Patent ID: 9533365
Date: 2017-01-03
CPC Classifications: B23H

Claim:
1. An electric discharge machining apparatus that performs electric discharge machining, the electric discharge machining apparatus comprising: a power supply; an electrode gap formed between an electrode and a workpiece; a current limiting resistor connected between the power supply and the electrode gap; a plurality of switching elements that turn on and off application of a voltage from the power supply to the electrode gap; an inductance element connected in series between the plurality of switching elements and the electrode gap; and a controller that controls the plurality of switching elements, wherein the electric discharge machining apparatus causes capacitor discharge, which makes use of capacitor capacitance of the electrode gap, to oscillate in a self-excited manner according to a circuit constant of an LCR circuit configured with the current limiting resistor, the inductance element, and the capacitor capacitance, the controller transmits an oscillation control signal to at least one of the plurality of switching elements, and the oscillation control signal includes an on-pulse time period, during which a voltage of the electrode gap reaches a voltage value of the power supply and the self-excited oscillation occurs two or more times, and a pause time period, which is longer than or equal to a time period during which current is discharged from the capacitor discharge and which is shorter than a cycle of the self-excited oscillation, to prevent the voltage of the electrode gap from exceeding the voltage value of the power supply.