| 摘要 |
PURPOSE:To prevent accidents due to damage of an electrode, by detecting the degree of insulation of an insulative machining fluid existing in the interpole gap and by comparing thus detected value with a reference value to control the servo-gain during the length of the gap between an workpiece and the electrode is servo-controlled. CONSTITUTION:High frequency voltage is superposed during a deionizing period or the quiescent time of pulse voltage applied between a wire electrode 2 and a workpiece 1 from a machining power source, and a current detector 6 detects interpole leakage current running due to the lowering of insulation of the machining fluid. When thus detected current value exceeds a predetermined value, a control instruction signal generating device delivers an insulation deteriorating signal V1<, and abnormal electric discharge is counted by a counter 25 which is reset by normal signal V1 through V2. Further, a control means 31 changes the servo-gain of a motor drive amplifier 105 through a amplifier 101 in addition to an intrinsic speed instruction voltage P in accordance with the output of the counter 25 to control the speed of a table feed motor Mx, and therefore, the interpole gap may be rapidly changed. Further, it is possible to surely prevent damage of the electrode without lowering the rate of machining.
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