Measurement control method of an injection molding machine

A measurement control method of an injection molding machine in which a measurement is performed by rotating a screw, and a measurement is ended when the screw retracts to a preset measurement ending position, comprising:

• calculating a ending target position by adding a prescribed length to the measurement ending position, the prescribed length selected to be within 0.01 through 0.05 mm;
• presetting a rotation rate pattern for rotating a screw so that the rotating screw is stopped at the ending target position;
• presetting a back pressure in relation to the screw and a retraction rate pattern for the screw to retract;
• detecting a screw position at a prescribed time interval at the time of the measurement;
• calculating the remaining rotation rate pattern for stopping the rotation of the screw at the ending target position from the detected screw position;
• controlling the rotation of the screw to stop while the rotation of the screw is controlled by the calculated rotation rate pattern when the screw reaches the measurement ending position;
• detecting a retraction rate of the screw at a prescribed time interval;
• and calculating the remaining retraction rate pattern based on the detected retraction rate and the amount of resin;
• controlling the retraction of the screw by selecting a smaller control amount of either a pressure control amount for performing the back pressure control or a position control amount for performing the position control to the measurement ending position at the time of prediction, and stopping the retraction of the screw when the screw reaches the measurement ending position.