Thermal characteristic analysis of Z-axis guideway based on thermal contact resistance

Abstract

The Z-axis feeding system of large computer numerical control (CNC) gear grinding machine tools generates lots of heat during processing, which leads to tilt and pitch deformation of the Z-axis guideway and reduces the machining accuracy. In view of this situation, a three-dimensional finite element analysis method is proposed to conduct transient thermal-structural coupling analysis of the Z-axis guideway and feeding system. Considering the microscopic contact state on machine tool joint surfaces and using the root mean square measurement method, the fractal parameter is identified and the thermal contact resistance at the joints is calculated. The friction heat on the guideway is calculated and the thermal value of the motor is obtained. Then, the heat generation rate of the bearing and the screw nut is calculated according to the friction torque. The convective heat transfer coefficient is determined according to the Reynolds number and the Nusselt number. The finite element model is established to obtain the finite element simulation results of thermal error. Finally, the experimental platform for measuring the temperature and thermal deformation of the large computer numerical control gear grinding machine tool is set up, and the accuracy and reliability of the method is verified.