PertanikaJ.Sci.&Techno!.Supplement12(2):85-99(2004)ISSN:0128-7680UniversitiPutraMalaysiaPressDesignandSimulationofPlasticInjectionMouldingProcessWong,C.T.,ShamsuddinSulaiman,NapsiahIsmail&A.M.S.HamoudaDepartmentofMechanicalandManufacturingEngineeringUniversitiPutraMalaysia,43400UPM,Serdang,Selangor,MalaysiaE-mails:.myABSTRAKKertasinimembentangkanprosesrekabentuksatuacuansuntikanplastikuntukmenghasilkansatuproduk.Iadibahagikankepadatigabahagianiaitu:bahagianrekabentuk,bahagiansimulasidanbahagiananalisa.Plastikprodukinidirekabentukkepadaduabentukyangberlainantetapimempunyaifungsiyangsamaiaitusatuprodukmenggunakanfungsiklipdansatuproduklagimenggunakanfungsilekat.UntukRekaBentukTerbantuKomputer(CAD),perisiankomputeryangdigunakanuntukmerakabentukprodukdalam3dimensi(3D)danacuanialahPro/Engineer(Pro/E).Duaplastikprodukyangberlainanakandirekabentukdalaminse:rtyangbolehditukar-tukardidalamsatuacuanuntukmenghasilkanduaprodukyangberlainan.UntukPembuatanTerbantuKomputer(CAM),Pro/Manufacturing(Pro/MFG)daripadaperisiankomputerProlEdigunakanuntukmenjanakanbeberapakodkawalanberangkauntukprosespemesinan.Analisisterhadappengalirancecairplastikdijalankandenganmenggunakanperisian(MoldFIow-PartAdvisorversion4).Daripadaanalisisinikedudukantempatsuntikan,suhubahandantekanansuntikandapatditentukan.Jangkaankecacatanproduksepertiweldlinesdanudaraterperangkapjugaditemuidandianalisis.ABSTRACfThispaperpresentsthedesignofplasticinjectionmouldforproducingaplasticproduct.Theplasticpartwasdesignedintotwodifferenttypesofproduct,butinthesameusagefunction.Onepartisusingclipfunctionandanotherpartisusingtickfunction.Inthecomputer-aideddesign(CAD),twoplasticpartsweredrawnin3dimension(3D)viewbyusingPro-Engineer(Pro-E)parametricsoftware.Inthecomputer-aidedmanufacturing(CAM),Pro-ManufacturingfromPro-Eparametricsoftwarewasusedtodevelopthemachiningprogram.Formoulddesign,theproductwasdesignedintotwochangeableinsertstoproducetwodifferenttypesofplasticproductinonemouldbase.Beforeproceedingtoinjectionmachineandmoulddesign,thispartwasanalysedandsimulatedbyusingMoldFloworPartAdvisorsoftware.Fromtheanalysisandsimulationwecandefinethemostsuitableinjectionlocation,materialtemperatureandpressureforinjection.Thepredictedweldlinesandairtrapwerealsofoundandanalysed.Keywords:Changeableinsertmould,injectionpressure,airtraps,injectionlocation,moulddesignINTRODUCTIONNowadays,thetechnologyofthetoolanddiefabricationinplasticinjectionisoneoftheworldsfastestgrowingindustries.Plasticisnowusedinalmosteveryapplication,rangingfromhouseholdarticlestospacetravel,fromtransportationtopacking,frommedicinetotoys,frombridgebuildingtosports.Generally,injectionmouldingisaprocessthatformstheplasticintoadesiredshapebymeltingtheplasticmaterialandforcingtheplasticmaterialunderpressureintothemouldcavity.Theshapeoftheplasticthatisdesiredisachievedbycoolinginthermoplasticorbychemicalreactionforthermosetting.Moulddesignandfabricationisacostlyandhightechnologyprocessbecauseitusesscience-basedcomputer-aidedengineering(CAE)softwaretoanalyseandsimulatetheWong,C.T.,ShamsuddinSulaiman,NapsiahIsmail&A.M.S.Hamoudaplasticparts,computer-aideddesign(CAD)softwaretodesignthecomplicatedplasticproductandcomputer-aidedmanufacturing(CAM)todotheprogrammingfabricationtorunthecomputernumericcontrol(CNC)formillingorlatch.Advancesincomputertechnologyhaveledtoanincreasinglyfavorablepowertocostratioforcomputers.Sothisadvantageousandcostlytechnologywillimproveproductivityandprocessconsistency.Thus,forthisfastgrowingindustry,newtechnologiesarevitaltoensurethatthistechnologyreachesperfection.S.ocomputer-aidedengineering(CAE)istheassistanttoprocessandcalculatetheplasticmaterialflowinsidetheinjectionmoulding.TheoryHowPlasticFillsaMouldTheinjectionmouldingprocesscanbebrokenintothreephases:1.Fillingphase2.Pressurizationphase3.CompensatingphaseFillingPhaseWhendesigningplasticpartsfortheinjectionmouldingprocess,theimportantelementtounderstandishowtheplasticisfillinginthemould.Inthemouldinjectionfillingphase,moltenplasticisinjectedintothecavityuntilthecavityisjustfilled.Asplasticflowsintothecavity,theplasticincontactwiththemouldwallquicklyfreezesandthiswillcreateafrozenlayerofplasticbetweenthemouldandthemoltenplastic.Plate1showshowtheflowfrontexpandsasmaterialfrombehindispushedforward.Theedgeoftheflowfrontcomesintocontactwiththemouldandfreezes.Themoleculesinthefrozenlayerarethereforenothighlyorientated,andoncefrozen,theorientationwillnotchange.Plate1:MolJ.enplasticflowinsidethemouldTheredarrowsshowtheflowdirectionofthemoltenplastic.Thedarkbluelayersagainstthemouldwallsshowthelayersoffrozenplastic.Thegreenarrowsindicatethedirectionofheatflowfromthepolymermeltintothemouldwalls.Thefrozenlayergainsheatasmoremoltenplasticflowsthroughthecavity,andlosesheattothemould.Whenthefrozenlayerreachesacertainthickness,equilibriumisreached.Thisnormallyhappensearlyintheinjectionmouldingprocess,afterafewtenthsofasecond.PressurizationPhaseThepressurizationphasewillhappenafterthefillingphasecompletelyfillsthecavityarea.Atthisstage,alltheflowpathswillbefilledupbymoltenplastic,theedgesand86PertanikaJ.Sci.&Techno!.SupplementVa!.12o.2,2004DesignandSimulationofPlasticInjectionMouldingProcesscornersofthefillingareainthecavitymaynotcontainplastic.Tocompletelyfilloutthegeometry,extraplasticispushedintothecavityduringthepressurizationphase.Plate2showsthedifferencebetweentheendofthefillingphase(leftimage)andtheendofthepressurizationphase(rightimage).oticetheunfilledcorners(insidethebluecircles)thatareleftattheendofthefillingphase.Theyellowconeindicatesthepolymerinjectionlocationandtheplasticisred.FillinRPhasePlate2:DifferencebetweenjiUingandpressurizationphasePressurizationPhaseCompensatingPhasePlasticmaterialhasahighvolumetricshrinkage,formthemeltingplastictosolid,itwillshrinkageaverageof25%.Thereforeafterthepressurizationphase,morematerialmustbeinjectedintothecavitytocompensatefortheplasticshrinkingafteritcools.Thisisthecompensatingphase(MoldFlowHelpFiles).MouldBasicConstructionMoulddesignandmouldmakingcanbeconsideredthemostcriticalprocessesoftheinjectionmouldingsystem.Thisisbecausethemoulddesignandmouldmakinghavetremendousimpactonproductivityandproductquality.Basically,thefunctionofthemouldistwofold.Thefirstisimpartingthedesiredshapetotheplasticizedpolymer,thesecondiscoolingtheinjectionmouldedparts.Themould,whichcontainsoneormorecavities,consistsoftwobasicparts:AstationarymouldhalfonthesidewheretheplasticisinjectedAmovinghalfontheclosingorejectorside.Theseparationofthetwomouldsiscalledthepartingline.Themouldwilldeterminethefinalproductpropertiessuchassize,shape,dimensionandfinishingsurface.Usually,themeltedplasticmaterialisfilledthroughthecentralfeedchannelcalledspruetothecavity.Themouldwillcoincidewiththeinjectionmachinecylindernozzle.Table1isthesummarylistformouldcomponentandthefunctionrespectively.MouldDesignTostartupanewmoulddesign,thedesignershouldknowsomeimportantpointstoavoidsomemistakesbeforegoingfurtherLductoutlookdesign,materialusage,correctshrinkageofthematerial,numberofcavitiesandselectionofthemouldbase.Makingamistakecancauseanill-fittingmouldatthefinalassemblyandalsomaketheplasticproductoutoftoleranceandberejectedbythecustomer.Fig.1showsthemoulddesignerschart.PertanikaJ.Sci.&Techno.SupplementVo.12No.2,200487/Wong,C.T.,ShamsuddinSulaiman,NapsiahIsmail&A.M.S.HamoudaCreateamodelinCADsoftware(convertinSTL)J.l.-OpenthemodelinSelectaplasticmaterialPartAdvisorandsupplier.Ifasingleinjectionlocationisrequired,goontothenextstepIfmultipleinjectionlocationswanted,skipthenextstepandgototheoneafterIRunthegatelocatorIJ.IRuntheanalysisLCreateoneormoreIinjectionlocations-Lookattheanalysisresult,decideifthemodelwillfilleasilyandcreategoodqualityparts-Iftheresultsarenotsatisfactory,goontothenextstep-Iftheresultsareacceptable,skipthenextstepandgototheoneafterChangeoneoftheparametersandthenCreateareportonthere-analyze-.analysisresult,usingtheTheseparametersare:reportgeneratorPositionornumberofinjectionlocationJ.MaterialMouldtemperatureSendthereporttotheMelttem