oftotalexpendituresbythesefirms in199917,18.Sotherearesignificanttechnicalandcommercial 0010-4485/$seefrontmatter 2010ElsevierLtd.Allrightsreserved. doi:10.1016/j.cad.2010.07.0031086 H.Wangetal./Computer-AidedDesign42(2010)10851094 Fig.1. Machiningfixtures(IMAOcorp.)19. Fig.2. Machiningfixturesofaircraft-usedbearinghousing. Fig.3. Grindfixtureforturbineblades(aerocaddesign,inc.)20. advantagesinthedevelopmentanddeploymentofweldingfixture designsystems. Thereareobviousdifferencesbetweenmachiningfixturede- signandweldingfixturedesign.Asinthefollowing: Fig. 5. Automotive stud weld fixtures on a trunion frame, (DBM innovation inc.)22. Theworkpieceinaweldingprocessisusuallyanassemblyof severalparts,whileworkpiecesundergoingamachiningpro- cesscontainonlyonepart. Usually,theaccuracyrequirementinaweldingprocessisless thaninmachining. Fixingforcesandmachiningforcesinaweldingprocesscom- monlyaresmallerthaninmachining. Thermalreactionsinweldingshouldbeseriouslyconsidered. Furthermore,thesefactorsalsoshouldbepaidsomeattentionin weldingfixturedesigncases: Electricalconductivityiscriticalforarcweldingstability. Inadditiontothermalconductivity,whenselectingfixturema- terialthermalexpansionpropertiesalsoshouldbeconsidered. Refinedweldingwaveformsrequireanoptimizedweldingcir- cuittomaintainshortarclengthswhilereducingspatter,stub- bing,arcflare,andarcoutagestomaximizetravelspeeds. Morecomplexapplicationsmayrequireadedicatedfixture. Thedesignandinstallationofadedicatedfixturefrequentlyin- volvesinstallingandroutingwiringandpneumaticorhydraulic lines. Inthepastdecade,onlyverylimitedCAFDresearchandappli- cationshavebeenreportedintheweldingsector.Inthisfield,due totheimportanceofweldingforsheetmetalassemblyinautomo- bileandaerospaceindustries,theassemblyandweldingofsheet metalhasreceivedsomespecialattention.Aweldfixtureisof- tendevelopedtoreducethedeformationofeachworkpiecedue toheatandresidualstressintheweldingprocessand,hence,to reducethedimensionalvariationoftheassembly.Therefore,some methodsofofflineoronlinedeformationanalysisweredeveloped toenhancethefixturesabilityondeformationcontrolling8,9.In Fig.4. Assemblyfixturetolocateshelvesforassemblyofcabinets(pioneerindustrialsystemsLLC.)21.H.Wangetal./Computer-AidedDesign42(2010)10851094 1087 Fig.6. Robotweldfixture(IMPROVEsolutionsLLC.)23. ab Fig.7. Pin-arrayfixtureapplication29. Fig.8. Modularfixtureforapartfortheconstructionmachinery(BLUCOcorp.)30. Fig. 9. Dedicated fixture for a part for the construction machinery (BLUCO corp.)30. sheetmetalassemblywithlaserweldingfixturesalsoshoulden- sureafit-upofthematingsurfacestoensureproperlaserbeam weldoperationandlaserweldquality.Asaresult,atraditional 3-2-1locatingschemeisextendedtoamixedlocatingidea,total locatinganddirectlocatingforwelds1013.Thetotallocating schemeisusedtolocatetheentireassembly,andthedirectlocat- ingschemeisusedtolocatetheweldjointstomeetthemetals fit-uprequirement. 2.2.Applicationsofmodularfixturesanddedicatedfixtures Accordingtothefixturesflexibility,fixturesalsocanbeclas- sified as dedicated fixtures and general purpose fixtures (e.g. reconfigurableandconformablefixtures,modularfixtures).Recon- figurableandconformablefixtures2426canbeconfiguredto acceptpartsofvaryingshapesandsizes.Particularly,conformable pin-arrayfixturetechnology27iswidelyusedinmanyfixturede- signsbecausesomecomponentscontaininternalvariablesthatcan beadjustedtomeetthedifferentfeaturesofworkpieces(asFig.7). Andphase-changematerials-relatedfixturesalsoareusedinsome precisionmanufacturing.Forinstance,intheaerospaceindustry, lowmelting-pointmetalsareusedtoencloseturbinebladesand producewell-definedsurfacesforpartlocationandclampingfor grindingoperations. Themostimportantandwidestusedwithinthegeneralpur- posefixtureclassificationsaremodularfixtures.Astheflexible manufacturingsystemhasbeenadoptedbymoreandmoreman- ufacturerswhoaretryingtoremaincompetitiveinthisrapidly changingmarketbyrunningproductionwithshortleadtimesand wellcontrolledcost,modularfixtureshavegainedinpopularitybe- causeofitsperformanceoneasyusage,versatility,anditsadapt- abilitytoproductchanges.1088 H.Wangetal./Computer-AidedDesign42(2010)10851094 Fig.10. Adedicatedtubebendingfixture(Wintonmachinecompany)31. Modularfixturesallowawiderflexibilitybymakinguseofstan- dardworkholdingdevicesandcomponents.Theirflexibilityisde- rivedfromthelargenumberofpossiblefixtureconfigurationsfrom thedifferentcombinationsoffixturecomponents.Theapplication ofmodularfixturescontributesconsiderablytoshorteningthelead timeandreducingthecostinsmall-volumeproductionwithver- satileproducts.However,italsohassomelimitations28: Onlylimitedcombinationscanbeachievedfromthesecompo- nents,meaningthatitispossiblethatnosuitablecombination canbebuiltforsomeworkpieceswithirregularorcomplexge- ometries. Structuralpropertiesofmodularfixturesaresometimesdiffi- culttobemaintained.Structuralpropertiesofmodularfixtures includelocatingaccuracy,stiffness,stability,loadingandun- loading,operatingspeed,etc.Itiscommonthatusingmodular fixturesmaynotachieveanoptimalfixturingquality. Notsuitableformassproduction,e.g.automotiveproduction anditscomponentsmanufacture. Forcomparisonssake,Fig.8showsamodularfixtureusedfor apartfortheconstructionmachinery,andthesamepartalsoused inFig.9,whereadedicatedfixturesolutionisgiven. Thededicatedfixturesarealsoimportantinmanufacturing, particularly,foradvanced,sophisticatedandprecisepartormass production.Becauseadedicatedfixtureisdesignedforaspecific product,thedesignercancarefullytailorthedesigntonotonly meetthebasicfixturingrequirementssuchasthelocatingac- curacy,stability,stiffness,butalsooptimallyfacilitatetheoper- ationalrequirementssuchasloading/unloadingconvenienceand efficiency,andeffectivechipdisposaletc.AndFig.10isadedicated tubebendingfixture. Comparedwithmodularfixtures,dedicatedfixturesarede- signedcarefullyaccordingtoworkpiecesdesignandmanufac- turingrequirements.Sotherearemoreuncertaintiesimposedon dedicatedfixturedesigntasks.Inmodularfixturedesign,thereisa componentlibrarywithpre-designedanddimensionedstandard- izedfixturecomponents.Thus,themodularfixtureconfiguration designisactuallytoassemblethefixturecomponentsintoacon- figuration. Duetoitsextensiveuseincurrentmanufacturingandstan- dardizedproduction,inmanyreportedCAFDresearchesandap- plications,modularfixturingprinciplesareemployedtogenerate fixturedesigns3243.EarlyCAFDinmodularfixturesmerely usedthedraftingcapabilitiesofaCADsysteminassembly.Modular fixtureelementssuchasbaseplates,locators,supportsandclamps arestoredinadatabase.Basedonthefixturingidea,first,thede- signerspecifiestheprimarylocatingsurface(point)anditslocator positions,thesuitableclampingsurfacesandpositions,andthen selectsandplacestheappropriatefixturingcomponentsinthede- siredpositions.Althoughthereisareductioninthetotaltimetaken Fig.11. Thebasicelementsofthefixturedesignprocess. toproduceafixtureassembly,thefinaldesigndependslargelyon thedesignersexperience.Thustheyonlyprovidefixtureengineers withasimpletooltodofixturedesignmanuallybasedonsomeex- tendedfunctionsofcommercialCADsoftware.Asaresult,current industrialapplicationsofCAFDareverylimitedeventhoughthere aremanyreportedresearchachievements. Overthepastdecade,muchfocushasbeenputonintelligent methodsforcomputeraidedfixturedesigntoseekatechnical breakthroughinembeddingmoredesignknowledgeintosemi- automaticorautomaticCAFDsystems.Adetaileddiscussionwill bedoneinthefollowingsections(Table1). 3. Stateoftheart 3.1.Intelligentandautomaticfixturedesignmethods Typically,fixturedesigninvolvestheidentificationofclamps, locators,andsupportpoints,andtheselectionofthecorresponding fixtureelementsfortheirrespectivefunctions.Therearefourmain stageswithinafixturedesignprocesssetupplanning(D 1 ),fixture planning(D 2 ),fixtureunitdesign(D 3 )andverification(D 4 ),as Fig.11illustrates48,63.Setupplanningdeterminesthenumber ofsetupsrequiredtoperformallthemanufacturingprocesses, thetaskforeachsetup,e.g.,theongoingmanufacturingprocess andworkpiece,orientationandpositionoftheworkpieceineach setup.Asetuprepresentsthecombinationofprocessesthatcan beperformedontheworkpiecebyasinglemachinetoolwithout havingtochangethepositionandorientationoftheworkpiece manually.Duringfixtureplanning,thesurfaces,uponwhichthe locatorsandclampsmustact,aswellastheactualpositionsof thelocatingandclampingpointsontheworkpiece,areidentified. Thenumberandpositionoflocatingpointsmustbesuchthat theworkpieceisadequatelyconstrainedduringthemanufacturing process.Inthethirdstageoffixturedesign,suitableunits,(i.e.,the locatingandclampingunits,togetherwiththebaseplate),are generated.Duringtheverificationstage,thedesignistestedto ensurethatallmanufacturingrequirementsoftheworkpiececan besatisfied.Thedesignalsohastobeverifiedtoensurethatit meetsotherdesignconsiderationsthatmayincludefixturecost, fixtureweight,assemblytime,andloading/unloadingtimeofboth theworkpieceandfixtureunits50. Currently,eventhoughnumeroustechniquesconcentratingon fixturedesignhavebeenproposedandmadesomeachievements,H.Wangetal./Computer-AidedDesign42(2010)10851094 1089 Table1 CurrentCAFDliterature. Method Levelofdetail Application D 1 D 2 D 3 D 4 Shen,etal.6 Reconfigurablefixtures,Automotiveengine machiningandassembly Liu,etal.7 Assemblyfixturefaultdiagnosis,sheetmetal joiningprocess Lienetal.8 Integratedmeasurementinclamping systems On-linecorrectionofweldingpaths,Robotic weldingofthin-walledaluminumstructures Sikstrom,etal.9 Superelement(SE)fixturemodeling, Coupledthermalmechanicalanalysis Fixturedesigninfusionwelding Zheng,etal.32 Precisemodularfixture Peng,etal.3335 Desktopvirtualrealitytechnology Modularfixturedesignandsimulation Kumar,etal.36 CAD-basedcollisiondetection Modularfixtures Mervyn,etal.38 Evolutionarysearchalgorithm IMAOmodularfixtures Subramaniam,etal.44,45 Multi-agentsystem,Genetic algorithmsandNeuralnetworks Fan,etal.46,47 XMLbasedinformation representation,Casebasedreasoning method Wua,etal.37 Linkagemechanismtheory:afour-bar mechanismandlinkagecurve Modularfixture Hou,etal.39 Modularfixtures Girish,etal.40 Tabusearch Fixtureelementsmanagement Modularfixtureelements Lin,etal.41 Modularfixturesformeasurement Kakish,etal.42 Knowledge-basedmodeling Universalmodularjigsand fixturesinformationmodeling Universalmodularjigsandfixtures Cai,etal.43 TRIZevolutiontechnology TRIZ-basedevolutionstudyformodularfixture Boyle,etal.48,49 Casebasedreasoning Wang,etal.50 Casebasedreasoning Modularfixturesforwelding Chen,etal.51 Casebasedreasoning Wardak,etal.52,53 Finiteelementmethod Drillingfixtures Krishnakumar,etal.54,55 Finiteelementmethod,Genetic algorithm Machiningfixtures Subramanian,etal.56,57 Geneticalgorithm Hamedi58 Artificialneuralnetwork,Genetic algorithm,Finiteelementmethod Choubey,etal.59 Geneticalgorithm Machiningfixtures Kaya60 Finiteelementmethod,Genetic algorithm Machiningfixture Aoyama,etal.61 Geneticalgorithm Li,etal.1013 Finiteelementmethod,Genetic algorithm Sheetmetalassemblywithlaserwelding Ding,etal.14,15 Fixturefaultdiagnosis,assemblyprocesses Kang,etal.6265 Amaral,etal.66 Finiteelementanalysis Zheng,etal.6769 Finiteelementanalysis Forfixturestiffness, Hurtado,etal.7072 Finiteelementmethod,modelingof fixture-workpiececontacts Machiningfixtures Ratchev,etal.73 Finiteelementmethod Thepredictionofpart-fixturedeformationand tolerance Asante74 Finiteelement-based Loadandpressuredistributioncalculation Wang7579 Toleranceanalysisinfixture-workpiecesystem Estrems,etal.80 Fixturesinmachiningprocesses Bansal,etal.81 Anintegratedfixtureplanningsystemfor minimumtolerances Li,etal.16 MultiobjectiveOptimization Toleranceallocation,assemblyfixture Wu28 Geometrygenerationoffixture Note:Setupplanning(D1),fixtureplanning(D2),fixtureunitdesign(D3)andverification(D4). matureandcommercialCAFDapplicationsalsoareverylimited. Fixture design still continues to be a major bottleneck in the promotion of current manufacturing. This work currently, is implementedbyatypicaldesigner-centeredpattern,thatis,all fixturedesignrelatedworkisheavilydependantontheexperience andknowledgeoffixturedesigner.Thissituationhampersthe improvementofproductivity,requiresalongtimetocultivate anexperiencedfixturedesignerandmakethefixturedesignjob weakwithamajorbottleneck.Thus,newintelligentorautomatic technologiesonsynthesizingtraditionalgeometricdesigntools, designknowledge,andpastdesigncaseshaveattractedmuch interestinbothacademicinstitutionsandindustries.Theefforts overpastdecadesinthisfieldhaveresultedinnumerouscomputer aidedfixturedesign(CAFD)applicationsusingvariousintelligent methods,suchasexpertsystem,casebasedreasoning,andgenetic algorithm(GA),etc. Inessence,developingfixturedesignmethodologyneedsto cleartwocrucialproblems:howtorepresentfixturedesignknowl- edgeinacomputerandhowtoimplementtheproblemsolving procedure. AttheinitialstageofCAFDtwodecadesago,expertsystems wereoftenusedasaheuristictool,whichcanenlightenfixture designertoacompletefixturedesignsolution,particularly,fixture configurationdesigninaninteractiveenvironment82.Inmost of these methods, design knowledge is modeled as a set of manyIF-THENrules.Then,duringtheinteractivefixturedesign process,thedesignsolutionwouldbeconcludedbyaseriesof questioningansweringactionsbasedontheserules.However,1090 H.Wangetal./Computer-AidedDesign42(2010)10851094 Table2 SomeCBRmethodsinCAFD. Caserepresentation CBRprocedure Chen, etal.51 Definefixturedesignby attributestemplate Interactivemode:Designer selectssomeimportant attributestomatchcurrent designcasewithstoredcases Fan, etal.46,47 XMLandUML Boyle, etal.48,49 Dividefixturedesign informationintotwo libraries:conceptualdesign libraryandfixtureunit library Combinationofthesearch resultsfromtwocase libraries Sun, etal.83 Usin