Blind Hole Fabrication in Aerospace Material Ti6Al4V Using Electric Discharge Drilling: A Tool Design Approach

The objective of the present experimental investigation is to improve the performance of electric discharge drilling using different electrode geometries as well as fabricating true blind holes into the workpiece. In order to avoid abnormal sparking, proper flushing during the process is an essential requirement which becomes less effective in case of the deep hole drilling. Modification in the tool geometry is an effective strategy for providing flushing and avoiding abnormal sparking. In this study, attempt has been made to reduce/eliminate the occurrence of abnormal sparking by cutting micro-slots of width 50 µm in the solid cylindrical electrodes of diameter 0.8 mm. Two electrode geometries (i.e., electrode with one micro-slot and electrode with two micro-slots) were compared with respect to material removal rate, tool wear rate, corner radius, and taper angle. The effect of different tool speeds has also been evaluated. The single slotted electrode with eccentric micro-slot was found best to fabricate truly blind holes into the workpiece. A high increase in aspect ratio (i.e., 150%) was recorded using single slotted electrode as compared to the solid electrode. It is interesting to note that the taper angle of the holes produced by slotted electrode has been reduced to 0.302º making a reduction of 54.24% as compared to the solid electrode. This reduction in the taper angle makes the holes much straighter which is a need of the hour.