The kinematics of ball-screw mechanisms via the slide-roll ratio

The motion state of balls in the ball screw mechanism is hard to observed or measured because of the complexity of the mechanism consisting of three main components: screw, nut and balls. In this paper, a kinematic model for the basic single arc ball screw mechanism driven by the rotation of the screw is established using the homogenous transformation matrix, and the kinematic characteristics and slide-roll ratios at contact points of the raceways are analyzed. There are five possible relative motion states: a) screw pure rolling and nut rolling-sliding mixed motion, b) nut pure rolling and screw rolling-sliding mixed motion, c) screw pure sliding and nut no relative motion, d) nut pure sliding and screw no relative motion, and e) both rolling-sliding mixed motion between the balls and the raceways of the screw and nut in the tangential direction of the helix path. A parametric study is also carried out to evaluate the effect of motion velocity on the slide-roll ratio based on the numerical calculations of the slide-roll ratio at the contact points. (C) 2014 Elsevier Ltd. All rights reserved.