Micro machining has become an important technique for fabrication of miniaturized components for automotive, aerospace and biomedical applications [1][2]. Many micro machining areas, such as, micro milling, micro drilling and micro grinding [3] require a cnc machine tool with a high speed spindle. High speed spindles are necessary for increasing cutting speeds with small tools. As researchers strive for more precise micro features and smaller unit removal, the error motion of the spindle [4] and tool runout become critical. Significant improvements in the precision and accuracy of linear positioning stages within machine tools now provide positioning resolutions on the order of a nanometer. However, reductions in the error motion of high-speed spindles remains limited to values on the order of a micrometer. This high dynamic runout causes poor tool life, decreased precision, and increased roughness. Spindles with speeds greater than 200,000 rpm are limited to conventional aerodynamic bearings [5]. These bearings are difficult to balance, which leads to whirling of the rotor [6]. Also, accurate alignment of a tool's centerline with a spindle's axis-of-rotation is challenging with taper and collet tool holders.
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