Researches on the EDM of magnetized sintered NdFeB permanent magnetic material

The magnetized sintered NdFeB (MS-NdFeB) permanent magnet material is difficult to machine due to high hardness, brittleness, and magnetic force. In this paper, the electrical discharge machining (EDM) of the MS-NdFeB workpiece is studied to improve the machining process of the MS-NdFeB. In addition to the material removal rate (MRR) and the surface roughness (SR), the change rate of the magnetic flux density (MCR) for the MS-NdFeB is proposed and used as the research index of their machining effect by the EDM process. By orthogonal experiments, using the intuitive analysis method and the analysis of variance (ANOVA) method, study the influences of the peak current, the pulse on time, the pulse off time, and the magnetic field intensity of the processing area (MF) on the MRR, the SR, and the MCR. The scanning electron microscope (SEM) pictures of the machined MS-NdFeB surfaces are obtained based on the experimental design with a one-factor variation. The comparative experiment is performed to reveal the change of the MCR in EDM. The intuitive analysis of the orthogonal experimental result reveals regularities of influences. The ANOVA reveals the significance of influences. The regularities and significance of influences of machining parameters on the machining effects are analyzed assisted by the analysis on these SEM pictures and the comparative experimental results. The optimal combinations of machining parameters for MRR, SR, and MCR are obtained by single-objective optimization. The verification experiments prove the reliability of the single objective optimization results.