The latest preload technology of machine tool spindles: A review

Abstract

Recently, the studies of machine tool spindles for high-speed and high-precision have been actively performed to produce high-valueadded products. The spindle has a great influence on the performance of the machine tool. In particular, the preload method and the amount of preload applied to the bearings inside the spindle are properly determined to maintain high performance of the spindle. The bearing preload refers to the internal load by interference of the axial or radial direction within a bearing, and elastic deformation between the rolling elements and the raceway can arise. The main purpose of the bearing preload is to improve the machining accuracy, rigidity and bearing life. At low speeds, a heavy preload should be applied to improve the machining accuracy by increasing the rigidity due to heavy cutting. In contrast, at high speeds, a light preload should be applied to light cutting. Therefore, a variable preload technology which depends on the operating conditions should be applied. In this paper, a summary related to preload technology is provided and an analysis of patent trends related to variable preload technology is conducted. Moreover, a literature review of new conceptual variable preload technology is carried out, and non-uniform preload technology is summarized.