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.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
学生姓名:
学号:
指导教师单位:
姓名:
职称:
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,
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