Comparative analysis of single-crater parameters in ultrasonic-assisted and unassisted micro-EDM of Ti6Al4V using discharge plasma imaging

Ultrasonic-assisted micro-electro-discharge machining (μEDM) has the potential to enhance processing responses such as material removal rate (MRR) and surface finish. To understand the reasons for this enhancement, the physical mechanisms responsible for the individual discharges and the craters that they form need to be explored. This work examines features of craters formed by single discharges at various parameter values in both conventional and ultrasonic-assisted μEDM of Ti6Al4V. High-speed imaging of the plasma channel is performed, and data on the individual discharges are captured in real-time. A 2D axisymmetric model using finite element software is established to model crater formation. On the basis of simulation and experimental results, a comparative study is then carried out to examine the effects of ultrasonic vibrational assistance on crater geometry. For every set of μEDM parameters, the crater diameter and depth from a single discharge are found to be higher in ultrasonic-assisted μEDM than in conventional μEDM. The improved crater geometry and the reduced bulge formation at the crater edges are attributed to the increased melt pool velocity and temperature predicted by the model.