The discharge channel formation and the mechanism of material removal during electrical discharge micromachining by nanosecond pulses

摘要

The conditions of improvement of the electrical discharge machining (EDM) by means of rational choice of the voltage pulse duration are considered. The shorter and smaller power voltage pulses (including, nanosecond pulses) are proposed to use. Streamer and heat mechanisms of the formation of the discharge channel in dielectric medium are considered. It is proved that in the small interelectrode gaps (1÷5 μm) the streamer mechanism of the initial formation of the discharge channel is most likely. Two periods of the formation of the discharge channel: without the conduction current and with passing the conduction current are considered. The conditions of the formation of the erosional craters at using nanosecond voltage pulses are considered. It is shown that under these conditions the diameter of the discharge channel significantly reduces, the crater depth increases and their diameter decreases. The estimation of the effectiveness of EDM on the basis of the fracture kinetics of materials is made. The estimates of the fracture activation energy for various metals are presented. These estimates are in good agreement with a specific energy consumption with a fixed amount of dispersion. It is shown that the effect of hydrodynamics on the mechanism of material removal at EDM with using nanosecond voltage pulses substantially weakens. The recommendations for the improvement of EDM with the use of nanosecond voltage pulses are presented.