The Analysis Of Oil Film Performance And Carrying Capacity On Heavy Rotary-table

Heavy milling compound NC machine tools is the typical product in theequipment manufacturing industry in China, which mainly services in energy,transportation, heavy machinery, aerospace, ship building, and national defense andother national key industries. Higher and higher demands are proposed on processingprecision of machine tools, size and carrying capacity with the development ofmodern science. Because of its high bearing capacity, high precision, small frictionresistance, long service life, good seismic performance, turntable technique has beenmore and more widely used. As the key features of heavy milling compound NCmachine tools, Static turntable are mainly used for large loading or heavy parts andaccomplish complex linkage parts of five-axis milling or turning processing withheavy machine tool. The oil film is the key function part of machining accuracy andoverload characteristics of hydrostatic turntable. Hydrostatic pads surface texture willaffect the performance of oil cushion. At the same time, heat effect, dynamic pressureeffect and coupling effect in the process of high rotating speed will also affect theperformance of oil cushion. Large static turntable determines workbench contactdeformation with lathe bed when rotating as characteristics of overload. In the case ofoverloading, hydrostatic guideway can produce elastic deformation, which makes theoil film thickness between static turntable guideway and hydrostatic oil pads changed.As results, the deformation of the turntable during the process of work are the keyfactor that affect the machining accuracy of workpiece and the bearing-capacity.Supported by the National Science and Technology Major Project: The keytechnology and the digital design of high-grade CNC machine tools specializing in R&D and typical applications, this paper mainly studies the influence of consideringsurface roughness of oil pad on the bearing capacity and considering the deformationof guide rail on turntable bearing capacity.In order to study the influence of the oil pad surface topography on the oil filmperformance and guide rail deformation on the bearing capacity of the hydrostaticturntable, Based on the Christensen’s stochastic model of rough surfaces, set up twomodels of radial and circumferential direction on the surface roughness. A coupledenergy equation and modified Reynolds equation based on the Christensen’sstochastic model of rough surfaces is presented to analyze the pressure distribution and load-carrying capacity of hydrostatic circular pads. According to approximatemethod of the unsymmetrical bending plate,we can calculate the basic solution ofelastic thin circular plate under the unit transverse concentrated load in thecomputation of the elastic deformation of guideway, Then, using the reciprocaltheorem of bending thin plate theory to calculate the elastic deformation of eachpoint in the static pressure guideway. On the basis of the flat plate theory, weestablished a coupling fluid-structure interaction model of the balance equations ofbearing pad statics and hydrostatic guideway elastic deformation, and we analyzed theinfluence of guideway elastic deformation on the pad pressure distribution and thebearing-capacity of the turntable. Computer numerical iteration method is used tosolve physical model and mathematical equations which have been established, usingthe finite difference method and choosing the appropriate language programming.Sorting, comparison and analysis numerical solution which solved by the computer,and making relevant conclusions.