Abstract: A waveform control device for an electrical discharge machine apparatus which supplies current pulses to the gap between an electrode and a workpiece for machining of the workpiece. A first D.C. source, which supplies at least a part of a voltage that is applied across the gap, is connected in parallel with first and second circuits comprising a series connection of a switch and a diode. Connected between a first and second series circuit is a switched conductive circuit which, together with an auxiliary D.C. source, maintains the current flow at a base current level. Control of operation of the switches in the first and second circuits permit a controlled discharge of current across the gap while permitting the output voltage to be clamped at a safe level. A plurality of inductive circuits may be used to provide selectivity, where the inductances are different and to provide further control of the discharge current shape.

Abstract: An electric discharge machining device, in which a pulse voltage is repeatedly applied between electrodes, which are an electrode and a workpiece to be machined, to cause electric discharge between the electrodes and thereby machine the workpiece. The electric discharge machining device includes a switching device (4) connected between a power source and the machining section, for controlling energy supplied by the power source; interelectrode impedance detecting apparatus (10) for detecting an interelectrode impedance affected by the variation in place of electric discharge which takes place between the electrodes; discharge detecting apparatus for detecting when electric discharge takes place between the electrodes; and a control device (18).