In-process evaluation of workpiece geometrical tolerances in bar turning

This paper presents the development of an on-fine system for the evaluation of workpiece size and geometrical tolerances in bar turning. The measurement is performed using three ultrasonic non-contact proximity sensors which operate in a wet cutting environment. Data conditioning of radius measurements based on spectral analysis and error separation methods are used in order to eliminate errors due to spindle runout and workpiece axis translation. Analytical formulation of cylindricity tolerance is presented. Non-linear numerical optimization techniques are used to fit the data. Two different fitting functions are compared: the least squares and the minimax fit. The sufficiency of the sampled data set is investigated. The determination of cylindricity tolerance of the workpiece from given experimental data is presented and recommendations are given.