外文翻译--立体光照成型的注塑模具工艺的综合模拟 英文版【优秀】.pdf -- 10 元

IntegratedsimulationoftheinjectionmoldingprocesswithstereolithographymoldsAbstractFunctionalpartsareneededfordesignverificationtesting,fieldtrials,customerevaluation,andproductionplanning.Byeliminatingmultiplesteps,thecreationoftheinjectionmolddirectlybyarapidprototypingRPprocessholdsthebestpromiseofreducingthetimeandcostneededtomoldlowvolumequantitiesofparts.ThepotentialofthisintegrationofinjectionmoldingwithRPhasbeendemonstratedmanytimes.WhatismissingisthefundamentalunderstandingofhowthemodificationstothemoldmaterialandRPmanufacturingprocessimpactboththemolddesignandtheinjectionmoldingprocess.Inaddition,numericalsimulationtechniqueshavenowbecomehelpfultoolsofmolddesignersandprocessengineersfortraditionalinjectionmolding.Butallcurrentsimulationpackagesforconventionalinjectionmoldingarenolongerapplicabletothisnewtypeofinjectionmolds,mainlybecausethepropertyofthemoldmaterialchangesgreatly.Inthispaper,anintegratedapproachtoaccomplishanumericalsimulationofinjectionmoldingintorapidprototypedmoldsisestablishedandacorrespondingsimulationsystemisdeveloped.Comparisonswithexperimentalresultsareemployedforverification,whichshowthatthepresentschemeiswellsuitedtohandleRPfabricatedstereolithographySLmolds.KeywordsKKKInjectionmoldingNumericalsimulationRapidprototyping1IntroductionIninjectionmolding,thepolymermeltathightemperatureisinjectedintothemoldunderhighpressure1.Thus,themoldmaterialneedstohavethermalandmechanicalpropertiescapableofwithstandingthetemperaturesandpressuresofthemoldingcycle.ThefocusofmanystudieshasbeentocreatetheinjectionmolddirectlybyarapidprototypingRPprocess.Byeliminatingmultiplesteps,thismethodoftoolingholdsthebestpromiseofreducingthetimeandcostneededtocreatelowvolumequantitiesofpartsinaproductionmaterial.ThepotentialofintegratinginjectionmoldingwithRPtechnologieshasbeendemonstratedmanytimes.ThepropertiesofRPmoldsareverydifferentfromthoseoftraditionalmetalmolds.Thekeydifferencesarethepropertiesofthermalconductivityandelasticmodulusrigidity.Forexample,thepolymersusedinRPfabricatedstereolithographySLmoldshaveathermalconductivitythatislessthanonethousandththatofanaluminumtool.InusingRPtechnologiestocreatemolds,theentiremolddesignandinjectionmoldingprocessparametersneedtobemodifiedandoptimizedfromtraditionalmethodologiesduetothecompletelydifferenttoolmaterial.However,thereisstillnotafundamentalunderstandingofhowthemodificationstothemoldtoolingmethodandmaterialimpactboththemolddesignandtheinjectionmoldingprocessparameters.Onecannotobtainreasonableresultsbysimplychangingafewmaterialpropertiesincurrentmodels.Also,usingtraditionalapproacheswhenmakingactualpartsmaybegeneratingsuboptimalresults.SothereisadireneedtostudytheinteractionbetweentherapidtoolingRTprocessandmaterialandinjectionmolding,soastoestablishthemolddesigncriteriaandtechniquesforanRTorientedinjectionmoldingprocess.Inaddition,computersimulationisaneffectiveapproachforpredictingthequalityofmoldedparts.Commerciallyavailablesimulationpackagesofthetraditionalinjectionmoldingprocesshavenowbecomeroutinetoolsofthemolddesignerandprocessengineer2.Unfortunately,currentsimulationprogramsforconventionalinjectionmoldingarenolongerapplicabletoRPmolds,becauseofthedramaticallydissimilartoolmaterial.Forinstance,inusingtheexistingsimulationsoftwarewithaluminumandSLmoldsandcomparingwithexperimentalresults,thoughthesimulationvaluesofpartdistortionarereasonableforthealuminummold,resultsareunacceptable,withtheerrorexceeding50.Thedistortionduringinjectionmoldingisduetoshrinkageandwarpageoftheplasticpart,aswellasthemold.Forordinarilymolds,themainfactoristheshrinkageandwarpageoftheplasticpart,whichismodeledaccuratelyincurrentsimulations.ButforRPmolds,thedistortionofthemoldhaspotentiallymoreinfluence,whichhavebeenneglectedincurrentmodels.Forinstance,3usedasimplethreestepsimulationprocesstoconsiderthemolddistortion,whichhadtoomuchdeviation.Inthispaper,basedontheaboveanalysis,anewsimulationsystemforRPmoldsisdeveloped.Theproposedsystemfocusesonpredictingpartdistortion,whichisdominatingdefectinRPmoldedparts.ThedevelopedsimulationcanbeappliedasanevaluationtoolforRPmolddesignandprocessoptimization.Oursimulationsystemisverifiedbyanexperimentalexample.AlthoughmanymaterialsareavailableforuseinRPtechnologies,weconcentrateonusingstereolithographySL,theoriginalRPtechnology,tocreatepolymermolds.TheSLprocessusesphotopolymerandlaserenergytobuildapartlayerbylayer.UsingSLtakesadvantageofboththecommercialdominanceofSLintheRPindustryandthesubsequentexpertisebasethathasbeendevelopedforcreatingaccurate,highqualityparts.Untilrecently,SLwasprimarilyusedtocreatephysicalmodelsforvisualinspectionandformfitstudieswithverylimitedfunctionalapplications.However,thenewergenerationstereolithographicphotopolymershaveimproveddimensional,mechanicalandthermalpropertiesmakingitpossibletousethemforactualfunctionalmolds.2Integratedsimulationofthemoldingprocess2.1MethodologyInordertosimulatetheuseofanSLmoldintheinjectionmoldingprocess,aniterativemethodisproposed.Differentsoftwaremoduleshavebeendevelopedandusedtoaccomplishthistask.ThemainassumptionisthattemperatureandloadboundaryconditionscausesignificantdistortionsintheSLmold.Thesimulationstepsareasfollows1Thepartgeometryismodeledasasolidmodel,whichistranslatedtoafilereadablebytheflowanalysispackage.2Simulatethemoldfillingprocessofthemeltintoaphotopolymermold,whichwilloutputtheresultingtemperatureandpressureprofiles.3Structuralanalysisisthenperformedonthephotopolymermoldmodelusingthethermalandloadboundaryconditionsobtainedfromthepreviousstep,whichcalculatesthedistortionthatthemoldundergoduringtheinjectionprocess.4Ifthedistortionofthemoldconverges,movetothenextstep.Otherwise,thedistortedmoldcavityisthenmodeledchangesinthedimensionsofthecavityafterdistortion,andreturnstothesecondsteptosimulatethemeltinjectionintothedistortedmold.5Theshrinkageandwarpagesimulationoftheinjectionmoldedpartisthenapplied,whichcalculatesthefinaldistortionsofthemoldedpart.Inabovesimulationflow,therearethreebasicsimulationmodules.2.2Fillingsimulationofthemelt2.2.1MathematicalmodelingInordertosimulatetheuseofanSLmoldintheinjectionmoldingprocess,aniterativemethodisproposed.Differentsoftwaremoduleshavebeendevelopedandusedtoaccomplishthistask.ThemainassumptionisthattemperatureandloadboundaryconditionscausesignificantdistortionsintheSLmold.Thesimulationstepsareasfollows1.Thepartgeometryismodeledasasolidmodel,whichistranslatedtoafilereadablebytheflowanalysispackage.2.Simulatethemoldfillingprocessofthemeltintoaphotopolymermold,whichwilloutputtheresultingtemperatureandpressureprofiles.3.Structuralanalysisisthenperformedonthephotopolymermoldmodelusingthethermalandloadboundaryconditionsobtainedfromthepreviousstep,whichcalculatesthedistortionthatthemoldundergoduringtheinjectionprocess.4.Ifthedistortionofthemoldconverges,movetothenextstep.Otherwise,thedistortedmoldcavityisthenmodeledchangesinthedimensionsofthecavityafterdistortion,andreturnstothesecondsteptosimulatethemeltinjectionintothedistortedmold.5.Theshrinkageandwarpagesimulationoftheinjectionmoldedpartisthenapplied,whichcalculatesthefinaldistortionsofthemoldedpart.Inabovesimulationflow,therearethreebasicsimulationmodules.2.2Fillingsimulationofthemelt2.2.1MathematicalmodelingComputersimulationtechniqueshavehadsuccessinpredictingfillingbehaviorinextremelycomplicatedgeometries.However,mostofthecurrentnumericalimplementationisbasedonahybridfiniteelement/finitedifferencesolutionwiththemiddleplanemodel.TheapplicationprocessofsimulationpackagesbasedonthismodelisillustratedinFig.21.However,unlikethesurface/solidmodelinmolddesignCADsystems,thesocalledmiddleplaneasshowninFig.21bisanimaginaryarbitraryplanargeometryatthemiddleofthecavityinthegapwisedirection,whichshouldbringaboutgreatinconvenienceinapplications.Forexample,surfacemodelsarecommonlyusedincurrentRPsystemsgenerallySTLfileformat,sosecondarymodelingisunavoidablewhenusingsimulationpackagesbecausethemodelsintheRPandsimulationsystemsaredifferent.Consideringthesedefects,the