Thermal Characteristics Analysis And Optimization Of Hydrostatic Turntable For Heavy CNC Vertical Lathe

With the rapid development of science and technology, the tendency of extreme demands on the machining requirements in manufacturing process of aviation, aerospace, energy, marine equipment, made the higher requirements to the machining precision, bearing capacity, processing speed and size of heavy machine tool. Currently due to the limitations of machine tool design and manufacturing technology in domestic, there is a big gap on technical indicators between static pressure turntable, the key component of heavy machine tool, and foreign advanced products. Furthermore, the research of heating mechanisms and thermal performances of hydrostatic turntable is not deep enough. Specially, under working situation of heavy load, the temperature of the lubricant film rise along with the speed of worktable increasing, resulting in heavy hydrostatic turntable body temperature rising. That causes the load bearing oil film to thin, as a result, the lubrication is failed attributed to the deformation of the hydrostatic turntable. then, it has a direct impact of the machining precision of heavy CNC machine tool, and the improvement and upgrading of the performance of worktable are limited. Hence, it is the key to solving all the problems that studying the flow filed, pressure filed, temperature filed and thermal deformation filed of hydrostatic turntable of heavy machine tool.This thesis takes the hydrostatic turntable of heavy CNC vertical latheVCM500×31/32L-MC as the research object, which comes from “Qiqihar Heavy CNC equipment Limited by Share Ltd”(hereinafter referred to as the Qizhong). By the research of thermal characteristics of oil film between the hydrostatic turntable guide rail gap, researching on the rules of oil film heating to the thermal deformation quantity of hydrostatic turntable. In this paper, the main research contents include the following aspects:Firstly, after analyzing the present research condition of hydrostatic technology at home and abroad, the research object of static pressure turntable rail with sector oil cavity structure and constant current supply mode is multi-oil pad circular guide way. Thesis based on the lubrication mechanism and the heat conduction theory research obtains the simplified fluid-solid-heat coupling finite element analysis model of the hydrostatic turntable, the finite element analysis model of single oil pad is also built.Secondly, based on the computational fluid mechanics and tribology theory knowledge, by establishing the mathematical model, including of the carrying equation, the flow equation, the friction power consumption equation and the temperature rise equation, of the single oil pad, the influence factors of oil film temperature rise are obtained, which are the speed of working table, hydraulic oil material properties(specific heat, viscosity, etc.), oil pad the geometric parameters, the flow of oil pump, the oil film thickness The pressure field, velocity field and temperature field of the oil film, are calculated and simulated by using fluid analysis software-fluent. Influence regularities of oil viscosity, worktable speed, pump flow of oil film to the temperature rise are discussed.Thirdly, using the theory of heat conduction and the principle of fluid-solid coupling analysis, based on the ANSYS Workbench platform the temperature field distribution of the static pressure turntable is simulated, and the numerical simulation results are treated as the temperature load applied to the worktable and the base to calculate the thermal deformation of hydrostatic turntable. After that, in order to compare with the numerical simulation results, the practical tests of oil film temperature rise and thermal deformation of hydrostatic worktable are performed on the heavy vertical lathe in Qizhong in different conditions.Finally, according to the structural characteristics of the working table and oil pad, the optimization design results of the reinforcing plate position and oil seal edge width of oil pad are obtained. And some improvement measures are proposed to reduce thermal deformation of hydrostatic turntable, which provide theoretical basis and simulation data for structural design of worktable. They also can provide reference for the oil heating control of heavy hydrostatic turntable in practical projects.