Rapid volumetric error mapping and compensation for a three-axis machining center

This dissertation presents the results of the research investigation on the rapid machine tool error mapping, modeling, and compensation using laser interferometer and telescoping ball bar.; A displacement method based on laser interferometer measurements is proposed to shorten measurement time and to simplify the measurement for machining centers. By measuring the positioning errors along the 15 lines in the machine work zone, the total 21 geometric component errors can be determined. The results from the experimental tests on a three-axis CNC machining center show that the proposed method is feasible and accurate enough for most machine tool applications.; An inverse kinematics analysis method is presented to rapidly and easily map the geometric or thermal errors based on the telescoping ball bar measurements. With only one set-up of the telescoping ball bar measurement system, total five tests in the three planes are used to assess the geometric or thermal errors of a three-axis machine. Instead of using conventional way to map the errors by measuring each component error separately, the proposed method measures the volumetric errors in radial direction by using the telescoping ball bar. This greatly simplifies the measurement setup and shortens the calibration time. The experimental results have shown that the method is accurate and effective.; In this research, a robust modeling procedure for thermally induced errors is developed by using production cutting data for a turning center. The proposed procedure suggests using robust criterion functions to detect extreme points of observations or measurement data and to construct an effective model in order to have a better performance for the future error prediction and compensation. Some examples are given to demonstrate the procedure. This research also presents the application of the technique of the real-time thermal and geometric error compensation on a three-axis CNC gantry machining center. The error calibration, modeling, compensation, implementation, and performance evaluation are discussed in details.