The DBB-Based Errors Modeling And Measurement Method For 5-axis High Speed CNC Machine Tools

This paper aimed at the measurment of the main errors of the 5-axis high speed machine tools, and foused on the key problems concernd for the measurement methods of the errors of rotary axis, the thermal errors of high speed spindle and linear motor systems. This paper based on double-ball-bar(DBB) theory and found the mathematic model including main geometrical errors and thermal errors of the 5-axis machine tools; and thermal-structure coupling analysis for high spindle and linear motor systems was done. Five DBB measurement models were designed for different errors. Lastly, the experiments of DBB for 5-axis machine tools were done. The following in-depth work had been completed.The synthesis error model of high speed 5-axis machine tools was founded based on homogeneous coordinate transformation theory, included 4 geometrical errors of C-aixs, thermal drift errors of high speed spindle and geometrical and thermal errors of linear motor systems, then the DBB measurement method was founded according to the error model.The FEA analysis for whole machine tools, high speed spindle and linear guide was done by ANSYS, the temperature field of machine tools, the thermal distortion of spindle and linear guide were got, by applying thermal and structural loads on the FEA models.The measurement models of DBB was founded and different trajectories of DBB for different errors were simulated, including 4 geometrical errors of C-aixs, thermal drift errors of high speed spindle and geometrical and thermal errors of linear motor systems.The method for separating the geometrical and thermal errors from DBB data was proposed based on the closed characteristic of the kinematical chain of 5-axis machine tools, the location errors of DBB could also be separated by using least square method.At last, the variation curves of spindle thermal drifting errors and thermal errrors of linear guide were drawn, and the distribution on the worktable surface of synthesis errors were also drawn, then the accuracy of the machine tools was evaluated based on all the analysis mentioned above.The outcome of this research had high value for the development of high performance mahine tools, and the methods proposed in the paper were also suitable for the other similar 5-axis and high speed machine tools.