Load Distribution and Accuracy·Rigidity of Linear Motion Ball Guides System

Abstract

The load distribution formula in LMBG (Linear Motion Ball Guides) system is derived under the combined loads and moments, supposing the table of machine tool. The load distribu-tion and the maximum distribution load in the system, the rigidity and the guiding accuracy of the table, the effect of the shape of both end portions of guide block raceways, the optimum preloading etc. are calculated. The results are as follows. (1) Generally, the rigidity of LMBG system is greater than the rigidity of the construction elements of machine tools. (2) Since the machine tool ways are subjected to various combined loads and moments, it needs to give an optimum preload to the system by the installation of the over size balls, which makes the maximum distribution load in the system decrease to the minimum value. (3) The displacement components, i. e., the vertical and horizontal displacement, pitching, rolling and yawing angle become greater in accordance with the increase of the radial clearance, but the rapid decrease of them can be obtained from the light preload to the optimum preload. In the case of the heavy preload, they do not decrease so much. (4) The shape of both end portions of guide block raceways affects considerably on the load distribution, the maximum distribution load and the guiding accuracy of the LMBG system.