Design and set up of an innovative ball screw endurance test bench

Ball screw mechanisms allow to transform a rotational movement into a linear one and vice versa. The two most important features of these mechanisms are the heightened precision in positioning and increased load capacity[1]. For these reasons they are widely used in a large number of applications in which high precision linear movements are required. Ball screw mechanisms are closed systems and it is difficult to experimentally investigate what happens between balls, screw and nut during the movement. Several mathematical models are developed to describe their behaviour. Between them, it is worth remembering the ones have been done by Levit [2], based on the settled theories developed for ball bearings [3]. Recently a revision of Levit’s work has been proposed [4, 5, 6] introducing the analysis of the micro-movements in the contact areas of the balls during the working cycle. Whereas there are extensive studies focusing on improving the mathematical description of the behaviour of these devices, there are no substantial developments in defining new experimental setups capable of characterizing these, in particular when used under real load conditions. The object of this work is to show an innovative ball screw endurance test bench capable of performing endurance tests under real load conditions. The aim of this paper is to present and describe a test bench for ball screw testing capable of reducing the problems in endurance tests for these devices. It has been especially developed in the case of large sized ball screws where high power is required to effect the test, and consequently there are high loads between the screw and the frame that holds it. This work presents the design of this device and the experimental setup developed in order to perform tests for 25 mm ball screw. The originality of this approach is regarding the use of the recirculating power principle. This article sets out the design and the building phase of the test rig with particular reference to evaluating the pros and cons of this innovative solution.