模具专业英语 教学课件 作者 王浩钢 14456第18章.ppt

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1、Lesson18ColdHobbingColdhobbingisaprocessinwhichahardenedsteelmasterhobisforcedintoasoftsteelblankunderconsiderablepressure.Hobbingisusedfortheproductionofcavitieswhichbyvirtueoftheirshapewouldbedifficulttodie-sinkonconventionalmachinetools.Thebasicprincipleofhobbingisillust

2、ratedinFigure18-1.Figure18-1stagesofmanufactureofcavityinsertbycoldhobbingtechniqueThehobbingprocessisparticularlyapplicablefortheproductionofcavitiesonmulti-impressionmoulds.Onemasterhobcanoftenbeusedtoproduceanumberofcavities,therebysavingconsiderablemachiningtime.Providi

3、ngthehobishighlypolished,thehobbingstoowillhaveagoodsurfacefinish,whichsavesbenchfinishingandpolishingtime.Ingeneralamalehobiseasiertomanufacturethanacorrespondingcavityofthesameform;howeversomeshapesareverydifficulttohobandcarefulconsiderationmustbegiventoaprojectbeforeatt

4、emptingtousethistechnique.①Foreaseofhobbing,alow-carbonsteelisusuallyusedforthehobbingblank.Asstatedabove,afterthehobbingoperationthehobbedinsertiscase-hardened.Thismeansthattheoutsidesurface(includingthecavityform)isextremelyhardwhereastheinternalcoreofthesteelremainsrelat

5、ivelysoft.Thusifinproductionalocalizedhighforceisdevelopedthereisapossibilitythatthesurfaceoftheimpressionmaybedepressed.Notes①Ingeneralamalehobiseasiertomanufacturethanacorrespondingcavityofthesameform;howeversomeshapesareverydifficulttohobandcarefulconsiderationmustbegive

6、ntoaprojectbeforeattemptingtousethistechnique.通常，对于同一轮廓形状，凸模的加工制造比凹模容易得多，但有些凸模形状也很难挤制成型，在采用这种加工方法前，对其工艺方案必须仔细斟酌。