模具专业英语 教学课件 作者 王浩钢 14456第8章.ppt

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1、Lesson8PartingSurfaceThepartingsurfacesofamouldarethoseportionofbothmouldplates,adjacenttotheimpressions,whichbutttogethertoformasealandpreventthelossofplasticmaterialfromtheimpression①.Thepartingsurfaceisclassifiedflatandnon-flat.FlatpartingsurfaceThematureofthepartingsurfacedependsentire

2、lyontheshapeofthecomponent.Forinstance,thepartingsurfaceoftherectangularmoldingisshowninFigure8-1(a).Thecavityforthisarticlecanbedie-sunkintoonemouldplate.Thepositionofthepartingsurfacewillthereforebeatthetopofthemolding,thepartingsurfaceitselfbeingperfectlyflat.Forappearancethisistheideal

3、arrangementasthepartinglineisnotnoticeableunlessflashdevelops.Afurtherconsiderationisthatthepartingsurfacemustbechosensothatthemoldingcanberemovedfromthemould.Figure8-1(b)showsthepartingsurfaceofaflatrectangularmoldingwhichincorporatesadouble-beveledge.Thesuitablechoiceforthepartinglineiso

4、nthecentreofthedouble-bevelwhichallowsforhalfoftherequiredformtobedie-sunkintoeachofthetwomouldhalves.Thepartinglinemustoccuralongthelineroundthepositionofmaximumdimensionwhenviewedinthedrawdirection.Figure8-1FlatpartingsurfaceNon-flatpartingsurfaceManymoldingsarerequiredwhichhaveapartingl

5、inewhichliesonanon-planarorcurvedsurface.Inthesecasesthemould’spartingsurfacemusteitherbeangled(a),profiled(b)orstepped(c)(inFigure8-2).Figure8-2Typesofnon-flatpartingsurfaceBalancingofmouldsurfacesWhenthepartingsurfaceisnotflat,thereisthequestionofunbalancedforcestoconsiderincertaininstan

6、ces.Figure8-3showsamouldwithasteppedpartingsurface.Theplasticmaterialwhenunderpressurewithintheimpression,willexertaforcewhichwilltendtoopenthemouldinthelateraldirection(seeFigure8-3(a)).Ifthishappenssomeflashingmayoccurontheangledface.Themovementbetweenthetwomouldhalveswillberesistedbythe

7、guidepillars,butevenso,becauseofthelargeforcesinvolved,itisdesirabletobalancethemouldbyreversingthestep(Figure8-3(b))sothatthepartingsurfacecontinuesacrossthemouldasamirrorimageofthesectionwhichincludestheimpression②.Itisoftenconvenienttospecifyanevennumberofi