模具专业英语 作者 王浩钢 14456第9章.pptVIP

Lesson 9  Mould Cavities and Cores 　　The cavity and core give the molding its external and internal shapes respectively, the impression imparting the whole of the form to the molding. 　　We then proceeded to indicate alternative ways by which the cavity and core could be incorporated into the mould and found that these alternatives fell under two main headings, 　　namely the integer method and the insert method. Another method by which the cavity can be incorporated is by means of split inserts or splits. Integer cavity and core plates 　　When the cavity or core is machined from a large plate or block of steel, or is cast in one piece, and used without bolstering as one of the mould plates, it is termed an integer cavity plate or integer core plate. 　　This design is preferred for single-impression moulds because of the strength, smaller size and lower cost characteristics. 　　It is not used as much for multi-impression moulds as there are other factors such as alignment which must be taken into consideration. 　　Of the many manufacturing processes available for preparing moulds only two are normally used in this case. 　　These are (a) a direct machining operation on a rough steel forging or blank using the conventional machine tools, or (b) the ‘precision’ investment casting technique in which a master pattern is made of the cavity and core①. 　　The pattern is then used to prepare a casting of the cavity or core by a special process. 　　A 4.25% nickel-chrome-molybdenum steel (BS 970-835 M30) is normally specified for integer mould plates which are to be made by the direct machining method. 　　The precision investment casting method usually utilizes a high-chrome steel. Inserts cavity and core 　　For moulds containing intricate impressions, and for multi-impression moulds, it is not satisfactory to attempt to machine the cavity and core plates from single blocks of steel as with integer moulds②. 　　The machining sequences and operation would be altoge