JPS6416317A - Electric discharge machine - Google Patents

Abstract

PURPOSE:To prevent the abnormal electric discharge and always carrying out the stable electric discharge machining by installing a means for controlling the pulling-up and down of an electrode with the optimum cycle, feeding speed, and distance in accordance with the state of the working gap. CONSTITUTION:The voltage generated in the working gap between a working electrode 1 and a workpiece 2 is averaged by the passing through the first low-path filter 4 whose time constant can be varied, and inputted into the (+) terminal of the first differential amplifier 5, and a standard output voltage (standard voltage) is inputted into the (-) terminal from a standard value gener ating device 6. When the output voltage of the amplifier 5 is set between a-b, the electrode is fed at an ordinary speed. Below the (a) point where the abnor mal electric discharge starts to increase, the electrode is pulled up speedily. After the working gap restores the original state, the electrode is speedily pulled down. In this case, the standard voltage is lowered by Vbd during only the completion of the speedy pulling down by a standard value selecting signal generating device 9. Therefore, the transition from the amplifier 5 to the state where the output voltage is less than (b) can be carried out in stable ways in a short time.