抄録
Electrical discharge machining is a precise working method for hard metals. The work is shaped into a desired configuration by arc erosion conforming to the configuration of the tool-electrode.
The transient arc discharge occurs in a very short discharge gap between the tool-electrode and the work immersed in a liquid insulator (working fluid).
In order to keep stable the repeating transient arcs, the tool-electrode has to be fed keeping a constant discharge gap. But the discharge gap cannot be measured directly while the discharge circuit is alive. And so the discharge voltage is measured and feeding the toolelectrode is controlled by an average value of the measured discharge voltage that the discharge gap may gets a constant length. In the optimal state of working, the measured gap voltage is believed to be optimal duty factor of the discharge pulses.
An abnormal arc occurs frequently due to debris staying between the tool-electrode and the work under a certain duty factor i.e. a constant working power. Accordingly, as working area or depth is increased for a certain working power, the damage of the work due to abnormal arcs increases.
In this research, the authors study a technique to detect the pre-abnormal arc by processing the voltage between the tool-electrode and the work, and propose an optimal controller, which has an optimizing algorithm, for the working power i.e. the duty factor of discharge pulses.