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外文翻译--可控注塑成型的发展趋势 英文版.pdf

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外文翻译--可控注塑成型的发展趋势 英文版.pdf

1COPYRIGHT1999BYASMEPROCEEDINGSOFMATERIALSPROCESSINGSYMPOSIUM1999ASMEINTERNATIONALMECHANICALENGINEERINGCONGRESSEXPOSITIONNOVEMBER1419,1999,NASHVILLE,TENNESSEETOWARDSCONTROLLABILITYOFINJECTIONMOLDINGDAVIDKAZMERDEPARTMENTOFMECHINDENGINEERINGUNIVERSITYOFMASSACHUSETTSAMHERSTDAVIDHATCHDEPARTMENTOFMECHINDENGINEERINGUNIVERSITYOFMASSACHUSETTSAMHERSTABSTRACTPROCESSCONTROLHASBEENRECOGNIZEDASANIMPORTANTMEANSOFIMPROVINGTHEPERFORMANCEANDCONSISTENCYOFTHERMOPLASTICPARTSHOWEVER,NOSINGLECONTROLSTRATEGYORSYSTEMDESIGNHASBEENUNIVERSALLYACCEPTED,ANDMOLDINGSYSTEMSCONTINUETOPRODUCEDEFECTIVECOMPONENTSDURINGPRODUCTIONTHECAPABILITYOFTHEINJECTIONMOLDINGPROCESSISLIMITEDBYTHETHERMALANDFLOWDYNAMICSOFTHEHEATEDPOLYMERMELTTHISPAPERDISCUSSESSOMEOFTHEDIFFICULTIESPOSEDBYCOMPLEXANDDISTRIBUTEDNATUREOFTHEINJECTIONMOLDINGPROCESSTHEFLOWANDTHERMALDYNAMICSOFTHEPROCESSAREANALYZEDWITHRESPECTTOTRANSPORTANDRHEOLOGYTHEN,TWONOVELPROCESSINGMETHODSAREDESCRIBEDTOENABLEINCYCLEFLOW,PRESSURE,ANDTHERMALCONTROLSIMULATIONANDEXPERIMENTALRESULTSDEMONSTRATEEFFECTIVENESSOFTHESEINNOVATIONSTOINCREASETHECONSISTENCYANDFLEXIBILITYINPOLYMERPROCESSINGSUCHSYSTEMDESIGNCHANGESSIMPLIFYTHEREQUISITECONTROLSTRUCTURESWHILEIMPROVINGTHEPROCESSROBUSTNESSANDPRODUCTIVITYINTRODUCTIONINJECTIONMOLDINGISCAPABLEOFPRODUCINGVERYCOMPLEXCOMPONENTSTOTIGHTSPECIFICATIONSTHEPROCESSCONSISTSOFSEVERALSTAGESPLASTICATION,INJECTION,PACKING,COOLING,ANDEJECTIONININJECTIONMOLDINGANDITSVARIANTSCOINJECTION,INJECTIONCOMPRESSION,GASASSISTMOLDING,ETC,THERMOPLASTICPELLETSAREFEDINTOAROTATINGSCREWANDMELTEDWITHAHOMOGENEOUSMELTCOLLECTEDINFRONTOFTHESCREW,THESCREWISMOVEDFORWARDAXIALLYATACONTROLLED,TIMEVARYINGVELOCITYTODRIVETHEMELTINTOANEVACUATEDCAVITYONCETHEMELTISSOLIDIFIEDANDTHEMOLDEDCOMPONENTISSUFFICIENTLYRIGIDTOBEREMOVED,THEMOLDISOPENEDANDTHEPARTISEJECTEDWHILETHENEXTCYCLE’STHERMOPLASTICMELTISPLASTICIZEDBYTHESCREWCYCLETIMESRANGEFROMLESSTHANFOURSECONDSFORCOMPACTDISCSTOMORETHANTHREEMINUTESFORAUTOMOTIVECOMPONENTSCONTROLOFINJECTIONMOLDINGISSIGNIFICANTLYCHALLENGEDBYTHENONLINEARBEHAVIOROFTHEPOLYMERICMATERIALS,DYNAMICANDCOUPLEDPROCESSPHYSICS,ANDCONVOLUTEDINTERACTIONSBETWEENTHEMOLDGEOMETRYANDFINALPRODUCTQUALITYATTRIBUTESAREVISEDSYSTEM’SVIEWOFTHEMODERNCONVENTIONALINJECTIONMOLDINGPROCESS1ISPRESENTEDINFIG1THEMACHINEPARAMETERSAREINDICATEDONTHELEFTSIDEOFTHEFIGURE,ANDSOMECOMMONMOLDEDPARTMEASURESOFQUALITYARELISTEDONTHERIGHTINTHISFIGURE,THEPROCESSISDECOMPOSEDINTOFIVEDISTINCTBUTCOUPLEDSTAGESTHEOUTPUTOFEACHSTAGENOTONLYDIRECTLYDETERMINESTHEINITIALCONDITIONSOFTHENEXTSTAGE,BUTALSOINFLUENCESSOMEOFTHEFINALQUALITIESOFTHEMOLDEDPARTBARRELTEMP1000PLASTICATIONINJECTIONPACKINGCOOLINGEJECTIONPROCESS/PARTQUALITYMELTPRESSURETHERMOPLASTICPELLETSSCREWPRES002SCREWRPM05DISTORTIONDIMENSIONSCLARITYECONOMICSRESIDSTRESSINTEGRITYEJECTEDPARTRELAXATIONSOLIDIFIEDLAYERDEVELOPMENTSTRENGTHAPPEARANCERESIDENCETIMEMELTVOLUMEMELTTEMPMELTQUALITYINJECTIONVELOCITYPROFILE002MAXIMUMINJECTIONPRESSURE01PACKINGPRESSUREPROFILE02PACKINGTIME001MELTVISCOSITYINLETPRESSUREFLOWRATEMOLDCOOLANTTEMPERATURE200COOLINGTIME001MELTFRONTVELOCITYMELTPRESMELTDENSITYMELTTEMPSOLIDIFIEDLAYERDEVELOPMENTCLAMPTONNAGESOLIDIFIEDLAYERDEVELOPMENTCYCLETIMEPARTTEMPPARTSTRAINPARTSTRESSEJECTIONSTROKE002EJECTIONVELOCITY001FLASHMOLDFAILURESHOTSIZE002MACHINEINPUTSQUALITYATTRIBUTESSTATEVARIABLESFIGURE1SYSTEM’SVIEWOFTHEINJECTIONMOLDINGPROCESSTHINCAVITYFILLINGOFPOLYMERMELTCORRESPONDSTOCREEPINGFLOWRE1WHICHISCOUPLEDTOATEMPERATUREFIELDCHARACTERIZEDBYATHINCOLDLAYERPE1SURROUNDINGAHOTCOREREGION2ASANEXAMPLE,CONSIDERAREFERENCEVELOCITYOF10CM/SEC,REFERENCETHICKNESSOF3MM,ANDAVISCOSITYOF100PASECONDSTHEREYNOLDSNUMBERBASEDONTHISCASEISVERYSMALL,Θ103,INDICATINGTHEVALIDITYOFTHEHIGHLYVISCOUSCREEPINGFLOWASSUMPTIONFURTHERMORE,THEFLOWREGIONSARECONSIDEREDFULLYDEVELOPED,ANDBOTHTHEUNSTEADYANDTHEGRAVITATIONALFORCEEFFECTSCANBEIGNOREDDUETONEGLIGIBLELOCALACCELERATIONONTHEOTHERHAND,THETHERMALDIFFUSIVITY,2COPYRIGHT1999BYASMEK/CP,OFTYPICALPOLYMERMELTSISΘ103CM3/SEC,ANDTHEKINEMATICVISCOSITY,Η/103CM2/SEC;HENCE,THEPRANDTLNUMBERISABOUTΘ106ANDPECLETNUMBER,PEREPR,ISΘ103USINGTHESEASSUMPTIONS,THEMASS,MOMENTUM,ANDENERGYEQUATIONSREDUCETOTHEFOLLOWINGFORMSINTHECARTESIANCOORDINATESYSTEM0∂∂∂∂∂∂WZVXTRRR1XPZVZ∂∂∂∂∂∂H2222GHR∂∂∂∂∂∂ZTKXTVTTCP3WHEREZANDXARETHETHICKNESSANDSTREAMWISEDIRECTIONS;VISTHEVELOCITYCOMPONENT;PISTHEPRESSURE;HISTHESHEARVISCOSITY;R,CP,ANDKARETHETHERMALPROPERTIES;GISTHESHEARRATE,AND2GHISTHEVISCOUSHEATINGTERMTHESOLUTIONOFTHEPRESSUREFIELDININJECTIONMOLDINGISOBTAINEDBYCOUPLINGTHEMASSANDMOMENTUMEQUATIONSGENERALLY,THEMASSEQUATIONPROVIDESACONVERGENCECRITERIONFORFLOWRATEABOUTWHICHTHEMOMENTUMEQUATIONISITERATIVELYSOLVEDTOPRODUCEANACCURATEPRESSUREFIELDFOREACHINSTANTOFTIME,ALLTHENODALPRESSURESONTHEMESHARESOLVEDSIMULTANEOUSLYITERATIONISREQUIREDTOUPDATETHESHEARRATE,VISCOSITY,ANDFLOWRATEESTIMATESUNTILFULLCONVERGENCEISACHIEVEDFORACOMPRESSIBLEFLOW,THENETMASSFLUXMUSTEQUALANYMASSGAINSORLOSSESWITHINTHEELEMENT3THENECESSARYSYSTEMOFEQUATIONSCANBEDEVELOPED,ASSEMBLED,ANDSOLVEDUSINGACONVENTIONALGALERKINFORMULATIONFORAFIXEDMESHANDTRANSIENTMELTFRONTSUCHASIMULATIONHASBEENDEVELOPED,ANDWILLBEUTILIZEDINASSESSINGSTRATEGIESFORPROCESSDEVELOPMENTALONGWITHEXPERIMENTALVALIDATIONPROCESSDEVELOPMENTANOVERVIEWOFINJECTIONMOLDINGCONTROLISSHOWNINFIG2ATTHEINNERMOSTLEVEL,ONLYTHEMACHINEACTUATORSAREREGULATEDTHISLEVELOFCONTROLWILLENSUREPROPEREXECUTIONOFTHEPROGRAMMEDMACHINEINPUTSFIG1ATTHESECONDLEVEL,STATEVARIABLESSUCHASMELTTEMPERATUREANDMELTPRESSUREARECONTROLLEDTOTRACKPRESPECIFIEDPROFILESTHISWILLPROVIDEMOREPRECISECONTROLOFTHESTATEOFTHEMELTATTHEOUTERMOSTLEVEL,THEMACHINEINPUTSAREADJUSTEDTOIMPROVETHEQUALITYOFTHEPARTTHROUGHBETTERSETPOINTSGIVENQUALITYFEEDBACKMACHINEACTUATORSPROCESSMACHINECONTROLSETPOINTCONTROLSTATEVARIABLECONTROLMACHINEFEEDBACKQUALITYFEEDBACKSTATEVARIABLEFEEDBACKPARTATTRIBUTESMACHINEINPUTSFIGURE2SYSTEMDIAGRAMOFINJECTIONMOLDINGCONTROLWHILEMACHINECONTROLISIMPORTANT,ITISTHEPOLYMERSTATEPRESSURE,TEMPERATURE,ANDMORPHOLOGYWHICHDIRECTLYDETERMINESTHEMOLDEDPARTQUALITY4,5ASSUCH,THISPAPERFOCUSESONCLOSINGTHELOOPBETWEENTHEMACHINEPARAMETERSANDTHEPOLYMERSTATEIFACHIEVED,THESEADVANCEDCONTROLSTRATEGIESWOULDPROVIDEINCREASEDMOLDEDPARTQUALITYANDCONSISTENCYCAVITYPRESSURECONTROLAFUNDAMENTALSTATEVARIABLETHATCANBEREGULATEDDURINGTHEMOLDINGCYCLEISCAVITYPRESSURECLOSEDLOOPCONTROLOFCAVITYPRESSURECOULDAUTOMATICALLYCOMPENSATEFORVARIATIONSINMELTVISCOSITYANDINJECTIONPRESSURETOACHIEVEACONSISTENTPROCESSANDUNIFORMSETOFPRODUCTATTRIBUTES6MANNINTRODUCEDONEOFTHEFIRSTPRESSURECONTROLSCHEMESBYUSINGMODULATEDPRESSURERELIEFVALVES7,ANDABUFARADEVELOPEDAPROCESSCONTROLMODELBYRELATINGTHECAVITYPRESSURERESPONSETOOPENLOOPPERTURBATIONS8SRINIVASANLATERUSEDTHESEMODELSTOPROPOSEALEARNINGCONTROLLERFORCLOSEDLOOPCAVITYPRESSURECONTROL9ADAPTIVECONTROLMETHODSHAVEALSOBEENPROPOSEDTOTRACKCAVITYPRESSUREPROFILEATUSUALLYONELOCATIONINTHEMOLD1012UNFORTUNATELY,CAVITYPRESSURECONTROLSUFFERSFROMTHELACKOFASYSTEMATICMETHODOFDETERMININGTHEPRESSUREPROFILEINADDITION,ITISHANDICAPPEDBYTHEABSENCEOFAPPROPRIATEACTUATORSFORDISTRIBUTEDPRESSURECONTROL,ASCONVENTIONALMOLDINGMACHINESAREEQUIPPEDWITHONLYONEACTUATORTHESCREWWHICHDOESNOTALLOWSIMULTANEOUSCAVITYPRESSURECONTROLATMULTIPLEPOINTSINTHEMOLDCONSIDERTHEMELTTRANSPORTSYSTEMINACONVENTIONALCOLDRUNNERMOLDASSHOWNINFIG3ITISEVIDENTTHATTHEGEOMETRYIS“HARDWIRED”INTOTHEMOLDTHERUNNERLOCATIONSAREFIXEDANDTHEGATEDIMENSIONSAREALSOFIXEDTHERESULTINGPRESSUREDISTRIBUTIONCANNOTBECONTROLLEDWITHOUTRETOOLINGMOLDSTEELFIGURE3TYPICALPACKINGPRESSUREDISTRIBUTIONTOINVESTIGATETHECONTROLLABILITYOFTHEINJECTIONMOLDINGPROCESS,AHALFFACTORIALDESIGNOFEXPERIMENTS13WASPERFORMEDTODETERMINETHEMAINEFFECTSBETWEENTHECRITICALPROCESSPARAMETERSANDTHEPARTDIMENSIONS3COPYRIGHT1999BYASME−−−SCREWSPEEDETEMPERATURVELOCITYPRESSURELLL1001800502300002901805100204301005703214INTHISEQUATION,THEMACHINEPARAMETERSHAVEBEENSCALEDTOTHERANGEOF0TO1,INDICATIVEOFTHEMAXIMUMFEASIBLEPROCESSINGRANGEFORTHISAPPLICATIONTHERESULTINGCOEFFICIENTSOFTHELINEARMODELAREACTUALCHANGEINPARTDIMENSIONSMEASUREDINMMITSHOULDBENOTEDTHATONCETOOLINGISCOMPLETED,THEDIMENSIONALCHANGESAVAILABLETHROUGHPROCESSINGAREQUITELIMITEDTHOUGHFUNCTIONALLYSIGNIFICANTTHEPRIMARYCONCLUSIONTHATSHOULDBEDRAWNFROMEQ4,HOWEVER,ISTHATALLTHEDIMENSIONSREACTSIMILARLYTOCHANGESINTHEPROCESSSETTINGSTHUS,THEMOLDINGPROCESSBEHAVESASAONEDEGREEOFFREEDOMPROCESSINWHICHONLYONEQUALITYATTRIBUTEISCONTROLLABLEONEOFNAMSUH’SAXIOMS14OFDESIGNSTATESTHAT“INDEPENDENCEOFFUNCTIONALREQUIREMENTSSHOULDBEMAINTAINED”THISAXIOMWASAPPLIEDTODEVELOPMULTIPLEDEGREESOFFREEDOMFORCONTROLOFMELTFLOWANDPRESSUREINTHEMOLDCAVITYASSHOWNINFIG4,THEVALVESMETERTHEFLOWOFMELTFROMTHERUNNERSINTOTHEMOLDCAVITYTHEPRESSUREDROPANDFLOWRATEOFTHEMELTISDYNAMICALLYVARIEDBYTHEAXIALMOVEMENTOFEACHVALVESTEMWHICHCONTROLSTHEGAPBETWEENTHEVALVESTEMANDTHEMOLDWALLBYDECOUPLINGTHECONTROLOFTHEMELTATDIFFERENTVALVESTEMPOSITIONS,MELTCONTROLATEACHGATECANOVERRIDETHEEFFECTSOFTHEMOLDINGMACHINEANDPROVIDEBETTERTIMERESPONSEANDDIFFERENTIALCONTROLOFTHEMELTEACHVALVEACTSASANINDIVIDUALINJECTIONUNIT,LESSENINGDEPENDENCYONMACHINEDYNAMICSFORCLOSEDLOOPCONTROL,MANIFOLDPRESSURETRANSDUCERSWEREUSEDINTHERUNNERDROPSINSTEADOFINTHECAVITYTHISIMPLEMENTATIONNOTONLYPROVIDESLOWERCOSTANDGREATERRELIABILITY,BUTALSORENDERSACONVENTIONALAPPEARANCEFORTHESYSTEMMELTINLETVALVE1VALVE2CAVITY1CAVITY2P1P2FIGURE4DYNAMICFLOWREGULATIONDESIGNTHERESULTINGCONTROLLABILITYOFTHEINJECTIONMOLDINGPROCESSISDEMONSTRATEDINFIG5WHEREMULTIPLEPRESSUREPROFILESCANBEMAINTAINEDINTHEMOLDCAVITYOFASINGLEPARTINTHESAMECYCLE,THREEDIFFERENTMAGNITUDESOFMELTPRESSUREWEREEXERTEDATDIFFERENTGATESINTHESAMEMOLDCAVITYTHECONTROLPRESSUREFORTHEHOLDINGSTAGEATGATE1IS414MPA6000PSI,GATE2IS414MPA6000PSI,GATE3IS207MPA3000PSI,ANDGATE4IS621MPA9000PSIINCONVENTIONALINJECTIONMOLDING,THEMELTPRESSUREWOULDBETHESAMEATALLGATESTHISLEVELOFPROCESSCONTROLHASNOTPREVIOUSLYBEENACHIEVEDBYANYMOLDINGTECHNOLOGYTHUSFAREACHGATECANEXERTASPECIFICHOLDINGPRESSURE010203040506070024681012TIMESECFIGURE5DYNAMICFLOWREGULATIONDESIGNTHEMATERIALSHRINKAGEANDDIMENSIONSCHANGEATDIFFERINGLOCATIONSINTHEPARTBASEDONTHEPRESSURECONTOURSANDHISTORIESAROUNDTHEGATESTHEABILITYTOCHANGEINDIVIDUALDIMENSIONSOROTHERQUALITYATTRIBUT

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