In plastic injection molding, stabilization of measurement accuracy is one of the important processes to stabilize molding. If the filling amount of the molten resin is unstable, molding will also be unstable. Even after the plasticization of the material is completed, pressure remains on the check valve of the screw, and this pressure causes the molten resin to be sent little by little to the tip of the screw.

As a way to reduce this amount, the screw rotation speed and back pressure can be set low to reduce the remaining pressure. Lowering the screw rotation speed shortens the screw stopping time after plasticization and shortens the time for molten resin to be sent to the front of the screw after plasticization, thereby reducing the variation in weighing accuracy.