Development of a Vibration Assisted Electrical Discharge Machining System for Surface Quality Improvement in NAK80 Steel

Hybrid machining, which combines conventional material removal processes with auxiliary energy source, has emerged as a promising approach to enhance machining efficiency and overcome the limitations of a single process. This study introduces a novel vibration-assisted EDM (VAEDM) module capable of applying low-frequency vibrations (500—1,200 Hz) with adjustable amplitudes (1.0—2.5 μm) directly to the tool electrode for machining NAK80 steel. The objective is to investigate how VAEDM influences bottom surface roughness, a key indicator of surface integrity in difficult-to-machine materials. Five process parameters, discharge current (I), pulse-on time (Ton), pulse-off time (Toff), vibration frequency (Fre), and amplitude (A) were varied using a Taguchi L16 design and analyzed via ANOVA. Results show that I and Ton are dominant factors, while vibration parameters contribute significantly through interaction with I. VAEDM reduced surface roughness by up to 16.10% compared to EDM, with an average improvement of 1.94% across all experimental runs. SEM analysis confirmed improvements in surface morphology, including shallower craters, thinner recast layers, and fewer microcracks. These findings highlight the potential of VAEDM to enhance surface quality, providing insights into the underlying surface formation mechanisms under vibratory assistance.