Simulation-based analysis of electrical current induction in a device for electrochemical precision machining of Nd Fe B permanent magnets

Abstract

Abstract. Sintered permanent magnets, consisting of the neodymium-iron-boron (Nd-Fe-B) alloy, are installed as rotor magnets in small and precision electric drives due to their high magnetic forces in small volumes. When permanent magnets are brought into their final shape by electrical discharge machining (EDM), the thermal influence of this manufacturing process has negative effects on the magnetic properties of the workpieces. In consequence, re-magnetization of the workpieces is necessary after the finishing process. As an alternative manufacturing technology, electrochemical precision machining with an oscillating electrode and pulsed direct current (PECM) has the potential to eliminate this subsequent processing step. Based on Faraday's law of induction, an electrical induction current is expected to be generated by the cathode oscillation during the manufacturing process. In this study, the effect of the magnetic field of the workpiece on the process current and on the ablation-effective local electrical current density of the PECM process is analyzed based on multiphysics simulation.