Electrical discharge machine with pulses of both polarities

摘要

An electrical discharge machine for applying a pulsed voltage to a machining gap between an electrode and a workpiece disposed opposite thereto. An insulating dielectric fluid, comprising an oil or water with compound additive, is disposed in the gap. A positive polarity voltage and an opposite polarity voltage are applied via switches and respective impedances to the machining gap in order to generate a discharge for machining the workpiece. The impedance values may be selectively set and the switching of the voltages controlled such as to apply a positive polarity voltage at the stop time of an opposite polarity pulsed voltage, whereby the average voltage approximates a predetermined value, preferably zero, during the stop time. Voltage control during the stop time will result in high speed and finish, especially for control in connection with a jump operation.