| 摘要 |
PURPOSE:To enhance the responsiveness of the control of electrode backward movement and as well to prevent the electrode from excessively moving backward, by controlling the backward speed of the electrode in such a way that the speed is increased by a high magnification for a predetermined time when the movement of the electrode is changed over from its forward movement to its backward movement or vice versa. CONSTITUTION:When the distance of an electrode gap calculated in accordance with the voltage between an electrode and a workpiece, becomes lower than a first predetermined value at which the backward movement of the electrode has to be initiated, a distance measuring circuit 301 delivers a timer drive signal to a timer 302 which drives a high magnification backward movement signal generating circuit 303 for a predetermined time to increase the backward speed by M2 times. Thereafter a low magnification backward signal generating circuit 304 is driven until a forward movement signal is produced, so that the backward speed is made to be M1 times. When the gap distance reaches a second predetermined distance at which the forward movement has to be initiated, the timer 305 starts its operation for changing over the forward movement in a similar way.
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