Speeds, lead and characteristic defect frequencies of arbitrary roller screws

Abstract

For many applications with high demands on axial forces and rigidity roller screws are being increasingly relied on. Lead and dynamic behavior are two of the key criteria concerning the design and use of roller screws. The lead results from the interaction of the threaded profile and the kinematics of each element of the roller screw. While their kinematics has been studied in recent literature, a compact equation for calculating the lead of arbitrary roller screws is still missing. Furthermore, their characteristic frequencies, as they offer a tool for the purpose of condition monitoring within the scope of a vibration analysis, are still unknown. In the following work the derivation of calculation methods for the lead of roller screws with arbitrary geometries is presented. Applying these methods, the lead of common roller screw types is calculated. In addition to the calculation of the lead, the methods allow an analysis of kinematic properties. For the purpose of condition monitoring, the characteristic frequencies of roller screws are analyzed. Exemplarily, a typical envelope spectrum of an acceleration signal that has been acquired in radial direction on a roller screw nut in good condition is presented.