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IntJAdvManufTechnol200117453–4612001SpringerVerlagLondonLimitedThreeDimensionalKernelDevelopmentforInjectionMouldDesignT.L.NeoandK.S.LeeDepartmentofMechanicalandProductionEngineering,NationalUniversityofSingapore,SingaporeToday,manysoftwarepluginshavebeendevelopedonhighlevel3DmodellingplatformstofacilitateprocessessuchasFEManalysis,CAM,injectionmoulddesign,simulationandvisualisation.Suchanarrangementisadvantageousinmanyways.However,itisnotwithoutshortcomings.Ideally,thesepluginscouldalsobedevelopedusinglowlevel3Dkernelsforhigherflexibilityandbetterportability.Thispaperexaminesthevariousissuesandmethodologiesrelatedtothedevelopmentofsuch3Dbasedapplications.Theemphasisisplacedonthesoftwareaspect.First,amethodologyforthedevelopmentof3Dbasedapplicationsisproposed.Theideaisthenimplementedbydevelopinganinjectionmoulddesignapplicationusingalowlevel3DkernelcalledParasolid.Basedondesignconceptsusedinanestablishedmoulddesignapplication,IMOLD,thedevelopmentofamouldbasedesignmoduleisillustrated.AnobjectorientedprogramminglanguagehasbeenchosenforthedevelopmentofthesoftwareonaWindowsNTplatform.Keywords3DkernelComputeraideddesignCADInjectionmoulddesignParasolid1.IntroductionThreedimensionalCADsystemshaveincreasinglybeenusedtospeeduptheproductrealisationprocess.Oneofthefirststepsinvolvedintheautomationoftheproductdesignprocessisthecreationofthecomponentpartsina3Dmodellingapplication.The3Dmodel,uponcreation,iscalledthedigitalmastercopy.This3Ddigitalmodelformsthekeytoawidespectrumofprocessautomation.Creatingthe3Ddigitalmodelofcomponentpartsisonlytheveryfirststep.Thereareseveralothersecondarytasksthatmusttobedonebeforethepartcanbemanufactured.Suchtasksincludefiniteelementanalysis,jigsandfixturesdesign,injectionmoulddesign,computeraidedmanufacturing,simulCorrespondenceandofprintrequeststoK.S.Lee,DepartmentofMechanicalandProductionEngineering,NationalUniversityofSingapore,119260Singapore.EmailmpeleeksKnus.edu.sgation,andvisualisation.Today,manyapplicationPluginshavebeendevelopedonhighlevel3Dmodellingplatformstofacilitatethesesecondarytasks.The3Dmodellingplatformprovidesthepluginsoftwarewithalibraryoffunctionsaswellasanestablisheduserinterfaceandstyleofprogramming.Asaresult,thedevelopmenttimesforthesepluginsaresignificantlyreduced.Suchanarrangementisadvantageousinmanyways.However,ithasitsshortcomings,especiallyinthelongrun.Inordertodevelopapluginforestablishedsoftware,thedevelopersmustadheretothemanyconstraintsimposed.Thereisaneedtobeconsistentwiththestyleoftheparentsoftware.Thedevelopersmustbeabletoachieveanyfunctionalitytheyneedwithonlythesetoflibraryfunctionsprovided.Mostendusersneedboththeparentsoftwareandtheplugin.Inmanycases,however,theymaybemoreinterestedinusingonlythepluginsoftware.Anexampleofsuchasituationisininjectionmoulddesign.Theseusers,however,mustpurchasetheentiresoftwarepackagewhichincludesmanyfeaturesandfunctionsthattheydonotneed.Suchalargeprogramisoftenverydemandingonthehardware,whichalsomeanshighercost.Thepluginsoftwareisalsoverydependentondevelopmentsintheparentsoftware.Wheneveranewversionisupdatedfortheparentsoftware,theplugindevelopershavetofollowuponthechanges.Theseshortcomingsmaynotexistiftheseapplicationsweredevelopedonalowlevelplatform.Ideally,thesepluginscouldbedevelopedusinglowlevel3Dkernelsforhigherflexibilityandbetterportability.Inmanyinstances,suchamoveisbothfeasibleandadvantageous.Traditionally,injectionmoulddesigniscarriedoutdirectlyonaCADsystem.Theentireinjectionmould,consistingofperhapshundredsofcomponents,ismodelledandassembledonCADsystemssuchasAutoCAD,Pro/Engineer,andUnigraphics.Astheinjectionmoulddesignprocessisrecursive,itisverytimeconsumingtoremodelandreassemblethedesign.Inthisaspect,3DCADsystemssuchasPro/EngineerandUnigraphics,whicharefeaturebased,haveasignificantadvantageover2DCADsystemssuchasAutoCAD.Tofurtherspeeduptheinjectionmoulddesignprocess,pluginsweredevelopedonthese3Dsystemstoautomatecertainstagesofthedesignprocess.ExamplesofsuchaddonapplicationsincludeIMOLDIntelligentMoldDesignandAssemblySystem,developedattheNationalUniversityofSingapore,basedonUnigraphics,ExpertMoldDesignerbasedonCADKEYandMoldmakerbasedonEUCLID.AseachisbasedonaspecificCADsystem,thereisnoplugcompatibility.In1994,MokandCheung1presentedworkonthedevelopmentofaninjectionmoulddesignapplicationbasedonUnigraphics.In1997,Shah2proposeda3tierarchitectureforstandardisingcommunicationsbetweengeometricmodellingkernelsandapplicationsthatrequiregeometricmodellingservices.Hisobjectiveistoachieveplugcompatibilitybetween3DapplicationsthatarebasedonParasolid3a3Dkernel,developedattheUniversityofCambridgeandACIS.This,however,involvedanextensivelydeveloped3tiermodellinghusk.Inthispaper,theauthorattemptstodevelopalightweightinjectionmoulddesignapplicationusingalowlevel3Dkerneldirectly.Thefocusisontheflexibilityandspeedofthesoftwaredevelopment.DesignconceptsandproceduresweretakenfromIMOLD4,5,acompletemoulddesignandassembly3Dapplication.Althoughthediscussionislimitedtoinjectionmoulddesignonly,themethodologyappliedcaneasilybeappliedinother3Dbasedapplicationsthatareofasimilarnature.Acombinationofdevelopertoolswaschosenforthispurpose.Beforethemethodologyisdiscussed,briefintroductionstosomeofthesetoolsarefirstpresented.Theyare,IMOLD,Parasolidversion10.1,VisualCversion6.0,andtheMicrosoftFoundationClasses.2.IMOLDasaMouldDesignApplicationIMOLDIntelligentMoldDesignandAssemblyisanestablished3Dbasedapplicationthatisdedicatedtoinjectionmoulddesign.ItisdevelopedontopofanadvancedCADsystemcalledUnigraphics.ThedevelopmentiscarriedoutusingtheapplicationsprogramminginterfaceAPIprovided.Thesoftwareenablesmoulddesignerstocreateadesignrapidlybyprovidingthetoolsthatarecommonlyneeded.Standardcomponentsparts,thatareoftenrequiredinthedesign,havebeenprecreatedinthesoftwareandcanbereadilyusedbythedesigner.Thisreducesthedesigntimesignificantly.Themoulddesignprocessisdividedintoseveralstages,providingthedesignerwithaconsistentmethodofcreatingthemoulddesign.Theyare,namely1.Datapreparation.2.Fillingsystemdesign.3.Mouldbasedesign.4.Insertsandpartingdesign.5.Coolingsystemdesign.6.Sliderandlifterdesign.7.Ejectionsystemdesign.8.Standardpartslibrary.Eachstagecanbeconsideredasanindependentmoduleoftheprogram.The3Dbasedrequirementsforeachmodulevaryonlyslightly.Thesuccessindevelopingthemouldbasemoduleimpliesfeasibilityindevelopingalltheothermodules.3.Parasolidasa3DKernelParasolidisdesignedtobethecentreorkernelofanysystemthatisbasedon3Dmodeldata.Itisessentiallyasolidmodeller,whichcanbeusedto1.Buildandmanipulatesolidobjects.2.Calculatemassandmomentsofinertia,andperformclashdetection.3.Outputtheobjectsinvariousways,includingpictorially.4.Storetheobjectsinsomesortofdatabaseorarchive,andretrievethemlater.Parasolidisoneofthemostadvanced3DkernelsamongCADapplications.Itisthe3DkernelofUnigraphicsandSolidWorks.Itsuniquetolerantmodellingfunctionalityenablesittoacceptdatastoredinothermodellerformats.Parasolidmodelfilesarethusverypotable.Itis,therefore,asuperiorplatformforthedevelopmentofstandaloneapplications.The3DbasedapplicationinteractswithParasolidthroughoneofitsthreeinterfacesseeFig.1.ThesearecalledtheParasolidkernelPKinterface,thekernelinterfaceKIandthedownwardinterface.ThePKinterfaceandthekernelinterfacesitontopofthemodellersidebyside,andarethemeansbywhichtheapplicationmodelsandmanipulatestheobjects,aswellascontrolsthefunctioningofthemodeller.Thedownwardinterfaceliesbeneaththemodeller,andiscalledbythemodellerwhenitneedstoperformdataintensiveorsystemtypeoperations.ItconsistsofthreepartsfrustrumgraphicaloutputGOandforeigngeometry.Thesearebrieflyexplainedbelow.3.1TheKIandPKInterfaceTheKIandthePKareinterfacesfortheprogrammertoaccessthemodellingcapabilitiesintheParasolidkernel.Theyarestandardlibrariesofmodellingfunctions.Theprogrammercallsthesemodellingfunctionsintheirprograms.AstheKIistobephasedoutsoon,wechosetousethePKinterface.Fig.1.Parasolidcomponents.454T.L.NeoandK.S.Lee3DKernelDevelopmentforInjectionMouldDesign4553.2TheFrustrumThefrustrumisasetoffunctions,whichmustbewrittenbytheapplicationsprogrammer.Thekernelcallsthemwhendatamustbesavedorretrieved.WhenusingParasolid,theapplicationsprogrammermustfirstdecidehowtomanagethestorageofdata,whichParasolidoutputsthroughthefrustrum.Transferringdatathroughthefrustrumusuallyinvolveswritingto,orreadingfrom,files.Theformatandlocationofthefilesisdeterminedwhenwritingthefrustrumfunctions.3.3TheGraphicalOutputGOThegraphicaloutputisanothersetoffunctions,whichistobewrittenbytheapplicationsprogrammer.WhenacallismadetothePKrenderingfunctions,thegraphicaldatageneratedareoutputthroughtheGOinterface.Thegraphicaldataarethenpassedtoa3Drenderingpackage.OpenGL,asoftwareinterfacetographiccards,isarenderingpackagethatisusedforourpurpose.3.4TheForeignGeometryTheforeigngeometryprovidesfunctionalityforthedevelopmentofcustomisedgeometricaltypessuchasinhousecurvesandsurfaces.TheseareusedtogetherwiththestandardgeometricaltypesformodellingwithinParasolid.4.ObjectOrientedProgrammingUsingVisualCandtheMicrosoftFoundationClassesObjectorientedprogrammingOOPhasbeentheundisputedoptionforsoftwaredevelopers.Itisamongthemostadvanceddevelopmentaltoolsavailable.TheMicrosoftVisualStudioissuchasoftwarepackage.ItfeaturesseveraldevelopmentaltoolsthataremeantforInternetbasedandWindowsbasedprogramming.AmongthesetoolsaretheVisualCVCandtheMicrosoftFoundationClassesMFC.TheVCisapowerfuldevelopmenttoolforobjectorientedprogramming,whereastheMFCisaframeworkofCclassesthatarededicatedtoWindowsbasedprogramming.Together,theseprovidedtheapplicationsprogrammerwithpowerfuldevelopmentfeaturesandfunctionalitiessuchasautocodegeneration,andwizardbasedoperations.Thesegreatlyimprovedproductivity.TheentireuserinterfaceforourprogramisdevelopedusingtheVCandtheMFC.5.SystemDesignThedirectdevelopmentofa3Dbasedaddonapplicationusinga3Dkernelrequiresseveralissuestobeaddressed.Theyconsistof3mainstagesatthehighestlevel.First,theidentificationofthecrucialfeaturesandfunctionsrequiredforthepluginapplication.Secondly,thedevelopmentofthedesignfortheapplicationframework.Lastly,thedesignanddevelopmentoftheindividualmodulesintheframeworkwithappropriatedevelopmentaltools.5.1IdentificationofEssentialModulesParasolid,asa3Dkernel,providesonlyanumberoflibrariesandaconceptualframeworkfor3Dapplicationdevelopment.Itisthusnecessaryforthedeveloperstoidentifyanddeveloptheotheressentialfacilitiesthatareprovidedina3DCADsystem.Inordertoidentifytherequiredfacilities,itisimportanttounderstandthediscrepanciesbetweenthetwo.Table1summarisesthemaindifferencesinthefacilitiesprovidedbya3Dkernelanda3DCADsystem.Someofthesefacilities,suchasfeaturesandparametricmodelling,arebothtimeconsumingandtechnicallydemandingtodevelop.Asmostpluginsdonotuseallthefacilitiesoftheparentsoftware,itispossibletodeveloponlythoserequiredbythepluginsusinglowlevel3Dkernels,producingastandaloneversion.Items7to9inTable1areprerequisitesforthedevelopmentof3DbasedapplicationsusingParasolid.Bystudyingtherequirementsofthepluginapplication,otheressentialfacilitiescanbeidentified.Aframeworkfortheapplicationisthenproposed,basedonthefacilitiesprovidedbytheParasolidkernel.5.2Frameworkfor3DBasedApplicationsAframeworkisdevelopedwithreferencetothefacilitiesprovidedbythedevelopmentaltoolsandtherequirementsoftheapplication.Itisdesignedsothatthereareminimumdependenciesbetweenindividualcodemodules.Thismayresultinasmalldegreeofcodeduplication.Inexchange,thereisbetterportabilityoftheprogramcodes,greatereaseofmaintenanceandabetterprospectforfutureexpansion.TheoverviewofthisframeworkisillustratedinFig.2.Thedetailsofthevariousmodulesarediscussedinthefollowingsections.5.2.1WindowsBasedUserInterfaceAParasoliddoesnotprovidetheprogrammerwithauserinterface.Thus,thedevelopmentofthe3Dbasedapplicationateverysinglestagewillinvolvedesigningtheuserinterfacefromscratch.Thenecessarydevelopmentsinvolve1.Environmentalsettinganddisplayofthe3Dbasedapplication.2.Interactivegraphicalinterfaceandexecutionprocedureforallapplicationfunctionality.5.2.23DDeveloperLayerBSincedifferent3Dbasedapplicationsrequire3Dfacilitiestodifferentextent,theframeworkmustprovideforthesevariations.A3DdeveloperlayerSeeFig.2,ItemBisconceptualisedtohandlesuchvariations.Itisalibraryofobjectsorclassesthataredeveloped,basedontheParasolidkernel.TheextentofdevelopmentdependsontherequirementsoftheTable1.Summaryoffacilitiesprovidedbya3DkernelandaCADsystem.Facilities3Dkernel3DCADsystem1.Basic3DmodellingLowlevelandgeneralfunctionsprovidedHighlevelandspecificfunctionsprovided2.AssembliesSeverallibraryfunctionsprovidedCompletesystemprovided3.FeaturebasedmodellingNotprovidedEstablishedfeaturesetprovided4.ParametricmodellingNotprovidedOftenprovided5.FreeformmodellingLowlevelfunctionsprovidedOftenprovided6.DraftingNotprovidedCompletesystemprovided7.InteractiveuserinterfaceNotprovidedAlwaysprovided8.Visualisationof3DobjectsConceptualframeworkandseverallibraryCompletelydevelopedfunctionsprovided9.FilemanagementsystemConceptualframeworkandseverallibraryCompletelydevelopedfunctionsprovidedFig.2.Overviewof3Dbasedapplication.applicationidentifiedintheprevioussection.Besidescateringforvariationsinapplicationrequirements,the3DdeveloperlayeralsoactsasaprogramminginterfacefornonParasoliddevelopers.Suchaninterfacecanalsobereusedforsubsequentdevelopmentofother3Dbasedapplications.The3Ddeveloperlayeressentiallyconsistsofthreemainsections.Theyareusedfor3Dmodellingandassembly,3Dvisualisationand3Ddatamanagement,respectively.I.3DModelingandAssembly.The3Dmodellingandassemblymoduleisthemostimportantandelaborateofallthreesections.ItisanalogoustotheapplicationprogramminginterfaceAPIprovidedbymostCADsystems.Themoduleconsistsofalibraryof3Dbasedobjectsorclasses,whichareusedforthedevelopmentofthecoreapplicationmodules.Thebasic3Dfunctionalitythatisrequiredbymost3Dapplicationsmustbedevelopedfirst.Dependingontherequirementsoftheindividual3Dbasedapplication,othermoreadvancefeaturesaresubsequentlyadded.II.3DVisualisation.Thedisplayof3DobjectsinaWindowsclientarearequiresasoftwaregraphicsinterface.Thegraphicaloutputtogetherwithaselectedgraphicalinterface,areusedfortherenderingof3Dobjectsinthe3Dbasedapplication,aswellasthemanagementoftheviewingprojectionsandtransformations.Here,alibraryofclassesisdevelopedforsuchpurposes.III.3DDataManagement.The3Ddatamanagementmoduleisdevelopedontopofthefrustrum.ThefrustrumisthemoduleintheParasolidkernelthatfacilitatesarchivingandaccessof3Dpartfiles.Alibraryofclassesaredevelopedusingthefrustrumforhandling1.3Dobjectfileformat.2.Filemanagementoperationssuchasopeningandsavinga3Dobjectfile.5.2.3ApplicationModulesCThesearetheactual3Dbasedapplicationmodulesthatsitbetweenthe3Ddeveloperlayerandtheapplicationuserinterface.Thedesignofthesemodulesdependsmainlyonthenatureoftheapplicationsandoftendiffersgreatly.Themainbulkofthedevelopmentalworkiscarriedoutinthisarea.Theeaseofthedevelopment,however,dependsonthecapabilitiesofthe3Ddeveloperlayer.5.2.4OtherSoftwareModulesDVeryoften,the3Dbasedapplicationmayrequirefunctionalityfromotherexistingsoftwaremodulesorapplicationmodules.Therefore,suchalinkmayexist.Anexampleofsucharequirementisillustratedintheimplementationsectionofthispaper.5.3DevelopmentofIndividualModulesEachmoduletobedevelopedisstudiedandanalysedbeforeasuitabledesignisproduced.Theeaseofdevelopmentdependsgreatlyonthedesignoftheframeworkandthedevelopertoolsselected.Thenextsectionillustratestheimplementationofthe454T.L.NeoandK.S.Lee
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