Design and realization of a miniature spindle test setup with active magnetic bearings

In this paper, the design and realization of a magnetically levitated high speed spindle for micro machining is presented. This spindle is built to investigate various micro machining processes. The main application is milling with extremely small diameter tools. The micro milling tools have a diameter in the range of 0.1 mm. To improve the milling accuracy extremely high rotational speeds are required. The spindle presented in this research is built to reach speeds over 200,000 rpm. The spindle is equipped with two radial bearings, one axial bearing and a permanent magnet synchronous motor. The radial bearings consist of permanent magnet biased homopolar active magnetic bearings. The axial bearing consists of reluctance type actuators in a differential driving mode. The motor is a commercially available permanent magnet motor, able to reach speeds over 250,000 rpm. This spindle is part of a micro factory, which is built in this research program. The first test results are presented.