外企结构工程师资料.docx
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外企结构工程师资料.docx
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外企结构工程师资料
Boss
Thebossshapeusedtoinstallascrewtoparts.
e.g.forajointofaplasticmodel
CavityandCore
Inthischapter,youwilllearnaboutthecavityandthecore.Youwilllearnthetypesofinsertsandtheirprocessmethods,position,materialanddifferentusagedependingonproductionquantitypermoldingcycle.
Inpreviouschapters,welearnedthatmoltenplasticwouldbeinjectedintothemold.Themoldiscomposedofacavityandacore.Thecavityisaconcavecavityplate.Thecoreisaconvexcoreplate.Wepreviouslystatedthatmoltenplasticisinjectedintothecavity.Actually,itisinjectedintothegapbetweenthecavityandthecore.
CavityandCore
Cavityandcorearecategorizedintointegralmethodandinsertmethod.Themethodisdeterminedbythepartquantityandthemoldingshape.
∙Integralmethod
Thecavityandthecorehavethesameshapeasthepart.
∙Insertmethod
Anotherpartisinsertedintothemoldtogetthefinalshapeofthepart.
oUsingamaterialdifferentfromthatofthemoldimprovesabrasionresistanceormakestemperaturecontroleasier.
oItisdifficulttodirectlymachineamoldwhencomplicatedshapesormultipleshapesarealigned,whereasattachinganinsertasaseparatepartmakestheprocesseasier.
oItispossibletochangethematerialofthepartthatissubjecttodamageduetorepeatedmoldingwithaspecialmaterialorreplaceonlythedamagedpart.
Aninsertattachedtothecavitysideiscalledacavityinsert.Aninsertthatisattachedtothecoresideiscalledacoreinsert.
Thefollowingfactorsdeterminewhetheraninsertisused.
MoldCondition
MoldingCondition
MoldMaterial
Singlepart
Multiplepart
SpecialShape
S55C
Integral
Coreinsert
Coreinsert,Cavityinsert
SpecialSteel
Coreinsert,Cavityinsert
Theshapeofapartdetermineswhetheraninsertisattachedtothecavity,thecore,orboth.
Also,theinsertmethodisusedtoprocessthecavityandthecorewithspecialmaterials,dependingonthemoldingmaterial.
TypesofInsert
AnInsertiscategorizedintothefollowingtypes.
∙Flangeinsert
Iftheshapeofthepartisround,aflangeinsertisused.Theinsertdoesnotneedabaffle,soonlyaflangeisneededtopreventaninsertfromlifting.
Aroundshapeiseasytoprocesswhenmakinganinsertoramold.
Also,aflangeisattachedonlytothelongsidewhenusingasquareflangeinsert.
Asinthefigure,ifH>L.,attachaflangetotheLdirection,andifH ∙PocketInsert Apocketinsertisgenerallyusedwhentheshapeofthepartissquare. Apocketinsertisattachedtothemoldbyanattachingbolt,asshownbelow. MakingInserts Whenmakinganinsertoramold,becarefulwiththeaccuracyofmeasurementsothattheinsertandthemoldcanbeattachedwithoutagap. Ifthemeasurementisnotaccurate,aninsertcannotbeattachedtoamold,oraburrmayresultduetothebiggap,andthepartwillnotlookgood. Attachaninsertandamoldbyprocessingasfollows. Foraflangeinsert: Astheinsertismountedthroughthemold,chamfersareappliedtothemoldsidewhosecornerwillbeconvex. Forapocketinsert: Astheinsertismountedinthemold,chamfersareappliedtothemoldsidewhosecornerwillbeconvex. Whenmakinganinsertoramold,chamfersareappliedtoitscorners. ThecornerscannotbeprocessedatarightangleduetotheedgeRofcutwareorreliefofcutware,evenwhenaninsertoramoldismadeaccuratelyasmeasured.Ifaninsertisattachedtoamoldwithoutchamfering,thecornerwillinterfereandpreventtheinsertfrombeingattachedattheproperposition. Also,anexcessivegapbetweenaninsertandamoldwillcausepartdefects.Therefore,besuretofulfillthematchingrequirement(positionaltoleranceofholeandaxis)thatisregulatedbytheJapaneseIndustrialStandard(JIS). Thechartbelowshowsthetypicalmatchingtolerances. Holetolerance(φD) Axistolerance(φd) RegularProcess H7 h6 PreciseProcess H6 h5 Inthechartabove,theholetolerance(φD)referstothetoleranceoftheholesize(φD)ofthemoldintheabovefigure,andtheaxistolerance(φd)referstothetoleranceoftheaxissize(φd)oftheinsertintheabovefigure. Asthematchingtolerancevariesdependingonouterdiameterofholeoraxisortypesofmatching(gapmatching,midpointmatching,ordrawmatching),refertotheJISreferencechart. PositionofInsert Thepositionofaninsertisdeterminedbypartquantityortypeofinsert. Thepositionsofinsertareasfollows: Whenaflangeinsertisused: Process Theinsertisattacheddirectlytothemold,Boththeinsertandthemoldneedtobemadeprecisely. Installation Itiseasytopositiontheinserttoamoldbecausetheinsertismadeprecisely. Whenapocketinsertisused: Process Themoldismadewiththemeasurementofaninsert+arunner. Evenifthereisanerrorinthemoldmeasurement,themoldiseasilyprocessedbecausearunner(madebyaseparatepart)isusedforadjustment. Installation Itisdifficulttopositiontheinsertbecauseitisattachedwiththerunnerinsertedin-betweenandameasurementerrorcaneasilyoccur. Whenapocketinsertisused: Process Themoldcanbeprocessedeasilybecauseawedgemeasurementisusedtoadjust,evenifthereisanerrorinamoldmeasurement. Installation Becauseaninsertisattachedsetout,anerrorbyattachmentoccurslessfrequentlyandinsertpositioningiseasy. CorePlate/CavityPlate Asteeldevicetomoldamoldingmaterialintoacertainshape.Thesectionthatisengagedinopening/closingmovementiscalledacoreplate,andthesectionthatisnotiscalledacavityplate.Generally,thefrontsideofapartisacavityplateandtherearsideisacoreplate. Thecoreplateleavesatraceonapart,becauseithasanejectorpintopushthepart. Thecavityplatehasaspruebush,whichistheentranceformoltenplastic. Cavity Thegapgeneratedwhereapartismoldedinthemold. Itsometimesreferstotheconcavepartofthemoldandusuallyisprocessedonthecavityplate. Insert(Core) Apartofamoldtoshapeamoldingmaterial Itismountedinasquareorroundholeonaretainerplateofamold. Abrasionresistanceisrequiredforaninsertbecauseitconstantlyreceivesfrictiongeneratedbyheatorflowofmoltenplasticduringmolding,andthus,ahighqualitymaterialisusedforaninsert.Moldingismadeeasierforacomplicatedshapeortherepetitionofthesameshapewithinsertswhicharesmallandlight. Theinsertinstalledonthecavitysideiscalledacavityinsert,andtheoneinstalledonthecoresideiscalledacoreinsert.Thepartshapeandmaterialdetermineswhichinserttouse. Runner Achannelthroughwhichmoltenplasticisguidedfromthespruebushintothecavityofthemold.Itssizeorshapeisdeterminedbythetypeofmoldingmaterial. Alargerunnerallowsbetterflowofthemoldingmaterial;however,coolingtakeslonger.Thus,arunnerisnormallymadesmallerthanthesectionofapartandgraduallymadebiggerwhiletesting.Inanycase,arunnershouldbebasicallysmallerthanthethickestareaofthepart. CoreStopBlock Apartthatdeterminesthepositionwhereaslidecoreretreatswhenopeningthemold. Inadditiontothecorestopblock,aballplunger,areturnspring,orastoppincanalsobeused. LockingBlock Ablocktopushaslidecorethatisejectedbackbyinjectionpressure. AngleofAngularPinandAngleofAngledSideofLockingBlock Angleofangularpin: α Angleofsideoflockingblock: β (1)Ifα>β: Iftheangleofanangularpinislargerthantheangledsideofalockingpin,thetiltedsidesofaslidecoreandthelockingblockmaycollidewitheachother,possiblydamagingthemold. (2)Ifα=β: Iftheangleofanangularpinandatiltangleofalockingblockareequal,theslidecorecannotbelowered,sinceitispusheddownbyaspring,whichputsthelockingblockovertheslidecorefortheclearanceoftheangledholeoftheslidecore. (3)Ifα<β: Sincetheangledsidesoftheslidecoreandthelockingblocktoucheachotheronlywhenthemoldiscompletelyclosed,themovementissmooth. From (1), (2),and(3),theangleoftheangularpinmustbesmallerthantheangleoftheside.Thenormalangleoftheangularpinis12-25degree,andtheangleofthepartingsideisbasicallylargerthanthepinangle. AngularPins Aangledpinusedtoslideaslidecore. Thetiltangleforanangularpinshouldbeunder25degreesatthemaximum. SlideCore Apartthatslidesinwarduponopeningandclosingofthemold. Itworksontheundercutprocessalongwithmoldopening/closingmovementtomoldtheundercutofapart. Thelargertheundercutbecomes,thelongeranangularpinneedstobeandthemorethemovementoftheslidecorewillbe;thereforeitmaynotbeeasilyused. Theslidecoremovestoavoidretreatingbyinjectionpressureatthelockingblockwhenclosingthemoldandatthecorestopblockwhenopeningthemold.Inbetweenthem,anangularpincontrolsthemovementoftheslidecore. CorePushBackSpring Apartusedtoholddownaslidecorewhenamoldisopen. Withoutthis,theslidecoremaybeoutofalignmentwhenthemoldisopen,andalsoanangularpinmaynotgointotheangledholewhenclosingthemold. Itischangeddependingontheslidingdirectionoftheslidecore,suchasup,down,orhorizontal. Undercut Ashapethatpreventsapartfrombeingremovedintheopeningdirectionofam
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