Fabrication of through-holes of different shapes using foil tool in EDM: Process development and analysis

The use of a foil tool in the electrodischarge machining (EDM) process has been shown to be effective for slicing, fabrication of micro slots, and various other applications. EDM with a foil tool has an advantage over wire-EDM as it allows the use of a foil tool with a thickness less than the wire diameter and to use higher discharge current due to the no risk of tool breakage. This work attempted to fabricate through-holes of various shapes on the D2 steel plate by removing material only from the periphery using a Cu foil tool, rather than the entire cross-sectional area. The thin foil tools are brought into respective shapes by wrapping them around Cu blocks having a cross-sectional area of the respective shapes. Gravity assistance is preferred to be employed as it has been experimentally found that it improves the linear material removal rate (LMRR) up to 24.86% compared to EDM without gravity assistance at various discharge current levels and pulse on time. Further, for a gravity-assisted EDM process using the foil tool, the LMRR has been improved up to 54.43%, with a selection of suitable duty cycle settings. The set of process parameters with the highest LMRR was chosen to fabricate through holes of circular, elliptical, square, and triangular cross-sections. The time required to machine through holes of various shapes was found to be proportional to the perimeter of the cross-section.