Research On Geometric Error Sensitivity And Spatial Error Field Of Five-axis Machine Tool With Double Turntable

The geometric error of the five-axis CNC machine tool is the main reason that affects the machining accuracy of the machine tool.Analyze the sensitivity of geometric errors,find the key geometric error items that affect the machine tool error,and study the machining space error of the machine tool can effectively improve the machining accuracy of thin-walled workpieces.In this paper,an in-depth analysis of the geometric error of a five-axis machine tool with a double turntable is carried out.First,based on the theory of multi-body systems,a geometric error model of a five-axis machine tool with a double turntable was established,thereby,the geometric error and spatial geometric error of the machine tool in the X,Y,and Z directions can be obtained.Based on the function differentiation method,the sensitivity expressions of various errors of the dual-turntable five-axis machine tool are identified.And two S-shaped specimens with different inclination angles of curved surfaces are used as the processing objects for experimental verification.Measure the comprehensive error of the surface of the S-shaped specimen after processing.The average error of the twisted part of the 0°S-shaped specimen is about60?m,and the average error of the twisted part of the 15°S-shaped specimen is about65?m.According to the various error data,the sensitivity of each geometric error is calculated.The sum of the error sensitivity coefficients corresponding to the various geometric errors of the rotary axis is 0.556,which accounts for more than 50% of the37 geometric errors of the machine tool.Among them,the A-axis rotation angle error in the X directionis the most sensitive error item among all geometric error items,reaching 0.124,effectively identifying the key geometric error items that have the greatest impact on the accuracy of CNC machine tools.Secondly,derive the mathematical model of the machine tool rotation axis when there are no geometric errors,And deduced the mathematical model of the machine tool rotation axis in the presence of various geometric errors.Subtract the geometric error model of the rotating shaft under ideal conditions without geometric error from the geometric error model of the rotating shaft under actual geometric errors,and find the root mean square for it,the comprehensive geometric error of the machining space of the machine tool is obtained.Then,the geometric error identification method of the dual-rotation axis of the dual-turntable five-axis machine tool is proposed.According to the position change of the two standard balls before and after the A-axis rotation of the machine tool,identify the six geometric error models of the A-axis of the machine tool,thus,the solution of the A-axis geometric error model is obtained.Taking into account the influence of the A-axis rotation,according to the changes in the positions of the two standard balls before and after the rotation of the C-axis,identify the six geometric error models of the C-axis,thus,the solution of the geometric error model of the C-axis considering the different rotation angles of the A-axis is obtained.And design experiments,obtain the coordinate data of the 12 geometric errors of the rotating axis,and obtain the geometric error values of the A-axis and the C-axis.Among them,the error value of the angle error of the A axis in the X direction is the largest,which is31.5?m.The rotation angle error of the C-axis along the Y direction is the largest item in the geometric errors of the C-axis,and its average value under different A-axis rotation angles reaches-21.5?m.The order of the size of each error item conforms to the order of sensitivity.Finally,according to the geometric error model of the rotation axis of the two-turntable five-axis machine tool established above,the geometric error field of the machining space of the machine tool is established.Detailed analysis of the distribution of machine tool processing spatial error under different A-axis rotation angles.Under different A-axis rotation angles,the machining space geometric error of the machine tool is different,the minimum value is at the center of the processing space,and the size is 4?m.The maximum value is at the edge of the processing space,and the size is 85?m.And compared the 12 geometric errors of the rotation axis obtained by the identification method proposed in this paper with the identification methods and results of other scholars.The accuracy of the error identification method in this paper is 96.4%,and the cost is low,and the detection process only needs 30-40 min.