Method of setting terminal position of forward motion of ejector pins of ejector mechanism

Abstract

A controller and a method for an ejector mechanism in an injection molding machine for appropriately setting a terminal position of a forward motion of ejector pins of the ejector mechanism. The terminal position of the forward motion is set to a position where an elastic force of return springs does not exceed a retaining force of a brake device for retaining the ejector pins at the terminal position. The elastic force of the springs are detected during the ejector pins are moved forward. A position of the ejector pins immediately before the detected elastic force of the springs exceeds the retaining force of the brake device is determined and displayed on a display device as a criterial position. The terminal position of the forward motion of the ejector pins is set not to exceed the determined criterial position.

1 . A method of setting a terminal position of a forward motion of ejector pins of an ejector mechanism in an injection molding machine, having means for moving the ejector pins forward to project into a mold, springs for generating an elastic force to return the ejector pins to a retracted position, and brake means for generating a retaining force to retain the ejector pins at the terminal position, said method comprising: 
 moving the ejector pins forward from the retracted position in a state where no molded product is present in the mold;    detecting the elastic force of the springs during the forward motion of the ejector pins;    determining a criterial position of the ejector pins where the detected elastic force of the springs is equivalent to the retaining force of the brake means; and    setting the terminal position of the forward motion of the ejector pins closer to the retracted position than the determined critical position.