Research On Evaluation Method Of Repeatability Of Positioning In Linear Motion Axis Of Machine Tools

In the process of machine tool assembly,adjustments must be made to ensure the repeatability of positioning of the machine tool linear axes.Therefore,how to evaluate the repeatability of positioning of linear axes is an important task.With the development of the manufacturing industry and the upgrading of measurement methods,the current single parameter evaluate method cannot meet some high-precision occasions.In this paper,the researches about the evaluation method of repeated positioning of linear axes are studied as follows:Through the homogeneous coordinate transformation,the horizontal machining center is taken as an example to establish a theorical model for analyzing the relationship between the repeatability of the end motion of the machine tool and the repeatability of the linear axes.The influences of the repeatability of the deviations and angle errors on the repeatability of the end motion of the machine tool are analyzed.Based on the study of spatial data uncertainty,the spherical probability error radius is used as the evaluation index to evaluate the three-dimensional spatial repeatability of positioning accuracy of linear motion axis.The advantages and disadvantages of calculating the radius by the joint probability density function,the chi-square approximation algorithm and the statistical method are analyzed.The accuracy of the other two calculation methods is compared with the joint probability density function.By the homogeneous coordinate transformation principle,the analytical model between the measurement position and the evaluation result is established,and the relationship between the different measurement positions and the final evaluation result under different repeatability of the angular errors is analyzed by the simulation data.The multi-position measurement evaluation method is proposed.Taking the repeated positioning error mechanism test platform and the JIG 630 horizontal machining center as the studied objects,the above analysis results is verified by experiments.