Calibration system based on a laser interferometer for kinematic accuracy assessment on machine tools

This paper deals with a method for the dynamic calibration of the kinematic accuracy of lathes and thread grinding machines in screw-cutting mode but free of load. It utilizes a precision polygon mounted on the spindle, in conjunction with a trigger device to generate angular pulses. A laser interferometer system assesses the longitudinal position of the saddle with respect to a cube-corner affixed on the chuck. As the spindle rotates, a string of pulses is generated by the angular trigger device. These pulses are used for triggering the laser interferometer. A software package has been elaborated to enable on-the-fly data acquisition and to display the kinematic errors in graphical form. The components of the kinematic error considered are the progressive pitch error, the cyclic error and spindle-free float. Application of this kinematic error calibrator on a universal and a CNC lathe has been carried out. Test results are presented and commented.