Small-hole EDM using Grooved Pipe Electrode

Abstract In small-hole electrical discharge machining (EDM), brass pipe electrodes of diameter 0.1 to 3 mm are typically used for machining. However, it has been empirically proven that in high aspect ratio machining, machining speed decreases because of deterioration in the discharge state, which is attributed to insufficient machining debris removal. This study investigates the use of straight groove electrodes in small-hole EDM to improve debris removal and thereby enhance discharge performance during deep hole machining. Machining experiments were conducted to compare the performance of EDM in normal pipe and straight groove electrodes. The electrode diameters tested were 3 and 1 mm. The experimental results are as follows. To machine stainless steel to a height of 125 mm, the machining speed declined in normal pipe electrode machining, but the reduction in the machining speed could be suppressed in the straight groove electrode machining. Furthermore, the effect on removing the debris of the straight groove electrode was confirmed by investigating discharge waveforms. Results indicated that the number of times of normal discharge decreased in the region where the machining speed was reduced in the normal electrode. Additionally, when the straight groove electrode was used, the normal discharge did not decrease and hence the machining speed. Therefore, the effect of the straight groove electrode to small-hole EDM was confirmed.