Preload adjustment for ball screw drives by means of passive mechanics

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Ball screw drives are mechanical elements used in machine tools to provide specified feed motion. Relevant characteristics for static and dynamical behavior of the applied feed drive in this project are load capacity, precision and stiffness. One essential design of the ball screw drive is the implemented preloaded double nut. The intensity of the preload, however, is a compromise between contradicting objectives and, furthermore, it decreases over time. Active actuators for adjustment of the preload are complex and have negative influence on the operation characteristics. In the proposed research project, a novel concept for a load-adaptive adjustment of the preload shall be developed. The approach is based on passive mechanical elements and is validated via simulative and experimental methods. Preliminary studies demonstrated the feasibility of using a spring mechanism, which affects the pitch offset of the nuts. The consequence is the adjustment of the preload based on the maximum axial load.