CONTOUR MAPPING OF PRECISION BALL DEFECTS WITH LASER-DOPPLER VIBROMETRY

Laser Doppler vibrometry is presented as an effective inspection techn ique for contour mapping of defects on precision roller bearing balls. Localized defects are characterized by measuring the Doppler shift of a laser beam incident on a rotating ball. Contour maps are obtained b y scanning the ball at equally spaced azimuths with the laser beam as the ball rotates about a vertical axis. A technique for characterizing the repeatable runout of a ferro-fluid spindle is discussed. Tests we re performed on two different grades of ceramic ball bearings. With th e experimental setup, a height resolution of 5.5 nm could be attained. Defects of 22 mum in width could be detected. Use of the contour mapp ing technique greatly enhances visualization of defects on ball bearin g surfaces.