Optimization of the grinding process on permanent magnets of high-performance electric motors

This thesis investigates the grinding process of two key automotive components: electric motor rotors and transmission gears. With the transition to electric mobility, stricter specifications and higher performance demands are shaping manufacturing processes, particularly for electric motors. The grinding of rare-earth permanent magnets (PMs) remains an underexplored field of growing technological interest, while gear grinding is well-established in the literature. Despite their different nature, both components were studied under dry conditions to minimize environmental impact by eliminating coolant usage. However, dry grinding poses challenges such as excessive heat generation, which can lead to surface burns, softening in gears, and magnetic property degradation in PMs. Extensive testing was conducted first on individual PMs and then on complete rotors to determine optimal finishing parameters. This research, funded by Ferrari S.p.A., supports the development of a fully electric vehicle equipped with a motor featuring a rotor with rare-earth PMs (Nd₂Fe₁₄B). These magnets, produced through sintering, exhibit high hardness and brittleness, requiring careful assessment of process parameters (cutting speed and feed rate) and working conditions (wet vs. dry). Three material removal strategies were examined for PMs: grinding (tangential and cylindrical), face milling, and contour milling. Due to severe tool wear, milling proved unfeasible, but laser-assisted contour milling yielded promising results. For gear grinding, an experimental analysis assessed the impact of process parameters on fatigue performance under wet and dry conditions. These tests were conducted within the FATECO project, funded by the European Commission, aiming to enhance the fatigue resistance of automotive components through eco-friendly finishing techniques. The findings confirmed the feasibility of dry grinding for both PMs and gears, identifying an optimal process window. However, conventional milling of PMs was impractical, whereas laser-assisted milling demonstrated notable industrial potential.