Design of an active magnetic bearing spindle for micro-milling applications

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. For such speeds, active magnetic bearing is a promising technology because it enables high-speed and contact-free rotation with active control of the spindle dynamics. Considering the application of the micro-milling process, we present the design of major components of magnetic bearing spindle including radial and axial magnetic bearing, air turbine, and rotor. Conventionally used analytical models, as well as three-dimensional finite element models, were used to aid the design process. A Pareto front using a genetic algorithm for radial magnetic bearing based on bearing force and volume is also determined to aid the selection of manufacturing dimensions based on the relative importance of bearing performance metrics.