Fig. 1. Ultrasonic composite EDM drilling system

Fig. 2. Material removal rate and electrode wear under peak current of 6 A and 10 A

Fig. 3. Variation of taper angle under different machining time

Fig. 4. Changes of machining depth and fillet radius at different machining times

Fig. 5. Small holes and their surface topography

Fig. 6. Process and morphology of small holes

Fig. 7. Electrode ultrasonic vibration gap flow field simulation

Fig. 8. Variation curve of gap flow velocity with machining depth