Cutter fracture detecting system

Abstract

A cutter fracture detecting system capable of easily detecting a fracture of a cutter having a plurality of cutting edges even when one of the cutting edges is broken. The cutter fracture detecting system has an observer for calculating a disturbance load torque of a spindle motor from a torque command value and a velocity feedback value, a band rejection filter for removing a given frequency component of the disturbance load torque which is determined by the number of cutting edges of the cutter and the rotational speed of the cutter, and a comparator for comparing an output signal from the band rejection filter with a predetermined reference value, and outputting a signal indicative of a fracture of the cutter when the output signal exceeds the predetermined reference value. In the event of a fracture of the cutter with plural cutting edges, a signal is generated that cannot be removed by the band rejection filter, and such a signal is monitored by the comparator.

Dependencies are inferred from the claim text.