An investigation has been made to combine ultrasonic vibration and wire electrical discharge turning (WEDT). Design of a submerged, precise, flexible and corrosion-resistant rotary spindle is introduced. The spindle was mounted on a five-axis wire EDM machine to rotate the workpiece in order to generate free form cylindrical geometries. An auxiliary device which produces ultrasonic vibration was installed between the two wire-guides. The ultrasonic system consists of an ultrasonic generator, a transducer and a wire holder. When the wire is being driven, the transducer together with the wire holder vibrate under the resonance condition Experimental results show that wire vibration induced by ultrasonic action has a significant effect on material removal rate (MRR). This study has been to evaluate the influence of four design factors: power, pulse off time, spindle rotational speed and ultrasonic vibration over material removal rate, surface roughness (Ra) and roundness. This has been done by means of design of experiments (DOE) technique. Analysis of variance was used to determine significant effective factors and also to obtain an equation based on data regression. Ra and out of roundness are increased slightly. Decreasing the recast layer thickness and micro cracks are shown in the SEM micrograph analysis by using ultrasonic vibration. A single discharge was experimentally and analytically studied and the effective forces and factors on plasma channel including Lorentz force, skin effect of current, increase of pressure, elongation of molten crater due to lateral displacement of wire and creation of positive and negative pressures of the ultrasonic wave on molten crater were investigated. The rate of pressure drop in the end of discharge was increased by using ultrasonic vibration. As a result, a great amount of the material was exploded out of the crater due to bulk boiling. The plasma channel sliding elongated the molten crater on workpiece surface, which lead to material removal increase. The volume and elongation of molten crater were modeled analytically considering the effect of ultrasonic vibration and have been validated by the experiments. Keywords: Wire electrical discharge turning, Ultrasonic vibration, Material removal rate, Surface roughness, Plasma channel, Crater, Discharge spot.
