模具专业英语 教学课件 作者 王浩钢 14456第7章.ppt

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1、Lesson7GatesThegateisachannelororificeconnectingtherunnerwiththeimpression.Ithasasmallcross-sectionalareawhencomparedwiththerestofthefeedsystem.Thissmallcross-sectionalareaisnecessarysothat:Figure7-1Typesofgate(i)Thegatefreezessoonaftertheimpressionisfilledsothattheinjectionplungercanbewithd

2、rawnwithouttheprobabilityofvoidbeingcreatedinthemoldingbysuck-back①.(ii)Itallowsforsimpledegatingandinsomemouldthisdegatingcanbeautomatic.(iii)Afterdegatingonlyasmallwitnessmarkremains.(iv)Bettercontrolofthefillingofmulti-impressionscanbeachieved.(v)Packingtheimpressionwithmaterialinexcessof

3、thatrequiredtocompensateforshrinkageisminimized②.Thesizeofthegatecanbeconsideredintermsofthegatecross-sectionalareaandthegatelength,thelatterbeingknownasgateland.Theoptimumsizeforagatewilldependonanumberoffactorsincluding:(i)theflowcharacteristicsofthematerialtobemolded;(ii)thewallsectionoft

4、hemolding;(iii)thevolumeofmaterialtobeinjectedintotheimpression;(iv)thetemperatureofthemelt;(v)thetemperatureofthemould.Notheoreticalsizeexistsfortheidealgate.Thegatesizechoseninpracticeforaparticularcomponentisnormallybasedonpastexperience.However,thereadermaynothavethisexperienceuponwhicht

5、obaseadecisionand,therefore,aguidetothedimensionsforeachgatetypeisgiven.Theguideapplies,exceptwhereotherwisestared,tothegeneralcaseofamoldingwithawallsectionbetween0.75mmand4mm.TypeofgateToobtaintheoptimumfillingconditionsthetypeofgatemustbecarefullychosen.Onmostoccasions,however,thechoicewi

6、llbeobviousasonlyonetypeofgatewillmeettheparticularrequirementsforthemoldingonhand.Thetypesofgate(seeFigure7-1)commonlyusedare:spruegate(f),edgegate(j),overlapgate(a),fangate(b),diaphragmgate(g),ringgate(h),filmgate(c),pingate(d),submarinegate(i)andtabgate(e).Notes①Thegatefreezessoonafterthe

7、impressionisfilledsothattheinjectionplungercanbewithdrawnwithouttheprobabilityofvoidbeingcreatedinthemoldingbysuck-back.型腔充满后，浇口处迅速凝固，可防止注射机螺杆后退时（引起的压力变化）造成塑件中的熔体回流。句中的soonafter引导的是时间状语从句修饰，sothat引导的目的状语从句修饰thegatefreezes。②Packingtheimpressionwithm