Integer Cavity and Core Plates
Let us consider the methods of incorporating cavity and core. We have now seen that in general the core is incorporated in the moving half and the cavity in the fixed half. However, there are various methods by which the cavity and core can be incorporated in their respective halves of the mold. These represent two basic alternatives: (a) the integer methods where the cavity and core can be machined from the steel plates which become part of the structual build-up of the mold, or (b) the cavity and core can be machined from samll blocks of steel, termed inserts, and subsequently, bolstered. The choice between these alternatives constitutes an important decision on the part of the mold designer. The final result, nevertheless, will be the same whichever method of manufacturer is chosen. In either design the plate or assembly which contains the core is termed the core plate and the plate or assembly which contains the cavity is termed the cavity plate.
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 mold plates, it is termed and integer cavity plate or integer core plate. This design is preferred for singke-impression molds because of the strength, samller size and lower cost characteristics. It is not used as much for multi-impression molds as there are other factors such as alignment which must be taken into consideration. Typical mold designs which incorporate an integer cavity and core.
Of many manufacturing process available for preparing molds only two are nomally used in this case. There are a direct machining operation on a rough steel forging blank using the conventional machine tools, or the ‘precision’ investment casting technique in which a master pattern is made of the cavity and core. The pattern us then used to prepare a casting of the cavity or core by special process. A 4-1% nickel-chrome-molybdenum steel ( BS 970-835 M30) is normally specified for integer mold plates which are to be made by the direct maching method. The precision investment casting method usually utilizes a high-chrome steel. For more plastic tools fabrication and parts molding plastic visit our website: http://www.plastics-china.com, thanks!