Study on the surface integrity in ultrasonic vibration and magnetic field complex assisted low speed WEDM under different magnetic field coupling

Abstract

In this paper, a complex process of ultrasonic vibration (USV) and magnetic field (MF) complex assisted WEDM-LS is proposed, which provides a new method to solve the problems of low machining efficiency and poor machining surface integrity of traditional WEDM-LS. The self-generated MF of wire electrode is taken as the medium, and the influence mechanism of USV and additional MF on the intensity of self-generated MF is explored. Firstly, combined with the Galvanomagnetic effect and Biot-Safar Law, the mathematical models of self-generated MF under USV assisted WEDM-LS and USV-MF assisted WEDM-LS were deduced respectively. And then the MF coupling law between inter electrode was revealed; Secondly, the distribution of self-generated MF of wire electrode under different working conditions was simulated and analyzed. The results showed that compared with traditional WEDM-LS, the self-generated magnetic density under USV assisted WEDM-LS and USV-MF assisted WEDM-LS was increased by 12.1 % and 17.5 % respectively. As a result, the volume of single discharge crater was increased by 12.3 %; Finally, Taguchi orthogonal method was used to complete the USV-MF assisted WEDM-LS orthogonal experiment and the MF coupling verification experiment. The results showed that the Ra was reduced by 23.8 % and the MRR was increased by 25.1 % compared with the traditional working condition. The number of microcracks and micropores on the workpiece surface was significantly reduced, and the degree of workpiece surface burn was effectively reduced, which showed that the surface integrity of the workpiece had been greatly improved. The verification experiment results showed that compared with the opposite coupling of the self-generated MF and the additional MF, when the self-generated MF and the additional MF were coupled in the same direction, the Ra of the workpiece surface was reduced by 18.21 % and the feed speed was increased by 16.68 %. In addition, the removed particles were more evenly adsorbed on the surface of the wire electrode, which increased the normal discharge probability, indicating that the inter electrode MF coupling was the main effect model of ultrasonic vibration and MF recombination.