Tool abnormality detecting device

Abstract

A tool abnormality detecting device capable of precisely detecting an abnormality of a tool of a machine tool and timely requiring a change of the tool. Disturbance torques ys and yz exerted on a spindle motor and a Z-axis feed motor, respectively, in machining are estimated and stored in a data table. Averages ysav 1 and yzav1 of ys and yz, respectively, in a period from a point of time preceding the present time by a time period T1 to the present time are obtained as presumed present loads. Running thresholds are determined based on averages ysav23 and yzav23 of ys and yz, respectively, in a period from a point of time preceding the present time by a time period T2 to a point of time preceding the present time by a time period T3 (T1<T2<T3). The presumed present loads ysav 1 and yzav1 are compared with the running thresholds, respectively, and if any of the presumed present loads ysav 1 and yzav1 deviates from the running threshold, it is discriminated that an abnormality of the tool occurred and a signal requesting a change of the tool is issued after the present machining cycle. The running threshold may be determined based on an average waveform of the disturbance torque in a plurality of past machining cycles.

Dependencies are inferred from the claim text.