Patent ID: 6937942

Claim:
A method of detecting tool abnormality in a machine tool having a spindle motor and a servomotor, said method comprising the steps of: determining permissible minimum and maximum values of load current for one or both of the spindle motor and the servomotor during normal operation of the machine tool; measuring a load current of one or both of the spindle motor and the servomotor while the machine tool is operated; extracting the load current measured only in a real cutting section other than a non-cutting section by way of filtering the measured load current; judging whether the extracted load current lies in a range between the permissible minimum and the maximum values; and confirming occurrence of a tool abnormality if the extracted load current falls outside the range; wherein said extracting step comprises excluding the load current measured in an approach section, a pocket section, a receding section, en accelerating section and a decelerating section.