An improved static stiffness analysis model for machine tools based on virtual material method

The static stiffness of machine tools can be used for the analysis of thermal deformation because of the uneven temperature field and can further be applied in the thermal error compensation. The prediction of static performance of machine tools is fundamental and essential during the design period. The purpose of this paper is to establish a precise static stiffness model for machine tools. Different from previous models, the proposed method in this paper, basing on the Fractal Geometry, takes both the elastoplastic deformation mechanism and friction into account. By analyzing the normal stiffness and tangential stiffness of joints, equivalent virtual material parameters are acquired for the finite element analysis calculation. An experimental set-up has been established to test X, Y and Z directional deformation of a vertical machine center with a magnitude of 200 kgf load applied to the node of the spindle along the respective direction. The results demonstrate that the proposed model can accurately simulate static characteristics of machine tools.