| 摘要 |
<p>PURPOSE:To exactly discriminate an abnormal tool even in case of a small diameter tool or light cutting, by comparing a value of a main shaft motor current required for cutting, with a reference data, only in case when the tool is in a cutting state. CONSTITUTION:A main shaft motor current detecting signal from an NC machine tool 1 is inputted to a comparing circuit 25 through a primary smoothing circuit 21 and a secondary smoothing circuit 22, and its minimum value is stored in a no-load rotating current memory 24. Subsequently, a difference between an output of the circuit 21 derived by a subtracting circuit 23, and an output of the memory 24 is supplied to a cutting state deciding circuit 27, and whether the tool is in a cutting stage or not is decided. On the other hand, in case of the instruction cutting mode, an output of the subtracting circuit 23 is stored in a reference data memory 29 through a mode switching circuit 28, and in case of the monitoring cutting mode, a current value purely required for cutting is compared with a reference data by an abnormal tool detecting circuit 31, and whether a fault of a tool has occurred or not is decided.</p> |
