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ORIGINALARTICLEY.-S.MaT.TongAnobject-orienteddesigntoolforassociativecoolingchannelsinplastic-injectionmouldsReceived:17December2002/Accepted:17December2002/Publishedonline:17October2003C211Springer-VerlagLondonLimited2003AbstractDuetothedemandforshortproductdevel-opmentcycles,plasticinjectionmoulddesignersarere-quiredtocompresstheirdesigntimeandtoaccommodatemorelatechanges.Thispaperdescribesanassociativedesignapproachembeddedinacoolingchannelmoduleofamoulddesignsoftwarepackage.Itgivesasetofcomprehensiveobjectdefinitionsforcoolingcircuits,andaddressesbalancedorunbalanceddesigns.CADalgorithmsthathavebeendevelopedarebrieflyexplained.Withthisnewapproach,moulddesignerscaneasilypropagatechangesbetweenmouldplatesorinsertsandthecoolingsystemwithouttheneedfortediousrework.Hence,thisapproachcansignifi-cantlyreducethetotaldesigntimeandtheimpactoflatechanges.KeywordsCoolingcircuitPlasticmoulddesignCAD/CAMAssociativedesignDesignautomation1IntroductionCurrently,mostCADsystemsareunabletocapturedesignintentcompletelyandunambiguously.Richde-signinformationcannotbefullyrepresentedinCADmodelsandlatechangesintheproductdevelopmentcyclecausealotofrework.IthasbeenacknowledgedthatCADinteroperabilityshouldcoverintegrationwithknowledge-basedengineering(KBE)systems1.How-ever,thereisnomechanismtoenabledesignintentinformationflow.Suchaninformationgapisveryobviousinplasticinjectionmoulddesignaswell.Moulddesignersarefacingincreasingpressuretoreducethedesigntime,andyetareexpectedtoassuremouldquality.VariousCADtoolsfordesigningplasticinjectionmouldshaveemergedsincetheearly1970s2,mostofwhichfocusedonmouldingflowanalysisandoptimi-sationalgorithms3,4,5.Recently,thedesignofmouldsub-systems,suchascore/cavityinserts6,7,runners8,9,gatelocations3,4,5andcoolingsystems10,havebeenthefocus.Forcoolingsystemdesign,Wangetal.11suggestedastrategywiththreestages,initialdesignwithone-dimensionalapproximation,two-dimensionaldesignwithoptimisation,andthree-dimensionaldesignwithcoolingeectanalysis.Theyhavedevelopedaprogramthatuses3D-boundaryelementmethodstoanalyse3Dheattransfer.Alltheabove-mentionedtoolsareonlyabletogenerategeometricalinformation.Therepresentationandreuseofrichdesigninformationatdierentlevelsarenotaddressed.Object-oriented(OO)softwaretechnologyhasbeenappliedtomeettheinformationrepresentationgapinmoulddesign12.Objectdefinitionscanprovideagreatdealofhelpinsortingoutcomplicatedentities,espe-ciallyforpart-independentpartsandfeatures.However,maintainingtherelationshipsamonggeometricalentitiesandmakingthemcustomisableisstillnotatrivialtask.TheCADsoftwaredevelopmentapproachthatcanachievepersistentrelationshipsamonggeometricalentitiesisreferredtoastheassociativedesignapproach.OnewaytobuilddesignintentandprocessknowledgeintoaCADsystemisintheformofaprocesswizard,whichisbasicallyanapplicationprogramcoupledwithasetofsequenceduserinterfaces(UIs)toguideuserstocompletecertaininteractionswiththecomputersystem.MouldWizardfromEDSInc.isonesuchprocess-basedwizard13.Thispaperintroducestheassociativedesignapproachappliedinitscoolingchannelmodule.Marketfeedbackshowsthatthisconceptcansignificantlyreducethegapbetweenhumanknowledgeandconsistentcomputerrepresentations.ThecoolingsysteminamouldaectsnotonlythequalityofresultantmouldingpartsbutalsoeciencyinY.-S.Ma(&)T.TongDesignResearchCentre,SchoolofMechanicalandProductionEngineering,NanyangTechnologicalUniversity,639798Singapore,SingaporeE-mail:.sgIntJAdvManufTechnol(2004)23:7986DOI10.1007/s00170-003-1630-1mouldingproduction.Inthecurrentindustrypractice,itiscommontouseatleastfourmajorcoolingcircuitsinamouldassembly.Theyarelocatedonthecavityinsert,thecoreinsert,A-plateandB-plate14.Wangetal.11andSingh15recognisedthattheparametersindesigningcoolingsystemarenumerous;designvariables,suchaslocations,typesofcoolingchannels,and3Dlayoutofcircuits,areusuallymodifiedfrequentlytoaddresslatepartdesignchangesaswellasmoulddesignoptimisation.ThemodificationprocessislaboriousanderrorpronebecausedesignershavetoeditandupdateCADmodelsrepetitively.Moketal.16developedacoolingsystemthatcanautomaticallyretrievecertaincircuitpatterns,suchasstraightorUtypes,buttheassociationamonggeometricalentitiesisnotdiscussed.AnexpertsystemfordesigningcoolingsystemswasintroducedbyKwonetal.10.Thesystemconsistsoffourlevels:layoutdesign,analysis,evaluationanddecision-making.Adecision-makingmoduleevaluatestheredesignofcoolingchannelsbasedontherulesstoredinaknowledgebase.However,thereisnointe-grationwithaparametricCADsystem.Insummary,anecientanduser-friendlycoolingsystemdesigntoolishighlysought;suchasystemcanbeexpectedtofreemoulddesignersfromtediousgeomet-ricalupdatingandtokeepdesignmodelsconsistent,sothatthetotalmoulddesigncycletimecanbeshortened.Thispaperpresentsacoolingchanneldesigntoolthatprovidessubstantialautomationforcoolingcircuitgenerationwithassociativelinksamongcoolingholesandtheirdrillingfaces.1.1GenericissuesassociatedwithcapturingdesignintentsIntheindustry,coolingchannelsareusuallydesignedintheformofcoolingcircuit,butrepresentedasHOLEfeaturesusingCADtools.Ontheotherhand,experi-encedmoulddesignersfoundthatsolidcylindersarealsocommonlyusedinsteadtorepresentcoolingchan-nels.Inthelatterapproach,whenthedesignisfinalised,allchannelsareunitedtoformacoolingcircuit.WithsuchunitedcircuitsdefinedwiththehelpofCAEanal-ysistools,thecoolingeectcanbeevaluated11.ThesecircuitsarenotconvertedintoholesuntilthedesignhasbeenfinalisedandisreadyforCAMtoolpathgenera-tion.Withthisformofrepresentation,aCADsystemcandisplay/drawcoolingchannelsforvisualinspection,withoutdisplayingdetailedfeaturesofthecore/cavityinsertsandmouldplates.RepositioningandmodifyingcylindersalsorequirefewerstepsthanusingHOLEfeatures.Itenablesautomaticcheckingforcollisionsbetweencoolingchannelsandothermouldfeatures,suchascavitiesandejecting-pinholes.However,representingcoolingchannelsintheformofsolidcylindershasseveralproblems.First,manystepsarestillrequiredforasimplechannel,suchascreatingacylinder,chamferingtheblindendinthecaseofablindhole,andrunningthroughaseriesofdialogueboxestopositionandorientit.Commonly,therearemanychannelsinacoolingcircuit,socreatingtheminvolvesalotofrepetitivecommands.Whenmodificationsareneeded,cylindershavetobeeditedrepetitivelyagain.Thissituationiserror-prone.Second,coolingchannelsarenotself-identified.Forautomaticheattransferanalysisorcollisionchecking,identifyingcoolingchan-nelsisparticularlyimportant.Third,theycannotpro-videorientationinformationforplugs,nozzles,orbaestobeinsertedintocoolingchannelsinauser-friendlydrag-and-dropmanner.Hence,moulddesignershavebeenfrustratedwithtedioussteps.1.2SemanticdefinitionsofacoolingsystemAnobject-orientedsoftwaredesignapproachcanbeappliedtoaddresstheissuesdiscussedintheabovesection.Definingasetofobjecttypesorclassesthatprovidesself-containeddefinitionsofcoolingsystemsandenablesdynamicupdatingtovalidatethecoolingsystem,isessential.InFig.1,thesimplifiedsemanticstructureofacoolingsystemanditsrelatedcomponentmembertypesisshown.Eachcomponenttypeisdefinedasanobjectclass.Acoolingchannelisdefinedasacontinuousstraightholethatcontainscoolingliquid(waterinmostcases).Itcanbecontainedinasinglemouldcomponent(platesorinserts),oritcutsacrossseveral.Inthispaper,holeisusedtodescribethegeometricalshapeofacoolingchannelonasinglemouldcomponent,however,itsrepresentationisnotthesameastraditionalHOLEfeatures(seethenextsection).AnexampleofacoolingcircuitisshowninFig.2.Holes15arecoolingchan-nels.Acoolingcircuitrepresentsalltheinter-connectedcoolingchannelsbetweenaninletandanoutlet.Severalcoolingcircuitsformacoolingsystem.InFig.2,holes15jointlyformacoolingcircuit.Acircuitcanhaveseveralcoolingchannelswithdierentorientations.Thesechannelsconsistofcoolingholeswhicharedrilledfromdierentfacesofthemouldplatesorinserts.Thefaceusedtodrillacoolingholeiscalledthepenetratingface.Naturally,acoolingholehasonepenetratingfaceandthehole-drillingvectoralwaysleavesfromthepe-netratingfaceandpointstotheotherend.Usually,Fig.1Semanticstructureofacoolingsystem80coolingholesareperpendiculartothepenetratingface.However,inordertocatertosomespecialcases,thisconstraintisnotimposedforthepurposesofthisarticle.Inpractice,somecoolingchannelscutacrossmultipleblocks;anexampleofthisisshowninFig.3.Itconsistsofseveralconnectedcollinearcoolingholes(hole1,hole2andhole3).Suchchannelsarespeciallynamedcol-linearcoolingchannels.Inmanycases,multi-impressiondesignisusedforthemouldlayout.Therearetwoapproachestocreat-ingcoolingcircuitsthen:balancedandunbalanced.Acoolingsystemisreferredtoasbalancedifthesamecoolingcircuitpatternisappliedtoeveryimpression.Otherwise,thecoolingsystemisunbalanced.Usually,ifthemouldisdesignedwithabalancedmulti-impressionpattern14,andthedesignerwishestohaveanidenticalcoolingcircuitforeachimpressionsection,thenthebalancedapproachisused.Inthiscase,becauseeachcircuitisdesignedmainlytocoveroneimpression;thecoolingeectcanbebettercontrolledtosatisfyheat-transferrequirements.Thisisespeciallyrecommendedforcomplexmouldingpartswherethecoolingeectcanbeoptimisedusingsimulationpackages11.Withthisapproach,aCADfunctionthatiscommonlyrequiredbymoulddesignersistoreflectthechangesinthecoolingcircuitpatternontheindividualimpressions.Ontheotherhand,thedesignermaywanttotreatthemouldasawholeanddesigncoolingcircuitswithoutconsideringtheimpressionpattern;ifthisisthecasehecanapplytheunbalancedapproach.1.3DetailedrepresentationsAdetailedcomponentstructureofacoolingsystemisgiveninFig.4.Aholeisrepresentedwithastraightlineandanoptionalcylindricalsolid.Thisstraightlineiscalledthecoolingguidelineforthehole.Moreprecisely,acoolingguidelineisastraight-linesegmentstartingfromthecooling-holepenetratingcentrepointtotheholesendcentrepoint.InFig.2,ABisthecoolguidelineforhole1,andCDisforhole2.Guidelinescontainhole-drillingvectors.Atboththestartandendpointsofeachcoolinghole,thefollowingtypesofhole-endscanbeselected,asshowninFig.5:(1)Drill-through,(2)Counter-bored,(3)Blindwithoutextensionand(4)Blindwithextension.SuchgeometricalfeatureinformationisrepresentedasFig.3AtypicalcollinearcoolingchannelFig.4DetailedcomponentstructuresofacoolingsystemFig.2Anexampleofcoolingcircuit81attributesattachedtoguidelines.Thecylindricalsolidscanbegeneratedanytimeifitisneededbasedontheinformationstoredwitheachguideline.Traditionally,coolinglinesarealsousedtorepresentacoolingcircuit11,buttheyareseparateentitiesfromthecontainingsolids,suchasmouldplatesorinserts.Oneofthedesignideasinthispaperisthateveryguidelinehasstartandendpointthatareassociatedwiththecorrespondingpenetratingandexitingfaces,exceptfortheendpointsofblindholes.Therefore,ifthesefaceschangetheirpositions,theassociatedpointscanbede-riveddynamicallyandupdatedaccordingly.Inotherwords,coolingguidelinesarealwaysassociatedwiththeirpenetratingandexitingfaces.Thecoolingguidelinesofalltheholeswithinacoolingcircuitaregroupedasaguidepath.InFig.2,fiveguidelines,AB,CD,EF,GH,andIJ,formaguidepath.Inthispaper,asshowninFig.4,aguidepathrepresentseachcoolingcircuitcompletelywhilecoolingguidelinescanhavecertainattributestodescribethecooling-holetypes,diameters,etc.Infact,coolingcylindricalsolidsaregeneratedonlywhenneededforviewing,checkingphysicalcollisionamongdierentfeatures/components,orcreatingde-tailedfeaturesonplatesorinserts.Thesecoolingsolidscanbedeletedtosimplifythedisplay;aslongastheguidepathsareavailable,thesecoolingsolidscanberegenerated.Atlaterstages,afterconfirmingthecoolingsystemdesign,geometricalholesmaybestillneededforCAMapplicationorcomponentstructuredetailing.Theycanbeachievedbysubtractingcoolingsolidsfromtheircorrespondingplate/insertbodies.Aguidepathisalsousedtomaintainconnectivityamongitsguidelines.Tovalidateandverifythiscondi-tion,avalidatormethodisdefinedintheguidepathclass.Thecollinearcoolingchannelisthespecialobjecttypethatiscreated.FromFig.4,itcanbeseenthatacoolingcircuitmaycontainsuchcollinearcoolingchannelsaswellassimplechannels.Eachcollinearchannelcanberepresentedbyagroupofguidelinescalledthecollinearpath.Obviously,itselementguide-linesmustbeconnectedfromheadtotailcontinuouslyalongastraightline.InFig.3,AB,CDandEFformacollinearpathandrepresentthroughhole1(withbothcounter-boredends),throughhole2,andblindhole3respectively.Itcanbeseenthatwithinacoolingcircuit,coolingelementsareassociatedbecausetheyarevali-datedinstantlyuponanychange.AsshowninFig.4,thecontentsandrepresentationofacircuitobjectchangeaccordingtothecontextanduserschoices,forexample,acircuitcanbedisplayedgraphicallyasasetofinter-connectedguidelines,orasasetofcylindricalsolids.Acoolingcircuitisself-con-tainedwithgeometricalandnon-geometricalinforma-tionintheformofrichattributes.Insummary,withthisobjectstructuredesign,coolingchannelsandtheirrelatedmouldplatesorinsertscanbeautomaticallyupdatedifsomeelements,suchaspene-tratingfacesordrilling-holetypesaremodifiedatlaterdesignstages.Sinceallthecoolingchannelsarecreatedinanassociativeapproach,thentheprocessknowledge,suchaspenetratingfaces,drillingdirectionsandconti-nuitywithinacircuitcanbeembeddedwithintheCADmodelandstoredpersistently.2Implementationaspects2.1EmbeddedlinksandparametersInacoolingdesignsessionwiththismodule,guidelinesareinitiallycreatedthroughagraphicaluserinterface.Toassociatethestartandendpointsofeveryguidelinewiththepenetratingandexitingfaces,withtheexceptionoftheendpointsofblindholes,asmartpointconceptisused13.Asmartpointisapointonthesurfaceassociatedwiththefaceatthekerneldatabaselevel.Itkeepsthepersistentlinkwiththecorrespondingface.Here,wordsmartrepresentstheassociativenatureofanentitytoanotherrelatedentity.Sinceguidelinesarecreatedbasedonsuchsmartendpoints,thenthecor-respondingguidelinesarealsocalledsmartlines.Eachofthemisconnectedtoone(forblindholes)ortwosmartpoints(forthroughholes).Acoolingsolidcylindercanbegeneratedautomati-callyalongitssmartguidelinebysweepingacircularsectionprofile13.Forablindhole,aconeendisadded.Foracoolingcircuit,itscylindricalsolidsarethenuni-tedasthesolidrepresentation.Thesegeometricalfea-turesarerepresentedwithattributesattachedtoguidelines.Suchrelatedattributesincludetypeofend(seeFig.5),coolingholediameter,anddepthanddiameterofthecounter-boredportion,ifapplicable.Theyareusedforcoolingholeeditingandcoolingsolidregeneration.2.2FunctionsandalgorithmsThemainfunctionsthathavebeendevelopedinthismoduletomeettherequirementsforcoolingsystemdesignarelistedhere:Fig.5Typesofcoolingcylinderends82a.Additionofsmartguidelinestoformguidepathsb.Modification/repositioningofguidelinesc.Deletingofcircuitguidepathsd.Creationofcoolingsolidse.Modificationofthecoolingsolidsf.Deletionofthecoolingsolidsg.Creationofbalancedorunbalancedcoolingdesignsforamulti-impressionmould.Thesefunctionsarebrieflydescribedbelow.2.3CreatingandeditingthesmartguidepathofacoolingcircuitTocreatethefirstguidelineofaguidepath,theuserneedstoselectafaceonanintendedsolidastheinletpenetrating(planar)faceofthecircuit(seeFig.2).Aplaneequationcanbeextractedfromtheselectedplanarface.TheinitialstartpointAfortheguidepathonthisfacecanbefoundbasedontheusersindicationpoint;asmartpointisthencreated.Thedefaultdirectiontogeneratethefirstcoolingguidelineissettothereversedirectionofthefacetonormal,anditisdisplayedonthegraphicwindow.Theusercaninteractivelymodifytheinitialpointpositionandguidelinedirectionwithdif-ferentsubmenusactivatedfromtheUIshowninFig.6.Then,theusercandynamicallydragacoolinglineorinputavalueofthelengthfortheguidelineofablindhole,orchooseanotherfacetoindicatetheendingfaceforathroughhole.Inthelattercase,anothersmartpointwillbecreatedattheendpointoftheguideline.Aftercreatingthefirstguideline,asequencenumber,1,isdisplayednearit.Tocreatethenextguideline(seeFig.2),adrillingvectorisrequired.TheusercanindicatethebottompenetratingfaceatpointP.Then,thenextguidelinedirectionissettobeinthereversenormaldirectionoftheselectedface.ThevectorsstartpointCisdeterminedwithreferencetothepreviousguidelineABandthenearestpointtotheusersindicatedpointP.Thisisanembeddedruleimplementedinthiswork.Tomakethevectordefinitionuser-friendlier,manysuchcontextrulesareappliedtoassistguidelinecreation.Inthiscase,whendefiningtheguidelineCD,fromthepreviousAB,itisextendedautomaticallytofindthedrillingpointConthebottomface.AsmartpointiscreatedatConthisfacetoassociatetheguideline.Again,sequencenumber2isdisplayedneartheguideline.Theusercanalsodefinethenextguidelinevectorbyselectingoneworkingcoordinatedirection,+X,)X,+Y,)Y,+Z,or)Z,andthenindicateaguidelinestartpoint.Inthesimilarmanner,acompleteguidepathcanbedefined.Uponconfirmingalltheguidelinesoftheintendedguidepath,thecontinuitywithinthepathischeckedwiththevalidatormethod(seeFig.4).Thisguidepathisthentreatedasasingleentity.Asexpected,guidelinescanbecreatedoraddedtoaguidepathbyCADfunctions.Existingguidelinescanalsoberemovedeasily.Duringtheinteractionstodefineguidelines,theusersinputparametersandsequencesaredierentiatedwiththecorrespondingalgorithmbranches.Forexample,tocreateasimpleblindhole,theusersselectionsequencescanbeanyofthesethreeoptions:(a)justthepenetratingface,(b)thepenetratingfaceandthenanexistingper-pendicularreferencecoolinghole,and(c)simplyanexistingcoolingholecollineartotheintendedone.Un-dereachoption,theusersselectionsequencesaredis-tinguished;necessaryadjustmentstotheintendedcoolinglinearemadetokeeptheguidepathconnected,andafriendlyUIisdesigned.Afteracoolingguidelineisselected,itsproperties,includingitslength,aredisplayedonthesameUIasshowninFig.6.Thesecanbechangedandupdated.Infact,whenaguidelineisselected,itsguidepathisalsoidentified.ThisisbecausealltheguidelinesinaguidepathareassociatedwithFig.6UIforcreatingguidinglines83continuityconstraints.Iftheinletpointpositionoftheguidepathismoved,thewholepathfollowsaccordingly.AusercansecurelydeleteaguidepathbyselectingtherelevantoptionfromtheeditingUI.2.4CreatingandeditingcoolingsolidsAfterdefiningaguidepath,coolingsolidscanbegen-eratedbasedontheattributesoftheindividualguide-lines.Coolingsolidsarecreatedonlywhentheuserneedsthem.AsshowninFig.4,coolingchannelscanhavedierenthole-types.Thesetypescanb