Friction torque in four contact point slewing bearings Effect of manufacturing errors and ring stiffness.pdfVIP

Mechanism and Machine Theory 112 (2017) 145–154 Contents lists available at ScienceDirect Mechanism and Machine Theory journal homepage: /locate/mechmachtheory Research paper Friction torque in four contact point slewing bearings: Effect of manufacturing errors and ring stiffness Iker Heras?, Josu Aguirrebeitia, Mikel Abasolo Department of Mechanical Engineering, University of the Basque Country, Bilbao, Spain article info Article history: Received 26 October 2016 Revised 17 February 2017 Accepted 20 February 2017 Keywords: Four contact point bearing Slewing bearing Friction torque Manufacturing errors Ring stiffness abstract This work outlines a procedure for the determination of the interferences between balls and raceways in four contact point slewing bearings due to manufacturing errors. The procedure is applied to a particular case and ?nite element analyses are performed for the friction torque calculation, considering different preloads. The results are used to evaluate the in?uence of manufacturing errors and the stiffness of the rings in the idling friction torque of the bearing. ? 2017 Elsevier Ltd. All rights reserved. 1. Introduction Friction torque is a key parameter when designing slewing bearings. This type of bearing is used for orientation purposes in machines like tower cranes or wind turbines, where large loads are involved (Fig. 1), and also in applications where highprecision operations are required, like robots, where loading conditions are less demanding. An actuation system is needed to trigger the rotation, so the friction torque must be estimated in order to dimension it. The ?rst step to calculate the friction torque consists on determining the load distribution among the balls. This problem was analytically solved by Zupan and Prebil [1] and Amasorrain et al. [2]; in those models the rings where assumed to be rigid. In the same line but with a different focus, Aguirrebeitia et al. [3–5] proposed a procedure for calculating the load combin