Injection molding machine and screw control method for injection molding machine

An injection molding machine comprising:

• a screw inserted in an injection cylinder and configured to be movable in an axial direction of the screw;
• a motor configured to advance the screw through a range of advancing positions to a foremost position;
• a torque detection unit configured to detect a torque of the motor;
• a position detection unit configured to detect a position of the screw in the range of advancing positions;
• a motor drive control unit configured to drive the motor while imposing torque limitation so that the torque of the motor does not exceed a limit torque, to thereby advance the screw to the foremost position in a direction of injection;
• and
• a determination unit configured to determine moving speeds of the screw in the range of advancing positions, the determination unit configured to determine if one of the moving speeds becomes lower than or equal to a predetermined speed while the screw is advancing along the range of advancing positions to the foremost position, and wherein the determination unit is configured to determine if unmelted resin remains inside the injection cylinder based on the moving speeds of the screw in the advancing positions.