Abstract: Geometric accuracy is an important performance criterion for NC machine tools, and the 9-line method based on laser measuring technology is widely used for error tracing. Three kinds of application problems of the traditional 9-line method are analyzed, and a new geometric error identification model is established by modifying the traditional method. The new model can improve the stability of identification results effectively, and make it possible that the manufacturing and assembly errors of the joints can be traced. Moreover, since the traditional 9-line method has principle errors in roll angle’s identification, an experiment-based method is proposed to eliminate the principle errors. The effectiveness of these approaches are verified by both computational and experimental results.

Key words: NC machine tool;geometric error;9-line method;error identification, high-speed railway, turnout, wheel-rail system dynamic characteristics, Wheel-rail vertical force., Polygonal wheels