| 摘要 |
PURPOSE:To obtain good roughness of a machined surface further stably perform electric discharge machining, by applying voltage of reverse polarity across an electrode and a work, when a machine performs finishing, and controlling the electric discharge machining so as to generate its average machining voltage in a direction of the voltage of reverse polarity while decrease power for an electric discharge of positive polarity. CONSTITUTION:If a pulse is introduced to a base G1 of a transistor T1, a machine, turning on the transistor T1 and applying voltage of positive polarity between an electrode P and a work W by a DC power supply E1, generates an electric discharge. Thereafter, the machine, turning off the transistor T1 and electrifying a transistor T2, applies voltage of reverse polarity between the electrode P and the work W from a power supply E2. Here the machine, changing output voltage VL of a smoothing circuit 1 by changing a value of variable resistance RV1, changes a time for applying the voltage of reverse polarity. In this way, the machine, setting a pulse width for applying the voltage of reverse polarity so that average machining voltage becomes the voltage of reverse polarity, performs finishing and obtains stable machining.
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