| CNC machine tool becomes the core of equipment manufacturing for its superior processability. As the rapid development of CNC machine tool technology and the improvement of advanced mechanical technology, the higher requirements to the machining accuracy of CNC machine tool are put forward. However, positioning errors and contour errors which are CNC machine tool working accuracy metrics are restricted by factors such as manufacturing, control, environmental factors etc. Therefore, in order to improve CNC machine tool working accuracy, mechanism of positioning errors and contour errors are analyzed in the paper. And positioning errors compensation strategy based on backlash errors compensation and pitch errors compensation is presented to improve the positioning accuracy of CNC machine tool, and analyze the effect of positioning errors on circular contour errors of contour errors.Firstly, base on the analysis of main error sources of CNC machine tool, two types of CNC machine tool main errors are explored in this paper: positioning errors and contour errors. The influence factors of positioning errors are detailed analysis. The influence rules of servo system gain parameters and the dynamic characteristics on contour errors are obtained through detailed analysis of impact on the contour errors of servo drive system.Secondly, in order to improve CNC machine tool positioning accuracy, backlash and pitch errors which have great influence on positioning accuracy of CNC machine tool are studied. To achieve backlash errors compensation, according to the backlash errors in the process of compensation, a compensation strategy which selects acceleration is proposed. To realize pitch errors compensation, a compensation strategy is designed which off-line average linear interpolation.Thirdly, according to nonlinear characteristics of backlash errors, the mathematical method based on the principle of circular contour motion synthesis is put forward to analyze the impact of circular contour errors and backlash errors. The impact of circular contour errors and pitch errors is analyzed based on the relationship of the positioning errors and pitch errors.Finally, the single axis positioning accuracy measurement experiment and the circular contour error experiment have been done separately on VGL40 CNC machine tool, which verify the effectiveness of the proposed positioning errors compensation strategy. General rules of positioning errors influence on circular contour errors are obtained as well. |
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