Investigation on the influence of interference fit on the static and dynamic characteristics of spindle system

The performance of high-speed and high-precision machine tool spindle is quite sensitive to the variation of system parameters. How to accurately predict the influences of key parameters on spindle characteristics is important for designers to achieve required machining accuracy. In the assembly of spindle system, the interference fit, which is always used to connect bearing and shaft, affects the performances of spindle system directly. Therefore, the quantitative investigation on the effects of interference fit on spindle characteristics are of great practical significance. In this paper, the effect mechanism of interference fit on spindle bearing system is explored and used to modify the analytical spindle bearing model. Firstly, the internal geometric relationships among the assembly bearing parts and shaft is analyzed under the influence of assembly deformation and centrifugal expansion. Then, the static and dynamic characteristics of spindle bearing system, including the bearing stiffness, maximum loosing speed, spindle stiffness as well as modal characteristics, are predicted under different interference fit values based on the modified spindle bearing model. The results show that the interference fit will stiffen the bearing and spindle system and result in obvious increments on bearing stiffness, spindle stiffness as well as the natural frequencies. A specially designed spindle test rig is built to verify the simulation results, and the variation of spindle stiffness and natural frequencies are measured under different interference fit values. The maximum error of the system natural frequencies between the analytical results and the experimental data is 7.36%, which confirmed the accuracy of the proposed analytical model.