US Patent 7462025 Controller for injection molding machine

There is provided the torque limiter for limiting a torque command to be output when pressure feedback control of the pressure holding step is performed. After the start of the pressure holding step, the torque limiter limits output torque of the servomotor for injection for a predetermined time period after the screw starts to move backward. As a result, the output torque in the backward direction of the screw is limited and reduced, whereby the speed of backward movement of the screw is reduced, and decrease of the pressure applied to the resin becomes moderate, thus abrupt drop of the pressure can be avoided.