METHOD FOR CONTROLLING INJECTION OF PLASTIC INJECTION MOLDER

摘要

PURPOSE:To make it possible to precisely detect injection starting position by realizing the state that the non-return valve of a plunger is put under completely sealed state so as to completely prevent molten plastic from flowing backward by a method wherein a pre-injection process is provided before the injection action of the molten plastic into a mold. CONSTITUTION:A pre-injection process is provided between a molten plastic filling process and an injection process. During the pre-injection process, a nozzle 22, which is provided between a feed cylinder 10 and a mold 24, is closed so as to apply the predetermined pressure to the molten plastic packed in the cylinder 10 by the advancement of a plunger 14. By the advancement of the plunger 14, the position, at which a non-return valve 18 is sealed, is detected. By adopting a position a little to the forward direction of the plunger 14 beyond said sealed position as the injection starting position, the leakage of the backflow of molten plastic after the start of the injection to the mold 24 is prevented from occurring.