Study on machining characteristics of micro EDM with high spindle speed using non-contact electric feeding method

Abstract

In order to improve the efficiency of micro electrical discharge machining (micro EDM), the rotational spindle is widely used at present. Since the EDM technology is invented, the relaxation-type pulse generator, transistor-type pulse generator, or their combinations have been generally used. However, with these pulse generators, it is difficult to supply electrical power to the tool electrode rotating at extremely high speed without causing the vibration and spindle wear due to the contact electric feeding using a brush. So the tool electrode rotating speed is less than thousands of revolutions per minute (rpm) usually. Based on the principle of electrostatic induction, the non-contact electric feeding can be realized in micro EDM. So the rotating speed of the tool electrode can reach high rotating speed. This paper studied the machining characteristics of micro EDM under the high spindle speed up to 60,000 rpm by the machining of micro rods and the micro holes. As a result, the minimum electrode of Φ 2 μm in diameter and 10 μm in length, and the micro rod of Φ 5 μm in diameter and 80 μm in length with a high aspect ratio of 16 were obtained by block electrical discharge grinding (BEDG) method. From the micro hole machining results, it was found that with the increase of the spindle speed, the material removal rate increases, while the electrode wear ratio decreases. Meanwhile, the higher aspect ratio and machining accuracy were realized and the surface roughness was also improved significantly.