Research And Application Of The Characteristics Of The Joint On Linear Rolling Guide

Precision and ultra-precision manufacturing technology is one of the most important trend of machining,which is an important symbol to measure the level of the development of a country.The static and dynamic stiffness of machine tool is an important factor affecting its machining accuracy,which mainly depend on the systematic stiffness properties composed of the constructional component stiffness and the joint stiffness.The j oint stiffness accounted for a large proportion of total machine rigidity,and the joint on linear rolling guide is one of the main components of machine tool joints.However,linear rolling guide models are often oversimplified or ignored in the process of predicting machine performance at the design stage,and without considering characteristics of joint.So,the machine performance is unable to accurately predict.Therefor,studying the characteristics of linear rolling guide and establishing accurate mathematical model of the joint is of great theoretical significance and broad application prospect.This paper studies the static characteristics of the joint on linear rolling guide by theoretical and experimental method based on the fundamental characteristic of joint surface in unit area,and measure the rigidity of machine tool by the simulating load test.The main content of the paper is as follows:(1)The mathematical model of cylindrical-spherical j oint surfaces and cylindrical-flat joint surfaces were established based on the fundamental characteristic parameters of joint surface which had obtained by experimental method.The results showed that displacement and load have a non-linear relationship,and the growth had a relatively slow rate with increasing load.The stiffness of joint surfaces vary with the rolling size under the same load condition.(2)The mathematical model of the joint on one column rolling elements and the joint on unit linear rolling guide were established by using the joint surface model of one rolling.The experimental features of static characteristics of joint were summarized,and the testing devices of the joint on one column balls,the joint on one column rollers and the joint on unit linear rolling guide were developed.The loading test were performed with these devices.The analytical results were compared with experiment results,and which showed that load displacement curves were consistent with each other.It has confirmed that the model of the joint on linear rolling guide was reasonable and correct.The model is able to reflect the static characteristics of the joint on linear rolling guide,and can be used in studying on the characteristics of the joint with this type joint surface.The model of the joint on linear rolling guide can provide technical support for predicting machine performance with virtual prototyping.(3)The characteristics of the joint on linear rolling guide were studied with analytical method based on the fundamental parameters of the joint surface and linear discrete method.Then,the equivalent stiffness calculating methods were derived by using linear discrete method,and which was used to calculate the equivalent spring stiffness of BMA45 linear guide.The calculated linear stiffness and angular stiffness are consistent with manual results,it indicates that the linear discrete method is correct.(4)The performances of the column of VMT100 was predicted and modified by considering the characteristics of the j oint on linear rolling guide.The experimental simulating devices which used in loading test simulating load test of changing location process were developed,and loading tests were performed for milling-turning machining center and profile grinding machine.The experimental results showed that the simulating load devices can accurately reflect the distribution of the machine stiffness in machining process.In the space of machining operations,load bearing conditions including load position and size of the machine components and joints change with machining position in machining process,so the static stiffness machine tool changes with machining position.(5)Since the characteristics of the joint on rolling guide might be greatly affected due to the vibration of lathe-bed,so we performed the dynamic experiments for mineral casting lath bed,and identified the modal frequencies,modal damping and modal types by using SmartOff-ice.Because thermal characteristics of mineral casting are quite different with metal parts,in order to solve different thermal expansion coefficients and reduce the impact of thermal deformation of the linear rolling guide,we design a kind of compound rolling guide with thermal displacement constraints.