FEM-Based Modeling to Simulate Thermal Deformation Process for High-Speed Ball Screw Drive Systems

Abstract

Along with increasing speed and acceleration of numerically controlled machine tools, the influence of thermal dynamics characteristics on operating accuracy becomes more and more important. Improvement of thermal dynamics characteristics has turned out to be one of the crucial problems to develop machine tool of high performance. The positioning error of a feed drive system, mostly caused by the thermal deformation of a ball screw shaft, can directly affect the working accuracy of the machine tool. In this study, we applied the computational approach using the finite element method (FEM) to simulate the thermal expansion process for estimating the deformation of the ball screw system. In the numerical analysis, the deformation of the ball screw shaft and nut was modeled via a linear elasticity approach along with the assumption that the material was elastic, homogeneous, and isotropic. To model the reciprocating motions of the nut at a speed of 60m/min respecting to the screw shaft, we utilized the three-dimensional unsteady heat conduction equation with the frictional heat from the sources of the ball screw shaft, nut and bearings to calculate the temperature distributions for determining the temperature rises and axial thermal deformations in a ball screw shaft under operating situations. Simulations were conducted to explore the connection between the temperature increase of nut and the thermal deformation of the ball screw drive system, revealing the need of a compensation scheme for thermal error to improve the operating accuracy of machine tools.