Abnormality of an injection molding machine

A movable unit in an injection molding machine is put into operation and the physical actual value and the actual time (or the actual position of the movable unit) are recorded. The physical actual value is stored as a physical reference value with respect to the elapsed operation time of the movable unit (or the position of the movable unit). A deviation of the physical actual size of the physical reference value is calculated and stored, a distribution index value is then calculated from the deviations of the physical quantities in the first to n-th cycles, and a limit value is determined by the distribution index value. If the deviation exceeds the threshold value, an alarm processing is performed.