Fundamentals of preload adaption in single nut ball screws

• Applicant: Professor Dr.-Ing. Berend Denkena
• Subject Area: Metal-Cutting and Abrasive Manufacturing Engineering
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 495763297

Ball screw drives (Ball Screw Drive (Ball Screw Units, BSD)) play a major role in determining the achievable dynamics and accuracy of feed axes in machine tools. The setting of the preload of the BSD represents an essential conflict of objectives. A high preload increases the dynamic stiffness and thus also the achievable machining quality. However, a higher preload also significantly reduces the service life of the BSD. A situational preload adaptation has the potential to significantly increase the service life of BSD. However, the focus of research on preload adaptation has so far been on double nuts. With these, the compliance influence of the actuators restricts the minimum settable preload and reduces the stiffness of the BSD compared to conventional BSDs. A direction-dependent stiffness also results from these actuators. With single nuts, however, preload adaptation is possible by radial deformation of the nut without the actuator affecting the stiffness of the nut. Therefore, the main goal of the project is to gain fundamental knowledge about the design and operation of single nut ball screws with adaptable preload and to investigate their interaction with machining processes with respect to machining quality. First, design fundamentals for preload controlled single nut BSD are developed and investigations on their operational and accuracy behavior are performed. Since only double nuts have been investigated so far, the design fundamentals for single nuts with variable preload have to be fundamentally reworked. In a subsequent second funding phase, it is planned to integrate the then preload-controlled BSD in a machine tool and to investigate its interaction with the machining process.

• DFG Programme: Research Grants