Characteristics of elliptical vibration cutting in micro-V grooving with variations in the elliptical cutting locus and excitation frequency

The characteristics of elliptical vibration cutting (EVC) in micro-V grooving in connection with variations of the elliptical cutting locus and the excitation frequency have been investigated with a cutting device consisting of orthogonally connected dual piezoelectric actuators. The elliptical cutting locus was modulated by changing the magnitude and phase difference of harmonic voltages supplied to the piezoelectric actuators, and the maximum excitation frequency used for EVC was 19 kHz. It was found that cyclic breaking of the contact between the tool and the workpiece is a pre-requisite for the merits of the EVC process to be realized. An index termed non-contact index (NCI) involving the vibration amplitude of the elliptical locus, the feed speed and the excitation frequency was defined to determine the existence of cyclic breaking of the contact under a given EVC condition. The surface roughness in the feed direction showed a tendency to increase with the vibration amplitude in the thrust direction and the square of the feed speed, and to decrease with the square of the vibration amplitude in the cutting direction and the square of the excitation frequency. The variation in the cutting resistance was in good agreement with the CR trend curve representing the contact ratio between the tool and the workpiece in EVC; in the EVC process involving breaking of the contact, marked decrease in the cutting force occurred at higher values of CR at which either slight increase in the excitation frequency or in the vibration amplitude results in significant decrease in the cutting force. Reduction in the cutting force preferably contributed to the improvement of machining quality of the micro features by inhibiting burr formation.