INJECTION MOLDING MACHINE

PURPOSE:To improve the efficiency of an injection molding cycle, and to enhance to quality of a molded form by detecting the speed of retreat of a plunger mounted into a barrel rotatably and movable front to rear and controlling a material pushing feeder or a rotating drive for the plunger so that the speed of retreat reaches a fixed value. CONSTITUTION:A plunger 24 is retreated gradually in a weighing process, but the speed of retreat of the plunger is detected by a detector 80, and input to a controller 82. In the controller 82, the reference speed of retreat previously set and the current speed of retreat are compared, and a control signal is output to valves 87, 88 in response to the difference of the speed of retreat. When both valves 87, 88 are throttle at that time, the number of revolution of a motor 35 is decreased and the speed of a stuffer plunger 30 is decelerated, and the speed of weighing (speed of retreat of the plunger) is reduced. When the openings of the valves 87, 88n are enlarged, inversely, the speed of the motor 35 is increased and the rate of fall of the stuffer plunger 30 is accelerated, and the speed of weighing is gathered. Accordingly, the speed of weighting is controlled so as to be brought to a fixed value or the fixed value or more.