An Experimental and Theoretical Approach for Stiffness of Machine Tool Spindle with Fluid Bearings

Abstract Machine tool spindle stiffness is a leading technical indicatoraffecting cutting ability. However, the stiffness of the machine tool spindle with fluid bearings has not been studied thoroughly. This paper proposes a new methodology for the spindle stiffness with fluid bearing including definition of the spindle nose stiffness, experimental method and calculation method for this stiffness. A motorized spindle with hydrodynamic water-lubricated spiral groove bearings developed in our laboratory is selected as an object, a theoretical and experimental investigation on the spindle nose stiffness is conducted. The result shows that the proposed experimental method can be utilized to measure the nose stiffness of spindle with the fluid bearings, meanwhile, the spindle stiffness can be obtained by simultaneously solving the rotor dynamic model and the fluid bearing dynamic model. The fluid bearing spindle stiffness depends strongly on the rotary speed and the external load. We expect an improvement for the experimental device by introducing another load device to apply a perturbation load with an any angle to the external load on the spindle nose.