Static Characteristics Analysis Of Closed-type Hydrostatic Guideways Of Precision Grinding Machine

The closed liquid hydrostatic guideway has been widely used in precision machine tools due to its advantages of good vibration resistance,high motion accuracy and stability.The static performance of the static pressure guide rail directly affects the machining accuracy and performance of the machine tool.Its static performance mainly includes the guide rail stiffness,bearing capacity,and oil outlet flow.There are many factors that affect the performance of the guide rail.With the continuous improvement of processing accuracy,the influence of the elastic deformation of the guide rail on its static performance cannot be ignored.This paper proposes a multi-step calculation method of static characteristics of static pressure guide rails considering the effect of elastic deformation for a new type of closed static pressure guide rail with coplanar main and auxiliary oil pads,and systematically analyzes the influence of elastic deformation on the static performance of the guide rails.The main research work of the thesis is as follows:(1)Based on the classical static pressure theory,the flow equation,bearing capacity equation and oil film stiffness equation of the single oil pad of the static pressure guide rail are derived.The effects of various design parameters on the static performance of liquid hydrostatic rails are analyzed taking oil film stiffness,outlet flow rate,and rail displacement rate as static performance indicators.(2)Aiming at the problem that the elastic deformation of the guide rail affects the static characteristics of the static pressure guide rail,this paper proposed a multi-step calculation method for the static characteristics of hydrostatic guideway considering its elastic deformation.Firstly,formula for calculating the static characteristics of the guideway considering elastic deformation was derived.Secondly,the oil supply pressure of the hydrostatic guideway was divided into mean values according to number of multiple steps,and the oil chamber pressure of the hydrostatic guideway was calculated using the developed formula for the guide considering the elastic deformation.Thirdly,the elastic deformation of hydrostatic guide under each step oil film pressure was calculated by aid of finite element method.Finally,the deformation amount of the guide was obtained by accumulating the value of each step,and then the static characteristics of the static guide was calculated.(3)For the closed liquid hydrostatic guide rails of the grinding feed system and the workpiece feed system,the static characteristics of the guide rail are analyzed and calculated using the traditional method and the multi-step method respectively,and compared with the static characteristics of the guide rail without considering the elastic deformation.The results show that the cavity pressure decreases after the hydrostatic guide rail deforms,causing the vertical oil film rigidity of the system decreases,and the oil outlet flow increases.In the actual design process of static pressure guide rail,the influence of guide rail deformation on its static characteristics should be considered.The multi-step calculation method for the hydrostatic guideway considering the elastic deformation has a higher precision than the traditional method;the deformation amount and static characteristics of the static guide are close to its actual values with an increase in number of steps.The oil supply pressure is divided into several equal parts on average,and the elastic deformation of the guide rail is iteratively calculated step by step,and then the elastic deformation of the guide rail is cumulatively calculated to improve the calculation accuracy of the static characteristics of the guideway.