Abstract
This paper deals with the development of a noncontact measurement system for evaluating three orthogonal thermal displacements of a machine tool spindle in operation. The measuring principle is based on the edge detection by quantifying transmitted laser beam power. The system consists of a high precision master bar with a steel ball at the end and three laser beams associated with photo detectors which are set in right angles to the spindle axis. One of these beams is used for evaluating the displacement of the spindle in the axial direction. This beam is intersected by the steel ball but hardly influenced by the spindle run-out. The other two beams, which are splitted into two orthogonal beams by a cubed half mirror respectively and are intersected by the master bar at the two separated cross sections, are used for evaluating the lateral displacement and the inclination component of the spindle axis. The theoretical background of this system was explained by means of the Kirchhoff's diffraction integrals and then the overall accuracy was discussed by carrying out the appropriate performance tests. Through experimental analyses it was concluded that this system could provide with appreciable knowledge of the thermal deformation of machine tool spindle in operation, although the thermal stability of the system was an essential factor and so either a thermal calibration or a certain temperature control device was required for the more precise measurements.
