Patent ID: 8350177

Claim:
An electric discharge machining device that performs processing by applying a voltage pulse between a processing electrode and a workpiece and suitably switching a polarity of the voltage pulse, comprising: a first DC power supply having a positive side electrically connected to a side of the workpiece and a negative side electrically connected to a side of the processing electrode; a first switch inserted in a current path connecting the first DC power supply to the workpiece and the processing electrode and connected to the first DC power supply in series; a second DC power supply having a positive side electrically connected to a side of the processing electrode and a negative side electrically connected to a side of the workpiece; a second switch inserted in a current path connecting the second DC power supply to the processing electrode and the workpiece and connected to the second DC power supply in series; a third switch electrically connected in parallel between the first DC power supply and the first switch that are connected in series and the workpiece and the processing electrode; a fourth switch electrically connected in parallel between the second DC power supply and the second switch that are connected in series and the workpiece and the processing electrode; at least one resistor inserted in a current path from the first DC power supply to the processing electrode and the workpiece and in a current path from the second DC power supply to the processing electrode and the workpiece; and a controlling unit that generates and outputs switching signals to control the first to fourth switches based on processing information necessary for discharge processing, wherein: the controlling unit switches the first switch from on-state to off-state, switches the second switch from off-state to on-state, and sets a period, in which the third switch is turned on right before reversing the polarity of the voltage pulse, and switches the second switch from on-state to off-state, switches the first switch from off-state to on-state, and sets a period, in which the fourth switch is turned on right before reversing the polarity of the voltage.