Machining Characteristics of an RC-type Generator Circuit With an N-channel MOSFET in Micro EDM

Abstract

An RC-type generator circuit is suitable for micro-electrical discharge machining (micro EDM) owing to its low single discharge energy. In micro EDM, negative tool polarity has the advantage of reducing the tool wear rate and the relative ratio. However, when using an RC-type generator circuit in micro EDM, the direction of the current fluctuates at the plasma channel between the tool and the workpiece due to stray inductance. Because the current flowing from the tool to the workpiece can intensify the tool wear rate, it is preferable to prevent the fluctuation of the current direction. In this study, we propose the RC-type generator circuit using an n-channel MOSFET to prevent the fluctuation of the current direction and to increase duty ratio to enhance the material removal rate. Using a micro ED drilling process, the material removal rate, relative ratio, and surface roughness were measured with respect to the feeding control conditions and electrical conditions. As a result, by using the RC-type generator circuit with a MOSFET, the relative ratio is reduced by up to 40%, with the same material removal rate and surface roughness, compared with the results without a MOSFET.