Influence of linear ball guide preloads and retainers on the microscopic motions of a feed-drive system

This paper describes the effects of preloading and ball retainer conditions of linear ball guides on a feed-drive system operating on a microscopic scale, as this is important for applications that employ linear guides in precision machines. To begin, relationships between nonlinear spring behaviors of the guide and the behavior of quadrant glitches were analyzed based on the proposed simple friction model. The behavior of the quadrant glitches, nanometer step responses, and steady vibrations were also measured for three guide conditions that differed with respect to the ball retainers and preloading. These experiments were carried out by using a special feed-drive system that comprises eight-grooved linear ball guides, an AC linear servo motor, and a linear encoder with a high position resolution of 31.25 pm. This system was set on a vibration isolation table and driven by a linear current amplifier. The time constants of each of the step responses were also analyzed based on the friction and control system model. From the analysis and experiments, it is demonstrated that the behavior of quadrant glitches and step responses are strongly influenced by the friction characteristics of the guides, and that this behavior can be adequately estimated via analysis. Additionally, it is shown that steady vibrations are also influenced by the friction characteristics, and that the amplitude of the vibration is proportional to the compliance of the nonlinear spring behavior.