1994 年 60 巻 2 号 p. 260-264
In order to enlarge industrial application of the ultra-precision metal cutting technique by single crystal natural diamond tools, a fundamental study to develop the ultra-precision machine tool with high cost performance is carried out. A newly developed air spindle unit is constructed compactly, and is driven by a built-in motor directly. In this paper, experimental results of rotational accuracy are presented. Vibration induced by magnetic attraction at the motor dominates the rotational accuracy. It is useful for reduction of the vibration to balance the magnetic attraction between the rotor and the stator. It is necessary to adopt a supplying voltage with an ideal sine wave for further improvement of rotational accuracy.