Electrode Set-Up for EDM-Drilling of Large Aspect-Ratio Microholes

Holes of 0.3-0.4 mm diameter and large depths are typical features in aerospace components of Ni-based and Ti-based alloys. The EDM process is a popular manufacturing method for this type of precision holes in difficult-to-machine materials. Optimization of this technology requires taking into account different aspects such as process parameters, electrode material and electrode set-up. These variables affect process performance in terms of processing time, dimensional tolerances and electrode wear. In this paper it is shown that the set-up of low-diameter electrodes can be carried out in conventional EDM machines, avoiding thus much more expensive processes such as the WEDG technology. Cu-W electrodes of diameter 0.2 mm and aspect ratio over 100:1 can be prepared on the same machine where EDM-drilling will take place with a radial error below 5 m and surface finish Ra=0.5 m. Electrode diameter as low as 50 m has been achieved using this method. Application to EDM-drilling of Ti6Al4 V using this type of electrodes is presented in this work.