Experimental research on electrodischarge drilling of high aspect ratio holes in Ti-6AL-4V alloy

The drilling of small cylindrical (D < 1 mm) holes with a high ratio of length to diameter (L/D > 10) in difficult-to-cut materials is significantly beyond mechanical drilling capabilities. Electrodischarge machining (EDM) is a good and cost effective alternative in such situations. The machinability of electrodischarge machined material is determined by its thermal and electrical properties; therefore, the high electrical resistivity, the relatively high melting point and low thermal conductivity of Ti-6Al-4V alloy cause problems during the machining of parts made of this material. In this article, the results of experimental research on electrodischarge microdrilling in Grade 5 Ti-6Al-4V alloy are presented. The influence of various machining parameters (pulse time, discharge voltage, current amplitude, dielectric pressure, electrode-tool rotation speed) on key technological factors such as hole depth, side gap, linear tool wear, mean drilling speed and hole taper angle was analysed.