在多材料注射模设计中要综合考虑可制造的工艺性毕业课程设计外文文献翻译、中英文翻译、外文翻译【带出处】

INCORPORATINGMANUFACTURABILITYCONSIDERATIONSDURINGDESIGNOFINJECTIONMOLDEDMULTIMATERIALOBJECTSASHISGOPALBANERJEE,XUEJUNLI,GREGFOWLER,SATYANDRAKGUPTA1MECHANICALENGINEERINGDEPARTMENTANDTHEINSTITUTEFORSYSTEMSRESEARCHUNIVERSITYOFMARYLAND,COLLEGEPARK,MD20742,USAABSTRACTTHEPRESENCEOFANALREADYMOLDEDCOMPONENTDURINGTHESECONDANDSUBSEQUENTMOLDINGSTAGESMAKESMULTIMATERIALINJECTIONMOLDINGDIFFERENTFROMTRADITIONALINJECTIONMOLDINGPROCESSTHEREFORE,DESIGNINGMULTIMATERIALMOLDEDOBJECTSREQUIRESADDRESSINGMANYADDITIONALMANUFACTURABILITYCONSIDERATIONSINTHISPAPER,WEFIRSTPRESENTANAPPROACHTOSYSTEMATICALLYIDENTIFYINGPOTENTIALMANUFACTURABILITYPROBLEMSTHATAREUNIQUETOTHEMULTIMATERIALMOLDINGPROCESSESANDDESIGNRULESTOAVOIDTHESEPROBLEMSTHENWEPRESENTACOMPREHENSIVEMANUFACTURABILITYANALYSISAPPROACHTHATINCORPORATESBOTHTHETRADITIONALSINGLEMATERIALMOLDINGRULESASWELLASTHESPECIFICRULESTHATHAVEBEENIDENTIFIEDFORMULTIMATERIALMOLDINGOURANALYSISSHOWSTHATSOMETIMESTHETRADITIONALRULESNEEDTOBESUPPRESSEDORMODIFIEDLASTLY,FOREACHOFTHENEWMANUFACTURABILITYPROBLEM,THISPAPERDESCRIBESALGORITHMSFORAUTOMATICALLYDETECTINGPOTENTIALOCCURRENCESANDGENERATINGREDESIGNSUGGESTIONSTHESEALGORITHMSHAVEBEENIMPLEMENTEDINACOMPUTERAIDEDMANUFACTURABILITYANALYSISSYSTEMTHEAPPROACHPRESENTEDINTHISPAPERISAPPLICABLETOMULTISHOTANDOVERMOLDINGPROCESSESWEEXPECTTHATTHEMANUFACTURABILITYANALYSISTECHNIQUESPRESENTEDINTHISPAPERWILLHELPINDECREASINGTHEPRODUCTDEVELOPMENTTIMEFORTHEINJECTIONMOLDEDMULTIMATERIALOBJECTSKEYWORDSAUTOMATEDMANUFACTURABILITYANALYSIS,GENERATIONOFREDESIGNSUGGESTIONS,ANDMULTIMATERIALINJECTIONMOLDING1INTRODUCTIONOVERTHELASTFEWYEARS,AWIDEVARIETYOFMULTIMATERIALINJECTIONMOLDINGMMMPROCESSESHAVEEMERGEDFORMAKINGMULTIMATERIALOBJECTS,WHICHREFERTOTHECLASSOFOBJECTSINWHICHDIFFERENTPORTIONSAREMADEOFDIFFERENTMATERIALSDUETOFABRICATIONANDASSEMBLYSTEPSBEINGPERFORMEDINSIDETHEMOLDS,MOLDEDMULTIMATERIALOBJECTSALLOWSIGNIFICANTREDUCTIONINASSEMBLYOPERATIONSANDPRODUCTIONCYCLETIMESFURTHERMORE,THEPRODUCTQUALITYCANBEIMPROVED,ANDTHEPOSSIBILITYOFMANUFACTURINGDEFECTS,ANDTOTALMANUFACTURINGCOSTSCANBEREDUCEDINMMM,MULTIPLEDIFFERENTMATERIALSAREINJECTEDINTOAMULTISTAGEMOLDTHESECTIONSOFTHEMOLDTHATARENOTTOBEFILLEDDURINGAMOLDINGSTAGEARETEMPORALLYBLOCKEDAFTERTHEFIRSTINJECTEDMATERIALSETS,THENONEORMOREBLOCKEDPORTIONSOFTHEMOLDAREOPENEDANDTHENEXTMATERIALISINJECTEDTHISPROCESSCONTINUESUNTILTHEREQUIREDMULTIMATERIALPARTISCREATEDNOWADAYS,VIRTUALLYEVERYINDUSTRYEG,AUTOMOTIVE,CONSUMERGOODS,TOYS,ELECTRONICS,POWER第1页共67页TOOLS,APPLIANCESTHATMAKESUSEOFTRADITIONALSINGLEMATERIALINJECTIONMOLDINGSMMPROCESSISBEGINNINGTOUSEMULTIMATERIALMOLDINGPROCESSESSOMECOMMONAPPLICATIONSINCLUDEMULTICOLOROBJECTS,SKINCOREARRANGEMENTS,INMOLDASSEMBLEDOBJECTS,SOFTTOUCHCOMPONENTSWITHRIGIDSUBSTRATEPARTSANDSELECTIVECOMPLIANCEOBJECTSTYPICALEXAMPLESOFEACHCLASSOFAPPLICATIONARESHOWNINFIG1THEREAREFUNDAMENTALLYTHREEDIFFERENTTYPESOFMULTIMATERIALMOLDINGPROCESSESMULTICOMPONENTINJECTIONMOLDINGISPERHAPSTHESIMPLESTANDMOSTCOMMONFORMOFMMMITINVOLVESEITHERSIMULTANEOUSORSEQUENTIALINJECTIONOFTWODIFFERENTMATERIALSTHROUGHEITHERTHESAMEORDIFFERENTGATELOCATIONSINASINGLEMOLDMULTISHOTINJECTIONMOLDINGMSMISTHEMOSTCOMPLEXANDVERSATILEOFTHEMMMPROCESSESITINVOLVESINJECTINGTHEDIFFERENTMATERIALSINTOTHEMOLDINASPECIFIEDSEQUENCE,WHERETHEMOLDCAVITYGEOMETRYMAYPARTIALLYORCOMPLETELYCHANGEBETWEENSEQUENCESOVERMOLDINGSIMPLYINVOLVESMOLDINGARESINAROUNDAPREVIOUSLYMADEINJECTIONMOLDEDPLASTICPARTEACHOFTHETHREECLASSESOFMMMISCONSIDERABLYDIFFERENTEACHSPECIFICMMMPROCESSREQUIRESITSOWNSETOFSPECIALIZEDEQUIPMENTHOWEVER,THEREARECERTAINEQUIPMENTREQUIREMENTSTHATAREGENERALLYTHESAMEFORALLTYPESOFMMMTECHNIQUESDESCRIBEDINTHISPAPERAREAPPLICABLETOOVERMOLDINGANDMULTISHOTMOLDINGCURRENTLYONLYLIMITEDLITERATUREEXISTSTHATDESCRIBESHOWTODESIGNMOLDEDMULTIMATERIALOBJECTSCONSEQUENTLYVERYFEWDESIGNERSHAVETHEREQUIREDKNOWHOWTODOSOCONSIDERANEXAMPLEOFATWOPIECEASSEMBLYCONSISTINGOFPARTAANDPARTBTOBEPRODUCEDBYMULTIMATERIALMOLDINGINFACT,MANYNEWUSERSBELIEVETHATIFPARTAANDPARTBMEETTHETRADITIONALMOLDINGRULESTHENASSEMBLYABWILLALSOBEMOLDABLEUSINGMULTIMATERIALMOLDINGBYMOLDABLEWEMEANTHATTHEASSEMBLYORPARTCANBEMOLDEDUSINGONEORMOREMMMORSMMPROCESSESSUCHTHATBASICFUNCTIONALANDAESTHETICREQUIREMENTSFORTHEPARTORASSEMBLYARESATISFIEDANDTHEMOLDCAVITYSHAPECANBECHANGEDIEMOLDCANBEOPENED,PIECESMAYBEREMOVEDORINSERTEDANDTHENMOLDCANBECLOSEDWITHOUTDAMAGINGTHEMOLDPIECESHOWEVER,THISNOTIONISNOTALWAYSCORRECTFIG2SHOWSANASSEMBLYTOBEMOLDEDBYMMMINTHISCASE,BOTHPARTSCANBEINDIVIDUALLYMOLDEDWITHOUTANYPROBLEMHOWEVER,MOLDINGTHEMASANASSEMBLYUSINGOVERMOLDINGPROCESSLEADSTOMANUFACTURABILITYPROBLEMSAFTERMOLDINGTHEINNERPARTINTHEFIRSTSTAGE,ITISNOTPOSSIBLETOCARRYOUTSECONDSTAGEMOLDINGASTHEINJECTEDPLASTICWILLFLOWOVERTHEINNERPARTANDDAMAGETHESURFACESOFTHEALREADYMOLDEDCOMPONENTTHISEMPHASIZESTHENEEDFORDEVELOPINGNEWDESIGNRULESTHATARESPECIFICTOADDRESSINGMANUFACTURABILITYPROBLEMSENCOUNTEREDINMULTIMATERIALMOLDINGDETECTIONOFTHISPROBLEMANDCORRESPONDINGREDESIGNSUGGESTIONWILLBEDESCRIBEDINSUBSECTION53ONTHEOTHERHAND,THEREAREMOLDEDMULTIMATERIALASSEMBLIESWHEREATLEASTONEOFTHEPARTSWOULDHAVENOTBEENMOLDABLEASANINDIVIDUALPIECEUSINGTRADITIONALMOLDINGHOWEVER,THISPARTCANBEMOLDEDWHENDONEASAPARTOFTHEASSEMBLYFIG3HIGHLIGHTSSUCHACASEALTHOUGHAPPLICATIONOFTRADITIONALPLASTICINJECTIONMOLDINGRULESWOULDHAVECONCLUDEDTHATCOMPONENTBCANNOTBEMANUFACTURED,ITISPOSSIBLETOMOLDASSEMBLYABBYCHOOSINGANAPPROPRIATEMOLDINGSEQUENCEFOREXAMPLE,INTHISCASEWEFIRSTNEEDTOMOLDPARTAANDTHENMOLDPARTBUSINGOVERMOLDINGOPERATIONTHEREASONWHYMMMAPPEARSTOBESIGNIFICANTLYDIFFERENTFROMSMMCANBEEXPLAINEDASFOLLOWSTHEPARTTHATHASBEENMOLDEDFIRSTCOMPONENTAACTSASTHE“MOLDPIECE”DURINGTHESECONDMOLDINGSTAGETHUS,APLASTICMOLDPIECEISPRESENTINADDITIONTOTHEMETALLICMOLDPIECES第2页共67页DURINGTHISMOLDINGSTAGEHENCE,THISSECONDSTAGEISFUNDAMENTALLYDIFFERENTINNATUREFROMCONVENTIONALSINGLEMATERIALINJECTIONMOLDINGFIG4ILLUSTRATESTHISCONDITIONBYDEPICTINGTHETWOMOLDINGSTAGESINROTARYPLATENMULTISHOTMOLDINGALTHOUGHTHESHAPEOFTHECOREREMAINSIDENTICALINBOTHTHESTAGES,THECAVITYSHAPECHANGESANDALREADYMOLDEDCOMPONENTAACTSASANADDITIONAL“MOLDPIECE”INTHESECONDSHOTMOREOVER,THEFIRSTSTAGEPARTTHATACTSASPLASTIC“MOLDPIECE”ISNOTSEPARATEDFROMTHEFINALASSEMBLYTHISFORCESUSTOAVOIDAPPLYINGSOMEOFTHETRADITIONALMOLDINGDESIGNRULESONCERTAINPORTIONSOFTHEGROSSSHAPEOFTHEOVERALLOBJECTALSOREFERREDASGROSSOBJECTBYGROSSOBJECT,WEMEANTHESOLIDOBJECTCREATEDBYTHEREGULARIZEDUNIONOFTHETWOCOMPONENTSTHATISWHY,SIMPLYENSURINGTHATTHEFIRSTSTAGEPARTANDTHEGROSSSHAPEAREMOLDABLEDONOTSOLVETHISPROBLEMEITHERFIG5ILLUSTRATESTHISFACTBLINDLYCHECKINGALLTHEFACESOFTHEGROSSOBJECTFORPRESENCEOFUNDERCUTSLEADSUSTOWRONGLYCONCLUDETHATITCANNOTBEMOLDEDINREALITY,THISISNOTTHECASEANDWESHOULDONLYTESTTHEFACESTHATNEEDTOBEDEMOLDEDIE,SEPARATEDFROMTHEMOLDPIECESDURINGTHATMOLDINGSTAGEWHILEDETERMININGAFEASIBLEMOLDINGSEQUENCEBASEDONTHEABOVEDISCUSSION,WECONCLUDETHATANEWAPPROACHNEEDSTOBEDEVELOPEDTOANALYZEMANUFACTURABILITYOFMOLDEDMULTIMATERIALOBJECTSINTHECURRENTPAPERWEONLYCONSIDERMANUFACTURABILITYPROBLEMSARISINGDUETOTHESHAPEOFTHECOMPONENTSANDTHEGROSSOBJECTFIG6SHOWSANEXAMPLEWHEREUNDERCUTSCREATEPROBLEMSTHEYNEEDTOBEELIMINATEDINORDERTOFORMAFEASIBLEMOLDINGSEQUENCETHEGROSSOBJECTSHOWNINTHATFIGURECANNOTBEMADEBYANYMMMPROCESS,BECAUSENEITHEROFTHETWOCOMPONENTSISMOLDABLEDUETOTHEPRESENCEOFDEEP,INTERNALUNDERCUTSSLIGHTREDESIGNOFCOMPONENTAENABLESUSTOCARRYOUTMMMOPERATIONCOMPONENTACANBEINJECTEDFIRSTANDTHENCOMPONENTB,PROVIDEDTHEYHAVESIMILARMELTINGPOINTSORAMELTSATAHIGHERTEMPERATURETHANBSECTION3SYSTEMATICALLYDERIVESFIVESUCHNEWMANUFACTURABILITYPROBLEMSTHATARISEINMULTIMATERIALMOLDINGFROMTHESTATETRANSITIONDIAGRAMREPRESENTINGTHEPROCESSFLOWTHENEXTTASKINDEVELOPINGASYSTEMATICMANUFACTURABILITYANALYSISMETHODOLOGYISTODEVELOPADETAILEDAPPROACHFORAPPLYINGTHESENEWRULESACOMPREHENSIVEAPPROACHTOOUTLINEHOWANDWHENTHENEWMULTIMATERIALMOLDINGDESIGNRULESNEEDTOBEAPPLIEDANDTRADITIONALSINGLEMATERIALMOLDINGRULESHAVETOBEAPPLIED,MODIFIEDORSUPPRESSEDHASBEENPROPOSEDINSECTION4FINALLY,ALGORITHMSHAVEBEENPRESENTEDTODETECTVIOLATIONSOFSUCHRULESANDGENERATEFEASIBLEREDESIGNSUGGESTIONSINSECTION5ALLTHEALGORITHMSHAVEBEENIMPLEMENTEDINACOMPUTERAIDEDMANUFACTURABILITYANALYSISSYSTEMWECONCLUDETHISPAPERBYSTATINGITSCONTRIBUTIONSANDLIMITATIONSINSECTION62RELATEDRESEARCHAWIDEVARIETYOFCOMPUTATIONALMETHODSHAVEEMERGEDTOPROVIDESOFTWAREAIDSFORPERFORMINGMANUFACTURABILITYANALYSISGUPT97A,VLIE99SUCHSYSTEMSVARYSIGNIFICANTLYBYAPPROACH,SCOPE,ANDLEVELOFSOPHISTICATIONATONEENDOFTHESPECTRUMARESOFTWARETOOLSTHATPROVIDEESTIMATESOFTHEAPPROXIMATEMANUFACTURINGCOSTATTHEOTHERENDARESOPHISTICATEDTOOLSTHATPERFORMDETAILEDMANUFACTURABILITYANALYSISANDOFFERREDESIGNSUGGESTIONSFORANALYZINGTHEMANUFACTURABILITYOFADESIGN,THEEXISTINGAPPROACHESCANBEROUGHLYCLASSIFIEDINTOTWOCATEGORIESINDIRECTAPPROACHESISHI92,ROSE92,SHAN93,SHAPEBASEDRULESAREUSEDTOIDENTIFY第3页共67页INFEASIBLEDESIGNATTRIBUTESFROMDIRECTINSPECTIONOFTHEDESIGNDESCRIPTIONININDIRECTORPLANBASEDAPPROACHESGUPT95,GUPT97B,GUPT98,HAYE89,HAYE94,HAYE96,THEFIRSTSTEPISTOGENERATEAMANUFACTURINGPLAN,ANDTHENTOEVALUATETHEPLANINORDERTOASSESSTHEMANUFACTURABILITYOFDESIGNTHISAPPROACHISUSEFULINDOMAINSWHERETHEREARECOMPLEXINTERACTIONSBETWEENMANUFACTURINGOPERATIONSSEVERALLEADINGPROFESSIONALSOCIETIESHAVEPUBLISHEDMANUFACTURABILITYGUIDELINESFORMOLDEDPLASTICPARTSTOHELPDESIGNERSTAKEMANUFACTURABILITYINTOACCOUNTDURINGTHEPRODUCTDESIGNPHASEBAKE92,TRUC87POLIPOLI01HASALSODESCRIBEDQUALITATIVEDFMRULESFORALLTHEMAJORPOLYMERPROCESSINGPROCESSESINCLUDINGINJECTIONMOLDING,COMPRESSIONMOLDINGANDTRANSFERMOLDINGMOREOVER,COMPANIESSUCHASGENERALELECTRICGENE60HAVEGENERATEDTHEIROWNGUIDELINESFORTHEDESIGNOFPLASTICPARTSSUCHGUIDELINESSHOWEXAMPLESOFGOODANDBADDESIGNSITISLEFTTOTHEDESIGNERSDISCRETIONTOAPPLYTHEMASANDWHENNECESSARYBASICALLY,THEREARETWOTYPESOFGUIDELINESTHEFIRSTTYPEDEALSWITHMANUFACTURABILITYISSUES,WHEREASTHESECONDTYPEDEALSWITHPARTFUNCTIONALITYWEWILLONLYCOVERTHEFIRSTTYPEOFGUIDELINESHERETHEYARELISTEDASFOLLOWSAFILLETSSHOULDBECREATEDANDCORNERSSHOULDBEROUNDEDSOTHATTHEMOLTENPLASTICFLOWSSMOOTHLYTOALLTHEPORTIONSOFTHEPARTUSEOFRADIIANDGRADUALTRANSITIONSMINIMIZETHEDEGREEOFORIENTATIONASSOCIATEDWITHMOLDFILLING,THEREBYRESULTINGINUNIFORMMOLDFLOWMALL94MOREOVER,THISALSOAVOIDSTHEPROBLEMOFHAVINGHIGHSTRESSCONCENTRATIONFIG7SHOWSANEXAMPLEOFHOWPARTDESIGNNEEDSTOBEALTEREDTOGETRIDOFSHARPCORNERSBTHEPARTINGLINEMUSTBECHOSENCAREFULLYSOTHAT“PARTING”ANDMETAL“SHUTOFF”FLASHESCANBEMINIMIZEDTYPICALLY,FLASHESSOLIDIFIEDLEAKAGESOFPLASTICMATERIALOCCURALONGTHEPARTINGLINE,WHERETHEMOLDPIECESCOMEINDIRECTCONTACTWITHEACHOTHERFIG8ILLUSTRATESHOWTHESTIFFENINGRIBSONAPARTHAVETOBEREDESIGNEDINORDERTOCHANGETHELOCATIONOFTHEPARTINGLINETHISCONSEQUENTLYCHANGESTHEFLASHFORMATIONPOSITIONINTHEFIRSTCASE,FLASHESRUNALLALONGTHEPART,DESTROYINGTHEPARTQUALITYHOWEVER,THEYOCCURONTHETOPSURFACEOFTHEPARTINTHESECONDDESIGN,ANDHENCECANBEEASILYREMOVEDLATERONCTHINANDUNIFORMSECTIONTHICKNESSSHOULDBEUSEDSOTHATTHEENTIREPARTCANCOOLDOWNRAPIDLYATTHESAMERATETHICKSECTIONSTAKEALONGERTIMETOCOOLTHANTHINSECTIONSFOREXAMPLE,INTHEFIRSTPARTSHOWNINFIG9,THETHICKER,HOTTERSECTIONSOFTHEMOLDINGWILLCONTINUETOCOOLANDSHRINKMORETHANTHETHINNERSECTIONSTHISWILLRESULTINALEVELOFINTERNALSTRESSINTHEPORTIONSOFTHEPARTWHERETHEWALLTHICKNESSCHANGESTHESERESIDUAL,INTERNALSTRESSESCANLEADTOWARPAGESANDREDUCEDSERVICEPERFORMANCESIFPOSSIBLE,THEPARTMUSTBEREDESIGNEDTOELIMINATESUCHTHICKNESSVARIATIONSALTOGETHEROTHERWISE,TAPEREDTRANSITIONSCANBEUSEDTOAVOIDRESIDUALSTRESSES,HIGHSTRESSCONCENTRATIONSANDABRUPTFLOWTRANSITIONSDURINGMOLDFILLINGWHENEVERFEASIBLE,WALLSECTIONTHICKNESSMUSTBEREDUCEDBYCORINGOUTSECTIONSOFTHEMOLDING,ANDBYUSINGRIBSTOCOMPENSATEFORTHELOSSINSTIFFNESSOFATHINNERPARTMALL94DSIDEACTIONSSIDECORES,SPLITCORES,LIFTERSETCMUSTBEUSEDTOCREATEUNDERCUTFEATURESONTHEPARTORTHEPARTSHOULDBEREDESIGNEDTOELIMINATEUNDERCUTFEATURESFIG10SHOWSANEXAMPLEOFAPLASTICPART,WHOSEUNDERCUTREGIONCANNOTBEMOLDEDBYANYSIDEACTIONASIMPLEREDESIGNSHOWNINTHISFIGURESOLVESTHISPROBLEMEDRAFTANGLESNEEDTOBEIMPARTEDTOVERTICALORNEARVERTICALWALLSFOREASEOFREMOVALOFTHEPARTFROMTHEMOLDASSEMBLYFIG11SHOWSTHATINCORRECTDRAFTANGLESMAKEITIMPOSSIBLETOEJECTTHEPARTTAPERINGTHESIDEWALLSINWARDTOWARDSTHECORESIDERESOLVESTHISISSUE第4页共67页SATISFACTORILYDRAFTINGALSOREDUCESTOOLANDPARTWEARCONSIDERABLYSLIDINGFRICTIONASWELLASSCUFFINGORABRASIONOFTHEOUTERCAVITYFACESOFTHEPARTAREELIMINATEDTOALARGEEXTENTTYPICALLY,THEREQUIREDDRAFTANGLERANGESFROMAFRACTIONOFADEGREETOSEVERALDEGREESANDDEPENDSONALOTOFPARAMETERSSUCHASDEPTHOFDRAW,MATERIALRIGIDITY,SURFACELUBRICITYANDMATERIALSHRINKAGEMALL94COMPUTATIONALWORKINTHEFIELDOFMANUFACTURABILITYANALYSISOFINJECTIONMOLDEDPARTSMAINLYFOCUSESONTWODIFFERENTAREASTHEFIRSTAREADEALSWITHDEMOLDABILITYOFASINGLEMATERIALPARTTHEDEMOLDABILITYOFAPARTISITSABILITYTOBEEJECTEDEASILYFROMTHEMOLDASSEMBLYCORE,CAVITYANDSIDEACTIONSWHENTHEMOLDOPENSDECIDINGIFAPARTISDEMOLDABLEISEQUIVALENTTODECIDINGIFTHEREEXISTSACOMBINATIONOFMAINPARTINGDIRECTION,SIDECORESANDSPLITCORESSUCHTHATTHECRITERIONOFDEMOLDABILITYISSATISFIEDCHENETALCHEN93DESCRIBEAVISIBILITYMAPBASEDAPPROACHTOFINDAFEASIBLEPARTINGDIRECTIONTHATMINIMIZESTHENUMBEROFSIDECORESHUIHUI97DESCRIBESAHEURISTICSEARCHTECHNIQUEFORSELECTINGACOMBINATIONOFMAINPARTING,COREANDINSERTDIRECTIONSAPPROACHESBASEDONUNDERCUTFEATURERECOGNITIONHAVEALSOBEENDEVELOPEDGU99,FU99,LU00,YIN01THEBASICIDEABEHINDTHESEAPPROACHESISTOFINDPOTENTIALUNDERCUTSONTHEPARTUSINGFEATURERECOGNITIONTECHNIQUESEACHTYPEOFFEATUREHASITSOWNSETOFCANDIDATEPARTINGDIRECTIONSTHEOPTIMALMAIN,PARTINGDIRECTIONISTHENCHOSENONTHEBASISOFSOMEEVALUATIONFUNCTIONSAHNETALAHN02DESCRIBEMATHEMATICALLYSOUNDALGORITHMSTOTESTIFAPARTIS,INDEED,MOLDABLEUSINGATWOPIECEMOLDWITHOUTANYSIDEACTIONSANDIFSO,TOOBTAINTHESETOFALLSUCHPOSSIBLEPARTINGDIRECTIONSBUILDINGONTHIS,ELBERETALELBE05HAVEDEVELOPEDANALGORITHMBASEDONASPECTGRAPHSTOSOLVETHETWOPIECEMOLDSEPARABILITYPROBLEMFORGENERALFREEFORMSHAPES,REPRESENTEDBYNURBSSURFACESMCMAINSANDCHENMCMA04HAVEDETERMINEDMOLDABILITYANDPARTINGDIRECTIONSFORPOLYGONSWITHCURVED2DSPLINEEDGESRECENTLY,KHARDERKARETALKHAR05HAVEPRESENTEDNEWPROGRAMMABLEGRAPHICSHARDWAREACCELERATEDALGORITHMSTOTESTTHEMOLDABILITYOFPARTSANDHELPINREDESIGNINGTHEMBYIDENTIFYINGANDGRAPHICALLYDISPLAYINGUNDERCUTSDHALIWALETALDHAL03DESCRIBEDEXACTALGORITHMSFORCOMPUTINGGLOBALACCESSIBILITYCONESFOREACHFACEOFAPOLYHEDRALOBJECTUSINGTHESE,PRIYADARSHIANDGUPTAPRIY04DEVELOPEDALGORITHMSTODESIGNMULTIPIECEMOLDSOTHERNOTABLEWORKINTHEAREAOFAUTOMATEDMULTIPIECEMOLDDESIGNINCLUDESTHATBYCHENANDROSENCHEN02,CHEN03THESECONDAREAOFACTIVEWORKDEALSWITHTHESIMULATIONOFMOLTEN,PLASTICFLOWININJECTIONMOLDINGPROCESSMANYCOMMERCIALSYSTEMSAREAVAILABLETOHELPDESIGNERSINPERFORMINGMANUFACTURABILITYANALYSISALSO,FINITEELEMENTANALYSISSOFTWARELIKEANSYS,ABAQUS,FEMLABETCCANBEUSEDTOPREDICTANDSOLVESOMEPROBLEMS,SUCHASWHETHERTHESTRENGTHOFSOMEPORTIONOFTHEPARTISADEQUATESINCETHESETYPESOFPROBLEMSARISINGDURINGMULTIMATERIALINJECTIONMOLDINGARETHESAMEASTHOSEEXPERIENCEDINCASEOFSINGLEMATERIALMOLDING,APPROPRIATECOMMERCIALPACKAGESCANBEUSEDTOOVERCOMETHEM3IDENTIFYINGSOURCESOFMOLDINGPROBLEMSMANYDIFFERENTREASONSCANCONTRIBUTETOMANUFACTURABILITYPROBLEMSDURINGMMMTHESEREASONSINCLUDEMATERIALINCOMPATIBILITY,INTERACTIONSAMONGCOOLINGSYSTEMSFORDIFFERENTSTAGES,PLACEMENTOFGATES,DEMOLDABILITY,ANDEJECTIONSYSTEMPROBLEMSINTHISPAPERWEMAINLYFOCUSONTHEMANUFACTURABILITYPROBLEMSTHATRESULTFROMTHESHAPEOFTHEMULTIMATERIALOBJECTSSPECIFICALLY,WEFOCUSONTHOSEMANUFACTURINGCOMPLICATIONSTHATARISEDUETOTHEPRESENCEOFPLASTICMATERIALINSIDETHEMOLDCAVITYDURINGTHESECONDSHOTTHEWORKPRESENTEDINTHISPAPERIS第5页共67页APPLICABLETOMULTISHOTROTARYPLATENSHOWNINFIG4ANDFIG12,MULTISHOTINDEXPLATESHOWNINFIG13ANDFIG14,ANDOVERMOLDINGPROCESSESSHOWNINFIG15APPENDIXADESCRIBESEACHOFTHESEPROCESSESINDETAILSITISIMPORTANTTONOTEHERETHATPARTDESIGNSNEEDTOBEMODIFIEDSIGNIFICANTLYDEPENDINGUPONTHENATUREOFTHEMMMPROCESSTHATWILLBEUSEDTOMOLDITFIG16ILLUSTRATESTHISIDEABYUSINGTHREEDIFFERENTPARTDESIGNSTHEFIRSTOBJECTCANBEMOLDEDBYOVERMOLDINGPROCESSONLY,WHEREASTHESECONDOBJECTCANBEMOLDEDUSINGEITHEROVERMOLDINGORINDEXPLATEMULTISHOTMOLDINGPROCESSROTARYPLATENPROCESSSHOULDBEUSEDTOMOLDTHELASTPARTTHUS,ITISCLEARTHATSPECIFICPROCESSDEPENDENTDESIGNRULESAREESSENTIALINMULTIMATERIALINJECTIONMOLDINGLETUSNOWTRYTOSYSTEMATICALLYIDENTIFYTHEMANUFACTURABILITYPROBLEMSSOTHATCORRESPONDINGDESIGNRULESCANBEFRAMEDTOHANDLETHEMTHESEDESIGNRULESWILLBELATERUTILIZEDBYTHEALGORITHMSINSECTIONS4AND5TOOFFERMEANINGFULSOLUTIONSONCETHEPROBLEMSHAVEBEENDETECTEDANEWWAYOFIDENTIFYINGALLTHEPOTENTIALSOURCESOFMANUFACTURABILITYPROBLEMSUSINGSTATETRANSITIONDIAGRAMSANDSTUDYINGFAILUREMODEMATRICESISPRESENTEDBELOWTHEEFFECTIVENESSOFTHISTECHNIQUEISFIRSTVALIDATEDBYCOMPARINGTHEIDENTIFIEDFAILUREMODESANDCORRESPONDINGDESIGNRULESWITHTHEESTABLISHEDGUIDELINESFORTRADITIONALINJECTIONMOLDINGAFTERWARDS,THESAMEAPPROACHISADOPTEDINORDERTODETECTANDDIAGNOSEALLTHEPOTENTIALMANUFACTURABILITYPROBLEMSINMMMPROCESSESTHISSCHEMEISCOMPREHENSIVEWITHRESPECTTOTHESTATETRANSITIONMODELITDOESNOTOVERLOOKANYOFTHEPOTENTIALPROBLEMSTHATARISESDUETOTHEGEOMETRYOFTHEMULTIPLE,HETEROGENEOUSOBJECTSFIG17SHOWSTHESTATETRANSITIONDIAGRAMFORSMMITISCLEARTHATFIVESTATESHAVETOBECOMPLETEDSUCCESSFULLYSOTHATANACCEPTABLEQUALITYPARTISOBTAINEDFOURCOMMONFAILUREMODESAREPOSSIBLESHOWNINFIGURE17ANDTABLE1EVENIFANYONEOFTHEMOCCURS,ADEFECTIVEPARTWILLBEFORMEDTHESEMODESHAVEBEENMAPPEDINTOCORRESPONDINGCAUSESINTHEMATRIXSHOWNINTABLE1FROMTHAT,DESIGNRULESHAVEBEENDERIVEDTOALLEVIATEEACHOFTHEPROBLEMSITMAYBENOTEDHERETHATAPARTICULARFAILUREMODECANBECAUSEDBYMULTIPLEPROBLEMSAND/ORASINGLESOLUTIONDESIGNRULEMAYBESUFFICIENTTOREMOVEMORETHANONEPROBLEMTHESEPROBLEMS,ALONGWITHTHECORRESPONDINGDESIGNRULESARELISTEDASFOLLOWS1INCOMPLETEFILLINGOFTHEMOLDCAVITYSOLUTIONISTHATSHARPCORNERSSHOULDHAVEFILLETSASIMPLEMETHODCANBEUSEDTODETECTSUCHCORNERSANDROUNDTHEMIFTHETWOTANGENTVECTORSATTHECOMMONINTERSECTIONPOINTBETWEENTWOEDGESCREATEASHARPANGLE,THENTHISCORRESPONDSTOASHARPCORNERINTHATCASE,THETWOMATINGEDGESHAVETOBETRUNCATEDANDASMALLRADIUSCIRCULARARCFILLETHASTOBECREATEDTOJOINTHETRUNCATEDSEGMENTSSUCHTHATTHETANGENTVECTORSCHANGEGRADUALLYALONGTHEARCOFTHECIRCLE2OCCURRENCEOFFLASHESTHEPARTINGLINESHOULDNOTCROSSFACESONWHICHFLASHISNOTPERMITTEDTOAVOIDTHISPROBLEMANUNEVENSLICINGMETHODSUGGESTEDBYWONG98CANBEUSEDTOFORMTHEPARTINGLINEFORPARTSHAVINGPLANARASWELLASCURVEDSURFACESSINCEFLASHESRESULTINERGONOMICANDAESTHETICPROBLEMS,PARTSSHOULDBEDESIGNEDSOTHATTHEFLASHESGENERATEDCANBEEASILYSCRAPEDOUTORMINIMIZED3PRESENCEOFRESIDUALSTRESSESTHEWALLTHICKNESSSHOULDBEUNIFOR