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第1页共25页INJECTIONMOLDINGGUIDEINTRODUCTIONOBJECTIVETHISDOCUMENTPROVIDESGUIDELINESFORPARTDESIGN,MOLDDESIGNANDPROCESSINGOFSTYRENICBLOCKCOPOLYMERSBCTPESTHEGLSPRODUCTFAMILIESTHATINCLUDESTYRENICTPESAREKRATONCOMPOUNDS,DYNAFLEXTPECOMPOUNDSANDVERSAFLEXTPEALLOYSSBCRHEOLOGYONEMAJORCHARACTERISTICOFSBCSISTHATTHEYARESHEARINGDEPENDENTAMATERIALISSHEARDEPENDENTWHENITSVISCOSITYISHIGHERATLOWSHEARRATESSUCHASEXTRUSIONANDLOWERATHIGHSHEARRATESASININJECTIONMOLDINGTHEREFORE,SBCCOMPOUNDSWILLFLOWMOREEASILYINTOTHINAREASOFTHEMOLDATHIGHSHEARRATESTHESHEARTHINNINGBEHAVIOROFSBCSSHOULDBECONSIDEREDWHENDESIGNINGINJECTIONMOLDSANDALSOWHENSETTINGMOLDCONDITIONSDURINGPROCESSING第2页共25页FIGURE1THEEFFECTOFSHEARRATEONTHEVISCOSITYOFGLSSTYRENICTPECOMPOUNDSMEASUREDAT390F200CTOOBTAININFORMATIONREGARDINGTHEVISCOSITYOFANINDIVIDUALGRADE,REFERTOTHEPRODUCTTECHNICALDATASHEET,AVAILABLEATWWWGLSCORPORATIONCOMORCONTACTYOURGLSREPRESENTATIVEPARTDESIGNGENERALPARTDESIGNCONCEPTSWHENDESIGNINGATPEPART,THEREAREAFEWGENERALRULESTOFOLLOWTHEPARTWALLTHICKNESSSHOULDBEASUNIFORMASPOSSIBLETRANSITIONSFROMTHICKTOTHINAREASSHOULDBEGRADUALTOPREVENTFLOWPROBLEMS,BACKFILLS,ANDGASTRAPSTHICKSECTIONSSHOULDBECOREDOUTTOMINIMIZESHRINKAGEANDREDUCEPARTWEIGHTANDCYCLETIMERADIUS/FILLETALLSHARPCORNERSTOPROMOTEFLOWANDMINIMIZENOFILLAREASDEEPUNVENTABLEBLINDPOCKETSORRIBSSHOULDBEAVOIDEDAVOIDTHINWALLSTHATCANNOTBEBLOWNOFFTHECORESBYAIRASSISTEJECTIONLONGDRAWSWITHMINIMUMDRAFTMAYAFFECTEASEOFEJECTIONFLOWLENGTHANDWALLTHICKNESSTHEMAXIMUMACHIEVABLEFLOWLENGTHISDEPENDENTONTHESPECIFICMATERIALSELECTED,THETHICKNESSOFTHEPART,ANDPROCESSINGCONDITIONSGENERALLY,GLSCOMPOUNDSWILLFLOWMUCHFURTHERINTHINNERWALLSTHANOTHERTYPESOFTPESTHEFLOWTOTHICKNESSRATIOSHOULDBE200MAXIMUMHOWEVERTHISISDEPENDENTONTHEMATERIALANDTHEPARTDESIGNHIGHFLOWGLSTPECOMPOUNDSSUCHASVERSALLOYHAVEBEENUSEDSUCCESSFULLYTOFILLFLOWRATIOSUPTO400第3页共25页THEMEASUREMENTOFSPIRALFLOWOFFERSACOMPARATIVEANALYSISOFAMATERIALSABILITYTOFILLAPARTTHESPIRALFLOWTESTISPERFORMEDBYINJECTINGAMATERIALINTOASPIRALMOLDSIMILARTOARIBBONFORMEDINTOASPIRALTHEDISTANCETHEMATERIALFLOWSISMEASUREDININCHESINTHISCASE,THESPIRALFLOWTESTWASCONDUCTEDUSINGTWODIFFERENTINJECTIONSPEEDS3IN/SECAND5IN/SECTHETYPICALSPIRALFLOWLENGTHSFORTHEVARIOUSGLSPRODUCTFAMILIESARESUMMARIZEDINTABLE1WITHSPECIFICCOMPOUNDS,FLOWLENGTHSOFUPTO40INCHESAT5IN/SECINJECTIONSPEEDAREPOSSIBLETABLE1TYPICALSPIRALFLOWLENGTHSFORGLSCOMPOUNDSFLOWLENGTH,INSERIES3IN/SEC5IN/SECDYNAFLEXD13151820DYNAFLEXG12221830VERSAFLEX9161326SPIRALFLOWTESTSPERFORMEDUSING00625INTHICKNESSAND0375INWIDTHCHANNELAT400FFORSPIRALFLOWINFORMATIONABOUTASPECIFICGRADEORADDITIONALDETAILSABOUTTHESPIRALFLOWTESTPROCEDURE,PLEASEREFERTOTHEGLSCORPORATIONTPETIPSSHEET7,AVAILABLEATWWWGLSCORPORATIONCOMORBYCONTACTINGYOURGLSREPRESENTATIVEUNDERCUTSTHEFLEXIBILITYANDELASTICNATUREOFTPESALLOWSFORTHEINCORPORATIONOFUNDERCUTSINTOTHEPARTDESIGNBECAUSEOFTHEIREXCELLENTRECOVERYCHARACTERISTICS,GLSCOMPOUNDSARECAPABLEOFBEINGSTRETCHEDANDDEFORMED,ALLOWINGTHEMTOBEPULLEDFROMDEEPUNDERCUTSFIGURE2IFBOTHINTERNALANDEXTERNALUNDERCUTSAREPRESENTONTHESAMEPART,SLIDESORCORESPLITSMAYBENECESSARYPARTSWITHINTERNALUNDERCUTSEGBULBSHAPEDPARTSMAYBEAIREJECTEDFROMTHECOREBYUSEOFAPOPPETVALVEINTHECOREMINORPERMANENTELONGATION38DUETODEFORMATIONMAYOCCURDURINGEJECTION第4页共25页FIGURE2ANEXAMPLEOFTPEPARTSWITHLARGEUNDERCUTSGATEANDKNITLINELOCATIONSTHEPRODUCTENGINEERSHOULDINDICATETHEAREASOFTHEPARTTHATARECOSMETICANDTHOSETHATAREFUNCTIONALANDINCLUDETHISINFORMATIONONTHEDRAWINGTHISWILLHELPTHEMOLDDESIGNERTODETERMINETHEALLOWABLEGATEANDKNITLINELOCATIONSANISOTROPYTHERMOPLASTICMATERIALSTHATHAVEDIFFERENTPROPERTIESINTHEFLOWDIRECTIONVERSUSTHECROSSFLOWDIRECTION90PERPENDICULARTOTHEFLOWDIRECTIONARECHARACTERIZEDAS“ANISOTROPIC”MATERIALSPROPERTIESTHATMAYBEAFFECTEDARESHRINKAGEANDTENSILEPROPERTIESANISOTROPYISCAUSEDWHENTHEPOLYMERCHAINSORIENTINTHEDIRECTIONOFFLOW,WHICHLEADSTOHIGHERPHYSICALPROPERTIESINTHEFLOWDIRECTIONWALLTHICKNESS,INJECTIONSPEED,MELTTEMPERATUREANDMOLDTEMPERATUREAREAFEWVARIABLESTHATAFFECTANISOTROPYDEPENDINGONTHEPROCESSINGCONDITIONSANDMOLDDESIGN,MOSTGLSSTYRENICTPECOMPOUNDSEXHIBITADEGREEOFANISOTROPYSHRINKAGEDUETOTHEIRANISOTROPICNATURE,GLSSTYRENICTPECOMPOUNDSSHRINKMOREINTHEFLOW第5页共25页DIRECTIONTHANINTHECROSSFLOWDIRECTIONGENERALLY,SEBSCOMPOUNDSHAVEHIGHERSHRINKAGEANDAREMOREANISOTROPICTHANSBSCOMPOUNDSTYPICALSHRINKAGEVALUESFORSEBSBASEDCOMPOUNDSARE1325,WHEREASTHOSEFORSBSBASEDCOMPOUNDSARE0305SOFTERSEBSCOMPOUNDSBELOW30SHOREAWILLSHRINKMORETHANHARDER6MATERIALSSOMEGRADES,SUCHASDYNAFLEXG7700,G7800,ANDG7900SERIESCONTAINFILLER,WHICHREDUCESTHEIRSHRINKAGETHESHRINKAGEVALUESREPORTEDBYGLSAREDETERMINEDUSINGA0125”THICKPLAQUEITSHOULDBENOTEDTHATSHRINKAGEISNOTANEXACTNUMBER,BUTARANGEVALUETHISRANGECANBEAFFECTEDBYTHEPARTWALLTHICKNESS,MELTTEMPERATURE,MOLDTEMPERATURE,INJECTIONSPEED,HOLD/PACKPRESSURESANDALSOTHETIMEBETWEENMOLDINGANDMEASURINGASARESULT,PROTOTYPINGISSTRONGLYRECOMMENDEDFORPARTSWITHCLOSETOLERANCESTOBETTERQUANTIFYTHEREALISTICSHRINKAGEOFASPECIFICGRADEOFMATERIALINASPECIFICAPPLICATIONFORSHRINKAGEVALUESFORSPECIFICGRADES,PLEASEREFERTOTHEPRODUCTTECHNICALDATASHEET,AVAILABLEATWWWGLSCORPORATIONCOMORBYCONTACTINGYOURGLSREPRESENTATIVEMOLDDESIGNTYPESOFMOLDSGLSSBCCOMPOUNDSCANBEMOLDEDINTWOANDTHREEPLATEMOLDSBOTHCONVENTIONALANDHOTRUNNERTOOLDESIGNSHAVEBEENUSEDWITHGLSCOMPOUNDSSELFINSULATINGHOTRUNNERTOOLDESIGNSARENOTRECOMMENDEDDUETOTHEPOTENTIALFORMATERIALDEGRADATIONINTHESTAGNATIONZONESTWOSHOTMOLDSANDINSERTMOLDSCANALSOBEUSEDIFAFAMILYMOLDISREQUIRED,THECAVITYVOLUMESSHOULDBESIMILAR,OTHERWISEOVERPACKINGANDFLASHINGOFTHESMALLERCAVITYMAYOCCURSTEELSELECTIONGLSSTYRENICTPESAREGENERALLYNONABRASIVEANDNONCORROSIVETHESELECTIONOFTOOLSTEELWILLDEPENDONTHEQUANTITYANDQUALITYOFPARTSTOBEPRODUCEDFORHIGHVOLUMEPRODUCTION,THEINITIALEXPENSEOFQUALITYTOOLINGISASOUNDINVESTMENTAWIDEVARIETYOFTOOLSTEELSAREAVAILABLEFORINJECTIONMOLDCONSTRUCTIONTABLE2LISTSTHEPROPERTIESOFCOMMONTOOLSTEELSANDTHETYPICALMOLDCOMPONENTSFORWHICHTHEYAREUSEDSOFTMETALS,SUCHASALUMINUMANDBERYLLIUMCOPPER,CANBEUSEDFORPROTOTYPEPARTSORSHORTPRODUCTIONRUNSUPTO10,000PARTS第6页共25页TABLE2TYPICALTOOLSTEELFORINJECTIONMOLDCONSTRUCTIONSTEELTYPESTEELPROPERTIESMOLDCOMPONENTP20PREHARDENED,MACHINESWELL,HIGHCARBON,GENERALPURPOSESTEELDISADVANTAGEMAYRUSTIFIMPROPERLYSTOREDMOLDBASES,EJECTORPLATES,ANDSOMECAVITIESIFNICKELORCHROMEPLATEDTOPREVENTRUSTH13GOODGENERALPURPOSETOOLSTEELCANBEPOLISHEDORHEATTREATEDBETTERCORROSIONRESISTANCECAVITYPLATESANDCOREPLATESS7GOODHIGHHARDNESS,IMPROVEDTOUGHNESS,GENERALPURPOSETOOLSTEELMACHINESWELL,SHOCKRESISTANT,POLISHESWELLDISADVANTAGEHIGHERCOSTCAVITYPLATES,COREPLATESANDLAMINATES,ASWELLASTHINWALLSECTIONSA2GOODHIGHTOUGHNESSTOOLSTEELHEATTREATSANDPOLISHESWELLEJECTORPINS,EJECTORSLEEVES,ANDEJECTORBLADESD2VERYHARD,HIGHWEARCHARACTERISTICS,HIGHVANADIUMCONTENT,SOMEWHATBRITTLEDISADVANTAGEDIFFICULTTOMACHINEGATEBLOCKS,GIBEPLATESTOPREVENTGALLING,GATEBLOCKSTOPREVENTWEAR420SSTOUGHCORROSIONRESISTANTMATERIALHEATTREATSANDPOLISHESWELLDISADVANTAGEHIGHCOSTCAVITYBLOCKS,EJECTORPINS,SLEEVES,ETCSOMEPARTDESIGNSMAYBENEFITFROMTHEUSEOFHIGHERTHERMALCONDUCTIVITYMATERIALSSUCHASBERYLLIUMCOPPERTHISMATERIALISLESSDURABLETHANSTEELANDMAYHOBORWEARFASTERTHANSTEELIFUSEDATTHEPARTINGLINEBERYLLIUMCOPPERCANBEUSEDFORINSERTS,SLIDESORCORESTOINCREASEHEATTRANSFERRATESANDREDUCECYCLETIMESINCASESWHERETHEREISALONGDRAWCORE,第7页共25页AFOUNTAINTYPEBUBBLERMAYBEBENEFICIALMOLDSURFACETREATMENT,FINISHINGANDTEXTURINGMOSTGLSMATERIALSREPLICATETHEMOLDSURFACEFAIRLYWELLTOPRODUCEAGLOSSYSURFACE,APOLISHEDMOLDISREQUIREDANDANUNFILLEDGRADESHOULDBEUSEDAHIGHLYPOLISHEDTOOLANDATRANSPARENTMATERIALAREREQUIREDTOPRODUCEAPARTWITHGOODCLARITYIFAMATTEFINISHSIMILARTOTHATOFATHERMOSETRUBBERISREQUIRED,AROUGHERMOLDTEXTURESHOULDBEUSEDORAGLSPRODUCTSUCHASGLSVERSALLOYTPVALLOYS,WHICHNATURALLYPRODUCEAMATTESURFACEINGENERAL,ANEDMSURFACEWILLPRODUCEAGOODTEXTUREANDMAYIMPROVERELEASEFROMTHETOOLDURINGPARTEJECTIONMATTESURFACESCANALSOHELPTOHIDEANYFLOWMARKSOROTHERSURFACEDEFECTSVAPORHONING,SANDORBEADBLASTINGANDCHEMICALETCHINGAREALSOUSEDTOPRODUCETEXTUREDSURFACESWITHVARYINGDEGREESOFGLOSSANDAPPEARANCETOAIDINRELEASE,THECAVITYORCOREMAYBECOATEDWITHARELEASECOATINGSUCHASPTFEIMPREGNATEDNICKELAFTERITHASBEENGIVENASANDBLASTOREDMFINISHSPRUEANDSPRUEPULLERDESIGNTHESPRUESHOULDHAVESUFFICIENTDRAFT,FROM1TO3TOMINIMIZEDRAGANDSPRUESTICKINGLONGERSPRUESMAYREQUIREMORETAPER35,ASSHOWNINFIGURE3TYPICALLY,THESPRUEDIAMETERSHOULDBESLIGHTLYLARGERTHANTHENOZZLEDIAMETERANEDMFINISHISACCEPTABLEFORMOSTSTYRENICTPEMATERIALSPERMANENTSURFACELUBRICANTTREATMENTSHAVEALSOBEENUSEDSUCCESSFULLYSPRUEPULLERDESIGNSVARYWITHTHEHARDNESSOFTHEMATERIALTHEDIFFERENTSPRUEDESIGNSPOSSIBLEANDTHEIRRELATIVEDIMENSIONSARESHOWNINFIGURES4THROUGH7INADDITION,TABLE3SHOWSTHETYPICALHARDNESSRANGEFORWHICHAPARTICULARSPRUEDESIGNISAPPLICABLETABLE3TYPICALSPRUEDESIGNSFORVARIOUSHARDNESSVALUESTYPICALTPEHARDNESSRANGEMOSTCOMMONSPRUEPULLERTYPESFIGURE50SHOREATAPERED,PIN,ZTYPE3,4AND64070SHOREAUNDERCUT5540SHOREAPINETREE7HOTSPRUEBUSHINGSANDEXTENDEDNOZZLESMAYALSOBEUSEDWITHGLSCOMPOUNDSINMANYMOLDS,THESPRUEISTHETHICKESTWALLSECTIONINTHEMOLDANDWILLCONTROLTHEMINIMUM第8页共25页COOLINGTIMETHEUSEOFAHOTSPRUE,WHICHMAYBEVIEWEDASANEXTENSIONOFTHEMACHINENOZZLE,CANSOMETIMESREDUCECYCLETIMEEXTENDEDMACHINENOZZLESMAYALSOBEUSEDTOREDUCESPRUELENGTHANDSIZEWHENHOTSPRUESAREUSED,THEMACHINENOZZLETIPSHOULDBEAFREEFLOWNOZZLERATHERTHANAREVERSETIPFIGURE3TAPEREDSPRUEPULLERFIGURE4ZPINSPRUEPULLER第9页共25页FIGURE5UNDERCUTSPRUEPULLER第10页共25页FIGURE6SUCKERPINSPRUEPULLER第11页共25页FIGURE7PINETREESPRUEPULLERCONVENTIONALRUNNERCONFIGURATIONANDDESIGNABALANCEDRUNNERCONFIGURATIONISCRITICALTOACHIEVEUNIFORMPARTQUALITYFROMCAVITYTOCAVITYINABALANCEDRUNNERSYSTEM,THEMELTFLOWSINTOEACHCAVITYATEQUALTIMESANDPRESSURETHERUNNERBALANCECANBEDESIGNEDBYUSINGCOMPUTERMOLDFLOWANALYSISPROGRAMSANDVERIFIEDBYPERFORMINGSHORTSHOTSTUDIESANUNBALANCEDRUNNERMAYRESULTININCONSISTENTPARTWEIGHTSANDDIMENSIONALVARIABILITYTHECAVITYCLOSESTTOTHESPRUEMAYBEOVERPACKEDANDFLASHINGMAYOCCURASARESULTOFOVERPACKING,PARTSMAYALSODEVELOPHIGHMOLDEDINSTRESSES,WHICHLEADTOWARPAGEEXAMPLESOFBALANCEDRUNNERSYSTEMSARESHOWNINFIGURES8AND9第12页共25页FIGURE8EXAMPLEOFBALANCEDSPIDERRUNNERFIGURE第13页共25页9EXAMPLEOFBALANCEDCROSSRUNNERFIGURE10SHOWSDIFFERENTRUNNERCROSSSECTIONSANDTHEIRASSOCIATEDEFFICIENCYFULLROUNDRUNNERSHAVETHELEASTRESISTANCETOFLOWANDSURFACEAREA,ALLOWINGTHEMATERIALTOSTAYMOLTENLONGERTHESECONDMOSTEFFICIENTRUNNERCROSSSECTIONISTHEMODIFIEDTRAPEZOIDTHISRUNNERGEOMETRYMOSTCLOSELYSIMULATESAFULLROUNDRUNNERBUTONLYREQUIRESMACHININGINONLYONEPLATEFIGURE11SHOWSTYPICALBALLCUTTERDIMENSIONSANDTHECORRESPONDINGMODIFIEDTRAPEZOIDRUNNERSIZESFIGURE12ILLUSTRATESTYPICALRUNNERDIMENSIONS第14页共25页FIGURE10TYPICALRUNNERCROSSSECTIONSFIGURE11MODIFIEDTRAPEZOIDRUNNERSIZES第15页共25页FIGURE12RUNNERDESIGNANDDIMENSIONSCOLDSLUGWELLSSHOULDBEUSEDATEACHRUNNERTRANSITIONTURNCOLDSLUGWELLSSERVETOREMOVETHELEADINGEDGEOFTHEMELTTHESLUGWELLASSOCIATEDWITHTHESPRUESHOULDBELARGEENOUGHTOTRAPTHECOLDMATERIALFORMEDINTHEMACHINENOZZLEDURINGTHEMOLDOPENCYCLETYPICALSLUGWELLDIMENSIONSAREAPPROXIMATELY15TO20TIMESTHEDIAMETERORWIDTHOFTHEFEEDRUNNERRUNNERKEEPERSRUNNERKEEPERSORSUCKERPINSPROVIDEUNDERCUTSTOKEEPTHERUNNERONTHEDESIREDPLATEBUTSHOULDNOTRESTRICTMATERIALFLOWTHROUGHTHERUNNERFIGURES8AND9SHOWTYPICALLOCATIONSFORRUNNERKEEPERSANDSUCKERPINSFIGURE13ILLUSTRATESANEXAMPLEDESIGNOFARUNNERKEEPER第16页共25页FIGURE13RUNNERKEEPERDESIGNGATEDESIGNANDLOCATIONMOSTCONVENTIONALGATINGTYPESARESUITABLEFORPROCESSINGGLSSTYRENICTPECOMPOUNDSTHETYPEOFGATEANDTHELOCATION,RELATIVETOTHEPART,MAYAFFECTTHEFOLLOWINGPARTPACKINGGATEREMOVALORVESTIGEPARTCOSMETICAPPEARANCEPARTDIMENSIONSINCLUDINGWARPAGE第17页共25页THETYPEOFGATESELECTEDISDEPENDENTONBOTHPARTANDTOOLDESIGNTHEGATELOCATIONISEQUALLYIMPORTANTTOPREVENTTHECHANCESOFJETTING,LOCATETHEGATEENTRANCEINANAREAWHERETHEFLOWWILLIMPINGEONACAVITYWALLFORAUTOMATICALLYDEGATINGTOOLS,THEHIGHLYELASTICNATUREOFSOFTERTPESMAKESSUBMARINEGATEDESIGNSORTHREEPLATETOOLSWITHSELFDEGATINGDROPSMOREDIFFICULTHIGHERHARDNESSANDFILLEDGRADESUSUALLYHAVELOWERULTIMATEELONGATIONANDTHEREFOREAREMOREEASILYDEGATEDTOASSURETHEGATESWILLBREAKATASPECIFICLOCATION,THEYSHOULDHAVEASHORTLANDLENGTHTOCREATEAHIGHSTRESSCONCENTRATIONTAB/EDGEGATESTABOREDGEGATESFIGURE14MOSTCOMMONLYUTILIZEACONVENTIONALSPRUEANDCOLDRUNNERSYSTEMTHEYARELOCATEDALONGTHETOOLPARTINGLINEASMALLUNDERCUTCANBEPLACEDWHERETHEGATEMEETSTHEPARTTOMINIMIZEGATEVESTIGECAUSEDBYDEGATINGADVANTAGESOFEDGEGATESAREEASEOFFABRICATION,MODIFICATIONANDMAINTENANCETHE14GATEDEPTHDSHOULDBE1530OFTHEWALLTHICKNESSATTHEGATEENTRANCECOMMONPRACTICEISTOSTART“STEELSAFE”AGOODSTARTINGPOINTFORTHEGATEWIDTHSHOULDBE1015TIMESTHEGATEDEPTHTHEGATELANDSHOULDBEEQUALTOORSLIGHTLYLONGERTHANGATEDEPTHTHEGATESIZEMAYALSODEPENDONTHEPARTVOLUMETHEGATEAREAMAYBEINSERTEDTOFACILITATEGATEMAINTENANCEORMODIFICATIONFIGURE14TABOREDGEGATEFIGURE15SUBMARINEGATE第18页共25页SUBMARINEORTUNNELGATESARESELFDEGATINGDURINGPARTEJECTION,THETOOLSTEELSEPARATESTHEPARTANDTHERUNNERFIGURE15SHOWSATYPICALDESIGNOFASUBMARINEGATECASHEWTYPESUBMARINEGATESSHOULDNOTBEUSEDFORMEDIUMTOSOFTHARDNESSCOMPOUNDSDUETOTHEIRHIGHCOEFFICIENTOFFRICTIONANDHIGHELONGATIONFANGATESAFANGATEISASTREAMLINEDVARIATIONOFATABGATEFIGURE16THEFANGATEDISTRIBUTESMATERIALINTOTHECAVITYMOREEVENLYTHUSITISNORMALLYUSEDINPARTSTHATREQUIREAHIGHDEGREEOFFLATNESSANDABSENCEOFFLOWLINESITALSOMINIMIZESTHEPOSSIBILITYOFGATEPUCKERORPARTWARPAGEFIGURE16FANGATESPRUEORDIRECTGATE第19页共25页THESPRUEORDIRECTGATEISOFTENUSEDONPROTOTYPEPARTSBECAUSEITISINEXPENSIVETHISTYPEOFGATINGISNOTRECOMMENDEDFORGLSSTYRENICCOMPOUNDSBECAUSEOFTHEIRHIGHELONGATIONINADDITION,THESPRUEWILLNEEDTOBETRIMMEDTHUSAPPEARANCEQUALITYOFTHEPARTISUSUALLYPOORIFSPRUEGATINGISSELECTED,CARESHOULDBETAKENTOKEEPBOTHTHESPRUELENGTHANDDIAMETERASSHORTANDSMALLASPOSSIBLEDIAPHRAGMGATETHEDIAPHRAGMGATEISUSEDTOMAINTAINTHECONCENTRICITYOFROUNDPARTSITALLOWSEVENFLOWINTOTHECAVITYANDMINIMIZESTHEPOTENTIALFORKNITLINESDUETOANISOTROPICSHRINKAGE,FLATROUNDPARTSUSINGCENTERORDIAPHRAGMGATINGMAYNOTLAYFLATARINGGATEMAYALSOBEUSEDONTHEOUTSIDEOFACIRCULARPARTTABLE4COMPARESTHEADVANTAGESANDDISADVANTAGESOFTHEVARIOUSGATETYPESDISCUSSEDINTHISSECTIONTABLE4ADVANTAGESANDDISADVANTAGESOFVARIOUSGATETYPESGATETYPEADVANTAGEDISADVANTAGEEDGE/TAB/FANGATEAPPROPRIATEFORFLATPARTSEASYTOMODIFYPOSTMOLDGATE/RUNNERREMOVALISDIFFICULTPOORGATEVESTIGESUBMARINEGATEAUTOMATICGATEREMOVALMINIMALGATEVESTIGEMOREDIFFICULTTOMACHINEDIAPHRAGMGATECONCENTRICITYAPPROPRIATEFORROUNDPARTSNOKNITLINESSCRAPPOSTMOLDINGGATEREMOVALPINGATE3PLATEAUTOMATICGATEREMOVALREQUIRESFLOATERPLATE第20页共25页MINIMALGATEVESTIGELOCALIZEDCOOLINGMORESCRAPHIGHERTOOLCOSTVALVEGATEHOTRUNNERSYSTEMSMINIMALGATEVESTIGEPOSITIVESHUTOFFMINIMIZESPOSTPACKHIGHERTOOLCOSTHIGHERMAINTENANCEONLYFORHOTRUNNERSYSTEMSGATELOCATIONSTYRENICTPECOMPOUNDSAREANISOTROPIC,THUSTHEYHAVEDIFFERENTPHYSICALPROPERTIESINTHEFLOWDIRECTIONVERSUSTHECROSSFLOWDIRECTIONDEPENDINGONTHEPRODUCTSINTENDEDUSAGE,THESEPROPERTYDIFFERENCESCOULDBECRITICALTOTHEPERFORMANCEOFTHEFINALPARTASARESULT,THEANISOTROPICNATUREOFTHESTYRENICTPENEEDSTOBETAKENINTOCONSIDERATIONWHENDETERMININGTHEGATELOCATIONONTHEPARTTHEMATERIALFLOWMAYBEESTIMATEDBYEYEORBYUSINGFLOWANALYSISPROGRAMSFORHIGHERSHRINKAGEGRADES,THEPARTMAYSHRINKNEARTHEGATE,WHICHCAUSES“GATEPUCKER”IFTHEREISAHIGHMOLDEDINSTRESSATTHEGATEPARTSSHAPEDLIKEAHANDLEGRIPMAYWARPTOWARDTHEGATESIDEOFTHEPARTLOCATINGTHEGATEATTHETOPOFTHEPARTMINIMIZESTHISPROBLEMUSINGTWOGATESONOPPOSITESIDESOFTHE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