The geometric error identification approach based on ballbar measurement, six step measurement, was proposed in order to obtain the ten geometric errors of turntable for multi axis machine tools systematically. Models between ballbar readings and geometric errors of turntable were obtained based on the direction vector of ballbar and the position of ballbar in each step of the six step measurement. According to the property of geometric errors, all the ten geometric errors of turntable were identified including squareness errors and offset errors. The corresponding simulation testified that the six step measurement was appropriate. To further improve the accuracy of six step measurement, the influence of the set up errors of ballbar was analyzed. The least square method was used to fit the ballbar readings without the set up errors. The six step measurement was applied to SmartCNC500 five axis machine tool to identify the geometric errors of turntable. The obtained geometric errors were also compensated. The ballbar readings with and without the compensation of geometric errors of turntable were compared. The ballbar readings with compensation decreased about 56% to 61.9%. The results show that six step measurement has high precision and only needs single rotation of turntable. Meanwhile, it's convenient to realize the motion of ballbar with six step measurement, and the installation of ballbar is easy．
FENG Gang, FU Guo qiang, SUN Lei, FU Jian zhong. New geometric error identification of turntable for multi axis machine tools. JOURNAL OF ZHEJIANG UNIVERSITY (ENGINEERING SCIENCE), 2015, 49(11): 2083-2091.
［1］ UDDIN M S, IBARAKI S, MATSUBARA A, et al. Prediction and compensation of machining geometric errors of five axis machining centers with kinematic errors ［J］. Precision Engineering Journal of the International Societies for Precision Engineering and Nanotechnology, 2009, 33(2): 194-201．
［2］ SHEN H, FU J, HE Y, et al. On line Asynchronous Compensation Methods for static/quasi static error implemented on CNC machine tools ［J］. International Journal of Machine Tools and Manufacture, 2012, 60(0): 14-26．
［3］ CHEN G S, MEI X S, LI H L. Geometric error modeling and compensation for large scale grinding machine tools with multi axes ［J］. The International Journal of Advanced Manufacturing Technology, 2013, 69(9/12): 2583-2592．
［4］ WANG J, GUO J. Research on volumetric error compensation for NC machine tool based on laser tracker measurement ［J］. Science China Technological Sciences, 2012. 55(11): 3000-3009．
［5］ ZHU S, DING G, QIN S, et al. Integrated geometric error modeling, identification and compensation of CNC machine tools ［J］. International Journal of Machine Tools and Manufacture, 2012. 52(1): 24-29．
［6］ FU G, FU J, XU Y, et al. Product of exponential model for geometric error integration of multi axis machine tools ［J］. The International Journal of Advanced Manufacturing Technology, 2014. 71(9/12): 1653-1667．
［7］ FU G, FU J, XU Y, et al. Accuracy enhancement of five axis machine tool based on differential motion matrix: Geometric error modeling, identification and compensation ［J］. International Journal of Machine Tools and Manufacture, 2015. 89(0): 170-181．
［8］ ZHANG Y, FU J Z, CHEN Z C. Machining tests to identify kinematic errors of machine tool table rotation axis based on sensitive directions ［J］. The International Journal of Advanced Manufacturing Technology, 2013. 67(1/4): 495-500．
［9］ LEI W T, HSU Y Y. Accuracy test of five axis CNC machine tool with 3D probe ball. Part II: errors estimation ［J］. International Journal of Machine Tools & Manufacture, 2002. 42(10): 1163-1170．
［10］ TSUTSUMI M, TONE S, KATO N, et al. Enhancement of geometric accuracy of five axis machining centers based on identification and compensation of geometric deviations ［J］. International Journal of Machine Tools & Manufacture, 2013. 68: 11-20．
［11］ TSUTSUMI M, SAITO A. Identification and compensation of systematic deviations particular to 5 axis machining centers ［J］. International Journal of Machine Tools and Manufacture, 2003. 43(8): 771-780．
［12］ ZARGARBASHI S H H, MAYER J R R. Assessment of machine tool trunnion axis motion error, using magnetic double ball bar ［J］. International Journal of Machine Tools and Manufacture, 2006. 46(14): 1823-1834．
［13］ LEE K I, LEE D M, YANG S H. Parametric modeling and estimation of geometric errors for a rotary axis using double ball bar ［J］. International Journal of Advanced Manufacturing Technology, 2012. 62(5/8): 741-750．
［14］ LEE K I, YANG S H. Measurement and verification of position independent geometric errors of a five axis machine tool using a double ball bar ［J］. International Journal of Machine Tools and Manufacture, 2013. 70(0): 45-52．
［15］ LEE K I, YANG S H. Robust measurement method and uncertainty analysis for position independent geometric errors of a rotary axis using a double ball bar ［J］. International Journal of Precision Engineering and Manufacturing, 2013. 14(2): 231-239．
［16］ ZHANG Y, YANG J, ZHANG K. Geometric error measurement and compensation for the rotary table of five axis machine tool with double ballbar ［J］. International Journal of Advanced Manufacturing Technology, 2013. 65(1/4): 275-281．
［17］ CHEN J, LIN S, HE B. Geometric error measurement and identification for rotary table of multi axis machine tool using double ballbar ［J］. International Journal of Machine Tools and Manufacture, 2014. 77(0): 47-55．
［18］ LIN Y, SHEN Y. Modelling of five axis machine tool metrology models using the matrix summation approach ［J］. The International Journal of Advanced Manufacturing Technology, 2003, 21(4): 243-248．
