| 摘要 |
PURPOSE:To attempt an accurate decision on an exchange time through a means indicating the exchange time of electricity-feeding portion by comparing a detected value with a reference value through providing a means detecting an electric current flowing from an electric discharge machining circuit to a wire disconnection detecting circuit and a means detecting a machining speed. CONSTITUTION:When the upper electricity-feeding die 2 gets to wear, its contact-state with a wire electrode 4 becomes bad, and a switching element 12 repeats 'ON-OFF'. By this, electricity-storage and reverse start-up power occur at a circuit inductance 15, and an electric current flows into a wire disconnection circuit 16. Because of this, a current value by means of an electric current detector 18 increases, and this value is inputted to a comparator 26 and compared with a reference current value. Also, because of the wear of the die 2, a machining speed lowers and a command value from a motor control circuit 25 to a drive motor 24 lowers, and this value, too, is inputted to the comparator 26 and compared with a reference value and indicated on a CRT 7. By this, the exchange time of an electricity-feeding portion can be accurately decided.
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