| 摘要 |
PURPOSE:To make it possible to simply and certainly set an adequate comparison reference value regardless of various elements, by multiplying a detection level, at the point of time when the rising change ratio of the AE level during a period directly after the beginning of processing is lowered, by a difinite quantity ratio. CONSTITUTION:Acoustic emission (AE), which is generated in a drill when a hole is opened to a workpiece 3 by a drilling in such a state that an AE sensor 2 is attached to the main body side of a boring machine 1, is detected by said sensor 2. The output of the sensor 2 is amplified to a predetermined level by an amplifier circuit 6 and, thereafter, a band component is taken out by a band pass filter (BPF) 7 to rectify a detector circuit 8. The output of the circuit 8 is succeedingly monitored by CPU11 through an A/D converter 10 and a detection output value, at the point of time when the change ratio of said output is lowered to a definite value or less, is detected and CPU11 feeds out the value, which is obtained by multiplying said detection value by a definite quantity ratio by a D/A converter 14, as the comparison reference value of a comparator circuit 9. |
