MONITORING OF INJECTION PRESSURE

PURPOSE:To enable to indicate an abnormal condition and a section in which the abnormal condition is generated and prevent reject articles from being generated, by a method wherein monitoring points are determined by measuring an actual injection cycle time and dividing it by a preset divisor, and a reference value is determined by measuring an actual injection pressure. CONSTITUTION:A CPU 12 calculates the injection high-temperature time (t) for the second shot from the start of the operation on the basis of an injection start signal and an injection high-pressure completion signal sent from a molding machine controller 11, and stores the calculated value into a memory 13. In addition, the CPU 12 divides said time (t) by a divisor N set on a divisor setter 14, to calculate a monitoring interval, and stores it into the memory 13. From the third shot onward, with an injection start signal received from the controller 11, the pressure sent from a pressure amplifier 8 is measured at the monitoring intervals stored in the memory, and is stored into the memory 13. This operation is repeated a number of times to obtain an upper limit and a lower limit, and thereafter control is performed on the basis of the upper and lower limits.