Abstract: In a power supply apparatus of an electrical discharge machine, a power supply high in efficiency and small in current ripple is provided to achieve a power supply reduced in size and price. In addition, a switching power supply system is used jointly to generate an optional waveform. A first switching device is switched on/off in an optional cycle under the control of a current command value signal corresponding to the waveform shape of a current pulse to be supplied to a machining gap, whereby an optional shape of current pulse is supplied to the machining gap and a current component which compensates for a current ripple generated by said switching at the time of supplying said current is superimposed on said optional shape of current pulse and is supplied to the machining gap.

Abstract: An electric discharge machining control apparatus in which the know how of a skilled person can be readily written which concerns the setting of machining conditions such as pause time, discharge duration time, servo reference voltage, and speed gain which are necessary for maintaining optimum electric discharge machining conditions and for offering a maximum electric discharge machining efficiency, as well as the criterions to the instability of electric discharge machining conditions. According to the know how, the machining control is carried out in a most suitable manner, and can be automatically adjusted when required.

Abstract: An electric discharge machining apparatus having a shielding mechanism for prevention of an occurrence of radio interference due to electromagnetic waves which are generated during an electric discharge machining operation. The shielding mechanism comprises a plurality of shielding floats at least the surface of which are made of a magnetic material high in magnetic permeability. The floats covers a surface of a machining solution contained in a machining reservoir made of a magnetic material high in magnetic permeability, in such a manner that the shielding floats are in contact with a side wall of the machining reservoir.