Design of active magnetic bearing spindles for micro-milling applications
Ahmed, Kazi Sher (2021) Design of active magnetic bearing spindles for micro-milling applications. [Thesis]
The application of micro-milling for the fabrication of micro-scale parts/features from a plethora of materials has found significantly increased usage. In this fabrication process, miniaturization of mechanical components requires smaller machine tools with ultra-high rotational speeds. However, such rotational speeds complicate the spindle’s dynamic response and affect the machining process’s quality. Although contact or air bearings are generally used in micro-milling spindles, active magnetic bearing is a promising technology because it enables high-speed and contact-free rotation with active control of the spindle dynamics. Active magnetic bearings are being extensively studied to provide the benefits of regulated magnetic levitation and ultra-high speeds to the machining industry with condition monitoring and disturbance rejection capabilities such as chatter suppression. The primary objective of this thesis is to design and optimize active magnetic bearing spindles for micro-milling applications and demonstrate a multiobjective optimization scheme that can be adapted to different application requirements. To achieve this objective, we developed an algorithm for the spectral element method based on the one-dimensional spectral-Chebyshev approach to predict the dynamics of high-speed spindles. Next, we developed three-dimensional finite element models for accurate performance analysis of active magnetic bearings. Afterwards, the bearing performance was optimized using gradient and nongradient-based methods. Finally, we designed the major components for spindle assembly and identified the manufacturing methods for the next steps of spindle realization.
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