SERVO CONTROL FOR MOLDING MACHINE

A method and apparatus are provided for servo control of injection molding machine devices. A signal processor periodically produces analogue control signals for controlling machine mechanisms at a first loop closure interval and periodically produces digital control signals for controlling energization of machine heaters at a second loop closure interval. Values of analogue and digital control signals are determined according to control algorithms relating set point values and measured parameter values. Calculation of values of analogue control signals includes calculation of a first command value according to a first control algorithm, calculation of a second command value according to a second control algorithm and selection of the lesser of the first and second command values. Compensation for "cold" thermocouple junctions created at the connection of remote temperature sensing thermocouple leads and the signal processor interface circuits is provided. DC output interface circuits including two stage over-current protection are provided.