Ignition process control in electrical discharge machining using an adaptively regulated step-rising voltage

In electrical discharge machining (EDM), the ignition process is the induction process for dielectric breakdown and plasma formation. It is generally believed that using a high ignition voltage is more effective in enhancing the breakdown probability and improving the machining efficiency. However, the discharge gap usually becomes relatively large when using the high ignition voltage. As a result, the contour machining accuracy and surface machining quality may be reduced. This study explores an ignition control method to reduce the probability of breakdown at high voltage without affecting the machining efficiency. A step-rising ignition voltage is proposed to test for ignition step by step from a low voltage. Only if no breakdown occurs during the low voltage stages will the highest voltage be used for ignition. On this basis, the voltage step-rising time is adaptively regulated and an active sweep pulse is generated according to the calculated discharge state index. The experimental results show that compared with ignition using a constant high voltage, the proposed ignition control method is conducive to reducing the tool electrode wear and improving surface quality, while the machining efficiency is still guaranteed.