US Patent 7435070 Control apparatus for injection molding machine

When a metering process is started, a screw rotates at a preset rotating speed, thereby carrying out back pressure control to keep the pressure of a resin at a preset pressure, and retreats. When the screw is located near a preset metering completion position, the control mode is switched to positioning control for the preset metering completion position, and a screw rotation stop command is outputted. The screw overruns for some distance before its rotation stops after it retreats and stops at the preset metering completion position. A resin quantity for the overrun is corrected to obtain a preset metered resin quantity by reversely rotating the screw by a rotational amount corresponding to the overrun.