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InternationalJournalofCAD/CAMVol.2,No.1,pp.6975(2002)AnIntelligentCavityLayoutDesignSystemforInjectionMouldsWeigangHuandSyedMasood*IndustrialResearchInstituteSwinburne(IRIS),SwinburneUniversityofTechnology,Hawthorn,Melbourne,Australia3122AbstractThispaperpresentsthedevelopmentofanIntelligentCavityLayoutDesignSystem(ICLDS)formultiplecavityinjectionmoulds.Thesystemisintendedtoassistmoulddesignersincavitylayoutdesignatconceptdesignstage.Thecomplexitiesandprinciplesofcavitylayoutdesignaswellasvariousdependenciesininjectionmoulddesignareintroduced.Theknowledgeincavitylayoutdesignissummarizedandclassified.Thefunctionality,theoverallstructureandgeneralprocessofICLDSareexplained.Thepaperalsodiscussessuchissuesasknowledgerepresentationandcase-basedreasoningusedinthedevelopmentofthesystem.Thefunctionalityofthesystemisillustratedwithanexampleofcavitylayoutdesignproblem.Keywords:Intelligentdesign,cavitylayoutdesign,injectionmoulddesign,case-basedreasoning,designsupportsystem1.IntroductionInmanufacturing,theinjectionmouldingisoneofthemostwidelyusedproductionprocessesforproducingplasticpartswithhighproductionrateandlittleornofinishingrequiredonplasticproducts.Theprocessconsistsofinjectingmoltenplasticmaterialfromahotchamberintoaclosedmould,allowingtheplastictocoolandsolidifyandejectingthefinishedproductfromthemould.Foreachnewplasticproduct,theinjectionmouldingmachinerequiresanewinjectionmould.Designandmanufactureofinjectionmouldisatimeconsumingandexpensiveprocessandtraditionallyrequireshighlyskilledtoolandmouldmakers.Aninjectionmouldconsistsofseveralcomponents,whichincludemouldbase,cavities,guidepins,asprue,runners,gates,coolingwaterchannels,supportplates,slidesandejectormechanism1.Designofmouldisalsoaffectedbyseveralotherfactorssuchaspartgeometry,mouldmaterial,partinglineandnumberofcavitiespermould.Withtheadvancesincomputertechnologyandartificialintelligence,effortshavebeendirectedtoreducethecostandleadtimeinthedesignandmanufactureofaninjectionmould.Injectionmoulddesignhasbeenthemainareaofresearchsinceitisacomplexprocessinvolvingseveralsub-designsrelatedtovariouscom-ponentsofthemould,eachrequiringexpertknowledgeandexperience.Moulddesignalsoaffectstheproductivity,mouldmaintenancecost,manufacturabilityofmould,andthequalityofthemouldedpart.Mostoftheworkexpertsystems,knowledgebasedsystemsandartificialintelligencetoeliminateorsupplementthevastamountofhumanexpertiserequiredintraditionaldesignprocess.KruthandWillems2developedanintelligentsupportsystemforthedesignofinjectionmouldsintegratingcommercialCAD/CAM,arelationaldatabaseandanexpertsystem.Leeet.al.3proposedasystematicmethodologyandknowledgebaseforinjectionmoulddesigninaconcurrentengineeringenvironment.Ra-viwongseandAllada4developedaneuralnetwork-baseddesignsupporttooltocomputethemouldcomplexityindextohelpmoulddesignerstoassesstheirproposedmoulddesignonmouldmanufacturability.KwongandSmith5developedacomputationalsystemfortheprocessdesignofinjectionmouldingbasedontheblackboard-basedexpertsystemandthecase-basedreasoningapproach,whichincludesmoulddesign,productionscheduling,costestimationanddeterminationofinjectionmouldingparameters.Brittonet.al.6discussedtheinjectionmoulddesignfromafunctionalperspectiveusingfunctionaldesignknowledgeandanumberofknowledgelibraries.Moket.al.7developedaninteractiveknowledge-basedCADsystemforinjectionmoulddesignincorporatingcomputational,knowledgeandgraphicmodules.Severalstudieshavealsobeenmadeonimprovingthedesignofspecificcomponentsofaninjectionmould.Onget.al.8developedaknowledge-basedandobject-orientedapproachforthedesignofthefeedsystemforinjectionmoulds,whichcanefficientlydesignthetype,inmoulddesignhasbeendirectedtotheapplicationoflocationandsizeofagatingsysteminthemould.Iraniet.al.9alsodevelopedasoftwaresystemforautomaticdesignofgatingandrunnersystemsforinjectionmouldsandprovideevaluationofgatingdesignbasedonspecifiedperformanceparameters.Neeet.al.10proposedamethodologyfordeterminationofoptimal*Correspondingauthor:Tel:+61-3-9214-8260Fax:+61-3-9214-5050E-mail:S.auG01G02InternationalJournalofCAD/CAMVol.2,No.1,pp.6975partingdirectionsininjectionmoulddesignbasedonautomaticrecognitionandextractionofundercutfeatures.ChenandChou11developedalgorithmsforselectingapartinglineinmoulddesignbycomputingtheundercutvolumesandminimisingthenumberofundercuts.ParkandKwon12workedonthedesignofcoolingsystemsininjectionmouldsandproposedanoptimaldesignbasedonthermalanalysisanddesignsensitivityanalysisofthecoolingstageoftheinjectionmouldingprocess.Lin13workedontheuseofgatesizeandgatepositionasthemajorparametersforsimulatedinjectionmouldperformanceprediction.Oneareaininjectionmoulddesign,whichhasreceivedlittleattention,isthedesignofcavitylayoutinamultiplecavityinjectionmould.Cavitylayoutdesignaffectsthewholeprocessofinjectionmouldingdirectly,sinceitisoneofthemostimportantphasesinmoulddesignprocess.Considerationofcavitylayoutdesignininjectionmouldatconceptdesignstagewillimprovethequalityofinjectionmouldedproductsbecauseitisassociatedwiththedeterminationofmanykeyfactorsaffectingthedesignandqualityofmould.Suchfactorsincludenumberofcavities；partingline；typeofmould；typeandpositionofgate；runnersystem；coolingsystemandejectionsystem.Someofthesefactorsaredifficulttobuildastruemathematicalmodelsforanalysisanddesign.Thispaperpresentsthedevelopmentofadesignsupportsystem,calledIntelligentCavityLayoutDesignSystem(ICLDS),formultiple-cavityinjectionmouldsbasedonknowledgebasedandobjectorientedapproaches.Itusesthecase-basedandruled-basedreasoninginarrivingatthelayoutsolution14.Itisbasedonthecommercialsoftwaresystemnamed“RETE+”,whichisanintegrateddevelopmentplatformforcustomerstodeveloptheirownknowledge-basedsystems15.Theobjectiveistomakefulluseofavailabletechniquesinartificialintelligenceinassistingmoulddesignersatconceptdesignstage.2.CavityLayoutDesigninInjectionMouldsCurrentpracticeforinjectionmoulddesign,especiallycavitylayoutdesign,dependslargelyondesignersex-periencesandknowledge.Itwouldthereforebedesirabletouseknowledgeengineering,artificialintelligenceandintelligentdesigntechniquesingeneratinganacceptablecavitylayoutdesignininjectionmouldaccuratelyandefficiently.Inmoulddesign,mostofpatternsofcavitylayoutandrulesandprinciplesofcavitylayoutdesigncanalsobeeasilyrepresentedintheformofknowledge,whichcanbeusedinmostofknowledge-baseddesignsystems.Forexample,forthelayoutpatternsshowninFig.1,thecriteriatoselectthesuitablelayoutpatternfordesignaremainlydependentonworkingenvironments,conditionsandrequirementsofcustomerandaremainlybasedondesignersskillandexperience.Tomakeachoiceofcontradictoryfactorswillrelyobviouslyondesignersknowledgeandexperiences.Itisrathersuitableforintelligentdesigntechniquestobeusedinsystemsdesignedforsuchsituations,especiallyforroutineorinnovationdesign.Designofinjectionmouldmainlyinvolvesconsiderationofdesignofthefollowingelementsorsub-systems:(1)mouldtype(2)numberofcavitiesFig.1.Somepatternsofcavitylayoutwithmultiplecavities.WeigangHuandSyedMasoodAnIntelligentCavityLayoutDesignSystemforInjectionMouldsG01G03(3)cavitylayout(4)runnersystem(5)ejectorsystem(6)coolingsystem(7)venting(8)mountingmechanismMostoftheelementsareinter-dependentsuchthatitisvirtuallyimpossibletoproduceameaningfulflowchartcoveringthewholemoulddesignprocess.SomeofthedesignactivitiesformacomplicateddesignnetworkasshowninFig.2.Obviously,ininjectionmoulddesign,itisdifficultfordesignertomonitoralldesignparameters.Cavitydesignandlayoutdirectlyaffectsmostofotheractivities.TheapplicationofadvancedknowledgebasedtechniquestoassistdesignerincavitylayoutdesignatconceptdesignstagewillgreatlyassistinthedevelopmentofaItisnotedfromFig.1thatanumberofdifferentlayoutpatternsarepossiblewithmultiplecavitiesinsideamould.Higherthenumberofcavitiesofmould,highertheproductivityoftheinjectionmould.Butthismayleadtodifficultieswithissuessuchasbalancingtherunnersorproductswiththecomplicatedcavityshapes,whichinturnmayleadtoproblemsofmouldmanufacturability.Itisalsopossiblethatthenumberofcavitiesandthepatternofcavitylayoutwillinfluencethedeterminationofpartingline,typeofgate,positionofgate,runnersystemandcoolingsystem.Mostofthemainactivitiesofmoulddesignarethereforelinkedtocavitylayoutdesign.Fig.3showstherelationsbetweencavitylayoutdesignandotherdesignactivities.Thecavitylayoutdesignproblemthereforedependsuponanumberoffunctionalitiesoftheoverallmoulddesignsystem,whichincludes: