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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

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NOMENCLATURE CCM: Conventional cutting method EVC: Elliptical vibration cutting V x (t),V x (t): Voltages applied to the horizontal (PZT x ) and vertical (PZT y ) piezoelectric actuators φ: Phase difference between two PZTs u(t),v(t): Displacements generated by PZT x (u(t)) and PZT y (v(t)) in the cutting(x) and thrust(y) direction v f : Feed speed [mm/s] d: Depth of cut [µm] f: Excitation frequency of elliptical vibration of cutting tool [kHz] A c (A t ): Amplitude of elliptical locus of cutting tool in the cutting (thrust) direction [µm] S v : Spacing between adjacent grooves [µm]Feasibility of direct machining of micro patterns for micro molds by 2-dimensional vibration assisted cutting or elliptical vibration cutting was investigated and its machinability was compared with the conventional cutting method. Micro patterns of successive V-grooves and micro pyramids were machined on workpieces of a pure nickel, nickel alloy and mold steels with single crystal diamond, cubic boron nitride and poly crystal diamond tools which move along a circular path with a diameter less than 2 µm at an excitation frequency of 18 kHz. It was observed that the utility of EVC, that is a decrease of cutting resistance and an improved machining quality, was retained regardless of materials of workpieces and tools, and the improvement compared to CCM was far clearer when machined with a worn cutting tool. The risk of catastrophic or fatigue failure of tool was, however, increased by the impulsive forces resulting from periodic contact making and breaking between the tool and workpiece of high strength and hardness.

The chip and burr formation in micro V-grooving using elliptical vibration cutting (EVC) was investigated. Elliptical vibration of the cutting tool was achieved by employing two parallel piezoelectric actuators excited with two sinusoidal voltages of 90° phase difference. Changes in the shape of the chip and the cutting force, and the surface texture in micro V-grooving with EVC were investigated. It was observed that the reversal of the direction of the frictional force and the marked increase in the shear angle, which are two major characteristics of the EVC process, changed the shear flow inside the chip and reduced the cutting force, the chip thickness and the radius of curvature of the chip. When the excitation frequency of the tool was increased to an ultrasonic frequency of 65 kHz, more pronounced characteristics of EVC were observed. The cutting force in micro V-grooving with EVC at 65 kHz was reduced to approximately 10% of the cutting force magnitude under ordinary cutting. Low cutting force in the EVC process suppressed plastic deformation on the workpiece, thereby creating a micro V-groove free of burrs, which contributed to significant improvement in the form accuracy of a micro V-groove.