Rotating Mechanism with Two Pairs of Spherical Bearings

The new rotating mechanism equipped with two pairs of spherical bearings, which are followed by polishing and hand working until the desired finish and contour are achieved, can be described here. This apparatus will be applicable to such a highly precise spindle as a roundness tester. The radius of a convex part is equal to or larger than that of a concave by a few micrometers, so the lubricant oil rouses spherical parts to squeezing action and prevents them from contact. The two drive systems for rotating axis are used. One is "indirect driving mechanism", of which the motor drives the spindle through gears and radial bearings for, vibration reduction. The other is called as "direct driving mechanism", then the axis of rotation is coaxial with the rotor part of the motor. It is difficult to compare both mechanisms owing to the difference of the ways of fixing the spherical bearings and the surroundings where two machines are situated, however, with the former development, the spindle radial motion under O.03μm and its repeatability under O.1μm can be obtained. The noiseless spindle radial motion of the latter one within 0.1-0.2μm and the variation of velocity under 0. 02% can be achieved. In order to achieve more accurate capability, at least two basic requirements must be met. These are lack of vibration and temperature control.