METHOD FOR CONTROLLING IN-MOLD PRESSURE OF COMPRESSION INJECTION MOLDER

摘要

PURPOSE:To simultaneously compress and plasticize and contrive to shorten cycle by a method wherein the sealing force of an opening and closing mechanism is changed in arbitrary pattern with time so as to resist against the flow of resin running from the mold side to the injection device side of the opening and closing mechanism during compression process in order to control in-mold pressure. CONSTITUTION:After the completion of in-mold filling, the compression of cavity starts simultaneously with the start of plasticization. At this time, the sealing pressure of an opening and closing valve 13 is determined by controlling the liquid pressure of the E part of a hydraulic cylinder 19 with a pressure valve 20 after the optimum pattern with time, which is determined by the molded item. Concretely, though the resin in an in-mold space A is compressed as the in-mold space A becomes small through the advancement of a core mold, when the pressure of the resin in the in-mold space A tends to become higher than the sealing pressure of the opening and closing valve 13 abutting against a cavity mold 4, the plunger 14 of the opening and closing valve 13 retreats so as to flow the resin backwards to the tip space B of a screw cylinder 11, resulting in controlling the pressure of the resin after the optimum pattern. Since the pressure in an injection cylinder necessary for plasticization can be set independently from the pressure necessary in compression process, compression and plasticization can be possible simultaneously.