mold-defects

Injectionmoldingisacomplextechnologywithpossibleproductionproblems.Theycaneitherbecausedbydefectsinthemoldsormoreoftenbypartprocessing(molding)MoldingDefectsAlternativenameDescriptionsCausesBlisterBlisteringRaisedorlayeredzoneonsurfaceofthepartToolormaterialistoohot,oftencausedbyalackofcoolingaroundthetoolorafaultyheaterBurnmarksAirBurn/GasBurn/DieselingBlackorbrownburntareasonthepartlocatedatfurthestpointsfromgateorwhereairistrappedToollacksventing,injectionspeedistoohighColorstreaks(US)Colourstreaks(UK)Localizedchangeofcolor/colourMasterbatchisn'tmixingproperly,orthematerialhasrunoutandit'sstartingtocomethroughasnaturalonly.Previouscoloredmaterialdragginginnozzleorcheckvalve.DelaminationThinmicalikelayersformedinpartwallContaminationofthemateriale.g.PPmixedwithABS,verydangerousifthepartisbeingusedforasafetycriticalapplicationasthematerialhasverylittlestrengthwhendelaminatedasthematerialscannotbondFlashBurrsExcessmaterialinthinlayerexceedingnormalMoldisoverpackedorpartinglineonthetoolisdamaged,toomuchinjectionspeed/materialpartgeometryinjected,clampingforcetoolow.Canalsobecausedbydirtandcontaminantsaroundtoolingsurfaces.EmbeddedcontaminatesEmbeddedparticulatesForeignparticle(burntmaterialorother)embeddedinthepartPartic**onthetoolsurface,contaminatedmaterialorforeigndebrisinthebarrel,ortoomuchshearheatburningthematerialpriortoinjectionFlowmarksFlowlinesDirectionallyofftonewavylinesorpatternsInjectionspeedstooslow(theplastichascooleddowntoomuchduringinjection,injectionspeedsmustbesetasfastasyoucangetawaywithatalltimes)JettingDeformedpartbyturbulentflowofmaterialPoortooldesign,gatepositionorrunner.Injectionspeedsettoohigh.KnitLinesWeldlinesSmalllinesonthebacksideofcorepinsorwindowsinpartsthatlooklikejustlines.Causedbythemelt-frontflowingaroundanobjectstandingproudinaplasticpartaswellasattheendoffillwherethemelt-frontcomestogetheragain.Canbeminimizedoreliminatedwithamold-flowstudywhenthemoldisindesignphase.Oncethemoldismadeandthegateisplacedonecanonlyminimizethisflawbychangingthemeltandthemoldtemperature.Polymerdegradationpolymerbreakdownfromhydrolysis,oxidationetcExcesswaterinthegranu**,excessivetemperaturesinbarrelSinkmarks[sinks]LocalizedHoldingtime/pressuretoolow,depression(Inthickerzones)coolingtimetooshort,withsprue**shotrunnersthiscanalsobecausedbythegatetemperaturebeingsettoohigh.Excessivematerialorthickwallthickness.ShortshotNon-fill/ShortmoldPartialpartLackofmaterial,injectionspeedorpressuretoolow,moldtoocoldSplaymarksSplashmark/SilverstreaksCircularpatternaroundgatecausedbyhotgasMoistureinthematerial,usuallywhenhygroscopicresinsaredriedimproperly.Trappingofgasinribareasduetoexcessiveinjectionvelocityintheseareas.Materialtoohot.StringinessStringingStringlikeremainfrompreviousshottransferinnewshotNozzletemperaturetoohigh.Gatehasn'tfrozenoffVoidsEmptyspacewithinpart(Airpocket)Lackofholdingpressure(holdingpressureisusedtopackoutthepartduringtheholdingtime).Fillingtofast,notallowingtheedgesoftheparttosetup.Alsomoldmaybeoutofregistration(whenthetwohalvesdon'tcenterproperlyandpartwallsarenotthesamethickness).WeldlineKnitline/Meldline/TransferlineDiscoloredlinewheretwoflowfrontsmeetMold/materialtemperaturessettoolow(thematerialiscoldwhentheymeet,sotheydon'tbond).Pointbetweeninjectionandtransfer(topackingandholding)tooearly.WarpingTwistingDistortedpartCoolingistooshort,materialistoohot,lackofcoolingaroundthetool,incorrectwatertemperatures(thepartsbowinwardstowardsthehotsideofthetool)UnevenshrinkingbetweenareasofthepartShortShot-Insufficientmaterialputincavity/materialsolidifiestoosoonEjectorPinMarks-Ejectorpinsnotflush/undersizedorplastictoosoftatejectionWeldLines-OccurwhereverflowpathscometogetherSinkMarks-MaterialshrinksawayfromwallsofmoldcavityResidualStresses-GeneratedbyconstrainingpartwhilecoolingPartingLines-PlasticseepsthroughseambetweenmoldsectionsJetting-Meltmovingrapidly,coolsunevenlyandtrapsflowlinesFlashing-Materialoverflowscavity(toomuchmaterial,notenoughclampforce)