The technical method of geometric error measurement for multi-axis NC machine tool by laser tracker

The machining accuracy is an important index to evaluate the machine tool characteristics, and error measurement and compensation are effective methods to improve the machining accuracy with low cost. Error measurement is a prerequisite and basis for error compensation, so how to quickly and accurately measure the machine error is particularly important. To quickly and accurately detect the geometric error of multi-axis NC machine tool, a new method with laser tracker based on the sequential multi-lateration measurement principle is proposed in the paper. The laser tracker is used to measure the same motion trajectory of the linear axis and rotary axis of machine tool at different base stations. Based on the GPS principle, the space coordinates of each measuring point can be determined by large amount of measured data. Then according to the error model of the linear axis and rotary axis, each error can be separated. In the paper, the principles of sequential multi-lateration measurement are analyzed in depth. By establishing the mathematical model of sequential multi-lateration measurement for the linear axis and rotary axis, the algorithms for linear axis measurement and rotary axis measurement are derived and proved feasible by simulations, respectively. Meanwhile, the error separation algorithm is also deduced. The results of experiments show that this method can achieve quick and accurate detection of errors in multi-axis NC machine tool.