Hole quality and interelectrode gap dynamics during pulse current electrochemical deep hole drilling

This paper presents the experimental investigation of pulse-current shaped-tube electrochemical deep hole drilling (PC-STED) of nickel-based superalloy. Influence of five process variables (voltage, tool feed rate, pulse on-time, duty cycle, and bare tip length of tool) on the responses, namely, depth-averaged radial overcut (DAROC), mass metal removal rate (MRRg) and linear metal removal rate (MRRl) have been discussed. Mathematical models have been developed to express the effects of the process parameters on DAROC, MRRg and MRRl. The proposed model permits quantitative evaluation of the hole quality and process performance simultaneously. The results have been confirmed for the profile of the drilled hole and MRRl obtained experimentally. In all the experiments, through holes of 26 mm depth and diameters ranging from 2.205 mm to 3.279 mm were drilled. The results have been explained by the interelectrode gap dynamics prevailing during pulse electrochemical deep hole drilling. Optimum parameters determined from these experiments can be used to efficiently drill high-quality deep holes of high aspect ratio in nickel-based superalloys.