An improved thermo-mechanical model for vertical machining center

Abstract

The prediction of thermo-mechanical behavior for machine tools is important during the designing period. The performance of high-speed machine tools depends not only on their stiffness but also on their thermal behaviors. Especially, the mechanical and thermal characteristics of joints affect the behaviors of machine tools notably. The purpose of this paper is to establish a thermo-mechanical model for machine tools, by using finite element analysis (FEA) method to study temperature expansion and thermal deformation. Unlike the methods developed by other researchers that mainly focused on specific kind of joints, the proposed model studied various joints on machine tools. To improve the accuracy of calculation, this model took both the thermal contact resistance (TCR) and contact stiffness of the joints into account, and the coupling between the TCR and contact stiffness was also studied here. Based on the Hertz theory, fractal geometry was used to analyze the TCR and contact stiffness on the joints. Experiments were set up to test the transient temperature change and the thermal deformation characteristics of a vertical machine center (VMC). The results showed that the proposed model can accurately simulate thermal characteristics of machine tools.