Development of a New Measurement Method of Central Position of Spindle Rotation : 1st Report : Steel Ball Method

A precision steel ball is attached to the end-face of the spindle and an electronic capacitance-type transducer mounted on the tool slides of a three-dimensional sliding stage. Relative displacement in the axial direction between the ball and the transducer is detected during spindle rotation. The measurement principle of the central position is based on the fact that the undulation component synchronized with the rotational speed of the spindle in the displacement signal reaches a minimum value at the central position of rotation. The results of preliminary experiments are summarized as follows. ( 1 ) The new method allows detection of the central position with a resolution of 0.5μm. ( 2 ) In the case of the spindle with hydrodynamic bearings, the rotational speed of the spindle and the resonance vibration of the headstock affect the central position of the spindle rotation.