Kinematic errors prediction for multi-axis machine tools' guideways based on tolerance

摘要

In this paper, a systematic approach on how to predict kinematic errors based on tolerance of machine tools' guideways is introduced. Firstly, the truncated Fourier series function is applied to fit curve of guideways surface. Since geometric profile errors are regarded as a bridge between tolerance and kinematic errors of machine tools' guideways, the mapping relationship between tolerance and geometric profile errors of machine tools' guideways is formulated, and the mapping relationship between geometric profile errors and kinematic errors of guideways is established. Then, kinematic errors prediction model based on tolerance of guideways is subsequently proposed. Finally, simulation verification is conducted with this method. Simulation results show the range of the predicted kinematic errors (positioning error, y direction and z direction straightness error, roll error, pitch error, and yaw error) is 17.12 mu m, 56.57 mu m, 70.71 mu m, 28.28 grad, 141.42 mu rad, and 113.14 mu rad, respectively. In order to verify the feasibility and effectiveness of the presented method, a measuring experiment is carried out on guideways of a gantry-type five-axis milling machine tools by using a dual-frequency laser interferometer. The measured and identified discrete data can be fitted precisely by Fourier curve fitting method. The fitting results show the range of the measured kinematic errors is 16.96 mu m, 59.43 mu m, 68.63 mu m, 28.65 mu rad, 135.40 mu rad, and 111.58 mu rad, respectively. The maximum residual errors between the predicted and measured values of kinematic errors are 1.67 mu m, 5.19 mu m, 5.50 mu m, 1.87 mu rad, 9.81 mu rad, and 7.07 mu rad, respectively. Comparing with the measured results of kinematic errors, residual errors are considerably small and can be neglected. Therefore, there is no doubt that this method is effective enough for predicting kinematic errors and can be used to replace the measurement of kinematic errors. In the design stage of machine tools, this approach is convenient for engineers to derive the distribution of kinematic errors. And its basic idea can be applied to other type of machine tools' guideways.