Precision Modeling and Measurement of Nut Stiffness in Ballscrews

Abstract

Ballscrews are precision positioning units applied to industrial machinery and precision machines. As the positioning accuracy of a feeddrive system depends upon ballscrew stiffness, the nut stiffness estimation of ballscrews is important for precision machine design. In this paper, accurate nut stiffness model incorporating Hertzian deformation as well as flexibility of the screw shaft and nut is developed through consideration of contact angle variation of balls in the grooves during loading. Experimental verification of the stiffness model under various loads and assembly conditions has been conducted on the enhanced measurement system.