Patent ID: 8901448

Claim:
An electric discharge machine for intermittently applying a voltage to a machining gap formed between a machining electrode and a workpiece opposite the machining electrode and thereby machining the workpiece, the electric discharge machine comprising: a machining power supply for applying a voltage to the machining gap and detecting a contact between the machining electrode and the opposite workpiece, the machining power supply including: a first power supply circuit for detecting a contact between the machining electrode and the workpiece, the first power supply circuit having a first output voltage less than an arc voltage; a second power supply circuit for machining the workpiece, the second power supply circuit having a second output voltage more than the arc voltage and configured for supplying a pulse current to the machining gap; and a control unit which is operable to determine that a contact exists between the machining electrode and the opposite workpiece when (i) the first power supply circuit supplies the first output voltage to the machining gap and (ii) the control unit detects that the voltage of the machining gap is equal to or less than a predetermined contact determination voltage, and when the control unit determines that a contact exists between the machining electrode and the opposite workpiece, immediately supply a pulse current from the second power supply circuit to the machining gap while the machining electrode and the workpiece are in contact with each other.