文献翻译原文一种使注射成型冷却更有效的系统设计方法.docx

文献翻译原文一种使注射成型冷却更有效的系统设计方法.docx

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文献翻译原文一种使注射成型冷却更有效的系统设计方法

编号：

毕业设计（论文）外文翻译

（原文）

学院：

国防生学院

专业：

机械设计制造及其自动化

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指导教师单位：

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2014年3月9日

AMETHODOLOGYFORTHEDESIGNOFEFFECTIVECOOLINGSYSTEMININJECTIONMOULDING

IntJMaterForm（2010）Vol.3Suppl1:

13–16

DOI10.1007/s12289-010-0695-2

Springer-VerlagFrance2010

ABSTRACT

Inthermoplasticinjectionmolding,partqualityandcycletimedependstronglyonthecoolingstage.Numerousstrategieshavebeeninvestigatedinordertodeterminethecoolingconditionswhichminimizeundesireddefectssuchaswarpageanddifferentialshrinkage.Inthispaperweproposeamethodologyfortheoptimaldesignofthecoolingsystem.Basedongeometricalanalysis,thecoolinglineisdefinedbyusingconformalcoolingconcept.Itdefinesthelocationsofthecoolingchannels.Weonlyfocusonthedistributionandintensityofthefluidtemperaturealongthecoolinglinewhichisherefixed.Weformulatethedeterminationofthistemperaturedistribution,astheminimizationofanobjectivefunctioncomposedoftwoterms.Itisshownhowthistwoantagonisttermshavetobeweightedtomakethebestcompromise.Theexpectedresultisanimprovementofthepartqualityintermsofshrinkageandwarpage.

KEYWORDS:

Inverseproblem；heattransfer；injectionmolding；Coolingdesign

1.INTRODUCTION

Inthefieldofplasticindustry,thermoplasticinjectionmoldingiswidelyused.Theprocessiscomposedoffouressentialstages:

mouldcavityfilling,meltpacking,solidificationofthepartandejection.Aroundseventypercentofthetotaltimeoftheprocessisdedicatedtothecoolingofthepart.Moreoverthisphaseimpactsdirectlyonthequalityofthepart[1][2].Asaconsequence,thepartmustbecooledasuniformlyaspossiblesothatundesireddefectssuchassinkmarks,warpage,shrinkage,thermalresidualstressesareminimized.Themostinfluentparameterstoachievetheseobjectivesarethecoolingtime,thenumber,thelocationandthesizeofthechannels,thetemperatureofthecoolantfluidandtheheattransfercoefficientbetweenthefluidandtheinnersurfaceofthechannels.Thecoolingsystemdesignwasprimarilybasedontheexperienceofthedesignerbutthedevelopmentofnewrapidprototypingprocessmakespossibletomanufactureverycomplexchannelshapeswhatmakesthisempiricalformermethodinadequate.Sothedesignofthecoolingsystemmustbeformulatedasanoptimizationproblem.

1.1HEATTRANSFERANALYSIS

Thestudyofheattransferconductionininjectiontoolsisanonlinearproblemduetothedependenceofparameterstothetemperature.Howeverthermophysicalparametersofthemouldsuchasthermalconductivityandheatcapacityremainconstantintheconsideredtemperaturerange.Inadditiontheeffectofpolymercrystallizationisoftenneglectedandthermalcontactresistancebetweenthemouldandthepartisconsideredmoreoftenasconstant.TheevolutionofthetemperaturefieldisobtainedbysolvingtheFourier’sequationwithperiodicboundaryconditions.Thisevolutioncanbesplitintwoparts:

acyclicpartandanaveragetransitorypart.Thecyclicpartisoftenignoredbecausethedepthofthermalpenetrationdoesnotaffectsignificantlythetemperaturefield[3].Manyauthorsusedanaveragecyclicanalysiswhichsimplifiesthecalculus,butthefluctuationsaroundtheaveragecanbecomprisedbetween15%and40%[3].Thecloserofthepartthechannelsare,thehigherthefluctuationsaroundtheaverageare.Henceinthatconfigurationitbecomesveryimportanttomodelthetransientheattransfereveninstationaryperiodicstate.Inthisstudy,theperiodictransientanalysisoftemperaturewillbepreferredtotheaveragecycletimeanalysis.Itshouldbenoticedthatinpracticethedesignofthecoolingsystemisthelaststepforthetooldesign.Neverthelesscoolingbeingofprimaryimportanceforthequalityofthepart,thethermaldesignshouldbeoneofthefirststagesofthedesignofthetools.

1.2OPTIMIZATIONTECHNIQUESINMOULDING

Intheliterature,variousoptimizationprocedureshavebeenusedbutallfocusedonthesameobjectives.Tangetal.[4]usedanoptimizationprocesstoobtainauniformtemperaturedistributioninthepartwhichgivesthesmallestgradientandtheminimalcoolingtime.Huang[5]triedtoobtainuniformtemperaturedistributioninthepartandhighproductionefficiencyi.e.aminimalcoolingtime.Lin[6]summarizedtheobjectivesofthemoulddesignerin3facts.Coolthepartthemostuniformly,achieveadesiredmouldtemperaturesothatthenextpartcanbeinjectedandminimizethecycletime.

Theoptimalcoolingsystemconfigurationisacompromisebetweenuniformityandcycletime.Indeedthelongerthedistancebetweenthemouldsurfacecavityandthecoolingchannelsis,thehighertheuniformityofthetemperaturedistributionwillbe[6].Inversely,