injection_molding_fault_and_prevention

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1、Injectionmoldingfaultsinstyrenecopolymersandtheirprevention4I.Injectionmoldingfaults1.Streaks1.1Moisturestreaks/splaymarks1.2Burningstreaks/silverstreaks1.3Darkstreaksduetoindrawnair1.3Colorstreaks82.Peeling/delamination3.Weldlines104.Airentrapments/bubbleformation125.Sinkmarks6.Voids147

2、.Glossyspotsordifferencesingloss/matspots168.Microcracks,crazing,stresswhitening189.Dieseleffect2010.Demoldingproblems2211.Pushmarks(“tigerstripes/tigerlines”)2412.Recordeffect2613.Shortshot2814.Flashformation3015.Jetting3216.Coldslug3417.Warpage36II.Overview:Controlofinjectionmoldingfau

3、ltsbychangingtheprocessingparametersIntroductionPlasticmoldingsproducedbytheinjectionmoldingprocessareusuallylong-livedconsumergoodswhosesuitabilityforthepurposeinquestiondependsnotonlyonthepropertiesofthefinishedpartbutalsohighlyonthesurfacequality.Thecomplexinter-playamongmoldingandmol

4、ddesign,processingconditionsfortherawmaterialandtheparametersfortheactualprocessrequireagreatdealofexperi-enceforoptimumresultsespeciallywhenfocusingontheshort-termremovalofprocessingfaults.Onthebasisofanindividualcaseadecisionhastobetakenastowhethersimpleandrapidfaultcorrection(bymodify

5、ingtheprocessingparametersforexample)ispossibleorwhetherinterventioninthedesignofthepartsorthelayoutofthemoldandgatingisnec-essary.Inconclusionthesurfacefaultsoccurringmostcom-monlyinstyrenecopolymersarenotedanddescribedandrecommendationsfortheirremovalaresetout.3I.Injectionmoldingfaults

6、1.Streaks1.1Moisturestreaks/splaymarksAppearanceCauseCorrectionUsuallyoblong,silverysurfaceMoisturecontenttoohigh;watervaporisproduceddur-1.Usematerialadequatelypredriedtoaresidualmois-streakswhichareopenintheingmeltingandthisresultsinthesurfaceofthemoldingturecontentof<0.1%.shapeofaUcou

7、ntertothebeingtornopen.2.Increasebackpressure.directionofflow.Thematerialpumpedoutofthecylinderisfoamedandshowsblistersonthesurface.1.2Burningstreaks/silverstreaksAppearanceCauseCorrectionSilveryordarksurfacestreaks1.Damagetotheplasticmeltduetoexcessivelyhigh1.Reductionof