Development of curved-hole drilling method by EDM with suspended ball electrode - EDM characteristics and curved-hole machining for aluminum alloy and die steel

This study has proposed a method of machining curved-holes using electrical discharge machining (EDM) with a suspended ball electrode. The EDM characteristics for aluminum alloy (JIS A5052) and die steel (JIS SKD11) using suspended ball electrode were investigated in this paper. Using a copper-tungsten ball electrode of 7.0 mm in diameter, the stable machining for both types of material were possible. Under almost EDM conditions, the machining speed using a suspended ball electrode was faster than that using a rod electrode with an electrode jump motion, when the hole was not so deep. The hole-diameter using the suspended ball electrode was larger than that using the rod electrode. It was found that the machining stability with the suspended ball electrode was affected mainly by the servo voltage. Additionally, the possibility of curved-hole machining using a suspended ball electrode was discussed. The experimental results showed that 15°, 30°, and 45° bended-holes could be successfully machined in these materials by tilting the workpiece.