Condition based preload adjustment at ball-screw-drives by hydraulic expansion actuators

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Ball-Screw-Drives are the most significant linear drive system of machine tools, they define produc-tivity, accuracy and dynamics. As in every mechanical transfer element, its behavior is influenced by wear, which has a negative influence to the systems behavior (e.g. dynamic Stiffness, control-behavior and accuracy). Changes of the mechanic preload leads to improvement of the dynamic system behavior, but also leads to higher pressure, friction, temperature and developing wear. Dif-ferent approaches for control of preload at ball-screw-nut or thrust bearing are known. A new actu-ation control principle, based on hydraulic expansion actuators should be realized in this project. Therefore, the actuation principle has to be developed in general. Hydraulic expansion actuators have the benefit of a easy integration in the ball screw elements and should have a verry long life-time. The integration of the system into the ball-screw-nut and the thrust bearing and different control-strategies are evaluated in this project.