Efficient Measurement And Comprehensive Compensation For Geometric Errors On Five-axis Machine Tools

The research and development of high-end CNC machine tool is one of the significant engineering project of 13^th five-year plan and Made in China2025.The research and development of five-axis machine tool is of great importance for industrial power and national defense construction.This research is funded by the State Key Science and Technology Project.This research is concerned with measurement,modeling and compensation for geometric errors on five-axis machine tools.An efficient error measuring method is proposed.An error element model and comprehensive model is established.An error compensation system is developed and compensation experiments showed that precision of the machine tool is improved greatly.The main content of this research is listed as follows.?1?A practical and accurate error comprehensive mathematical model of five-axis machine tool is established.Error elements of translational axis,rotary axis and spindle are analyzed.Taking a two-turntable five-axis machine tool as an example,the comprehensive error mathematical model is established based on homogeneous transformation matrix?HTM?.The issue of the multiplication of error and ideal motion matrix is clarified in this model.Moreover,the error matrix of the rotary axis'position independent geometric error?PIGE?with relevant definition is added to comprehensive model.Thus the error comprehensive model becomes more practical and accurate.?2?An optimized method based on laser step body diagonal measurement is proposed.Based on the conventional laser step body diagonal measurement,a simplified error identification method is recommended.The simplified method could achieve the same results with conventional method with measuring only 3 diagonal lines.The time of measurement is saved.Besides,an optimized method is proposed according to the research on installation errors of laser step body diagonal measurement.After measuring positioning errors of 3 diagonals and 3 translational axes,the installation errors could be removed.With the optimized method,laser step body diagonal measurement becomes more accurate,while the efficiency is still maintained.Measurement on rotary positioning errors of rotary axis is also introduced.Error elements of translational and rotary axis are obtained by measuring experiment.?3?Self-adaptive cubic spline interpolation model is established for fitting error elements.This model takes advantage of interpolation nodes adaptive selection algorithm,which could just choose weighted data points as interpolation nodes,while the estimation error is less than allowable error.This model has high accuracy and efficiency.Therefore,self-adaptive cubic spline interpolation model is perfect for fitting error data with great fluctuation and large quantities.?4?The error compensation system is developed,and compensation experiments are conducted on a five-axis machine tool.The compensation system is developed based on the zero point shifting function of CNC.The compensation experiments were conducted on a two-turntable five-axis machine tool,including positioning error tests,body diagonal errors tests and standard ball machining tests.The results of compensation experiments showed that the accuracy of the two-turntable five-axis machine tool was improved significantly.The measurement,modeling and compensation methods which are proposed in this research are validated.