A comprehensive study on capabilities and limitations of roller–screw with emphasis on slip tendency

Transmission screw is a mechanism to convert the rotation into linear movement. Since sliding between screw and nut affects the motion accuracy, ball screws and roller–screws are used. Lead of a ball screw equals to screw pitch, which is usually in the order of millimeter while a roller–screw can present a wide range of leads. This paper comprehensively studies the capabilities and limitations of roller–screw and shows that large leads and extremely small leads are easily obtainable. The slip phenomenon has been studied regarding the forces acting on the roller during the rotation of screw. It is also shown for small leads between zero and pitch that the roller and the screw have inherent tendency to roll on each other with constant and stable lead. In addition, optimization of profile of threads has been studied. An investigation on the possible and permissible number of rollers around a screw has been carried out. The results of this study, confirmed by experiments, show that the roller–screw can be used for both fine and rough movement with flexible leads and desired accuracy.