One aspect of ballscrew drives that requires a great deal of attention when modeling is the interface between the ballscrew and nut. This is because it plays an important role in the transmission of motion, vibrations and forces from the ballscrew to the table. Current models of the screw-nut interface consider only the axial and/or torsional deflections of the ballscrew while assuming that the lateral deformations of the ballscrew are decoupled from its torsional and axial deformations so cannot be transmitted through the screw-nut interface to the table. This paper however develops a model for the screw-nut interface that considers the lateral deformations of the ballscrew in addition to its axial and torsional deformations. The result of the modeling shows that, contrary to the aforementioned assumptions, the torsional, axial and lateral deformations of the ballscrew are coupled through the screw-nut interface. Therefore a torque applied to the ballscrew via the motor actually gives rise to lateral deformations on the ballscrew which could both affect its fatigue life and potentially the positioning accuracy of the ballscrew drive. These findings are verified by experiments on a single-axis ballscrew drive.
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