Study on Structure Stiffness and Process Dynamic Behavior for Grinding Machines

• Main Authors: Wei-Jhih Lin, 林暐智
• Other Authors: 林盛勇
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/r6h844

碩士 === 國立虎尾科技大學 === 機械與電腦輔助工程系碩士班 === 105 === In order to pursuit low economic cost, high performance and high production efficiency for machine tools, the general trend has been to move towards the goal of high-speed and light-weight developing. However, the cutting performance of a machine-tool is closely related to its structural vibration. In order to obtain better grinding quality, there is a need further to investigate the rigidity and dynamic characteristics of the machine tools, to achieve a better reinforcement of the structural design of the machine tools and avoid structural vibrations. Generally, issues of vibration during the grinding processes may cause problems such as poor surface roughness and dimensional accuracy, even leading to a reduction of the machining accuracy and life of the machine tool. Therefore, the investigations of the structural stiffness and factors causing vibration of the machine-tool are the most important topic at present for machine-tool industry and related manufacturers. This study investigates the structural characteristics and dynamic behavior of a large gantry-type surface grinding machine and the small general surface grinding machine in a practical approach. First of all, the numerical and experimental modal analyses are performed for these surface grinding machine structures, and the structural characteristics and weaker zones of the important structure parts and whole systems are obtained. Comparisons are made between the results of the numerical and the experimental modal analyses to identify their differences, which form the basis for modifying the assumptions of the analytical model for numerical modal analysis and for subsequent improvement design on structures. Furthermore, the impact of the different geometrical configurations of spindle seat on the entire structure stiffness of the small surface grinding machine was examined. The modal parameters obtained from the experimental modal analysis were compared crossly to identify whether if the stiffness has been increased or not. Finally, in order to investigate the dynamic behavior of the small surface grinding machine during its grinding process, the grinding experiments were carried out through the accelerometer and microphone to detecting the dynamic response during the grinding processes. The results obtained from the experimental modal analysis indicate that there are two modes in which the structural resonance is easily to be excited in the large gantry-type surface grinding machine while there are three modes in which the structural resonance is easily to be excited in the small surface grinding machine within the possibly resonant vibration frequency range. According to the grinding experimental results, the faster feed rate and the larger grinding depth, the higher the vibration signals are and the poorer the surface roughness becomes.