| 摘要 |
PURPOSE:To prevent accidents due to damage of an electrode without lowering the rate of machining, 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 tension of a wire electrode. 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 the 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, the tension of the wire electrode 2 applied by a wire feed and tension roller 10 is reduced so that the wire electrode whose proof-tension is weakened due to wire- consumption is prevented from being broken. Thus, it is possible to prevent breakage of the wire electrode without the machining rate being lowered.
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