Measurement of impulsive forces and crater formation in impulse discharge

摘要

Recently, many new machining technologies which utilize electrical discharge machining (EDM) have been developed. However, the mechanism of material removal in EDM has not yet been sufficiently explained. To clarify the mechanism of material removal, the transitions in the impulsive forces that act on the melted region should be experimentally examined. In this study, first, the transitions in the impulsive forces in an impulse discharge were measured. Second, how the impulsive forces affect the formation of a crater by impulse discharge was examined. The following results were obtained. (1) A typical waveform obtained from an impulse discharge in kerosene consists of primary, secondary, tertiary and quaternary waves, and the intervals between the peaks of waves gradually become smaller. (2) The peak value of the primary wave, ranging from 15 to 20N, depends on the peak current. The interval ranging from 200 to 350 μs from the start of discharge to the peak of the secondary wave depends on the discharge energy. (3) Because the shape of the crater is strongly dependent on the polarities under the same working conditions in EDM, the effect of the impulsive force acting between the workpiece and the electrode on the formation of a crater by impulse discharge may be insignificant.