Dynamic Characteristics Analysis And Finite Element Modeling Of Linear Rolling Guide

Linear rolling guide with high sensitivity, high precision, small traction, wear, lubrication, easy maintenance, etc, have gradually replaced the traditional sliding linear guide(except for heavy machine tools), become an important feature of CNC machine tools. Linear guide is usually connected to the table and the spindle box, which directly affects the dynamic characteristics of machining accuracy and machining efficiency. Thus, testing, modeling, analysis dynamics of rolling guide is the base of dynamic analysis of CNC machine tools, and also has important significance for the design of vibration and stability of CNC machine tools.In this paper, LH35NSK linear rolling guide is studied, focusing on modeling of the linear roller guide dynamics considerd the joint characteristics. The analytical mode and finite element model of the linear motion guide is established, which proved to be correct through the multi-body dynamics software and modal experiment. The guide model is applied to the analysis of the machine to investigate the influence of the guide joint to the machine performance.Specific contents are as follows:(1) The research methods and present research of the joint of machine tools is summarized, a variety of dynamic model proposed by scholars were classified, enumerated5rail joint approach, including using of spring damper element simulation the joint, the analytical expression describing the joint characteristics, hypothetical materials, the joint element established for simulating the joint, a surface element to simulate the junction, and processing the5methods a simple evaluation.(2) Based on the previous dynamic model, using spring damper element, studing on LH35linear motion guide, the analytical model is established. Using Lagrange method, a five degrees of freedom coupled equations are made, the analytical expressions of five natural frequencies of the linear motion guide is obtained. When take parameters into those equations, the five natural frequencies values are obtained, and then the simulation is carried out in ADAMS, the results show that the validity of the analytical modeling.(3) Using the method of adding an imaginary material, the guide static analysis is carried out; Using the method of adding the spring damper element, the guide modal analysis is carried out, the first five natural frequencies and corresponding vibration mode are obtained; according to the modal model, the guide harmonic analysis is carried out.(4) The modal experiment is carried out using the B&K and other equipments, the slider vibration response of points are obtained, then the frequency response graph of rail system is got, and further to get the natural frequency and damper ratio. The comparison of experimental results with analytical results and finite element analysis results, verified the analytical modeling and finite element modeling reasonable.(5) A simplified model of vertical milling machine including the rail is established, static analysis and modal analysis of the machine are carried out without considering the guide joint. Using the method of adding an imaginary material to simulate the rail joint, considering the guide in light and medium pre-load conditions, the study of static mechanical properties of the whole machine is carried out; using the method of adding the spring damper element to simulate the rail joint, considering the guide in light and medium pre-load conditions, the study of the dynamic performance of machine is carried out. The results are compared with the results which does not consider the rail joint.The result indicate that rail joint dynamics greater impact on overall performance.