A unified approach to study coupling behavior of friction and ball motion in ball screws

There is a strong coupling relationship between the friction characteristics of the ball-groove interface and the ball motion behavior. However, available studies tend to consider ball motion and frictional behavior separately. In this paper, a unified tribology-kinematic model is established considering the coupling effect between friction and the ball velocity vector. The friction in ball-groove contact and ball speed are simultaneously measured by a newly developed disc-ball-disc device for studying friction and movement in ball screws. A comprehensive analysis of rubbing interface behavior and ball motion is conducted. The results show that the coupling effect between friction in ball-groove contact and ball motion is quite obvious. The sliding velocity of the ball is much higher with coupling effect than that when ignoring coupling influence, especially at high-speed conditions. The friction in ball-groove contact decreases at first and then shows a dramatic increase with the gradual rise of rotation speed, which is caused by the coupling variation of sliding speed. The studies show that the disc-ball-disc approach is an innovative and valuable method to investigate friction and ball motion in ball screws.