Theoretical and experimental study of magnetic-assisted finish cutting ferromagnetic material in WEDM

In this paper, a method of magnetic assisted is firstly proposed to improve the machining performance of finish cutting ferromagnetic material in WEDM, and theoretical and experimental study of this method is implemented to illustrate its improving mechanism. Firstly, a simple motion trajectory model of electron beam is established in forming discharge channel process, and it indicates that additional constant magnetic field can efficiently suppress the divergence phenomenon of electron beam and shorten discharge gap breakdown time. Besides, a set of single pulse discharge experiment agrees well with the inference of the simple electron beam motion trajectory model, and the discharge crater volume increases by 22.2% when 0.14 T magnetic field is applied to discharge machining. Secondly, the charged debris motion curve of magnetic assisted finish cutting is worked out, and it reveals that more charged debris can be washed away when the direction of Lorentz force is the same with dielectric flushing. Additionally, a set of continuous discharge experiment is accomplished to investigate the improving effect of constant magnetic field, and experiment result represents that significantly improvement (material removal rate (MRR) maximum increase by 44.0%, and surface roughness (Ra) maximum reduce by 30.5%) has been obtained. Eventually, by the method of multi-objective optimization, a group of Pareto optimal set of MRR and Ra is worked out to satisfy different requirement of practical manufacturing.