模具专业英语 教学课件 作者 王浩钢 14456第6章.ppt

《模具专业英语 教学课件 作者 王浩钢 14456第6章.ppt》由会员上传分享，免费在线阅读，更多相关内容在应用文档-天天文库。

1、Lesson6RunnerTherunnerisachannelmachinedintothemouldplatetoconnectthespruewiththeentrancetotheimpression.Thewalloftherunnerchannelmustbesmoothtopreventanyrestrictiontoflow.Also,astherunnerhastoberemovedwiththemolding,theremustbenomachinemarksleftwhichwouldtendtoretaintherunnerinthemouldpla

2、te.Toensurethatthesepointsaremet,itisdesirableforthemoulddesignertospecifythattherunnerispolished‘inlineofdraw’.Therearesomeotherconsiderationsforthedesignertobearinmind:(i)theshapeofthecrosssectionoftherunner;(ii)thesizeoftherunner;(iii)therunnerlayout.Runnercross-sectionshapeThecross-sec

3、tionalshapeoftherunnerusedinamouldisusuallyoneoffourforms(Figure6-1):(a)fullyround,(b)trapezoidal,(c)modifiedtrapezoidaland(d)hexagonal.Figure6-1RunnerprofilesThecriterionofefficientrunnerdesignisthattherunnershouldprovideamaximumcross-sectionareafromthestandpointofpressuretransferandamini

4、mumcontactontheperipheryfromthestandpointofheattransfer①.Theratioofcross-sectionalareatoperipherywill,therefore,giveadirectindicationoftheefficiencyoftherunnerdesign;thehigherthevaluethegreatertheefficiency.RatiosforvarioustypesofrunnersectionaregiveninFigure6-2.Ascanbeseen,theroundandsqua

5、retypesofrunnerarethetwomostsatisfactorydesignsfromthisstandpoint;whereastheratiosexhibitedbythesemicircularandrectangulartypesmaketheirusegenerallyundesirable.Figure6-2EfficiencyofvariousrunnerprofilesRunnersizeWhendecidingthesizeoftherunnerthedesignermustconsiderthefollowingfactors:(i)th

6、ewallsectionandvolumeofthemolding;(ii)thedistanceoftheimpressionfromthemainrunnerorsprue;(iii)runnercoolingconsiderations;(iv)therangeofmouldmaker’scuttersavailable;(v)theplasticsmaterialtobeused.RunnerlayoutThelayoutoftherunnersystemwilldependuponthefollowingfactors:(i)therunnerofimpressi

7、on;(ii)theshapeofthecomponents;(iii)thetypeofmould(i.e.,two-plateormulti-platemould);(iv)thetypeofgate.Whendesigningarunnersystemtherearetwomainconsiderations.Therunnerlengthshouldalwaysbekepttoaminimumtoreducepressurelosses,andtherunnersystemshouldbebalanced.