Analysis Of Static And Dynamic Characteristics Of Hydrostatic Cylindrical Guideway

As a typical type of linear motion support component,hydrostatic guideway are widely used in CNC grinding machines.Among them,hydrostatic cylindrical guide has the advantages of large rigidity,high bearing capacity,and good guiding performance.At the same time,it can well overcome the shortcomings of traditional hydrostatic guideway processing difficulty,and has good application prospects.As one of the important performance indicators of the guide rail,the stiffness has a profound impact on the performance of the machine tool.So far,most of the previous studies have focused on traditional planar guides.There are few studies on hydrostatic cylindrical guides,and there are no reports on the five-degree-of-freedom stiffness model of hydrostatic cylindrical guides.Therefore,it is of great scientific significance to establish a theoretical model of the stiffness of the hydrostatic cylindrical guide with five degrees of freedom.This thesis takes the hydrostatic cylindrical guide rail as the object,and carries out the systematic research around its static stiffness.The main work is as follows:1)Based on the beam bending deformation theory,a linear superposition is used to derive the bearing film bearing capacity model considering the influence of the guide column deflection.The Gaussian integral is used to calculate the static characteristic parameters of the guideway,and the influence of the deformation of the rail and the displacement of the bush relative to the rail on the static performance of the bearing is analyzed.2)Considering the hydrostatic cylindrical guide system as the rail and the hydrostatic linear bearing series system,the five-degree-of-freedom static stiffness model of the static pressure cylindrical guideway is studied,and the geometry between the table displacement and the rail deformation and the hydrostatic linear bearing displacement is given.According to the definition of the five-degree-of-freedom static stiffness of the hydrostatic cylindrical guide,the mathematical expression of each stiffness coefficient is derived.A hydrostatic cylindrical guide stiffness test rig is developed for comparing the test value with the theoretical value to verify the accuracy of the theoretical model.Based on the established stiffness model,the displacement generated when the table is fed is obtained.On this basis,a guideway motion error model is established,and the straightness of the guideway motion is analyzed.3)Establish the guideway vibration model,and derive its natural frequency expression.The influence of the axial position of the worktable on the natural frequency of the guideway system is analyzed.The results shows that:1)The flexural deformation of the guide rail compensates the change of the oil film gap to a certain extent,thereby improving the oil film stiffness,but has little effect on the bearing capacity.In addition,when the eccentricity ?>0.3,the deflection of the guide rail has a significant effect on the static pressure parameters such as the stiffness and flow rate of the hydrostatic bearing,which should be considered in the design.2)The five-degree-of-freedom stiffness theoretical model proposed in this thesis can quickly and accurately analyze the stiffness of the hydrostatic cylindrical guide.The axial position of the worktable,the span of the guide rail and the initial oil film thickness have varying degrees of influence on the stiffness of the five degrees of freedom of the hydrostatic cylindrical guide.3)The influence of the axial position of the worktable on the natural frequency of the guide cannot be ignored,and different natural frequencies and the axial position of the worktable have different influence rules.