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JournalofMaterialsProcessingTechnology171(2006)259267AbstracttheinUnigraphics,usingdistribresultsatK1.industries,AlmostusagebymoldingtoatTherearetionappropriatesystemThiswithitypacke0924-0136/$doi:10.1016/j.jmatprotec.2005.06.075DesignandthermalanalysisofplasticinjectionmouldS.H.Tang,Y.M.Kong,S.M.Sapuan,R.Samin,S.SulaimanDepartmentofMechanicalandManufacturingEngineering,UniversitiPutraMalaysia,43400Serdang,Selangor,MalaysiaReceived3September2004；accepted21June2005Thispaperpresentsthedesignofaplasticinjectionmouldforproducingwarpagetestingspecimenandperformingthermalanalysisformouldtoaccessontheeffectofthermalresidualstressinthemould.Thetechnique,theory,methodsaswellasconsiderationneededdesigningofplasticinjectionmouldarepresented.DesignofmouldwascarriedoutusingcommercialcomputeraideddesignsoftwareVersion13.0.ThemodelforthermalresidualstressanalysisduetounevencoolingofthespecimenwasdevelopedandsolvedacommercialfiniteelementanalysissoftwarecalledLUSASAnalyst,Version13.5.Thesoftwareprovidescontourplotoftemperatureutionforthemodelandalsotemperaturevariationthroughtheplasticinjectionmoldingcyclebyplottingtimeresponsecurves.Theshowthatshrinkageislikelytooccurintheregionnearthecoolingchannelsascomparedtootherregions.Thisunevencoolingeffectdifferentregionsofmouldcontributedtowarpage.2005ElsevierB.V.Allrightsreserved.eywords:PlasticInjectionmould；Design；ThermalanalysisIntroductionby“coolingstage”wherethemouldiscooleduntilthepartissufficientlyrigidtobeejected.Thelaststepisthe“ejectionPlasticindustryisoneoftheworldsfastestgrowingrankedasoneofthefewbillion-dollarindustries.everyproductthatisusedindailylifeinvolvestheofplasticandmostoftheseproductscanbeproducedplasticinjectionmoldingmethod1.Plasticinjectionprocessiswellknownasthemanufacturingprocesscreateproductswithvariousshapesandcomplexgeometrylowcost2.Theplasticinjectionmoldingprocessisacyclicprocess.arefoursignificantstagesintheprocess.Thesestagesfilling,packing,coolingandejection.Theplasticinjec-moldingprocessbeginswithfeedingtheresinandtheadditivesfromthehoppertotheheating/injectionoftheinjectionplasticinjectionmoldingmachine3.isthe“fillingstage”inwhichthemouldcavityisfilledhotpolymermeltatinjectiontemperature.Afterthecav-isfilled,inthe“packingstage”,additionalpolymermeltisedintothecavityatahigherpressuretocompensatethexpectedshrinkageasthepolymersolidifies.ThisisfollowedCorrespondingauthor.E-mailaddress:.my(S.H.Tang).stage”after4mericnatedactualthecoreandfmouldgatingtostressesdemoldedconductimolteneseefrontmatter2005ElsevierB.V.Allrightsreserved.inwhichthemouldisopenedandthepartisejected,whichthemouldisclosedagaintobeginthenextcycle.Thedesignandmanufactureofinjectionmoldedpoly-partswithdesiredpropertiesisacostlyprocessdomi-byempiricism,includingtherepeatedmodificationoftooling.Amongthetaskofmoulddesign,designingmouldspecificsupplementarygeometry,usuallyontheside,isquitecomplicatedbytheinclusionofprojectiondepression5.Inordertodesignamould,manyimportantdesigningactorsmustbetakenintoconsideration.Thesefactorsaresize,numberofcavity,cavitylayouts,runnersystems,systems,shrinkageandejectionsystem6.Inthermalanalysisofthemould,themainobjectiveisanalyzetheeffectofthermalresidualstressormolded-inonproductdimension.Thermallyinducedstressesvelopprincipallyduringthecoolingstageofaninjectionpart,mainlyasaconsequenceofitslowthermalvityandthedifferenceintemperaturebetweentheresinandthemould.Anuneventemperaturefieldxistsaroundproductcavityduringcooling7.260Processingenceschannel.eSignificantfore,ofunderstandingtion,beproducingmalresidual2.2.1.specimenthatthinuctthemouldedshell120materialwtemperature,respectiduced.2.2.testingerationstestinginjectioncarbontheiii.iimen,designsionismachineTheTherefore,notreservsetting-upS.H.Tangetal./JournalofMaterialsDuringcooling,locationnearthecoolingchannelexperi-morecoolingthanlocationfarawayfromthecoolingThisdifferenttemperaturecausesthematerialtoxperiencedifferentialshrinkagecausingthermalstresses.thermalstresscancausewarpageproblem.There-itisimportanttosimulatethethermalresidualstressfieldtheinjection-moldedpartduringthecoolingstage8.Bythecharacteristicsofthermalstressdistribu-deformationcausedbythethermalresidualstresscanpredicted.Inthispaperthedesignofaplasticinjectionmouldforwarpagetestingspecimenandforperformingther-analysisforthemouldtoaccessontheeffectofthermalstressinthemouldispresented.MethodologyDesignofwarpagetestingspecimenThissectionillustratesthedesignofthewarpagetestingtobeusedinplasticinjectionmould.Itisclearwarpageisthemainproblemthatexistsinproductwithshellfeature.Therefore,themainpurposeoftheprod-developmentistodesignaplasticpartfordeterminingeffectivefactorsinthewarpageproblemofaninjection-partwithathinshell.Thewarpagetestingspecimenisdevelopedfromthinplastics.Theoveralldimensionsofthespecimenweremminlength,50mminwidthand1mminthickness.Theusedforproducingthewarpagetestingspecimenasacrylonitrilebutadienestylene(ABS)andtheinjectiontimeandpressurewere210C,3sand60MPa,vely.Fig.1showsthewarpagetestingspecimenpro-DesignofplasticinjectionmouldforwarpagespecimenThissectiondescribesthedesignaspectsandotherconsid-involvedindesigningthemouldtoproducewarpagespecimen.ThematerialusedforproducingtheplasticFig.1.Warpagetestingspecimenproduced.imumbasefittedlosionsha(reactiontherespectionspacewithTherefore,TMouldComponentsTCaCoreSideEjectorEjectorBottomTechnology171(2006)259267mouldforwarpagetestingspecimenwasAISI1050steel.Fourdesignconceptshadbeenconsideredindesigningofmouldincluding:i.Three-platemould(Concept1)havingtwopartinglinewithsinglecavity.Notapplicableduetohighcost.ii.Two-platemould(Concept2)havingonepartinglinewithsinglecavitywithoutgatingsystem.Notapplicableduetolowproductionquantityperinjection.Two-platemould(Concept3)havingonepartinglinewithdoublecavitieswithgatingandejectionsystem.Notapplicableasejectorpinsmightdamagetheproductastheproductistoothin.v.Two-platemould(Concept4)havingonepartinglinewithdoublecavitieswithgatingsystem,onlyusedspruepulleractasejectortoavoidproductdamageduringejection.Indesigningofthemouldforthewarpagetestingspec-thefourthdesignconcepthadbeenapplied.Variousconsiderationshadbeenappliedinthedesign.Firstly,themouldwasdesignedbasedontheplatendimen-oftheplasticinjectionmachineused(BOY22D).Therealimitationofthemachine,whichisthemaximumareaofplatenisgivenbythedistancebetweentwotiebars.distancebetweentiebarsofthemachineis254mm.themaximumwidthofthemouldplateshouldexceedthisdistance.Furthermore,4mmspacehadbeenedbetweenthetwotiebarsandthemouldformouldandhandlingpurposes.Thisgivesthefinalmax-widthofthemouldas250mm.Thestandardmouldwith250mm250mmisemployed.ThemouldbaseistothemachineusingMatexclampattheupperrightandwerleftcornerofthemouldbaseormouldplaten.Dimen-ofotherrelatedmouldplatesareshowninTable1.Themouldhadbeendesignedwithclampingpressurevingclampingforcehigherthantheinternalcavityforceforce)toavoidflashingfromhappening.Basedonthedimensionsprovidedbystandardmouldset,widthandtheheightofthecoreplateare200and250mm,vely.Thesedimensionsenableddesignoftwocavitiescoreplatetobeplacedhorizontallyasthereisenoughwhilethecavityplateisleftemptyanditisonlyfixedspruebushingforthepurposeoffeedingmoltenplastics.itisonlyonestandardpartinglinewasdesignedatable1platesdimensions.Size(mm)widthheightthicknessopclampingplate25025025vityplate20025040plate20025040plate/supportplate3725070-retainerplate12025015plate12025020clampingplate25025025Processingthereleasedopening.islandonlywforrunneringcase.moretype.Thisthediameterorsametheairandflashinginorthatoccurring.caecacientshocoretheFig.2.Cavitylayoutwithairventsandcoolingchannels.plate.Thespruepullerlocatedatthecenterofcoreplatenotonlyfunctionsasthepullertoholdtheproductinpositionwhenthemouldisopenedbutitalsoactsasejectortopushtheproductoutofthemouldduringejectionstage.Noaddi-tionalejectorisusedorlocatedatproductcavitiesbecausetheproductproducedisverythin,i.e.1mm.Additionalejec-torintheproductcavityareamightcreateholeanddamagetotheproductduringejection.Finally,enoughtoleranceofdimensionsisgivenconsid-erationtocompensateforshrinkageofmaterials.Fig.3shows3DsolidmodelingaswellasthewireframemodelingofthemoulddevelopedusingUnigraphics.S.H.Tangetal./JournalofMaterialssurfaceoftheproduct.TheproductandtherunnerwereinaplanethroughthepartinglineduringmouldStandardorsidegatewasdesignedforthismould.Thegatelocatedbetweentherunnerandtheproduct.Thebottomofthegatewasdesignedtohave20slantingandhas0.5mmthicknessforeasyde-gatingpurpose.Thegateasalsodesignedtohave4mmwidthand0.5mmthicknesstheentranceofmoltenplastic.Inthemoulddesign,theparaboliccrosssectiontypeofwasselectedasithastheadvantageofsimplermachin-inonemouldhalfonly,whichisthecoreplateinthisHowever,thistypeofrunnerhasdisadvantagessuchasheatlossandscrapcomparedwithcircularcrosssectionTblemwasreducedbydesigninginsuchawaythatrunnerisshortandhaslargerdiameter,whichis6mmin.Itisimportantthattherunnerdesigneddistributesmaterialmoltenplasticintocavitiesatthesametimeunderthepressureandwiththesametemperature.Duetothis,cavitylayouthadbeendesignedinsymmetricalform.Anotherdesignaspectthatistakenintoconsiderationwasventdesign.Thematingsurfacebetweenthecoreplatethecavityplatehasveryfinefinishinginordertopreventfromtakingplace.However,thiscancauseairtotrapthecavitywhenthemouldisclosedandcauseshortshotincompletepart.SufficientairventwasdesignedtoensureairtrapcanbereleasedtoavoidincompletepartfromThecoolingsystemwasdrilledalongthelengthofthevitiesandwaslocatedhorizontallytothemouldtoallowvencooling.Thesecoolingchannelsweredrilledonbothvityandcoreplates.Thecoolingchannelsprovidedsuffi-coolingofthemouldinthecaseofturbulentflow.Fig.2wscavitylayoutwithairventsandcoolingchannelsonplate.Inthismoulddesign,theejectionsystemonlyconsistsofejectorretainerplate,spruepullerandalsotheejector3.3.1.testingrun.shortairFig.3.3DsolidmodelingandwireframeTechnology171(2006)259267261ResultsanddiscussionResultsofproductproductionandmodificationFromthemoulddesignedandfabricated,thewarpagespecimensproducedhavesomedefectsduringtrialThedefectsareshortshot,flashingandwarpage.Theshotissubsequentlyeliminatedbymillingofadditionalventsatcornersofthecavitiestoallowairtrappedtomodelingofthemould.262Processingescape.packingbyinjectionitylittletheeliminate3.2.oftionthedirectedthe35mensureselectedingfiniteandcoreformed.Fig.5.Modelforthermalanalysis.TMaterialCarbonDensityYPoissonYTThermalConductiSpecificS.H.Tangetal./JournalofMaterialsFig.4.Extraairventstoavoidshortshot.Meanwhile,flashingwasreducedbyreducingthepressureofthemachine.Warpagecanbecontrolledcontrollingvariousparameterssuchastheinjectiontime,temperatureandmeltingtemperature.Afterthesemodifications,themouldproducedhighqual-warpagetestingspecimenwithlowcostandrequiredfinishingbyde-gating.Fig.4showsmodificationsofmould,whichismachiningofextraairventsthatcanshortshot.DetailanalysisofmouldandproductAfterthemouldandproductsweredeveloped,theanalysismouldandtheproductwascarriedout.Intheplasticinjec-mouldingprocess,moltenABSat210Cisinjectedintomouldthroughthespruebushingonthecavityplateandintotheproductcavity.Aftercoolingtakesplace,productisformed.Onecycleoftheproducttakesaboutsincluding20sofcoolingtime.Thematerialusedforproducingwarpagetestingspeci-wasABSandtheinjectiontemperature,timeandpres-were210C,3sand60MParespectively.ThematerialforthemouldwasAISI1050carbonsteel.Propertiesofthesematerialswereimportantindetermin-temperaturedistributioninthemouldcarriedoutusingelementanalysis.Table2showsthepropertiesforABSAISI1050carbonsteel.ThecriticalpartofanalysisformouldisonthecavityandplatebecausethesearetheplacewheretheproductisTherefore,thermalanalysistostudythetemperaturedistribperformedcalled(2D)ofmodelingsidetogetheranalysisandelementresponsedurationanalysisBasicallythethethe3.3.analysistimeable2propertiesformouldandproductSteel(AISI1050),mould,7860kg/m3oungsmodulus,E20