注塑模具原理与基本方法外文文献翻译中英文翻译.docx
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注塑模具原理与基本方法外文文献翻译中英文翻译.docx
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注塑模具原理与基本方法外文文献翻译中英文翻译
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文章名:
Tribologicalassessmentoftheinterfaceinjectionmold/plasticpart
书刊名:
tribologyinternational
作者:
crossmark
出版社:
journalhomepage
文章译名:
注塑模具原理及基本方法
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文原文:
Thesectorofplasticsprocessingisrelativelyyoungcomparedtocastiron,steelorglassindustry.Soitstillhasaverystrongdevelopmentpotential.Oneofthecurrentchallengesoftheplasticinjectionprocessislinkedtotheimportancegiventoproductdesignthatenablesastrongdifferentiation
[1].Plasticpartswithanincreasedtechnicallevelofsurfaceaccuracyarerequiredintheareasofluxury,packaging,automotive,includingthemedicalandoptics.Theirdevelopmentinvolvestheimprovementofthefabricationprocess,andoneofthekeysliesinthemasteryofthesurfaceconditionsofthemolds.
Injectionmoldingisacyclicprocess,characterizedby5phases:
dosing,injection,packing,coolingandejection.Therawmaterialthatisdosedinthemachinemustbepureandconservedbeforeuseatanadequatetemperatureinordertobeasdriedaspossible.Thisisnecessarytoavoidcondensationinsidethemold.Theinjectionphaseischaracterizedbyhighflowratesandhencehighshearrate(tangentialeffect).Asthemoltenmaterialentersthemold,twoheattransfermechanismsoccur:
convection(betweenthemeltedmaterialandmoldsurface)andviscousdissipation(duetotheeffectofinjectionspeedontheinjectedmaterialviscosity).Asthefillingiscomplete,themoldisupholdatapredeterminedpressureandsothepackingphaseisinitiated.Duringthisphase,themoltenpolymercontinuestobeintroducedintothemoldtocompensatefortheshrinkageofthealreadyinjectedmaterialasitcoolsdown.Afteraspecifictime,thecoolingphase(contrarytothecoolingstatewhichbeginsduringinjectionandpackingphase)oftheentireassemblystartsandsoalsothesolidificationprocessoftheplasticpart.Asthematerialsolidifiesandshrinksinthemold,thedominantheattransfermechanismisconduction.Whenthepartissufficientsolidified,itisejectedfromthemold.Duringthislastphase,anormaleffectcanbeattributedtotheejectionforceandadhesionphenomenacanoccurbetweenthemoldsurfaceandtheplasticpart
[2].
Despitetheundeniablediversityofconfigurationsavailable(intermsofcombination:
moldmaterial,surfacefinishandprocessedmaterials),theproducersarefacedwithsimilardifficulties.Thus,thekeyshortcomingsthatstandout,moreorlesscombined,canbesummarizeasfollows:
●thefoulingphenomenawhichrequirefrequentstopsforcleaning;
●corrosionphenomenathatcangreatlylimitthelifetimeofthemoldcavityasafunctionofthetypeofinjectedpolymer;
●problemsofstickingandreleasinginfunctionoftheinjectedmaterialsandsurfacequality;
●problemsinkeepingthepolishingquality;
●scratchesorshocksduringuseorstorage.
Theavailableliteratureapproachesexperimentaland/ornumerical,variousaspectsregardingtheplasticinjectionmoldingprocess.Oneofthemisthefillingandflowbehaviorofmoltenpolymers.
[3]BociagaandJarugastudiedtheformationofflow,weldandmeldlinesbydevelopinganewmethodofflowvisualization,whichcanprovehelpfulintheidentificationofweak
areasoninjectedparts.Alsotheeffectofpressureandcavitythicknesswereassessed.SametopicwastreatedbyOzdemiretal.
[4],comparingthebehaviorofmoltenHDPE(highdensitypoly-ethylene)andPEexperimentallyandnumerically.
Duringmolding,frictionforcesactfirstbetweenthemoldsurfaceandthemoltenpolymerandsecondwhentheplasticpartisejectedfromthemold.Bulletal.
[5]adaptedtheASTMrubberwheelabrasiontesttosimulatetheconditionsofwearproducedbytheglassfilledpolymersonthebarrelsurfaceofaninjectionmoldingmachine.Variouscoatingsweretested,butunfortunatelytheytendedtohaveaweakperformanceonaccountofthetestconditions.
[6]developedaprototypeapparatustostudythefrictionpropertiesofmoldingthermoplasticsduringejectionphase.Themeasuredfrictioncoefficienthadatendencytoincreasewiththeroughness.Butwhentheroughnesswasreducedthefrictioncoefficientincreaseduetotherisingadhesionforceseffect.Thescanningelectronmicroscopyimagesofthemoldsurfaceandtheonesforthepolycarbonate(PC)andpolypropylene(PP)plasticparts,revealedaclearreplicationofthemoldsurfaceontheparts.
Transientinnature,injectionmoldingprocessinvolvesnotonlyseveralheattransfermechanisms,phasechangeandtimevaryingboundaryconditions,butgoesfurtherinaddingtheeffectofmaterialpropertiesandgeometryoftheinjectedpart.
[7]Bendadaetalperformedastudytoevaluatethenatureofthermalcontactb
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