Abstract: If a tool breakage occurs, a cutting time T and a maximum value (absolute value) G of a slope of a drop in a cutting load become small. A cutting load integrated value S increases as a tool wears and becomes small when the breakage occurs. Therefore, these values T, G, and S are obtained in a machining cycle, moving variable thresholds are obtained (updated) based on values T, G, and S obtained in a preceding machining cycle, and the thresholds and the values T, G, and S obtained in the current machining cycle are compared with each other to thereby determine an abnormal condition of the tool.

Abstract: A tool damage/abnormality detecting device capable of easily appropriately setting an allowable range for a value of comparison between a present value and a near past average for indexes indicative of loads on a tool. A machining cycle counter index i is adjusted to i=0, machining is performed as the loads are detected in a given period, and indexes H(i) (area S of load values, absolute value (G?) of a maximum inclination between two points obtained during a decrease of loads, etc.) are acquired for n number of cycles. Thereafter, the indexes and values of comparison between the index value for a present cycle and the indexes for the n number of cycles are acquired. A first comparison value can be used for initial value setting for threshold values. If any of the comparison values is deviated from the allowable range, the threshold values are updated so that the allowable range extends, and an update history is saved.

Abstract: A tool damage/abnormality detecting device capable of easily appropriately setting an allowable range for a value of comparison between a present value and a near past average for indexes indicative of loads on a tool. A machining cycle counter index i is adjusted to i=0, machining is performed as the loads are detected in a given period, and indexes H(i) (area S of load values, absolute value (G?) of a maximum inclination between two points obtained during a decrease of loads, etc.) are acquired for n number of cycles. Thereafter, the indexes and values of comparison between the index value for a present cycle and the indexes for the n number of cycles are acquired. A first comparison value can be used for initial value setting for threshold values. If any of the comparison values is deviated from the allowable range, the threshold values are updated so that the allowable range extends, and an update history is saved.

Abstract: If a tool breakage occurs, a cutting time T and a maximum value (absolute value) G of a slope of a drop in a cutting load become small. A cutting load integrated value S increases as a tool wears and becomes small when the breakage occurs. Therefore, these values T, G, and S are obtained in a machining cycle, moving variable thresholds are obtained (updated) based on values T, G, and S obtained in a preceding machining cycle, and the thresholds and the values T, G, and S obtained in the current machining cycle are compared with each other to thereby determine an abnormal condition of the tool.

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).