Development of a Three-Degree-of-Freedom Ultrasonic Vibration Tool Holder for Milling and Drilling

This paper presents a three-degree-of-freedom (3-DOF) ultrasonic vibration tool holder for milling and drilling operations. The 3-DOF vibrations are generated by a novel actuator that contains three groups of piezoelectric rings actuating in X -, Y- , and Z -directions at the natural frequencies of the structure. The vibrations in XY plane are excited at the frequency but with slightly different amplitudes to produce an elliptical locus for intermittent tool-workpiece contact, which assists milling process, and the vibrations along Z -axis are used in drilling operations. The 3-DOF ultrasonic vibration actuator excites the structure's natural frequencies, which are above 16 kHz with amplitudes up to 20–25  $\mu$ m. A control system has been developed for tracking the resonance frequencies during cutting from the phase of actuator's impedance. Preliminary cutting tests show that the cutting forces are reduced by over 30% with the ultrasonic vibration assisted milling and drilling operations.