Critical study on the thermal-structural characteristics of worktable assembly of a dry hobbing machine

Dry hobbing machine is a kind of specialized machine tool to manufacture high-quality small-module gears. With the development of shipbuilding, automobile, and wind power industries, higher request on the dry gear hobbing accuracy is called. The thermal-induced error, which accounts for 50–70% of machining error, needs to be reduced more efficiently. Hence, in-depth investigation on the thermal-structural characteristics of the dry hobbing machine is indispensable. In this paper, thermal-structural coupling numerical simulations were conducted to investigate the heat transfer process as well as thermal-induced deformation of the worktable of a YDE3120CNC gear hobbing machine in the large-volume gear production. New equations were used here to describe the convection heat transfer happened on the worktable assembly. Verifying test results proved the feasibility of the newly proposed numerical method. Following numerical simulation, results indicated that during the gear hobbing process, the highest surface temperature of the worktable assembly appeared at the top surface of the fixture, and corresponding thermal-induced deformation reached the maximum of 49.9 μm. Besides, in a large-volume production, the worktable assembly would attain thermal equilibrium in 15,000 s. Hence, the assumption widely used in previous studies on gear hobbing machines that the worktable assembly could be treated as an ideal solid without any thermal deformation is wrong. The thermal-induced deformation of the worktable assembly should be considered in the subsequent development of the thermal error compensation system.