注塑件成型与设计.pptx

InjectionMoldingandDesign注塑成型与设计 InjectionMoldingProcessOverviewPartandToolDesignTerminologyCommonMoldingDefectsMoldedPartDesignBestPractices InjectionMoldingProcessOverview InjectionMoldingProcessOverview Injectionmoldingisusedtoproducemostofourcomplexplasticparts Injectionmoldingisaprocesswhichinvolvesforcingmoltenplasticintoamachinedmoldcavityunderhighpressure InjectionMoldingPress Theinjectionmoldingpressoperationincludesameansto Openandcloseandclamptheinjectionmold Measure melt andinjecttheplasticresin Coolthemoltenplasticinthemold Ejectthefinishedpartfromthemold Computercontrolsystem InjectionMold Theinjectionmoldformsboththeshow A sideandtheback B sideofthepart Theshowsideofthepartisgenerallythecavitysideofthetool andthebacksideisthecoreside Theinterfacebetweenthecavityandcoreisthepartingline Thenumberofcavitiesisthenumberofpartsproducedpercycle InjectionMoldComponents CavityCoreClampPlatesEjectorPlate PinsLiftersSlidesWaterLinesGatesandSpruesHotRunnerSystem etc HotRunnerManifold MultipleValveGates Themanifoldinalargemoldheatsanddeliversthehotplasticfromthemoldingmachinetothegatelocationsonthepart Lifters FormDie LockedFeatures Liftersaremechanismswhichmoveapproximatelyinthedirectionofthemoldopening dieangle Theyareusuallyactivatedbylifterrodsoperatedbytheejectorplate Liftersoftenmoveonanangletothepartduringmoldopeningandejectiontounlockadie lockedfeature MoldOpen MoldClosed DieDirection moldopeningangle Lifter CoreSlides FormDie LockedFeatures Acoreslideisamechanismonthecorewhichmovesnormal 90 todieangledirectiontoformdie lockfeaturesorundercutsinthepartdesign Theslideisactuatedbypins cams orhydraulicorpneumaticcylindersduringandafterthemoldcavityopens SimpleCoreSlideandEjection PlasticPart EjectionPin CoreWithSlide CavityWithHornPin Actually thecavityisstationary andthecoresidemovestoopenthetoolwhenmountedinthemoldingmachine AcceleratingEjectionPin InjectionSprue EjectionwithLifter CavityandCorewithLifterandPin PlasticPart EjectionPin Corewithlifter Cavity TravelingAngledLifterFormsribwithflange InjectionSprue CamOperatedCorePinFormsholeinflange Actually thecavityisstationary andthecoresidemovestoopenthetoolwhenmountedinthemoldingmachine Cam DesignTerminology PartandToolDesignTerminology PartandToolDesignTerminology DieAngles DraftAngles 拔模角 ASurface BSurface etc A面 B面 PartingLines LifterLines 分模线 Doghouses Ribs Flanges安装支座 加强筋 翻边 TrueHoles MoldedHoles 注塑孔 ToolingConsiderations 注塑模考虑 DieAngle PartingLine DieAngle DieVector Moldopeningdirection PartingLine wherethecore cavity andpartmeettogether Part 2cavity Core Cavity DraftAngles Partsmusthaveopendraftanglesinthepartgeometrydesign Partdraftangleismeasuredrelativetothedieopeningangle Ifthereisnodraftangle thepartwillcoolandshrinkontothetoolandwillbedifficultorimpossibletoremovewithoutdamage Wegenerallyuseminimum3degreesdraftperside Moredraftisneededforgrainedsurfaces Cavity A surfacevs Core B surface OriginalPart tooledwrong core cavity Ejectionpinsonshowsurface Asurface RevisedPart eliminatepinsonAsurface Doyouknowthedifference Doesyoursupplierandtoolshop Didyouindicateitclearlyinyourmathdatafile Oops MoldingIssuesandCommonDefects MoldingIssuesandCommonDefects MoldExpansion PartShrinkage Thermoplasticsshrinkastheycoolandsolidifyduringthemoldingprocessandafterpartejection Themoldcavityismachinedlargerthanthefinaldesiredpartsizeinordertocompensateforpartshrinkageasthepartcools Moldshrinkagedataforthespecificplasticmaterialcanbeusedtocalculatetheamountofmoldexpansionneeded Moldshrinkageunitsareexpressedaslength perunit length orasapercentage andiscalculatedusingthefollowingformula molddimension partsize molddimension ShrinkFactor MoldingIssuesandCommonDefects DimensionalSizeErrors toolong tooshort toothin toothick etc DimensionalWarpage Distortion StressSink ShrinkMarksLifterLineRead ThroughFlowLines Weld Knit LinesMetallicFlakeOrientationPorosityNon isotropicBehavior differentbehaviorindifferentdirections FlowLines MetalFlakeOrientation Thissectionofmetallicmolded in colorrockermoldingshowappearancedefectscausedbyflowlinesandmetalflakealignmentsformedaroundtheattachingholepins Gate FlowObstruction FlowLine MetalFlakeOrientation WeldLines KnitLines Weld knit linesareappearanceandstructuraldefectswhichareformedwhenthemoltenplasticmustdividetogoaroundanobstructionandthenrejoinitself Weoftenfindthisproblemondoghousesandalsoatattachingholesnearapartedge SinkMarks SinkMarksformaroundthecenterofthelargermassofmaterialandshrinktowardsthecenterofthemass Sinkmarksareappearancedefectscausedbypoorpartdesign Sinksmarksaredifficulttoimprovebytoolingorprocessing RibsandGussets Ribsandgussetsshouldhaveangledcornerstoavoidtrappingairduringfilling Squarecornersaremoredifficulttofillcomparedtoangledorradiusedcorners ChromePlatingConsiderations Chromeplatingisanelectrochemicalprocess andthedepositionofthemetaltothepartisattractedtosharpoutsideradiiandisrejectedbysharpinsideradii Non uniformchromedepositcausessurfaceprofileappearanceproblems Useradiiandfilletstoeliminatesharpfeaturesandmakethechromedepositionmoreuniform ChromePlatingConsiderations Stiffenedgesifpossibletoreducedamage Avoidflatsurfacesduetoriskofnon uniformchromedepositionandalsoplasticshrinkagesinkmarks Usecrowned largeradius notflat surfacestomaintainuniformchromethicknessandavoidshrinkmarks Runner Gating FillingMoldingAnalysis Doanalysisbeforeyoudesignandbuildthetool PartDesignBestPractices PartDesignBestPractices DesignForSuccess FollowaPlan Afteryougatherandunderstandthepartrequirements Selecttheproperpartconstruction materialsselection andprocess materialtype stiffness weatherable paintable moldable etc Studyandunderstandthematerialbehavioranddesignrequirements minimumwallstockthickness ribsensitivity holesensitivity shrinkage etc SeekassistancefromMaterialsEngineers suppliers LeadEngineers colleagues etcfordesignreviewandadvice ConductPeerReviewsofyourdesignwithmoldersandtoolshopsasitdevelops InjectionMaterialFamilies Thermoplastic Categoryofplasticswhichdeformsandre meltswhenreheated recyclable CommonFillers GlassFiber Short Long Continuous MatMineral MicaTalc ThermoplasticMaterials Thermoplasticscommoninautomotive TPO PPABS ABS PC ASA ASA PCPC PC PBT PMMAPA6 PA66 Nylon mineralorglassfiberThermoplasticmaterialsareusuallyhighpressureinjectionmoldedbutsomegradescanalsobeblow moldedorextrudedorthermoformed PartMaterialsUsageMatrix UniformWallStock thickness PoorDesign GoodDesign Designingpartsforuniformwallstock thickness isprobablythesinglemostimportantthingyoucandotomakeadesignwhichisrobustformoldingandpainting Uniformwallstockpartsmoldwithbetterfillingandreducedinternalstresses Uniformwallstockpartscoolandshrinkmoreuniformly reducingdimensionaldistortionandwarpage CornerRadii Maintainconstantpartthicknessincornerradii Avoid Thick thin thick or Thin thick thin sectiontransitions Non uniformthicknesscreatesflow stress shrinkage andwarpageconditionsinthepartastheplasticcoolsandshrinksatdifferentratesduetodifferentthicknesses Good ThicknessTransitions Avoidsuddenorsharpchangesinsectionshape Suddenchangesaffectflowandfillcharacteristics andalsocreatehighstressconcentrationsinthepart Usesmoothtransitionsbetweensections AvoidSolidMasses PoorDesign GoodDesign Thickmassesofsolidplastic Coolsslowly Someareasarethinner Shrinksunevenly Uniformconstantthickness OffsetRibs Offsetribscanhelphidesinkmarksandmakethemlessvisible Sinkmarksandshrinkageareeasierto hide whentheyoccuronsmallradiussurfaces Sinkmarksaredifficulttohideonlargeradius flat surfaces Itisgenerallygoodpracticetoplaceanyribsbehindpartsurfacefeaturelines ratherthanbehindflatsurfaces RibDesignPractices Avoidthickribfeatureswhichcancausepartwarpageandsurfacesinkmarks Avoidtallthinribfeatureswhichcanbuckleorbendunderload RibDesignGuidelines Ribdesignislargelyaffectedbymaterialselection ConsultwithResinsuppliersandmoldersforassistance Generally wedesignaminimumof3degreesdraftpersideforribsandsurfacesforrobustmoldingandejection Smallerdraftcansometimesbeusedifyouhaveagreementfromyourmolderandtoolshop However largeribsincreasethechanceofsurfacesinkmarks 0 3 0 4T RibWarpage Itisalwaysbettertogainstructurethroughsurfaceshapechange ratherthanaddedribsandgussetsonthebackside Ribsaddstructurebutcancausewarpageduetocoolingofnon uniformgeometry Fillershaveavariedeffectoncoolingandwarpage Itisdifficulttopredict analyze orcontrolwarpagefromplasticribstructure GlassFilledresin Un Filledresin MultipleRibs Sometimesasinglelargeribcanbereplacedbymultiplesmallerribstoavoidsinkmarks etc BossDesigns ThisshowsatypicalbossdesignforascreworstudforreferenceDetailsvarydependingonmaterialsandfastenerdesign Consultfastenerandmaterialsassistance Theimportantideashownistoreducethewallthicknessofthemoldingatthebottomofthebosstoreducethesinkmarkonthesurfaceduetotheexcessmassofmaterial BossDesigns Open bossdesignmaintainsuniformthicknessinthepartwall andavoidsathintoolsteelcondition BossCoreDepth Willformsinkmark Willformsinkmark Good pincouldbealittlelonger Pinmaybetoolong Partmaybetoothin BasicPartDesignPractices SomeoilsandcoatingsonfastenersattackPCandABS PC UseHi LotypethreadedscrewsfordirectengagementintoTPO ASA andNylonplasticbosses Usemetalthreadedstudsandinsertsforhighloadattachments BasicPartDesignPractices Avoiddesigningvariablecrosssectionareasbecauseitallowsmaterialtoflowfasterinsomeareasthaninothers Ejectorpinssometimesinterferewithcoolingwatercircuits andpinsapplyforceonlyinsmallareas Somepartsejectbetterbycontrollingcoolingratherthanexertingmechanicalforce BasicPartDesignPractices Draftangleof3degreesisnormallyusedforpaintedexteriorparts Moreisaddedforgrainedparts 3 1 5 0 001 graindeepthAvoidsharpcornersandstressconcen