Investigations on wire-EDT for precision turning of cylindrical mild steel bars using gear-driven rotary setup

This paper highlights the aspects of circularity error 'CE', mean surface irregularity depth 'Rz', and machining erosion rate 'MER' for straight-turning cylindrical mild steel bars (CMSBs) by wire electrical discharge turning (wire-EDT). Rz reflects surface quality, MER indicates machining speed and productivity, and CE measures the deviation from the ideal circular shape. Micrograph analysis was performed on the bar turned at the optimal combination with minimum surface roughness. Nine combinations of wire-EDT variable parameters-pulse-on duration (Ton), pulse-off duration (Toff), and servo voltage (SV)-were arranged using a Taguchi L9 (33) orthogonal array, with each combination repeated twice. This resulted in eighteen experiments to evaluate the potential of wire-EDT and the influence of variable parameters on CE, Rz, and MER. The spark-on duration was found to be significant for the machining erosion rate, while both spark-on duration and spark-off duration were found to be significant for the average surface irregularity depth. A circularity error of 17.06 µm, an Rz of 8.1 µm, and a MER of 8.86 mm³/min were achieved at the optimum combinations. The results from confirmation tests closely match the optimum, showing strong agreement with a variance of less than 6% for CE, Rz, and MER. The results of this study are useful for the turning of cylindrical bars made of various materials.