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外文翻译--注塑成型的智能模具设计工具.doc

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外文翻译--注塑成型的智能模具设计工具.doc

英文原文SessionVA4IntelligentMoldDesignToolForPlasticInjectionMoldingJagannathYammada,TerrenceL.Chambers,SurenN.DwivediDepartmentofMechanicalEngineeringUniversityofLouisianaatLafayetteAbstractPlasticInjectionmoldingisoneofthemostpopularmanufacturingprocessesformakingthermoplasticproducts,andmolddesignisakeyaspectoftheprocess.Designofmoldsrequiresknowledge,expertiseandmostimportantlyexperienceinthefield.Whenoneoftheseislacking,selectionofanappropriatemoldformanufacturingaplasticcomponentisdoneonatrialanderrorbasis.Thisincreasesthecostofproductionandintroducesinconsistenciesinthedesign.Thispaperdescribesthedevelopmentofanintelligentmolddesigntool.Thetoolcapturesknowledgeaboutthemolddesignprocessandrepresentstheknowledgeinlogicalfashion.Theknowledgeacquiredwillbedeterministicandnondeterministicinformationaboutthemolddesignprocess.Oncedevelopedthemolddesigntoolwillguidetheuserinselectinganappropriatemoldforhisplasticpartbasedonvariousclientspecifications.IntroductionTheplasticinjectionmoldingprocessdemandsknowledge,expertiseand,mostimportant,experienceforitssuccessfulimplementation.Oftenitisthemoldingparametersthatcontroltheefficiencyoftheprocess.Effectivelycontrollingandoptimizingtheseparametersduringthemanufacturingprocesscanachieveconsistency,whichtakestheformofpartqualityandpartcost.Thelevelofexperienceofthemanufacturersdetermineshoweffectivelytheprocessparametersarecontrolled.Thissometimesleadstoinconsistencyintroducedbyhumanerror.Thereisalsothecasewherethereisinexperience,shortageoftime,resourcesandlittlescopeforinnovation.Knowledgebasedengineeringprovidesafeasiblesolutiontoalltheseproblemsbycreatingwhatiscalledanintelligentmodeloftheproblem.1IKEMIntelligentKnowledgebasedEngineeringmodulesfortheplasticinjectionmoldingprocessIKEMisasoftwaretechnologythatisastepaheadoftheconcurrentengineeringandCAD/CAMsystems.Itintegratescurrentknowledgeaboutthedesignandmanufacturingprocessesandhelpstoreduceseveralmanhoursbyreducingengineeringchangesinthedesignphaseofproductdevelopmentbygivingusersinstructionaboutvariousdesignaspects.Thesystemwillbeusedforinjectionmoldingdesign,designiterations,andprocessintegration.Thecurrentprocessconsistsofmanymanualcomputations,CADgraphicalconstructions,andexperienceattainedfrompreviousprojects.Oncetheengineercompletesthedesign,itwillbeevaluatedforperformance.TheIKEMprojecthasbeendividedintothreemajormodules.1.Thecostestimationmodule2.Themolddesignmodule3.TheManufacturingmoduleInputtotheIKEMsystemisoftwoforms.InputintheformofaCADmodelProEfileandinputgivenattheUserInterfaceform.Figure1illustratesthekindofinputthatgoesintoeachmoduleandtheoutputgiventotheuser.Figure1.OrganizationoftheIKEMProject2IntelligentMoldDesignToolThemolddesigntoolinitsbasicformisaVisualBasicapplicationtakinginputfromatextfilethatcontainsinformationaboutthepartandaUserInputform.ThetextfilecontainsinformationaboutthepartgeometryparsedfromaPro/Einformationfile.Theinputisusedtoestimatethedimensionsofmoldandvariousotherfeatures.2.1LiteratureReviewDesignofmoldsisanotherstageoftheinjectionmoldingprocesswheretheexperienceofanengineerlargelyhelpsautomatetheprocessandincreaseitsefficiency.Theissuethatneedsattentionisthetimethatgoesintodesigningthemolds.Often,designengineersrefertotablesandstandardhandbookswhiledesigningamold,whichconsumeslotoftime.Also,agreatdealoftimegoesintomodelingcomponentsofthemoldinstandardCADsoftware.Differenresearchershavedealtwiththeissueofreducingthetimeittakestodesignthemoldindifferentways.KoelschandJameshaveemployedgrouptechnologytechniquestoreducethemolddesigntime.Auniquecodingsystemthatgroupsaclassofinjectionmoldedparts,andthetoolingrequiredininjectionmoldingisdevelopedwhichisgeneralandcanbeappliedtootherproductlines.Asoftwaresystemtoimplementthecodingsystemhasalsobeendeveloped.Attemptswerealsodirectedtowardstheautomationofthemolddesignprocessbycapturingexperienceandknowledgeofengineersinthefield.Thedevelopmentofaconcurrentmolddesignsystemisonesuchapproachthatattemptstodevelopasystematicmethodologyforinjectionmolddesignprocessesinaconcurrentengineeringenvironment.Theobjectiveoftheirresearchwastodevelopamolddevelopmentprocessthatfacilitatesconcurrentengineeringbasedpractice,andtodevelopaknowledgebaseddesignaidforinjectionmoldingmolddesignthataccommodatesmanufacturabilityconcerns,aswellasproductrequirements.Researchershavebeentryingtoautomatethemolddesignprocesseitherbycapturingonlythedeterministicinformationonthemolddesignprocessorthenondeterministicinformation,invariousways.Thisresearchuniquelyattemptstodevelopamolddesignapplicationthatcapturesinformationinbothformsdeterministicandnondeterministic.2.2ApproachAdoptedInordertodevelopanintelligentmolddesigntool,theconventionalmethodofdesigningmoldsisstudied.Theapplicationdeveloperandthedesignengineerworktogetherindesigningamoldforaparticularplasticpart.Duringthistime,theapproachadoptedbytheengineertoselectthemoldbaseiscloselyobservedandaspectsoftheselectionprocessthatrequirehisknowledge/experienceareidentified.Also,therewillbetimeswhentheengineerwillrefertotablesandhandbooksinordertostandardizehisselectionprocess.Thistimeconsumingprocessisalsorecordedtoincorporateitlaterintheapplication.Formulatingtheproblemfortheapplicationintermsofinputsandoutputsisthenextstage.Thisinvolvesdefiningwhatinformationaboutthemoldlayoutismostrequiredfortheuserandalsotheminimumnumberofinputsthatcanbetakenfromhimtogivethoseoutputs.Ininjectionmolding,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.Basedontheinformationgatheredinthemolddesignexercise,theconventionsfollowedbytheengineeraretransformedintoifthenrules.Decisiontablesareusedtoaccountforallpossiblecasesthatarisewhendealingwithaparticularaspectofthemolddesignprocess.Therulessoframedarethenorganizedintomodulesinteractingwitheachother,usinganapplicationdevelopmentenvironment.Finallytheapplicationistestedforitsvaliditywhenitcomestodesigningmoldsforplasticpartsmanufacturedintheindustry.2.3SelectionofAppropriateMoldBaseTypically,selectionofappropriatemoldbaseformanufacturingaplasticpartinvolvesEstimatingthenumberofcavitiesThenumberofcavitiesisdecideddependingonthenumberofpartsrequiredwithinagiventime.Therearealsootherissuesliketheplasticizingcapacityofthemachine,rejectrateetcthataffectthenumberofcavitiestobepresentinthemoldbase.DecidingonthepresenceofinsertsandtheirdimensionsInsertsfacilitatethereusabilityofthemoldbaseandthereforehelpinreducingcostofmanufacturing.Whenitcomestoselectingthedimensionsandthenumber,adecisionismadedependingonthereusabilityofexistingoldinsertsandcostoforderingnewones.DeterminingthesizeandlocationofrunnersTherunnersizedependsonthematerialbeingmolded.Althoughthereareotherconsiderationsmaterialpropertiesdeterminesthechannelsizerequiredforitsflow.Locationofrunnersmainlydependsonthetopologyofrunnersbeingused.Thoughacircularrunnersystemisalwayspreferable,thebranchedrunnersystemthatavoidsrunnerbalancingistheonemostwidelyused.DeterminingthediameterofsprueThediameterofthesprueisdecidedbasedonthesizeofthemold,numberofcavities,orthe

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