Extraction and Experiments of Effective Properties for the Joints of Machine Tools

• Main Authors: Wen-Hsiang, Liu, 劉文翔
• Other Authors: Kun-Nan Chen
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/64302860257735806012

碩士 === 東南科技大學 === 機械工程研究所 === 103 === Equipped with rolling elements to achieve the purpose of motion, the linear guides used in machine tools are ones of the most important drive-elements in industry. The steel balls are small, relative to the machine tool structure. However, if all the steel balls in the linear guides are to be modeled and meshed in a finite element analysis, the number of the elements and nodes will be too large, causing heavy calculation burden and even computational difficulties. Effective springs may be used to replace the steel balls and simplify the finite element model, reducing the analysis time for the model. This research built a U-shaped platform, which contains two sets of linear guides with two sliding rails and four sliding blocks, to simulate a portion of a machine tool. On one hand, multiple modal testing experiments were performed to extract the natural frequencies and mode shapes of the parts and assembly of the platform; on the other hand, finite element models of the parts and assembly were created and analyzed with effective springs substituting the steel balls in the sliding rails and blocks. Then the results from both methods were correlated. If the frequency differences are too great, the stiffness coefficients of the effective springs are tuned to amend the errors. The final outcome is a finite element model with effective springs of optimized spring coefficients, which is capable of predicting the responses of design modification.