Injection molding controller with process variable learning

Claim 1

A controller for use with an injection molding machine having a ram to inject plastic material into a mold cavity during at least one stage of an injection molding cycle, the injection molding machine having a valve for receiving a control signal and controlling the ram, and a transducer for producing a process signal related to a response of the ram to the control signal, the controller comprising: a memory for storing profile data for the at least one stage, the profile data being comprised of a plurality of segments of data each segment having a start and end delineated by startpoint data and each segment associated with a velocity setpoint; a segment pointer for addressing the memory and identifying a current segment and the segment's current setpoint and for producing a transition signal at the end of a segment; an open-loop control means for receiving the current setpoint determined by the segment pointer and converting the current setpoint to a first control signal for controlling the valve during a first period during the current segment; a closed-loop control means for receiving the process signal from the injection molding machine and the current setpoint determined by the segment pointer to produce a second control signal for controlling the valve during a second period during the current segment and after the first period; and a setpoint correcting means responsive to the transition signal to compare the process signal at the end of the segment to the current setpoint in the memory to reduce a difference between the process signal and the current setpoint by changing the current setpoint in memory.