Static load distribution and axial static contact stiffness of a preloaded double-nut ball screw considering geometric errors.

l An SLD and ASCS model of a preloaded DNBS considering geometric errors are proposed. l An SLD algorithm is proposed for a preloaded DNBS considering non-loaded balls. l The critical external axial force increases with the geometric error l The initial ASCS of a preloaded DNBS decreases with increasing geometric error. l The ASCS can be kept more stable by selecting the appropriate preload. The preloaded double-nut ball screw (DNBS) is widely used in precision transmission for its high load capacity and contact stiffness. However, few researches have been done on the influence of load distribution on the loading performance of a DNBS, and no solution has been found for the problem of non-loaded balls in the raceway. Therefore, we propose a static load distribution (SLD) model of a preloaded DNBS considering geometric errors, which takes into account the influence of non-loaded balls and the interaction between the elastic deformation of a screw/nut and the Hertz contact forces of screw–ball/nut–ball contact areas. This model is verified experimentally. The maximum deviation between the theoretical and experimental values is 6.21%. We numerically simulate the effects of geometric errors on the SLD and axial static contact stiffness (ASCS) of a preloaded DNBS. The SLD varies significantly with the geometric error, preload and external axial forces, and the critical external axial force on the preloaded DNBS increases with the preload and geometric error. For a preloaded DNBS with a given geometric error, the ASCS can be kept more stable by selecting the appropriate preload. [ABSTRACT FROM AUTHOR]