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ID:11270805
大小:128.00 KB
页数:9页
时间:2018-07-11
《注塑模具runner-design concept》由会员上传分享,免费在线阅读,更多相关内容在行业资料-天天文库。
1、Nowadays,injectionmoldersareunderincreasingpressure(punintended).Demandsfortighttolerances,near-zerorejects,andever-lowercostthatwereoncelimitedtoautomotiveandmedicaljobsarenowcommonevenformoldersofconsumerproducts.Moldershaveoftenrespondedbylimitingthemselvestomoldsoflowc
2、avitationbecausetheyareeasiesttobalancenaturally.Butlowcavitationrequiresmoremolds,moremachines,morefloorspaceforthemachines,andmorepeopletorunthem.Toremaincompetitiveinaglobalmarketplace,costcanonlybereducedbyproducingpartsfasterwithmoreconsistencyandlessscrap.Ifhigher-qu
3、alitypartscanbeproducedfromaneight-cavitymoldratherthanafour-cavitytool,orfrom16cavitiesinsteadofeight,costsavingsandgreatercustomersatisfactionwillfollow.Thequestionishowtogetthere.MeltFlipperinsertsusechangesinrunnerelevationto"flip"themeltorientationby90°,eliminatingasy
4、mmetricaldistributionofhotterandcoolermelttodivergingrunnerbranches.Thebasisofthesolutioncametomein1997whenIwaswrestlingwiththeissueofmold-fillingimbalance.Foryears,Ihadobservedimbalancesinwhathavealwaysbencalled"naturallybalanced"runners.Amemberofmycomputer-aided-engineer
5、ingconsortiumatPennStateEriewasencounteringjustsuchaproblem.Hiseight-cavitymoldwas"naturallybalanced,"andyetthepartsfromthemold'sinnercavitieswereconsistentlyheavierthanthosemadeincavitiesfartherfromthesprue.Tightweighttolerancesforthispartdidn'tallowforsuchvariation,andat
6、nearly$20/lb,materialwastehadtobeheldtoaminimum.Ifirstblamedthetwousualsuspects:coolingvariationscreatedbyhigherthermalloadoftheplasticpartsnearthecenterofthemold,andplatedeflectionwithinthemold.Thesestandardscapegoatshadservedindustrywellforyears.Butthismoldhadawell-desig
7、nedcoolingsystemthatprovidedincreasedcoolingtotheinnercavities.Onelookatthemold'srigidsupportcolumnsandtheparts'thickwallstoldmeplatedeflectionwasn'ttheproblemeither.Fig.1—Highshearandfrictionalheatingneartheouterwallofarunnerchannellowertheviscosityinthisregion.Thisisther
8、ootcauseoffillingimbalances.Fig.2—FIDAPanalysisoutputshowstheasymmetricaltemperaturedistr
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