INJECTION AND DWELLING CONTROL DEVICE OF INJECTION MOLDER

PURPOSE:To prevent pressure surging from generating and flash from developing in a molded item by a structure wherein a cascade control system, outside of which a screw position feedback control system to control the screw position for the injection of resin is provided, is equipped and a limiter, which limits the maximum pressure applied to resin in the injection process of resin, is provided at the onputting section of setpoint of a pressure feedback control system. CONSTITUTION:An adder 11 catches the output out of a position compensator 8 in the form of pressure value so as to give it as it is to a limiter 14 in injection process and, at the same time, to give the sum of the pressure value out of the position compensator 8 and the set point of pressure to the limiter 14 in dwelling process. The limiter 14 limits the pressure applied to resin below the predetermined maximum value in injection process and, at the same time, gives no limitation to the pressure applied to resin is dwelling process. The output of the limiter 14 or set point of pressure is compared by means of a comparator 17 with the measured value sent from a pressure detector 18 and the result of comparison is given to a pressure compensator 19. The output of the pressure compensator 19 is amplified with an amplifier 20 and given to a servo valve 2h. At the same time, the servo valve 2h controls the position of a screw 2d, resulting in preventing pressure surging from developing.