| 摘要 |
PCT No. PCT/JP84/00601 Sec. 371 Date Aug. 7, 1985 Sec. 102(e) Date Aug. 7, 1985 PCT Filed Dec. 18, 1984 PCT Pub. No. WO85/02800 PCT Pub. Date Jul. 4, 1985.A position finding apparatus of an electric discharge machine has a switching device including a relay 3 set into operation when tool electrode position finding starts, so that the switching device turns off machining power applied across a workpiece W and a tool electrode P. At such time, a differentiated waveform, which is obtained by differentiating in a differentiating circuit 15, a square wave produced by a pulse oscillator, is applied across the workpiece W and tool electrode P. Thereafter, position finding is performed with regard to the tool electrode P. A resistor in the differentiating circuit 15 can be made variable in value to alter the differentiated waveform applied across the workpiece W and tool electrode P.
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