Investigations on contact characteristics of ball screw considering flexible deformation of screw and nut

The contact properties of the screw-nut pair play a decisive role in the wear rate and service life of ball screws. The difficulty of the ball contact loads directly detected has resulted in the development of many flexible contact models to predict what happens inside the ball screw during its working process. However, few contact models account for nut flexibility when axial load is applied. This article proposes a screw-nut pair contact model with the flexible screw and nut, which are modeled as elastic beams with axial deformations. The geometric relationship of the centers of the raceways and balls is used to describe the variation of the contact loads with the positions of the balls. Effects of the axial, transverse, and torsional deformations of the screw and nut and the geometric error of balls on centers of the raceways and balls are taken into account in the model. For the dynamic model of the feed system, the screw is considered a continuum rod, while the worktable and bearings are treated as lamped masses. The effect of the contact stiffness of the screw-nut pair on the axial and torsional vibration modes of the screw is investigated using a numerical simulation. Moreover, the influences of the worktable position on vibration modes of the feed systems are discussed for the screw with fixed-free and fixed–fixed support modes, respectively. The load-deformation and dynamic experiments are conducted to verify the effectiveness of the proposed models.