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CONCURRENTDESIGNOFPLASTICSINJECTIONMOULDSAbstractTheplasticproductmanufacturingindustryhasbeengrowingrapidlyinrecentyears.Oneofthemostpopularprocessesformakingplasticpartsisinjectionmoulding.Thedesignofinjectionmouldiscriticallyimportanttoproductqualityandefficientproductprocessing.Mould-makingcompanies,whowishtomaintainthecompetitiveedge,desiretoshortenbothdesignandmanufacturingleadingtimesofthebyapplyingasystematicmoulddesignprocess.Themouldindustryisanimportantsupportindustryduringtheproductdevelopmentprocess,servingasanimportantlinkbetweentheproductdesignerandmanufacturer.Productdevelopmenthaschangedfromthetraditionalserialprocessofdesign,followedbymanufacture,toamoreorganizedconcurrentprocesswheredesignandmanufactureareconsideredataveryearlystageofdesign.Theconceptofconcurrentengineering(CE)isnolongernewandyetitisstillapplicableandrelevantintodaysmanufacturingenvironment.Teamworkingspirit,managementinvolvement,totaldesignprocessandintegrationofITtoolsarestilltheessenceofCE.TheapplicationofTheCEprocesstothedesignofaninjectionprocessinvolvesthesimultaneousconsiderationofplasticpartdesign,moulddesignandinjectionmouldingmachineselection,productionschedulingandcostasearlyaspossibleinthedesignstage.Thispaperpresentsthebasicstructureofaninjectionmoulddesign.Thebasisofthissystemarisesfromananalysisoftheinjectionmoulddesignprocessformoulddesigncompanies.Thisinjectionmoulddesignsystemcoversboththemoulddesignprocessandmouldknowledgemanagement.Finallytheprincipleofconcurrentengineeringprocessisoutlinedandthenitsprincipleisappliedtothedesignofaplasticinjectionmould.Keywords:Plasticinjectionmoulddesign,Concurrentengineering,Computeraidedengineering,Mouldingconditions,Plasticinjectionmoulding,Flowsimulation1.IntroductionInjectionmouldsarealwaysexpensivetomake,unfortunatelywithoutamoulditcannotbepossiblehohaveamouldedproduct.Everymouldmakerhashis/herownapproachtodesignamouldandtherearemanydifferentwaysofdesigningandbuildingamould.Surelyoneofthemostcriticalparameterstobeconsideredinthedesignstageofthemouldisthenumberofcavities,methodsofinjection,typesofrunners,methodsofgating,methodsofejection,capacityandfeaturesoftheinjectionmouldingmachines.Mouldcost,mouldqualityandcostofmouldproductareinseparableIntodayscompletiveenvironment,computeraidedmouldfillingsimulationpackagescanaccuratelypredictthefillpatternsofanypart.Thisallowsforquicksimulationsofgateplacementsandhelpsfindingtheoptimallocation.Engineerscanperformmouldingtrialsonthecomputerbeforethepartdesigniscompleted.Processengineerscansystematicallypredictadesignandprocesswindow,andcanobtaininformationaboutthecumulativeeffectoftheprocessvariablesthatinfluencepartperformance,cost,andappearance.2.InjectionMouldingInjectionmouldingisoneofthemosteffectivewaystobringoutthebestinplastics.Itisuniversallyusedtomakecomplex,finishedparts,ofteninasinglestep,economically,preciselyandwithlittlewaste.Massproductionofplasticpartsmostlyutilizesmoulds.Themanufacturingprocessandinvolvingmouldsmustbedesignedafterpassingthroughtheappearanceevaluationandthestructureoptimizationoftheproductdesign.Designersfaceahugenumberofoptionswhentheycreateinjection-mouldedcomponents.Concurrentengineeringrequiresanengineertoconsiderthemanufacturingprocessofthedesignedproductinthedevelopmentphase.Agooddesignoftheproductisunabletogotothemarketifitsmanufacturingprocessisimpossibleortooexpensive.Integrationofprocesssimulation,rapidprototypingandmanufacturingcanreducetheriskassociatedwithmovingfromCADtoCAMandfurtherenhancethevalidityoftheproductdevelopment.3.ImportanceofComputerAidedInjectionMouldDesignTheinjectionmouldingdesigntaskcanbehighlycomplex.ComputerAidedEngineering(CAE)analysistoolsprovideenormousadvantagesofenablingdesignengineerstoconsidervirtuallyandpart,mouldandinjectionparameterswithouttherealuseofanymanufacturingandtime.Thepossibilityoftryingalternativedesignsorconceptsonthecomputerscreengivestheengineerstheopportunitytoeliminatepotentialproblemsbeforebeginningtherealproduction.Moreover,invirtualenvironment,designerscanquicklyandeasilyassesthesensitivityofspecificmouldingparametersonthequalityandmanufacturabilityofthefinalproduct.AlltheseCAEtoolsenablealltheseanalysistobecompletedinameterofdaysorevenhours,ratherthanweeksormonthsneededfortherealexperimentaltrialanderrorcycles.AsCAEisusedintheearlydesignofpart,mouldandmouldingparameters,thecostsavingsaresubstantialnotonlybecauseofbestfunctioningpartandtimesavingsbutalsotheshortensthetimeneededtolaunchtheproducttothemarket.Theneedtomeetsettolerancesofplasticparttiesintoallaspectsofthemouldingprocess,includingpartsizeandshape,resinchemicalstructure,thefillersused,mouldcavitylayout,gating,mouldcoolingandthereleasemechanismsused.Giventhiscomplexity,designersoftenusecomputerdesigntools,suchasfiniteelementanalysis(FEA)andmouldfillinganalysis(MFA),toreducedevelopmenttimeandcost.FEAdeterminesstrain,stressanddeflectioninapartbydividingthestructureintosmallelementswheretheseparameterscanbewelldefined.MFAevaluatesgatepositionandsizetooptimizeresinflow.Italsodefinesplacementofweldlines,areasofexcessivestress,andhowwallandribthicknessaffectflow.Otherfiniteelementdesigntoolsincludemouldcoolinganalysisfortemperaturedistribution,andcycletimeandshrinkageanalysisfordimensionalcontrolandpredictionoffrozenstressandwarpage.TheCAEanalysisofcompressionmouldedpartsisshowninFigure1.TheanalysiscyclestartswiththecreationofaCADmodelandafiniteelementmeshofthemouldcavity.Aftertheinjectionconditionsarespecified,mouldfilling,fiberorientation,curingandthermalhistory,shrinkageandwarpagecanbesimulated.Thematerialpropertiescalculatedbythesimulationcanbeusedtomodelthestructuralbehaviourofthepart.Ifrequired,partdesign,gatelocationandshrinkageandwarpagecanbesimulated.Thematerialpropertiescalculatedbythesimulationcanbeusedtomodelthestructuralbehaviourofthepart.Ifrequired,partdesign,gatelocationandprocessingconditionscanbemodifiedinthecomputeruntilanacceptablepartisobtained.Aftertheanalysisisfinishedanoptimizedpartcanbeproducedwithreducedweldline(knownalsoknitline),optimizedstrength,controlledtemperaturesandcuring,minimizedshrinkageandwarpage.Machiningofthemouldswasformerlydonemanually,withatoolmakercheckingeachcut.ThisprocessbecamemoreautomatedwiththegrowthandwidespreaduseofcomputernumericallycontrolledorCNCmachiningcentres.SetuptimehasalsobeensignificantlyreducedthroughtheuseofspecialsoftwarecapableofgeneratingcutterpathsdirectlyfromaCADdatafile.Spindlespeedsashighas100,000rpmprovidefurtheradvancesinhighspeedmachining.Cuttingmaterialshavedemonstratedphenomenalperformancewithouttheuseofanycutting/coolantfluidwhatsoever.Asaresult,theprocessofmachiningcomplexcoresandcavitieshasbeenaccelerated.Itisgoodnewsthatthetimeittakestogenerateamouldisconstantlybeingreduced.Thebadnews,ontheotherhand,isthatevenwithalltheseadvances,designingandmanufacturingofthemouldcanstilltakealongtimeandcanbeextremelyexpensive.Manycompanyexecutivesnowrealizehowvitalitistodeploynewproductstomarketrapidly.Newproductsarethekeytocorporateprosperity.Theydrivecorporaterevenues,marketshares,bottomlinesandshareprices.Acompanyabletolaunchgoodqualityproductswithreasonablepricesaheadoftheircompetitionnotonlyrealizes100%ofthemarketbeforerivalproductsarrivebutalsotendstomaintainadominantpositionforafewyearsevenaftercompetitiveproductshavefinallybeenannounced(Smith,1991).Formostproducts,thesetwoadvantagesaredramatic.Rapidproductdevelopmentisnowakeyaspectofcompetitivesuccess.Figure2showsthatonly37%oftheproductmixfromtheaverageindustrialorelectronicscompanyislessthan5yearsold.Forcompaniesinthetopquartile,thenumberincreasesto1525%.Forworld-classfirms,itis6080%(Thompson,1996).Thebestcompaniescontinuouslydevelopnewproducts.AtHewlett-Packard,over80%oftheprofitsresultfromproductslessthan2yearsold!(Neel,1997)Figure1Importanceofnewproduct(Jacobs,2000)Withtheadvancesincomputertechnologyandartificialintelligence,effortshavebeendirectedtoreducethecostandleadtimeinthedesignandmanufactureofaninjectionmould.Injectionmoulddesignhasbeenthemainareaofinterestsinceitisacomplexprocessinvolvingseveralsub-designsrelatedtovariouscomponentsofthemould,eachrequiringexpertknowledgeandexperience.Leeet.al.(1997)proposedasystematicmethodologyandknowledgebaseforinjectionmoulddesigninaconcurrentengineeringenvironment.4.ConcurrentEngineeringinMouldDesignConcurrentEngineering(CE)isasystematicapproachtointegratedproductdevelopmentprocess.Itrepresentsteamvaluesofco-operation,trustandsharinginsuchamannerthatdecisionmakingisbyconsensus,involvingallperspectivesinparallel,fromtheverybeginningoftheproductlife-cycle(Evans,1998).Essentially,CEprovidesacollaborative,co-operative,collectiveandsimultaneousengineeringworkingenvironment.Aconcurrentengineeringapproachisbasedonfivekeyelements:（1）.process（2）.multidisciplinaryteam（3）.integrateddesignmodel（4）.facility（5）.softwareinfrastructureFigure2Methodologiesinplasticinjectionmoulddesign,a)Serialengineeringb)ConcurrentengineeringIntheplasticsandmouldindustry,CEisveryimportantduetothehighcosttoolingandlongleadtimes.Typically,CEisutilizedbymanufacturingprototypetoolingearlyinthedesignphasetoanalyzeandadjustthedesign.Productiontoolingismanufacturedasthefinalstep.Themanufacturingprocessandinvolvingmouldsmustbedesignedafterpassingthroughtheappearanceevaluationandthestructureoptimizationoftheproductdesign.CErequiresanengineertoconsiderthemanufacturingprocessofthedesignedproductinthedevelopmentphase.Agooddesignoftheproductisunabletogotothemarketifitsmanufacturingprocessisimpossible.IntegrationofprocesssimulationandrapidprototypingandmanufacturingcanreducetheriskassociatedwithmovingfromCADtoCAMandfurtherenhancethevalidityoftheproductdevelopment.Foryears,designershavebeenrestrictedinwhattheycanproduceastheygenerallyhavetodesignformanufacture(DFM)thatis,adjusttheirdesignintenttoenablethecomponent(orassembly)tobemanufacturedusingaparticularprocessorprocesses.Inaddition,ifamouldisusedtoproduceanitem,therearethereforeautomaticallyinherentrestrictionstothedesignimposedattheverybeginning.Takinginjectionmouldingasanexample,inordertoprocessacomponentsuccessfully,ataminimum,thefollowingdesignelementsneedtobetakenintoaccount:（1）geometry; draftangles,Nonre-entrantsshapes, nearconstantwallthickness, complexity,splitlinelocation,andsurfacefinish,（2）materialchoice;（3）rationalisationofcomponents(reducingassemblies);（4）.cost.Ininjectionmoulding,themanufactureofthemouldtoproducetheinjection-mouldedcomponentsisusuallythelongestpartoftheproductdevelopmentprocess.Whenutilisingrapidmodelling,theCADtakesthelongertimeandthereforebecomesthebottleneck.Theprocessdesignandinjectionmouldingofplasticsinvolvesrathercomplicatedandtimeconsumingactivitiesincludingpartdesign,moulddesign,injectionmouldingmachineselection,productionscheduling,toolingandcostestimation.Traditionallyalltheseactivitiesaredonebypartdesignersandmouldmakingpersonnelinasequentialmanneraftercompletinginjectionmouldedplasticpartdesign.Obviouslythesesequentialstagescouldleadtolongproductdevelopmenttime.Howeverwiththeimplementationofconcurrentengineeringprocessintheallparameterseffectingproductdesign,moulddesign,machineselection,productionscheduling,toolingandprocessingcostareconsideredasearlyaspossibleinthedesignoftheplasticpart.Whenusedeffectively,CAEmethodsprovideenormouscostandtimesavingsforthepartdesignandmanufacturing.Thesetoolsallowengineerstovirtuallytesthowthepartwillbeprocessedandhowitperformsduringitsnormaloperatinglife.Thematerialsupplier,designer,moulderandmanufacturershouldapplythesetoolsconcurrentlyearlyinthedesignstageoftheplasticpartsinordertoexploitthecostbenefitofCAE.CAEmakesitpossibletoreplacetraditional,sequentialdecision-makingprocedureswithaconcurrentdesignprocess,inwhichallpartiescaninteractandshareinformation,Figure3.Forplasticinjectionmoulding,CAEandrelateddesigndataprovideanintegratedenvironmentthatfacilitatesconcurrentengineeringforthedesignandmanufactureofthepartandmould,aswellasmaterialselectionandsimulationofoptimalprocesscontrolparameters.QualitativeexpensecomparisonassociatedwiththepartdesignchangesisshowninFigure4,showingthefactthatwhendesignchangesaredoneatanearlystagesonthecomputerscreen,thecostassociatedwithisanorderof10.000timeslowerthanthatifthepartisinproduction.Thesemodificationsinplasticpartscouldarisefrommouldmodifications,suchasgatelocation,thicknesschanges,productiondelays,qualitycosts,machinesetuptimes,ordesignchangeinplasticparts.Figure3Costofdesignchangesduringpartproductdevelopmentcycle(Rioset.al,2001)Attheearlydesignstage,partdesignersandmouldershavetofinalisepartdesignbasedontheirexperienceswithsimilarparts.Howeverasthepartsbecomemorecomplex,itgetsratherdifficulttopredictprocessingandpartperformancewithouttheuseofCAEtools.Thusforevenrelativelycomplexparts,theuseofCAEtoolstopreventthelateandexpensivedesignchangesandproblemsthatcanariseduringandafterinjection.Forthesuccessfulimplementationofconcurrentengineering,theremustbebuy-infromeveryoneinvolved.5.CaseStudyFigure5showstheinitialCADdesignofplasticspartusedforthesprinklerirrigationhydrantleg.Oneoftheessentialfeaturesofthepartisthattheparthastoremainflatafterinjection;anywarpingduringtheinjectioncausesoperatingproblems.Anotherimportantfeaturetheplasticparthastohaveisahighbendingstiffness.AnumberoffeedersindifferentorientationwereaddedtothepartasshowninFigure5b.Thesefeedersshouldbedesignedinawaythatithastocontributetheweightofthepartasminimumaspossible.Beforethedesignofthemould,theflowanalysisoftheplasticpartwascarriedoutwithMoldflowsoftwaretoenabletheselectionofthebestgatelocationFigure6a.Thefigureindicatesthatthebestpointforthegatelocationisthemiddlefeederatthecentreofthepart.Asthedistortionandwarpageofthepartafterinjectionwasvitalfromthefunctionalitypointofviewandithastobekeptataminimumlevel,thesamesoftwarewasalsoutilisedtoyiledthewarpageanalysis.Figure5bshowstheresultsimplyingthefactthatthewarpagewellafterinjectionremainswithinthepredefineddimensionaltolerances.6.ConclusionsIntheplasticinjectionmoulding,theCADmodeloftheplasticpartobtainedfromcommercial3Dprogramscouldbeusedforthepartperformanceandinjectionprocessanalyses.WiththeaidofCEAtechnologyandtheuseofconcurrentengineeringmethodology,notonlytheinjectionmouldcanbedesignedandmanufacturedinaveryshortofperiodoftimewithaminimisedcostbutalsoallpotentialproblemswhichmayarisefrompartdesign,moulddesignandprocessingparameterscouldbeeliminatedattheverybeginningofthemoulddesign.Thesetwotoolshelppartdesignersandmouldmakerstodevelopagoodproductwithabetterdeliveryandfastertoolingwithlesstimeandmoney.塑料注塑模具并行设计摘要塑料制品制造业近年迅速成长。其中最受欢迎的制作过程是注塑塑料零件。注塑模具的设计对产品质量和效率的产品加工非常重要。模具公司想保持竞争优势,就必须缩短模具设计和制造的周期。模具是工业的一个重要支持行业，在产品开发过程中作为一个重要产品设计师和制造商之间的联系。产品开发经历了从传统的串行开发设计制造到有组织的并行设计和制造过程中,被认为是在非常早期的阶段的设计。并行工程的概念(CE)不再是新的,但它仍然是适用于当今的相关环境。团队合作精神、管理参与、总体设计过程和整合IT工具仍然是并行工程的本质。CE过程的应用设计的注射过程包括同时考虑塑件设计、模具设计和注塑成型机的选择、生产调度和成本中尽快设计阶段。介绍了注射模具的基本结构设计。在该系统的基础上,模具设计公司分析注塑模具设计过程。该注射模设计系统包括模具设计过程及模具知识管理。最后的原则概述了塑料注射模并行工程过程并对其原理应用到设计。关键词:塑料注射模设计、并行工程、计算机辅助工程、成型条件、塑料注塑、流动模拟。1、简介注塑模具总是昂贵的,不幸的是没有模具就不可能生产模具制品。每一个模具制造商都他/她自己的方法来设计模具,有许多不同的设计与建造模具。当然最关键的参数之一,要考虑到模具设计阶段是大量的计算、注射的方法,浇注的的方法、研究注射成型机容量和特点。模具的成本、模具的质量和制件质量是分不开的在针对今天的计算机辅助充型模拟软件包能准确地预测任何部分充填模式环境中。这允许快速模拟实习,帮助找到模具的最佳位置。工程师可以在电脑上执行成型试验前完成零件设计。工程师可以预测过程系统设计和加工窗口,并能获得信息累积所带来的影响,如部分过程变量影响性能、成本、外观等。2、注射成型法注塑成型是最有效的方法之一,将塑料最好的一面呈现。这是普遍用于制造复杂的制件,优点是简单、经济、准确与少浪费。塑料零件的批量生产主要采用模具。产品设计制造过程包括模具的结构必须经过外观评价和结构优化。当设计师创造注射模具组件时，他们面临一个巨大的多种选择，并行工程需要一个工程师考虑制产品在发展阶段时的过程设计。一个好的产品设计为了满足市场其制造过程是不可能太贵的。CAD/CAM整合了过程仿真、快速成形制造能减少风险,进一步提高产品开发的有效性。3、注塑模具设计重要的计算机辅助注射模具设计任务是相当复杂的。计算机辅助工程(CAE)分析工具提供了巨大的优势让设计工程师考虑几乎所有模具、注塑参数没有真正利用的地方。在可能性的设计、理念设计师，给工程师们机会去消除潜在的问题,开始真正的生产。此外,在虚拟环境中,设计师可以快速而方便地评估特定的成型参数敏感性的质量和生产最终产品。所有这些分析工具使所有模具设计将在一天甚至数小时完成,而不需要几周或几个月来做真正的实验反复试验。CAE用于早期设计的部分,模具和注塑模具参数、节约成本是实质功能不仅是最好的部分,而且还能节省和缩短开发产品推向市场的时间。在所有方面的成型过程中需要满足塑料部分设置的公差,包括零件的尺寸和形状,树脂的化学结构、填料使用,模具型腔布置、浇注、模具冷却并释放机制使用。面对这复杂性,设计师经常使用电脑设计工具,如有限元分析(FEA)和充型分析(MFA),减少开发时间和成本。有限元分析确定部分结构的应变、应力和挠度,在那里这些参数可以很好地被定义。冲型分析位置和大小进行优化树脂流动。它还定义了焊缝的位置、面积过大的压力,以及如何影响墙壁和肋厚度流动。其它有限元分析设计工具包括模具冷却温度分布,分析周期时间和收缩为空间控制和预测冻结应力、翘曲变形等情况。采用CAE分析部分压缩模如图1所示。分析周期始于创造一个CAD模型和有限元网格的模具腔。在注入条件规定,充型、纤维取向、固化和热历史、收缩和翘曲变形等情况进行仿真。该材料的性能计算模型模拟可用于结构的行为的一部分。如果需要部分设计浇口位置及加工条件可以在电脑上修改,直到一个可接受的零件的表达式。摘要分析了一个优化完成部分可采用降低weldline(亦即也knitline),优化力量、控制温度和固化、最小收缩和翘曲变形等情况。模具加工的前身是手工制作,如检查每一剪机床维修工。自动化的增长和普遍使用的电脑数值控制或CNC加工中心使这过程变得更加简便。设计的时间也被大大降低通过使用特殊的软件能够产生刀具路径直接从CAD数据文件提取。主轴速度高达100000每分钟转速提一步提出了高速加工。切削材料已经证明了惊人的表现而不使用任何的剪切/冷却液,什么都没有。作为一个结果,加工过程复杂的型心和型腔已经加快了。这是一个好消息,产生一个模具所花费的时间不断的被减少。坏消息是,另一方面,甚至所有这些进步、设计和制造的模具仍然要花很长时间,是非常昂贵的。许多公司的经理人现在体会部署新产品推向市场迅速发展是多么的重要。企业的繁荣关键在于新产品。他们推动企业的收入、市场份额、底线和股票价格。一个公司能够发明优质的产品和合理的价格领先其竞争不仅实现了100%的打败市场竞争对手的产品,但之前到达也倾向于保持主导地位甚至几年之后终于宣布竞争产品(史密斯,1991)。对大多数产品来说,这两个优势是戏剧性的。现在产品快速发展的一个关键方面的竞争成功。图2显示,只有3-7%的产品结构与一般的工业或电子公司是小于5岁。公司在第一四分位,这个数字增加到15-25%。一流的公司,它是60-80%(汤普森,1996)。最好的公司在不断开发新产品。在惠普,超过80%的利润结果从产品小于2岁!(Neel,1997)图1重要的新产品(雅克布,2000)以先进的计算机技术和人工智能,努力已经被指向降低成本和交货时间在设计和制造注塑模具。注塑模具设计主要感兴趣的地区,因为它是一个复杂的过程涉及到很多表面设计等各零件的模具,每个都需要专家的知识和经验。李et.艾尔。(1997)提出了一种系统的方法关于注塑模具设计的知识库和并行工程环境。4、并行工程在模具设计中并行工程(CE)是一个系统性的方法来集成产品开发过程。它代表了团队合作的价值观、信任和分享,以这样的方式,决策是通过协商一致,包括视角并联,从一开始就产品的整个生命周期(埃文斯,1998)。从本质上讲,CE提供合作、合作、集体和同步工程的工作环境。一个并行工程的方法是基于五个关键要素：（1）、过程（2）、多学科小组（3）、综合设计模型（4）、设施（5）、软件基础设施
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