PURPOSE: To permit suckback motion quickly and effectively, by a method wherein the suckback motion of a screw is effected in high speed during the timing of a timer and is effected in low speed after the timing-out of the timer.
CONSTITUTION: In the control method of the suckback of an injection molder, a timer, which starts timing by the starting signal of suckback, is provided to effect the suckback motion in high speed during the timing of the timer and in low speed after the timing-out of the timer. The timer starts the timing thereof simultaneously with the starting of the suckback motion and a large delivery pump 5 as well as a small delivery pump 4 are operated in C zone in a diagram, in which the timer is being operated, and pressure oil of a large capacity is applied on an oil chamber 6b for retreating an injection cylinder 6 whereby the screw 3 is retreated in a high speed. Subsequently, the large delivery pump 5 is unloaded by the time-out signal of the timer and the amount of oil, which is applied on the oil chamber 6b, becomes only the oil delivered by the small delivery pump 4 whereby the retreating speed becomes low while the suckback motion is stopped when a suckback time D is finished.
ITO YOSHIAKI
IKEDA TAKESHI
