Prediction of Thermal Deformation for a Ball Screw System Under Composite Operating Conditions

Abstract

The position error of a feed drive system is mostly caused by thermal deformation of a ball screw shaft. A high-speed ball screw system can generate massive heat with greater thermal expansion produced, and consequently have a negative effect on the positioning accuracy. 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 emulate the reciprocating movements of the nut at the speeds of 20, 40 and 60 m/min corresponding to the screw shaft, we also employed a three-dimensional unsteady heat conduction equation with the heat generation from the main sources including the ball screw shaft, nut and bearings as the heat transfer model to solve the temperature distributions for determining the temperature rises and axial thermal deformations in a ball screw shaft under composite operating conditions. The simulated results demonstrated that the countermeasures must be taken to thermally compensate great deterioration of the positioning accuracy due to vast heat production at high rotating speeds of shaft for a ball screw system.