Modeling and analysis of axial thermal error in machining space of double-swing five-axis machine tool

Abstract

The axial thermal error of five-axis CNC machine tools is a significant factor affecting the machining accuracy. To predict the axial thermal error during the machining process, a method is proposed to model axial thermal error in the machining space of five-axis machine tools with a double swing table. The comprehensive thermal error model of the machining space is first established, which includes the axial thermal error of the spindle, worktable, and other components. The spindle is then simplified as a rod, and an analytical model for the axial thermal error of the spindle is developed based on the heat transfer governing equations. This model enables the determination of the time-varying behavior of the axial thermal error at different speeds. Furthermore, the worktable is simplified as a circular plate and the analytical model for the axial thermal error of the worktable is established based on the thermal bending differential equation of the small deflection circular plate. This model allows for the determination of the time-space variation of the axial thermal error at different radii of the worktable. Finally, based on the axial comprehensive thermal error field of the five-axis CNC machine tool processing space, the distribution of the axial thermal error in the machine tool processing space under thermal equilibrium conditions is revealed. Experimental verification of the proposed model is conducted on the VMC-C50 double swing five-axis CNC machine tool. The experimental results show that the error between the measured axial thermal error value and the axial comprehensive thermal error model value is within 26.6 %, thus confirming the accuracy of the proposed model.