US Patent 7311508 Control device for injection molding machine

A control device includes: a memory 29r for storing, in a process from a mold tool 10 being open until being closed, the value X(t) of a current flowing in a motor 3 at multiple points in time synchronized to the closing command signal; a mean-and-variance calculating for each of the points in time means for calculating a mean value Mx(t) and a variance value Vx(t) that correspond to current values X(t) that have been read from the memory 29r; a threshold calculating means for calculating a current threshold Xf(t) for each of the points in time using the mean value Mx(t) and the variance value Vx(t) from an arbitrary number of times up to (A−1) times, according to the following equation: Xf(t)=Mx(t)+N·{Vx(t)}1/2