Verfahren und Apparat zum Spritzgießen

摘要

An injection molding method in which a metal mold 1 has a valve gate 7 for mechanically opening and closing a passage to an injection molding cavity 3. The timing of the closing of the valve gate 7 is set with reference to molten resin pressure in the cavity 3 during a holding pressure step in the molding cycle. Alternatively, the timing of valve gate closure is set with reference to the start of the pressure holding step, eg from 0.2 second after the start up to the time of gate sealing, according to the period which gives the best dimensional accuracy in the obtained product. The molding method and apparatus result in high-accuracy injection molding of their products by utilizing a valve gate system; and also result in molded products from different cavities of a multiple mold, having less variation even where a plurality of products are molded at the same time. <IMAGE>