Pulse Efficiency and Gap Status of Rotary Ultrasonic Assisted Electrical Discharge Machining and EDM Milling

This study proposed an ultrasonic assisted (UA-EDM) and rotary ultrasonic assisted EDM (RU-EDM) spindle with ultrasonic transducer for die sinking EDM and EDM milling processes. The research includes investigation of the ultrasonic amplitude effects, spindle revolution speed, peak current, feed-rate control of EDM on the removal rate and tool wear rate for machining of SKD 61 steel. The significant factors that affect the removal efficiency and the tool wear are further verified. Especially, the fundamental studies of the gap status including gas bubble morphology and movement, debris expelling efficiency and waveform of voltage and current pulses are also investigated through experiments with a transparent observation window. Experiment results reveal that RU-EDM is superior to conventional EDM in removal rate in both sinking and milling EDM, but with the cost of a larger tool wear rate. Explanation from gap status and characteristics of the EDM pulse trains with and without rotary ultrasonic waves are compared. (c) 2018 The Authors. Published by Elsevier B.V.