A modified electrode design for improving process performance of electric discharge drilling

Abstract

The present experimental investigation aims at improvement of the response characteristics during electric discharge drilling process. It is a well-established fact that aspect ratio of a drilled hole in Electric Discharge Drilling (EDD) process is limited due to the occurrence of arcing and short circuiting, resulting from ineffectiveness of flushing at larger depth. The prevention of accumulation of debris during EDD is important in order to improve the material removal rate (MRR) and aspect ratio of the hole. This can be achieved by designing shaped tool electrodes which can easily evacuate the debris from the machining zone. In the present experimental investigation, a novel tool electrode has been fabricated by drilling an inclined through hole into the tool electrode (Patent pending). The proposed electrode was found effective in eliminating the accumulation of debris in the machining zone. Moreover, the need of flushing during the process has been totally eliminated making it a self-flushing electrode. The images captured using high speed camera supports the mechanism explained for the debris evacuation. The proposed electrode (diameter 0.8 mm) can drill a hole of depth greater than 9.8 mm in Ti6Al4V which is the highest depth ever reported in the literature for Ti6Al4V using electric discharge drilling. The effect on other response parameters such as machining time, hole taper and corner radius has also been investigated and compared with the holes drilled by solid cylindrical electrode. The fabrication time of the proposed electrode is lower than time reported in the literature. Therefore, the proposed electrode is capable of producing holes of high aspect ratio with minimum electrode fabrication time, thus, improving the overall productivity and reducing the cycle time.