Patent ID: 6011376
Filing Date: 2000-01-04
Classification: G05B

Abstract:
A method of controlling a motor driven element of an injection molding machine, the machine element being driven along an axis by a motor through a drive mechanism, the method comprising the steps of:sensing an actual position of the machine element along the axis;sensing angular position of the motor shaft;determining an expected position of the machine element from the angular position;determining the difference between the actual position and the expected position; andgenerating an error signal representing an aberrant operating condition of the machine when the difference exceeds a predetermined tolerance value for a predetermined period of time, wherein measuring the predetermined period of time comprises the steps of:setting a counter to a reset value when the difference exceeds the predetermined tolerance value;periodically decrementing the counter at a predetermined interval for so long as the difference exceeds the tolerance value;generating the error signal when the counter reaches a predetermined value; andresetting the counter to a predetermined initial value when the difference does not exceed the tolerance value.