Explicit modeling and investigation of friction torques in double-nut ball screws for the precision design of ball screw feed drives

Explicit friction torque model composed of an applied load and viscous friction terms is formulated for two-point contact double-nut ball screws. Precision friction torque test rig is developed to verify the model. Forward and reverse direction measurements show a small friction difference due to the asymmetric nut geometry. Experiments confirm the friction prediction accuracy of 89%. Although a large axial load is applied to a ball screw, a lower and smoother friction torque is obtained by a proper preload selection through the developed model. It is also applicable as a thermal boundary condition for the finite element analysis. Efficient, smooth and accurate feed systems are obtained through the optimization of ball screw design parameters by minimizing the friction model.