注塑模具英文翻译.docx
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注塑模具英文翻译.docx
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注塑模具英文翻译
Minimizingmanufacturingcostsforthininjectionmoldedplasticcomponents
1.Introduction
Inmostindustrialapplications,themanufacturingcostofaplasticpartismainlygovernedbytheamountofmaterialusedinthemoldingprocess.
Thus,currentapproachesforplasticpartdesignandmanufacturingfocusprimarilyonestablishingtheminimumpartthicknesstoreducematerialusage.
Theassumptionisthatdesigningthemoldandmoldingprocessestotheminimumthicknessrequirementshouldleadtotheminimummanufacturingcost.
Nowadays,electronicproductssuchasmobilephonesandmedicaldevicesarebecomingevermorecomplexandtheirsizesarecontinuallybeingreduced.
Thedemandforsmallandthinplasticcomponentsforminiaturizationassemblyhasconsiderablyincreasedinrecentyears.
Otherfactorsbesidesminimalmaterialusagemayalsobecomeimportantwhenmanufacturingthinplasticcomponents.
Inparticular,forthinparts,theinjectionmoldingpressuremaybecomesignificantandhastobeconsideredinthefirstphaseofmanufacturing.
Employingcurrentdesignapproachesforplasticpartswillfailtoproducethetrueminimummanufacturingcostinthesecases.
Thus,tacklingthinplasticpartsrequiresanewapproach,alongsideexistingmolddesignprinciplesandmoldingtechniques.
1.1Currentresearch
Today,computer-aidedsimulationsoftwareisessentialforthedesignofplasticpartsandmolds.Suchsoftwareincreasestheefficiencyofthedesignprocessbyreducingthedesigncostandleadtime[1].
Majorsystems,suchasMoldFlowandC-Flow,usefiniteelementanalysistosimulatethefillingphenomena,includingflowpatternsandfillingsequences.Thus,themoldingconditionscanbepredictedandvalidated,sothatearlydesignmodificationscanbeachieved.Althoughavailablesoftwareiscapableofanalyzingtheflowconditions,andthestressandthetemperaturedistributionconditionsofthecomponentundervariousmoldingscenarios,theydonotyielddesignparameterswithminimummanufacturingcost[2,3].
Theoutputdataofthesoftwareonlygiveparametervaluerangesforreferenceandleavesthedecisionmakingtothecomponentdesigner.Severalattemptshavealsobeenmadetooptimizetheparametersinfeeding[4–7],cooling[2,8,9],andejectionTheseattemptswerebasedonmaximizingtheflowabilityofmoltenmaterialduringthemoldingprocessbyusingempiricalrelationshipsbetweentheproductandmolddesignparameters.
SomeresearchershavemadeeffortstoimproveplasticpartqualitybyReducingthesinkmark[11]andthepartdeformationaftermolding[12],analyzingtheeffectsofwallthicknessandtheflowlengthofthepart[13],andanalyzingtheinternalstructureoftheplasticpartdesignandfillingmaterialsflowsofthemolddesign[14].Reifschneider[15]hascomparedthreetypesofmoldfillingsimulationprograms,includingPartAdviser,Fusion,andInsight,withactualexperimentaltesting.Alltheseapproacheshaveestablishedmethodsthatcansavealotoftimeandcost.However,theyjusttackledthedesignparametersoftheplasticpartandmoldindividuallyduringthedesignstage.Inaddition,theydidnotprovidethedesignparameterswithminimummanufacturingcost.
Studiesapplyingvariousartificialintelligencemethodsandtechniqueshavebeenfoundthatmainlyfocusonoptimizationanalysisofinjectionmoldingparameters[16,17].Forin-stanceHeetal.[3]introducedafuzzy-neuroapproachforautomaticresettingofmoldingprocessparameters.Bycontrast,Helpsetal.[18,19]adoptedartificialneuralnetworkstopredictthesettingofmoldingconditionsandplasticpartqualitycontrolinmolding.Clearly,thedevelopmentofcomprehensivemoldingprocessmodelsandcomputer-aidedmanufacturingprovidesabasisforrealizingmoldingparameteroptimization[3,16,17].Moketal.[20]proposeahybridneuralnetworkandgeneticalgorithmapproachincorporatingCase-BasedReasoning(CBR)toderiveinitialsettingsformoldingparametersforpartswithsimilardesignfeaturesquicklyandwithacceptableaccuracy.Mok’sapproachwasbasedonpastproductprocessingdata,andwaslimitedtodesignsthataresimilartopreviousproductdata.However,norealR&Defforthasbeenfoundthatconsidersminimizingmanufacturingcostsforthinplasticcomponents.
Generally,thecurrentpracticalapproachforminimizingthemanufacturingcostofplasticcomponentsistominimizethethicknessandthedimensionsofthepartattheproductdesignstage,andthentocalculatethecostsofthemolddesignandmoldingprocessforthepartaccordingly,asshowninFig.1.
Thecurrentapproachmaynotbeabletoobtaintherealminimummanufacturingcostwhenhandlingthinplasticcomponents.
1.2ManufacturingrequirementsforatypicalthinplasticcomponentAsatestexample,thetypicalmanufacturingrequirementsforathinsquareplasticpartwithacenterhole,asshowninFig.2,aregiveninTable1.
Fig.1.Thecurrentpracticalapproach
Fig.2.Testexampleofasmall
plasticcomponent
Table1.Customerrequirementsfortheexamplecomponent
2.Thecurrentpracticalapproach
AsshowninFig.1,thecurrentapproachconsistsofthreephases:
productdesign,molddesignandmoldingprocessparametersetting.Amainobjectiveintheproductdesignistoestablishthephysicaldimensionsofthepartsuchasitsthickness,widthandlength.Thephasesofmoldedsignandmoldingsubsequentlytreattheestablishedphysicaldimensionsasgiveninputstocalculatetherequireddetailsformoldmakingandmoldingoperations.
Whenapplyingthecurrentpracticalapproachfortacklingthegivenexample,thekeyvariablesarehandledbythethreephasesasfollows:
Productdesign
*Establishtheminimumthickness(height)HP,andthencalculatethematerialcost.HPisthentreatedasapredeterminedinputforthecalculationofthecostsofmold
designandmoldingoperations.HP
Molddesign
*Calculatethecoolingtimeforthedeterminedminimum
thicknessHPinordertoobtainthenumberofmoldcavitiesrequired.Themoldmakingcostisthenthesumofthecoststomachinethe:
–Depthofcutting(thickness)HP
–Numberofcavities
–RunnerdiameterDR
–GatethicknessHG
Moldingprocess
*DeterminetheinjectionpressurePin,andthenthecostofpowerconsumption
●Determinethecoolingtimetco,andthenthecostofmachineoperations.Theoverallmoldingcostisthesumofthepowerconsumptioncostandmachineoperatingcost.
Thetotalmanufacturingcostisthesumofthecostsofplasticmaterial,moldmakingandmoldingoperations.Notethat,inaccordancewithtypicalindustrypractice,allofthefollowingcalculationsareintermsofunitcosts.
2.1Productdesign
Thisisthefirstmanufacturingphaseofthecurrentpracticalapproach.ThedesignminimizesthethicknessHPoftheplasticcomponenttomeetthecreeploadingdeflectionconstraint,Y(<1.47mmafter1yearofusage),andtominimizeplasticmaterialusagecostCm.MinimizingHPrequires[21]:
Figure3plotschangesinHPthroughEqs.1and2.Thegraphsshowthatthesmallestthicknessthatmeetsthe1.47mmmaximumcreepdeflectionconstraintis0.75mm,withaplasticmaterialcostof$0.000483558/unitandabatchsizeof200000units.
Thisthicknesswillbetreatedasagiveninputforthesubsequentmoldedsignandmoldingprocessanalysisphases.
2.2Molddesign
2.2.1Determinationofcoolingtime
Thedesiredmoldtemperatureis25C.Thedeterminedthicknessis0.75mm.Figure4showsthecoolingchannelslayoutfollowingstandardindustrypractices.Thecoolingchanneldiameterischosentobe3mmforthisexample.
From[22],thecoolingtimetco:
Andthelocationfactor,
BysolvingEqs.3and4,andsubstitutingHP=0.75mmandthegivenvaluesofthecoolingchanneldesignparameters,thecoolingtime(3.1s)isobtained.
Thecycletimetcycle,givenbyEq.5,isproportionaltothemoldingmachineoperatingcosts,andconsistsofinjectiontime(tin),ejectiontime(tej),drycycletime(tdc),andcoolingtime(tco).
2.2.2DeterminationofthenumberofmoldcavitiesIngeneral,thecostofmoldmakingdependsontheamountofmachiningworktoformtherequirednumberofcores/cavities,runners,andgates.Thegivenexamplecallsforatwo-platemold
Fig.3.
DeflectionandplasticmaterialscostsversuspartthicknessFig.4.Coolingchannellayoutthatdoesnotrequireundercutmachining.Therefore,themachiningworkforcuttingtherunnersandgatesisproportionaltotheworkinvolvedinformingthecores/cavitiesandneednotbeconsidered.Intheexample,moldmakingcostCmmisgovernedby(n,HP).
Generally,theminimumnumberofcavities,Nmin,ischosentoallowfordeliveryofthebatchofplasticpartsontime图3。
Aftersubstitution
whichisroundedTon=3,sincethemoldcannotcontain2.64cavities.Themachineoperationcapacityandthelead-timeofproductionintheexamplearegivenas21.5h/dand21d,respectively.Moreover,asmentionedintheprevioussection,thecycletimeisdirectlyproportionaltothepartthicknessHP.AcurveofbatchsizeagainstthicknessisplottedinFig.5.Asshown,atHP=0.75mm,theproductioncapability(batchsize)is242470units.Thustheproductioncapabilityofn=3islargerthantherequiredlotsize(200000units).
Forsimplicity,thetimetakenformachiningthedepthofathincomponentistreatedasagivenconstantandaddedtotherequiredtimetCCformakingacavityinsert.TheCmmcanthenbecalculatedbynasexpressed[1]
2.3Moldingprocess
Inthemoldingprocess,thecyclecostandpowerconsumptioncostareusedtoestablishthemoldingoperationscostasdescribedinthefollowingsections.
Fig.5
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