Development of curved hole drilling method by EDM with suspended ball electrode-electrical discharge machining characteristics and curved hole machining of titanium alloy

Curved hole drilling technique for a titanium alloy was needed for a efficient flow path such as water jet nozzle because of its light weight and high corrosion resistance. In this paper, EDM characteristics for titanium alloy workpicce using a cop per-tungsten ball electrode with 7.0 mm in diameter were experimentally investigated. While drilling titanium alloy using a suspended ball electrode, the workpicce needs to be vibrated using a vibrator for stable machining performance. Under almost EDM conditions, the removal rate using the suspended ball electrode with workpiece vibration was significantly higher than that using a fixed rod electrode. Furthermore, the electrode wear rate using the suspended ball electrode was lower than that using the rod electrode. While titanium carbide was formed on the machined workpicce surface using the rod electrode, the surface using the suspended ball electrode did not form such phase. Additionally, the possibility to machine a curved hole in the titanium alloy using the suspended ball electrode was investigated. The results indicated that bended holes with various angles such as 15°, 30°, and 45° could be machined successfully by tilting the workpiece.