| 摘要 |
An improved servo system and method in an EDM machine for controlling the relative electrode displacement or the gap spacing between a tool electrode and a workpiece, wherein the electrodes are brought to a machining position to permit a succession of electrical discharges to be developed therebetween across the machining gap. A counter is used to count the number of machining pulses and, when the number reaches a value preset in conjunction with the machining area defined by the confronting electrodes, to provide an "advance" or "advance-enabling" signal. Only upon development of this signal or concurrent development of it and a usual servo "advance" signal from a gap sensor/servo signal generator responsive to a gap variable, e.g. gap voltage, a servo drive circuit acting on a motor or actuator for driving the movable electrode is actuated to allow the electrode to be advanced or stepped forward to a next machining position. The preset level of the discharge counter is varied from one value to another in response to a change in the machining area, setting or gap condition during the course of the machining operation.
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