US Patent 7261538 Monitoring device for an injection molding machine

A monitoring device for an injection molding machine whereby the state of resin sheared by a rotating screw can be easily monitored. During the period from the start to end of metering process, the rate of heat generated by a heater for heating an injection cylinder is obtained by multiplying an on/off ratio B of the heater by a coefficient K and stored in a memory location THmem(n). Also, a time elapsed from the start of the metering is obtained by adding up a processing period T and stored in a memory location Tim(n). The heat generation rates of the heater stored in memory and corresponding to the respective elapsed times are displayed in graph form. The temperature of the injection cylinder represents heat generated by the heater plus heat generated due to resin shearing. Since the heat generation rate of the heater is detected, the rate of heat generated due to resin shearing can be grasped relatively from the detected heat generation rate, making it possible to monitor the state of the resin sheared by the rotating screw. The resin shearing state can be monitored by simple processing of detecting and displaying the heat generation rate of the heater.