1、Journal of Materials Processing Technology 171(2006)259267Design and thermal analysis of plastic injection mouldS.H.Tang,Y.M.Kong,S.M.Sapuan,R.Samin,S.SulaimanDepartment of Mechanical and Manufacturing Engineering,Universiti Putra Malaysia,43400 Serdang,Selangor,MalaysiaReceived 3 September 2004;acc
2、epted 21 June 2005AbstractThis paper presents the design of a plastic injection mould for producing warpage testing specimen and performing thermal analysis forthe mould to access on the effect of thermal residual stress in the mould.The technique,theory,methods as well as consideration neededin des
3、igning of plastic injection mould are presented.Design of mould was carried out using commercial computer aided design softwareUnigraphics,Version 13.0.The model for thermal residual stress analysis due to uneven cooling of the specimen was developed and solvedusing a commercial finite element analy
4、sis software called LUSAS Analyst,Version 13.5.The software provides contour plot of temperaturedistribution for the model and also temperature variation through the plastic injection molding cycle by plotting time response curves.Theresults show that shrinkage is likely to occur in the region near
5、the cooling channels as compared to other regions.This uneven cooling effectat different regions of mould contributed to warpage.2005 Elsevier B.V.All rights reserved.Keywords:Plastic Injection mould;Design;Thermal analysis1.IntroductionPlastic industry is one of the worlds fastest growingindustries
6、,ranked as one of the few billion-dollar industries.Almost every product that is used in daily life involves theusage of plastic and most of these products can be producedby plastic injection molding method 1.Plastic injectionmolding process is well known as the manufacturing processtocreateproducts
7、withvariousshapesandcomplexgeometryat low cost 2.The plastic injection molding process is a cyclic process.There are four significant stages in the process.These stagesare filling,packing,cooling and ejection.The plastic injec-tion molding process begins with feeding the resin and theappropriateaddi
8、tivesfromthehoppertotheheating/injectionsystemoftheinjectionplasticinjectionmoldingmachine3.This is the“filling stage”in which the mould cavity is filledwithhotpolymermeltatinjectiontemperature.Afterthecav-ityisfilled,inthe“packingstage”,additionalpolymermeltispacked into the cavity at a higher pres
9、sure to compensate theexpectedshrinkageasthepolymersolidifies.ThisisfollowedCorresponding author.E-mail address:saihongeng.upm.edu.my(S.H.Tang).by“cooling stage”where the mould is cooled until the part issufficiently rigid to be ejected.The last step is the“ejectionstage”in which the mould is opened
10、 and the part is ejected,after which the mould is closed again to begin the next cycle4.The design and manufacture of injection molded poly-meric parts with desired properties is a costly process domi-nated by empiricism,including the repeated modification ofactual tooling.Among the task of mould de
11、sign,designingthe mould specific supplementary geometry,usually on thecore side,is quite complicated by the inclusion of projectionand depression 5.In order to design a mould,many important designingfactors must be taken into consideration.These factors aremouldsize,numberofcavity,cavitylayouts,runn
12、ersystems,gating systems,shrinkage and ejection system 6.In thermal analysis of the mould,the main objective isto analyze the effect of thermal residual stress or molded-instresses on product dimension.Thermally induced stressesdevelop principally during the cooling stage of an injectionmolded part,
13、mainly as a consequence of its low thermalconductivity and the difference in temperature between themolten resin and the mould.An uneven temperature fieldexists around product cavity during cooling 7.0924-0136/$see front matter 2005 Elsevier B.V.All rights reserved.doi:10.1016/j.jmatprotec.2005.06.0
14、75260S.H.Tang et al./Journal of Materials Processing Technology 171(2006)259267During cooling,location near the cooling channel experi-ences more cooling than location far away from the coolingchannel.This different temperature causes the material toexperience differential shrinkage causing thermal
15、stresses.Significantthermalstresscancausewarpageproblem.There-fore,itisimportanttosimulatethethermalresidualstressfieldof the injection-molded part during the cooling stage 8.Byunderstanding the characteristics of thermal stress distribu-tion,deformation caused by the thermal residual stress canbe p
16、redicted.In this paper the design of a plastic injection mould forproducingwarpagetestingspecimenandforperformingther-mal analysis for the mould to access on the effect of thermalresidual stress in the mould is presented.2.Methodology2.1.Design of warpage testing specimenThis section illustrates the design of the warpage testingspecimen to be used in plastic injection mould.It is clearthat warpage is the main problem that exists in product withthin shell feature.Therefore,the main purpose of the
