| 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 gap between the electrode and a workpiece and by comparing thus detected value with a reference value to control the rise of pulse voltage applied across the interpole gap. CONSTITUTION:A control instruction signal generating device 17 superposes high frequency alternate voltage from an electrical sources 18 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 15, and a current detector 6 detects interpole leakage current running due to the lowering of insulation of the machining fluid 3 which is caused by machined chips, so that thus detected current is compared with a preset reference value to discriminate the interpole condition. With the result of the discrimination a control instruction signal is fed to a control device 14 and the machining power source 15, and if there would be any risk that the degree of insulation of insulative machining fluid 3 is lowered so that abnormal electric discharge occurs, control is made such that the rise of pulse voltage is slowly changed. Thus, it is possible to prevent breakage of the wire electrode without the machining rate being lowered.
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