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英文原文SessionVA4IntelligentMoldDesignToolForPlasticInjectionMoldingJagannathYammada,TerrenceL.Chambers,SurenN.DwivediDepartmentofMechanicalEngineeringUniversityofLouisianaatLafayetteAbstractPlasticInjectionmoldingisoneofthemostpopularmanufacturingprocessesformakingthermoplasticproducts,andmolddesignisakeyaspectoftheprocess.Designofmoldsrequiresknowledge,expertiseandmostimportantlyexperienceinthefield.Whenoneoftheseislacking,selectionofanappropriatemoldformanufacturingaplasticcomponentisdoneonatrial-and-errorbasis.Thisincreasesthecostofproductionandintroducesinconsistenciesinthedesign.Thispaperdescribesthedevelopmentofanintelligentmolddesigntool.Thetoolcapturesknowledgeaboutthemolddesignprocessandrepresentstheknowledgeinlogicalfashion.Theknowledgeacquiredwillbedeterministicandnon-deterministicinformationaboutthemolddesignprocess.Oncedevelopedthemolddesigntoolwillguidetheuserinselectinganappropriatemoldforhisplasticpartbasedonvariousclientspecifications.IntroductionTheplasticinjectionmoldingprocessdemandsknowledge,expertiseand,mostimportant,experienceforitssuccessfulimplementation.Oftenitisthemoldingparametersthatcontroltheefficiencyoftheprocess.Effectivelycontrollingandoptimizingtheseparametersduringthemanufacturingprocesscanachieveconsistency,whichtakestheformofpartqualityandpartcost.Thelevelofexperienceofthemanufacturer(s)determineshoweffectivelytheprocessparametersarecontrolled.Thissometimesleadstoinconsistencyintroducedbyhumanerror.Thereisalsothecasewherethereisinexperience,shortageoftime,resourcesandlittlescopeforinnovation.Knowledge-basedengineeringprovidesafeasiblesolutiontoalltheseproblemsbycreatingwhatiscalledan“intelligentmodel”oftheproblem.1IKEMIntelligentKnowledgebasedEngineeringmodulesfortheplasticinjectionmoldingprocess(IKEM)isasoftwaretechnologythatisastepaheadoftheconcurrentengineeringandCAD/CAMsystems.Itintegratescurrentknowledgeaboutthedesignandmanufacturingprocessesandhelpstoreduceseveralman-hoursbyreducingengineeringchangesinthedesignphaseofproductdevelopmentbygivingusersinstructionaboutvariousdesignaspects.Thesystemwillbeusedforinjectionmoldingdesign,designiterations,andprocessintegration.Thecurrentprocessconsistsofmanymanualcomputations,CADgraphicalconstructions,andexperienceattainedfrompreviousprojects.Oncetheengineercompletesthedesign,itwillbeevaluatedforperformance.TheIKEMprojecthasbeendividedintothreemajormodules.1.Thecostestimationmodule2.Themolddesignmodule3.TheManufacturingmoduleInputtotheIKEMsystemisoftwoforms.InputintheformofaCADmodel(Pro-Efile)andinputgivenattheUserInterfaceform.Figure1illustratesthekindofinputthatgoesintoeachmoduleandtheoutputgiventotheuser.Figure1.OrganizationoftheIKEMProject2IntelligentMoldDesignToolThemolddesigntoolinitsbasicformisaVisualBasicapplicationtakinginputfromatextfilethatcontainsinformationaboutthepartandaUserInputform.ThetextfilecontainsinformationaboutthepartgeometryparsedfromaPro/Einformationfile.Theinputisusedtoestimatethedimensionsofmoldandvariousotherfeatures.2.1LiteratureReviewDesignofmoldsisanotherstageoftheinjectionmoldingprocesswheretheexperienceofanengineerlargelyhelpsautomatetheprocessandincreaseitsefficiency.Theissuethatneedsattentionisthetimethatgoesintodesigningthemolds.Often,designengineersrefertotablesandstandardhandbookswhiledesigningamold,whichconsumeslotoftime.Also,agreatdealoftimegoesintomodelingcomponentsofthemoldinstandardCADsoftware.Differenresearchershavedealtwiththeissueofreducingthetimeittakestodesignthemoldindifferentways.KoelschandJameshaveemployedgrouptechnologytechniquestoreducethemolddesigntime.Auniquecodingsystemthatgroupsaclassofinjectionmoldedparts,andthetoolingrequiredininjectionmoldingisdevelopedwhichisgeneralandcanbeappliedtootherproductlines.Asoftwaresystemtoimplementthecodingsystemhasalsobeendeveloped.Attemptswerealsodirectedtowardstheautomationofthemolddesignprocessbycapturingexperienceandknowledgeofengineersinthefield.Thedevelopmentofaconcurrentmolddesignsystemisonesuchapproachthatattemptstodevelopasystematicmethodologyforinjectionmolddesignprocessesinaconcurrentengineeringenvironment.Theobjectiveoftheirresearchwastodevelopamolddevelopmentprocessthatfacilitatesconcurrentengineering-basedpractice,andtodevelopaknowledge-baseddesignaidforinjectionmoldingmolddesignthataccommodatesmanufacturabilityconcerns,aswellasproductrequirements.Researchershavebeentryingtoautomatethemolddesignprocesseitherbycapturingonlythedeterministicinformationonthemolddesignprocessorthenon-deterministicinformation,invariousways.Thisresearchuniquelyattemptstodevelopamolddesignapplicationthatcapturesinformationinbothforms；deterministicandnon-deterministic.2.2ApproachAdoptedInordertodevelopanintelligentmolddesigntool,theconventionalmethodofdesigningmoldsisstudied.Theapplicationdeveloperandthedesignengineerworktogetherindesigningamoldforaparticularplasticpart.Duringthistime,theapproachadoptedbytheengineertoselectthemoldbaseiscloselyobservedandaspectsoftheselectionprocessthatrequirehisknowledge/experienceareidentified.Also,therewillbetimeswhentheengineerwillrefertotablesandhandbooksinordertostandardizehisselectionprocess.Thistimeconsumingprocessisalsorecordedtoincorporateitlaterintheapplication.Formulatingtheproblemfortheapplicationintermsofinputsandoutputsisthenextstage.Thisinvolvesdefiningwhatinformationaboutthemoldlayoutismostrequiredfortheuserandalsotheminimumnumberofinputsthatcanbetakenfromhimtogivethoseoutputs.Ininjectionmolding,thepolymermeltathightemperatureisinjectedintothemoldunderhighpressure1.Thus,themoldmaterialneedstohavethermalandmechanicalpropertiescapableofwithstandingthetemperaturesandpressuresofthemoldingcycle.Thefocusofmanystudieshasbeentocreatetheinjectionmolddirectlybyarapidprototyping(RP)process.Byeliminatingmultiplesteps,thismethodoftoolingholdsthebestpromiseofreducingthetimeandcostneededtocreatelow-volumequantitiesofpartsinaproductionmaterial.ThepotentialofintegratinginjectionmoldingwithRPtechnologieshasbeendemonstratedmanytimes.ThepropertiesofRPmoldsareverydifferentfromthoseoftraditionalmetalmolds.Thekeydifferencesarethepropertiesofthermalconductivityandelasticmodulus(rigidity).Forexample,thepolymersusedinRP-fabricatedstereolithography(SL)moldshaveathermalconductivitythatislessthanonethousandththatofanaluminumtool.InusingRPtechnologiestocreatemolds,theentiremolddesignandinjection-moldingprocessparametersneedtobemodiedandoptimizedfromtraditionalmethodologiesduetothecompletelydifferenttoolmaterial.However,thereisstillnotafundamentalunderstandingofhowthemodicationstothemoldtoolingmethodandmaterialimpactboththemolddesignandtheinjectionmoldingprocessparameters.Onecannotobtainreasonableresultsbysimplychangingafewmaterialpropertiesincurrentmodels.Also,usingtraditionalapproacheswhenmakingactualpartsmaybegeneratingsub-optimalresults.Sothereisadireneedtostudytheinteractionbetweentherapidtooling(RT)processandmaterialandinjectionmolding,soastoestablishthemolddesigncriteriaandtechniquesforanRT-orientedinjectionmoldingprocess.Inaddition,computersimulationisaneffectiveapproachforpredictingthequalityofmoldedparts.Commerciallyavailablesimulationpackagesofthetraditionalinjectionmoldingprocesshavenowbecomeroutinetoolsofthemolddesignerandprocessengineer2.Unfortunately,currentsimulationprogramsforconventionalinjectionmoldingarenolongerapplicabletoRPmolds,becauseofthedramaticallydissimilartoolmaterial.Forinstance,inusingtheexistingsimulationsoftwarewithaluminumandSLmoldsandcomparingwithexperimentalresults,thoughthesimulationvaluesofpartdistortionarereasonableforthealuminummold,resultsareunacceptable,withtheerrorexceeding50%.Thedistortionduringinjectionmoldingisduetoshrinkageandwarpageoftheplasticpart,aswellasthemold.Forordinarilymolds,themainfactoristheshrinkageandwarpageoftheplasticpart,whichismodeledaccuratelyincurrentsimulations.ButforRPmolds,thedistortionofthemoldhaspotentiallymoreinuence,whichhavebeenneglectedincurrentmodels.Forinstance,3usedasimplethree-stepsimulationprocesstoconsiderthemolddistortion,whichhadtoomuchdeviation.Inthispaper,basedontheaboveanalysis,anewsimulationsystemforRPmoldsisdeveloped.Theproposedsystemfocusesonpredictingpartdistortion,whichisdominatingdefectinRP-moldedparts.ThedevelopedsimulationcanbeappliedasanevaluationtoolforRPmolddesignandprocessoptimization.Oursimulationsystemisveriedbyanexperimentalexample.AlthoughmanymaterialsareavailableforuseinRPtechnologies,weconcentrateonusingstereolithography(SL),theoriginalRPtechnology,tocreatepolymermolds.TheSLprocessusesphotopolymerandlaserenergytobuildapartlayerbylayer.UsingSLtakesadvantageofboththecommercialdominanceofSLintheRPindustryandthesubsequentexpertisebasethathasbeendevelopedforcreatingaccurate,high-qualityparts.Untilrecently,SLwasprimarilyusedtocreatephysicalmodelsforvisualinspectionandform-tstudieswithverylimitedfunctionalapplications.However,thenewergenerationstereolithographicphotopolymershaveimproveddimensional,mechanicalandthermalpropertiesmakingitpossibletousethemforactualfunctionalmolds.Basedontheinformationgatheredinthemolddesignexercise,theconventionsfollowedbytheengineeraretransformedintoif-thenrules.Decisiontablesareusedtoaccountforallpossiblecasesthatarisewhendealingwithaparticularaspectofthemolddesignprocess.Therulessoframedarethenorganizedintomodulesinteractingwitheachother,usinganapplicationdevelopmentenvironment.Finallytheapplicationistestedforitsvaliditywhenitcomestodesigningmoldsforplasticpartsmanufacturedintheindustry.2.3SelectionofAppropriateMoldBaseTypi