Design and development of a 3D system for the measurement of tube eccentricity

Abstract

We present a novel method for the 3D optical measurement of tube eccentricity. The prototype is based on two pairs of laser slits that illuminate the external and internal walls of the tube respectively. Each laser slit captures a 3D semi-profile in the zone close to the cut section of the tube. The laser slits are assembled following a suitably designed layout, which allows us to obtain the circumferential profiles of the internal and external tube surfaces. These profiles are fitted to two circles, and the eccentricity is measured as the distance between their respective centres. The system is suitable for monitoring the wall thickness in correspondence of tube cross sections characterized by scratches and chippings left by the cutting tool in a static way. In this paper, the method and the procedures developed to implement the measurement are described. The characterization of the laser slits, as well as the measurement performance of the system, is detailed. A number of experimental results highlighting the system performance in comparison with a 2D vision approach are discussed.