| 摘要 |
PURPOSE:To promote the improvement of machining accuracy, by controlling a machining feed speed so that a difference between discharge generating rates in the central part of a work and its upper or bottom part obtains a predetermined value or less. CONSTITUTION:An amplifier 13 outputs a signal D showing a difference between signals C and B detected by current detectors 10, 9. Comparators 15, 16 and an AND gate 18 discriminate a signal of preset voltage E3 or more and E2 or less of the signals D, outputting a signal E showing a discharge to be generated in the central position of a work 1. While a comparator 14 discriminates a signal of preset voltage E1 or more of the signals D, outputting a signal F showing the discharge to be generated in the upper position. The signals F and E are counted and input to a differential amplifier 27. A control device, which outputs a signal of level corresponding to a difference between numbers of discharges in the central part of the work 1 and its upper part from the amplifier 27 while a command value corresponding to a differential signal between the signal of said level and the reference voltage E0 from a differential amplifier 28, controls a machining feed speed so that a barrel amount decreases to a small value.
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