环境下的电话机底座模具设计外文翻译.docx

环境下的电话机底座模具设计外文翻译.docx

《环境下的电话机底座模具设计外文翻译.docx》由会员分享，可在线阅读，更多相关《环境下的电话机底座模具设计外文翻译.docx（9页珍藏版）》请在冰豆网上搜索。

环境下的电话机底座模具设计外文翻译

外文翻译

专业材料成型及控制工程

学生姓名

班级材控08-1

学号

指导教师

AutomatedGenerationofLifters

forInjectionMoulds

Y.F.Zhang,H.H.LiuandK.S.Lee

DepartmentofMechanicalEngineering,NationalUniversityofSingapore,RepublicofSingapore

Analgorithmforautomatedidentificationofundercutsandthecreationoftheliftersubassemblyinplasticinjectionmoulddesignisdescribed.Thealgorithmissuitableforinjectionmoulddesignina3Dmode.Theinputtothesoftwareisa3Dpartmodel,partingdirectionandlines,andamould-base.Thesoftwarethengeneratestheliftersubassemblyandplacesitproperlyinthemould-base.Thisisaccomplishedinfoursteps.First,theso-calledvirtualcoreandcavityaregeneratedwithoutconsideringanyundercuts.Undercutfacesonthepartarethenidentifiedandundercutgroupsareformed.Secondly,thereleasingdirectionofeachundercutgroupisfound.Thirdly,foreachundercutgroup,alifterheadbasedonitsreleasingdirectioniscreated.Fourthly,otherstandardcomponentsofalifterassemblyareretrievedandattachedtothecorrespondinglifterheadwithinthemould-baseatthecorrectlocation.Acasestudyispresentedthatillustratestheefficacyofthetechniquefortheautomateddesignoflifterstofulfilarealindustrialrequirement.

Keywords:

CAD;Injectionmoulddesign;Lifter;Undercut

1.Introduction

Asonemethodforthemanufactureofplasticparts,injectionmouldinghasbeenwelldeveloped.Aninjectionmouldassembly,typicallyconsistsofamouldbase,runners,coreandcavity,coolingchannels,ejectors,andotherauxiliarycomponents.Amongthesefunctionalparts,thecoreandcavity,whichformtheshapeofthemoulding,areatthecentreofamould.Anundercutisanyportionofthemouldingthatpreventsitfrombeingextractedfromtheimpression,alongthepartingdirection.Anundercutadjacenttothecavityisusuallyreferredtoasanexternalundercut,andoneadjacenttothecoreasaninternalundercut.Foranexternalundercut,aslidermechanism,suchasafingercamortogglecamcanbeadopted.Foraninternalundercut,aliftermechanismisprobablythemostcommonlyusedmethod.Thismechanismisillustratedbytheexampleshown.Duringtheejectionstroke,thelifterisdriveninwards,therebywithdrawingtheobstructionandallowingthemouldingtobeextractedinthepartingdirection.

Traditionally,moulddesignistypicallycarriedoutonthedrawingboardorbyusing2Dcomputer-aideddrawingpackages.Withthedevelopmentof3Dcomputer-aideddesign（CAD）techniques,productdesignandNCtool-pathgenerationarecommonlycarriedoutinthe3Dmode.Itisthereforedesirabletodesignthemouldinthe3Dmode,inordertoshortentheleadtime.Recently,ithasbeenobservedthatseveralCADpackages,suchasIMOLD,weredevelopedtomeetsuchaneed.Thesepackagesprovidesomecommonlyusedmouldlayoutsandvariouscomponentlibrariesfortheusertochoosefrom.Thedesigntasksinvolvinggeometricreasoning,suchassliderandlifterdesign,arestillperformedinteractively.Therehasalsobeensomepublishedworkonundercutdetectionandthedesignofsidecores（sliderandlifter）.However,thereportedautomationtechniquesarestillatanexperimentalstage.Noneofthemhavebeenreportedinanyindustrialapplication.Thispaperfocusesontheautomatedidentificationofinternalundercutsandthegenerationoflifers.However,thetechniquedevelopedcouldbeextendedtothedesignofsliders.

2.PreviousWork

Intheareaofidentificationandresolvingundercutsformoulddesign,mostofthepublishedworkfocusesonsearchingfortheoptimalpartingdirectionandthepartinglines,inordertominimisethenumberofundercuts.Therearealsoafewreportedtechniquesonhowtoincorporatesidecorestoresolveundercuts.Thefollowingsectionsreviewsomeofthepreviousworkinthesetwocategories.

2.1OptimisationofPartingDirectionandLines

Theselectionofthepartingdirectionandthepartinglinesofapartiscriticaltothemoulddesign,asthedecisionwilldecidethenumberofundercuts,andultimatelyaffectthecostofthemould.RaviandSrinivasanproposedasetofcriteriathataffectthepartingdirectionandlineselection.Fromageometricpointofview,thepossiblecandidatesforsuchselectionareinfinite.Variousknowledge-basedoroptimizationschemeshavebeenproposed.

HuiandTandevelopedaheuristic-basedapproachfordeterminingpartingdirectionsbasedonthebalanceofthepreferencevalue（theratiooftheprojectedareainagivendirectiontothemaximumprojectedarea）andtheblockingfactor.SawaiandKakazuconstructedasimilarevaluationfactorbyintersectingvectorsalongacandidatepartingdirectionfromrandomlycreatedpointsonthepartmodel,coupledwithageneticalgorithm.Chenetal.employedthevisibilitymapmethodtoidentifypotentialundercuts,leadingtotheselectionoftheoptimalpartingdirection.

Oneproblemwiththeabovemethodsisthatoptimisingthepartingdirectionwithoutconsideringpartinglinesisincomplete,asapotentialundercutcouldbeavoidedbyappropriatelyplacingthepartinglines.Tanetal.presentedamethodforgeneratingpartinglinesbyaddingartefactstoverticalsidefaceswithrespecttothepartingdirection.However,thistaskhastobedonebytheuser.Atpresent,thetechniquesreportedfortheautomaticdeterminationofthepartingdirectionandlinesarestillfarfrommature.

2.2ResolvingUndercuts

Oncethepartingdirectionandlinesaredetermined,themouldcoreandcavitycanbegeneratedbysubtractingthepartfromablockandsubsequentlysplittingtheblockalongthepartingsurface.Atthislevel,thecoreandcavityarereferredtoasvirtualcore（v-core）andvirtualcavity（v-cavity）,astheslidersandliftersareyettobeincorporated.Inrespecttothepartingdirection,theundercutsonboththev-coreandthev-cavitycanbeidentified,andslidersand/orliftersdesigned.

ShinandLeepresentedamethodthatidentifiesundercutfacesfromthev-coreandthev-cavity.Sidecoresaregeneratedbymanuallyspecifyingthereleasingdirections.Thev-coreandv-cavityarethenmodifiedtoincorporatethesidecores.Rosenalsodevelopedanalgorithmusingasimilarapproachforcreatingslidersandlifters.Strictlyspeaking,theslidersandliftersgeneratedbybothoftheabovemethodsareonlyatanabstractlevel,whichisfarfrombeingusableinindustry.

Manymoreaspectsmustbeconsideredanddesignedtomakethemechanismacompletefunctionalpartinthewholemouldassembly.

Thepresentstudyaimsatcreatingcompleteliftersubassembliesforindustrialuse.Inindustrialpractice,thepartingdirectionandlinesaremainlypredeterminedbytheplasticpartdesigner,ratherthanbythemoulddesigner.Apartfromthenumberofundercuts,theappearanceofthepartinglineonthepartisalsoanimportantfactortoconsider.Thepresentalgorithmtakesthev-coreandthev-cavityastheinput.Inaddition,themould-basewhichistobeusedtoincorporatetheliftersubassemblyisalreadydetermined.First,thesilhouettecurvesofthefacesonthev-core,withrespecttothepartingdirection,areextractedandusedtosplitthecorrespondingfaces.Secondly,undercutfacesarederivedbasedontheirsurfacenormalandgroupedintoindividualundercuts.Thirdly,releasingdirectionsareidentifiedforeachundercut.Fourthly,foreachundercut,alifterheadisgeneratedbasedonitsreleasingdirection.Finally,otherstandardcomponentsareselectedandaddedtoeachlifterheadtoformawholeliftersubassembly.

3.IdentifyingInternalUndercuts

Onthev-core,afacethatisadjacenttothepartsurfaceisreferredtoasaCoF.Themovingdirectionofthecoreduringmouldopeningisspecifiedby“PD-”.Forlifterdesign,thefirststepistoextractundercutfacesfromallCoFs.Ideally,thenormalateverypointonaCoFshouldbechecked.ApointwhosenormalhasapositiveelementalongPD-issaidtobeblockedduringmouldopening,anditsparentCoFisaundercutface.However,itispossiblethatnotallthepointsonaundercutfaceareblocked,andacompletesearchofallthepointsisnotpossible.Therefore,weproposeapreprocessingmethodfortheCoFs.TheideaistosplitaCoFsothatthepointsoneachresultingfacehaveahomogeneousnormalelementalongPD.Toachievethat,thesilhouettecurvesoneachCoFinrespecttoPD-areextractedandusedtosplittheCoF.Foreachresultingface,asinglepointischecked.Ifitisblocked,itsparentfaceandsubsequentlytheparentCoFisanundercutface.ThisapproachisfurtherillustratedbytheexampleshowninFig.3.Theparthastwoundercuts,oneofthemhasafreeformsurface.Figure3（d）showstheextractedsilhouettecurvesandthefourfacesaftersplittingwheretwoofthemarefoundtobeundercutfaces.

OncealloftheindividualundercutCoFsareidentified,thenextstepistoallocatethemtodifferentundercutgroups（UGp）,whereeachUGpcanbehandledbyasinglelifter.Sincealiftermovesalongitslateraldirectionduringmouldopening,anytwoundercutCoFsthatareoverlapping,viewedfromthepartingdirection,shouldbehandledbyasinglelifter.Althoughinindustrialpractice,twoormoreUGpsfoundusingthisheuristicaresometimeshandledbyasinglelifter,suchpracticedependsmainlyonthedesigner’sexperienceandthusisnotconsideredinthisstudy.IneachUGp,theundercutCoFsmaynotbeadjacent（ortheycannotbesewedintoasingleface）.Insuchcases,thenon-undercutCoFsthatareadjacenttotheundercutCoFswillbeidentifiedandaddedtotheUGp.Finally,theCoFsinanUGparese