Patent ID: 8309876
Filing Date: 2012-11-13
Classification: B23H

Abstract:
1. An electric discharge machining apparatus that applies a plurality of sequential voltage pulses between a machining-purpose electrode and a workpiece and performs a machining process while switching polarities for each certain number of voltage pulses, the electric discharge machining apparatus comprising: an electric power supply device that supplies a direct-current voltage; a full-bridge circuit in which four switching elements are connected in a full-bridge connection, the full-bridge circuit having a pair of direct-current terminals, to which the electric power supply device is connected, and a pair of alternating-current terminals, to which the machining-purpose electrode and the workpiece are connected, the full-bridge circuit being configured to convert the direct-current voltage supplied from the electric power supply device to a voltage pulse for performing a normal polarity machining process and to a voltage pulse for performing a reversed polarity machining process, and to output the voltage pulses resulting from the conversions; and a controlling unit that, based on machining information that is required to perform an electric discharge machining process, generates switching signals containing a normal polarity pulse group and a reversed polarity pulse group used for controlling an output timing of the voltage pulses output from the full-bridge circuit and controls the four switching elements by using the generated switching signals, wherein within a waveform of the switching signals, a duty cycle of the normal polarity pulse group formed of a plurality of normal polarity pulses is configured so as to be different from a duty cycle of the reversed polarity pulse group formed of a plurality of reversed polarity pulses.