Structure Analysis And Driving System Design On Five-axis Linkage Ultra-Precision Grinding Machine

In recent years,ultra-precision machining technology has been the technical support for aviation,deep space exploration,electro-optical display and other fields,in which ultra-precision machining parts have been widely applied.As the machine tool for ultra-precision machining of parts,the development of ultra-precision machine has attracted wide attention from many countries.In practical application,the five-axis linkage ultra-precision machine can meet the high quality machining of complex surface type optical curved surfaces,large ultra-precision optical elements and other parts.It can solve so many processing problems as to have wide application prospect and great application value.However,the development level of the five-axis ultra-precision machine in China is still not mature in the aspects of structural design,motion controlling and assembly.The development level of ultra-precision machine needs to be improved,and at the same time we are facing the f·1oreign technical blockade.In order to solve the problem of optical elements of hard and brittle material machining,this dissertation designed and analyzed the five-axis linkage ultraprecision grinding machine structure,in which hydrostatic screw was choosen as the driving device of ultra precision linear motion system and an experimental platform was built to carry out experimental research.Firstly,the structure design and analysis of the five-axis linkage ultra-precision grinding machine were carried out.According to the processing quality requirements of hard and brittle optical parts,this dissertation analyzed the functional requirements of the machine tool and determined the layout and the form of the key moving parts.Hydrostatic guideway was adopted for all linear axes to ensure guiding accuracy and the hydrostatic screw was selected as the driving device for X-axis and Z-axis of the machine.Then this dissertation designed all the hydrostatic guideway structure according to the theory of hydrostatic bearing and completed the 3D model of the machine.What's more,the five-axis grinding machine was abstracted as a multi-body system and the geometric error model of the machine,through which the geometric error sources of the sensitive direction of the machining was determined,was established.Based on all the above work,the accuracy index of the key moving parts of machine was determined by error distribution.Considering the high requirements for the dynamic characteristics of the fiveaxis grinding machine,on the basis of designing the machine structure,the finite element model(FEM)of the machine and key moving parts was built to predict static and dynamic performances.The FEM analysis included the static deformation,thermal deformation and modal characteristics of the hydrostatic guideway and the vertical axis,as well as the modal characteristics and the harmonic response characteristics of the machine.The purpose of the simulation analysis was to evaluate the structural characteristics by means of structural deformation,natural frequency,vibration mode and stiffness,and to find out the structural weakness to guide the optimization of the structure.Finally,this dissertation designed and built an ultra-precision linear motion system driven by hydrostatic screw and completed the assembly and debugging work of the mechanical structure and controlling system.After building a highperformance hydrostatic station to ensure the stable operation of the linear axis,the closed-loop servo parameters of the controlling system were optimized and the servo characteristics of the system were tested under the condition of current loop.Experimental results show that the motion system can achieve 10 nm motion resolution,and has good static characteristic,anti-interference characteristic and dynamic characteristic.