Abstract: Dynamic characteristic of ball screw feed system is of significant influence on positioning precision, machining performance and vibration characteristic of machine tools. In illusion to the problem that stiffness of joints are difficult to determine in theoretical modeling of the ball screw feed system, with a self-designed and manufactured ball screw feed system as research object, fixed joints stiffness of the feed system is obtained by Takashi Yoshimura method; According to the common feature of ball screw assembly, rolling guide pair and rolling bearing, a stiffness calculating method of the rolling joints is proposed based on the Hertz contact theory, upon which a finite element (FE) model is established. On this basis, theoretical and experimental modal analysis are conducted, the validity of the FE model is verified by the comparisons of modal shapes and natural frequencies. According to the established FE model, effects of workbench’s mass and location, ball screw assembly’s stiffness, rolling guide pair’s stiffness and bearing’s stiffness on dynamic characteristic of the ball screw feed system are analyzed. The proposed method provides a reference for the stiffness identification of machine tool’s rolling joints, and the research conclusions provide a foundation for optimal design of the ball screw feed system.

Key words: ball screw feed system, dynamic characteristic, Hertz contact theory, rolling joints, stiffness characteristic