Debris motion and taper suppression in EDM deep hole machining assisted by longitudinal/torsional ultrasonic vibration

Ti-6Al-4 V is usually machined using EDM methods due to its hard-to-cut characteristics. However, the challenge of chip removal in micro-deep hole machining causes ablation product buildup, leading to electrode wear and tapered holes. An Ultrasonic-assisted spark discharge energy model was developed in this study. The force state of individual debris in the gap was analyzed, and a solid-liquid two-phase fluid simulation was performed using COMSOL software to explore the positive effects of Ultrasonic assistance on debris discharge. A self-developed high-frequency longitudinal/torsion ultrasonic transducer was installed on a DK-703 machine tool for testing. The impact of ultrasonic amplitude and machining depth on electrode wear, microhole taper, and internal wall defects was evaluated. Experimental results showed that machining depth reduced the effect of ultrasonic vibration. Compared to EDM, ultrasonic-assisted EDM (UEDM) achieved a 51.7 % reduction in electrode wear, a 33.5 % reduction in hole taper, and fewer microscopic defects. Ultrasonic longitudinal vibration improved fluid motion and reduced debris volume, while torsional vibration cut the arc, resulting in more uniform electrode wear and fewer internal wall defects.