Research on axial dynamic stiffness of fix-pressure spindle

Dynamic stiffness of a spindle in condition of service state changes with the operating conditions and loads, and is the main indicator of the dynamic performance of the spindle. The deficiency of the current study is that the model is very complex with large amount of calculation, and the load characteristic of bearing is always ignored during analysis. The relationship between axial load and stiffness of fixed-pressure spindles is systematically researched through the combination of theoretical methods and experimental tests. A model of fixed-pressure preload spindle is built based on the empirical formula of relationship between axial load and axial deformation, and the dynamic relationship between axial dynamic stiffness of spindle and axial load is theoretically derived. Then an experiment to test the dynamic stiffness is designed. Axial force is applied to the working spindle and its displacement is tested using three displacement sensors. The stiffness of the spindle is calculated and compared with simulation data. Experimental results show that the dynamic stiffness of the fixed-pressure preload spindle increases with the increase of axial load when the outer ring and inner ring of the front bearing of the spindle are compressed, and the stiffness reduces first and then tends to be constant with the increase of axial load when the outer ring and inner ring of the front bearing of the spindle separate.