Research On Static And Dynamic Characteris Tics Of Hydrostatic Guide Rail

The ultra-precision CNC machine tool feed system widely uses liquid hydrostatic guide rails as supporting parts,and its static and dynamic characteristics are the key to ensuring the relative motion accuracy and performance of the entire machine between the moving parts.Therefore,under the processing conditions,real-time and accurate grasp of the static and dynamic characteristics of the guide rail and ensuring the processing accuracy are always hot spots and key issues in the research of precision CNC machine tools.High stiffness,fast response and good vibration suppression performance are the main performance requirements of precision machine tools for hydrostatic guide rails.This article has conducted corresponding analysis,simulation and experimental research on the structural design and static and dynamic performance of liquid hydrostatic guide rails.The main work is as follows:According to the design guidelines of the hydrostatic guide rail,the structure design of the closed-film hydrostatic guide rail with unequal oil chamber feedback was carried out.Based on the principle of hydrostatic support,the oil film thickness of the guide rail,the structure and size of the oil cavity,and the oil supply pressure were analyzed and determined.,Key structural parameters such as the size of the throttle.Based on the theory of hydraulic resistance,the calculation formulas of the bearing capacity and stiffness of the entire system were deduced,the influence rule of oil supply pressure and oil film thickness on the static characteristics of the guide rail was studied,and the oil film thickness range of the best static characteristics of the guide rail was analyzed.The theoretical rigidity of the guide rail was verified.The flow field model of a single oil cavity is established.Based on the fluid mechanics control equations,the velocity field and pressure field of the rail oil pad are obtained by numerical simulation of computational fluid dynamics,and the distribution law of the oil pad flow field is analyzed;the numerical simulation is studied by modifying a single parameter The influence of parameters such as the oil supply pressure of the guide rail,the viscosity of the oil,the width of the sealing edge,the running speed of the slider,and the shape of the oil cavity on the bearing characteristics of the oil pad are compared.The accuracy of the simulation results is verified by comparing the theoretical and simulation results.In order to understand the vibration characteristics of the hydrostatic guideway under dynamic load,the oil film is equivalent to a liquid spring with stiffness and damping.The dynamic model of the hydrostatic guideway system is established,and the oil supply pressure under dynamic load conditions is analyzed.,The influence of the thickness of the oil film,the width of the sealing edge and the viscosity of the oil on the dynamic characteristics such as the natural frequency,dynamic stiffness and damping coefficient of the guide rail system.Based on the second development of FLUENT,the dynamic grid technology of dynamic layering is used to integrate the description of the dynamic behavior of the hydrostatic rail into the UDF code.The dynamic displacement response of the hydrostatic rail under different dynamic load conditions is numerically simulated and the load is analyzed.The effects of size,oil supply pressure,damping coefficient,and load frequency on the system amplitude,transition time,and oil pad pressure field reveal the vibration response mechanism in the rail system,and the dynamic response characteristics of the rail system are verified through experiments.