| 摘要 |
PURPOSE:To detect the instant of contact, by blowing an AC, e.g., a very weak high- frequency current, between a material to be machined or its driving table and a main spindle head, and detecting the inductance change of a high-frequency circuit, which is generated at the instant when a surface to be machined and a cutting tool are contacted from the state they are separated. CONSTITUTION:Figure (e) shows the output voltage of a comparator IC1, i.e., the voltage at a point E, when input voltages shown in Figures (c) and (d) are applied to input terminals. The output voltage at the point E is obtained as a pulse output, which becomes positive only during a period DELTAt, wherein a non-inverted input voltage becomes larger than the inverted input voltage to the comparator IC1. The pulse width DELTAt is approximately determined by the time constant of an RC integrating circuit. Figure (f) shows the output voltage of memory circuit 10 comprising a flip-flop, which is triggered by the pulse output shown in the Figure (e), i.e., the output voltage at a point F. The amount of change in high-frequency oscillating voltage when a cutting tool is contacted with a surface where a hole is to be machined is small, but the rate of change is very large. The memory circuit 10 has a function of outputting the definite change of the DC voltage. The main-spindle driving of a machine tool 1 is controlled by the memory circuit 10. |
