Investigations of the static and dynamic characteristics of the precision hydrostatic spindle with mid-thrust bearing under different loads

This paper investigates the static and dynamic characteristics of the precision hydrostatic spindle with a mid-thrust bearing under different working conditions. Firstly, the paper establishes the fluid governing equations of the coupled journal and thrust bearings based on orifice restrictors; and the dynamic and static Reynolds equations are solved using the perturbation and finite difference methods to obtain the steady and transient pressure distribution functions. Then the stiffness and damping characteristics of matrixes of the spindle are obtained by integrating the steady and transient pressure. Furthermore, by establishing the motion equation for the spindle rotor with five degrees of freedom, the quasi-static equilibrium position and stability criterion of the rotor under different working conditions are determined. Finally, the relationships between the dynamic and static characteristics of the spindle and cutting force, rotational speed, and cutting distance are simulated and analyzed. The simulation results show the patterns of variation in performance indices such as stiffness, damping, quasi-static position, and stability of the spindle under different working conditions, which provides important design information to be taken into consideration concerning the precision hydrostatic spindle.