On-machine measurement of thermal influence of the long-span crossbeam of gantry machine tools using a 3D laser profiler

Abstract

For gantry machine tools, the large-span beam is an important structural component, and its deformation is significantly affected by temperature. It is still a crucial problem to identify the thermal error of the motion axis continuously and in real-time. This paper proposed an on-machine measurement (OMM) method to evaluate the thermal influence on long-span crossbeam of the gantry machine tools, using a high-precision 3D laser profiler and a set of artifacts. Firstly, kinematic model to compute the deformation of the crossbeam is established considering the position calibration of the laser profiler. As the Y-axis relies on the crossbeam, thermal errors of the Y-axis are identified to evaluate the thermal influence on long-span crossbeam. Secondly, algorithms for the position calibration and the point cloud registration are proposed to solve the calibration matrix and the relative transformation matrix of the 3D laser profiler in the kinematic model. The thermal error of the Y-axis can then be identified by utilizing the developed kinematic model. Finally, a continuous warm-up experiment was carried out on a three-axis gantry machine tool, and the six thermal errors of the Y-axes during the warm-up process were calculated. The results verify the effectiveness of the proposed method. In addition, uncertainty analysis is conducted to evaluate the effect of the 3D laser profiler calibration error on thermal error identification based on the experimental results. It is proved that the proposed thermal error identification method is insensitive to position calibration errors.