Abstract: A positioning correction method for a motor-operated injection molding machine, intended to eliminate waste of power supply to or overheat of servomotors by locking up in an ideal state the motor-operated injection molding machine, which uses a toggle mechanism or crank for mold clamping and other operations. During the lockup period, a load RA acting on a mold clamping servomotor 7 is detected (S8), and a position command value PM for the servomotor 7 is increased or decreased in the next cycle in a direction such that the value of the load RA is reduced, if the value of the load RA is greater than a preset reference value V0 (S12, S13). As a result, a rotation center Q1 of a crank 2 and two opposite ends Q2 of a link 3 are locked up in a straight line, so that a moment of rotation produced by a mold clamping reaction force is removed from the rotation center Q1 of the crank 2.

Abstract: An ejector mechanism which is simple in structure and facilitates the manufacture and assembling thereof, wherein a ball screw-spline shaft (10) of the ejector mechanism has a spline portion (11) fitted into a ball spline nut (20) fixed to a movable platen (1) of an injection molding machine, and a ball screw portion (12) threadedly engaged with a ball nut (30) which is rotatably supported by a casing (40) fixed to the movable platen. The ball nut is coupled to a motor (51) by toothed pulleys (52, 53) respectively secured to the ball nut and the output shaft of the motor, and a timing belt (54) looped round these pulleys. As the ball nut is rotated through motor rotation, the spline portion advances together with the ball screw portion, and a molded article is ejected by the distal end of the spline portion which acts as a molded article-ejecting portion.