磨床結構剛性與實磨動態行為之研究

Study on Structure Stiffness and Process Dynamic Behavior for Grinding Machines

林暐智(Wei-Jhih Lin)

指導教授 ： 林盛勇

國立虎尾科技大學/工程學院/機械與電腦輔助工程系碩士班/碩士(2017年)

摘要

為了追求工具機的低經濟成本、高性能及高生產效能，普遍朝向高速化與輕量化的目標發展。然而工具機之加工性能與其結構振動問題息息相關，為了得到較好的研磨品質，須進一步瞭解工具機結構本身的剛性與動態特性，將有助於機台結構設計製造上的補強及避免結構共振的發生。在實際磨削加工過程中，振動的問題可能會帶來加工表面粗糙度不佳、尺寸精度降低等問題，甚至縮短了工具機之加工精度與使用壽命。因此，探討工具機結構剛性以及振動的成因，已成為工具機業者積極努力的目標。
本研究主要以實務性的做法來探討大型龍門平面磨床及小型平面磨床結構特性與研磨過程的動態行為。首先，針對平面磨床結構進行數值與實驗模態分析，獲得磨床結構重要部件及整機系統的結構特性及較脆弱的位置。將數值模態分析結果與實驗模態分析結果做一比對驗證，比較兩者間的差異，據以修正數值模擬分析模型的假設，作為後續結構改善設計之依據。再者，探討不同主軸座對小型平面磨床整機的剛性影響，利用實驗模態分析所求得之模態參數進行比較確認剛性是否得到提升。最後，進行實磨動態量測，藉由加速度規及麥克風線上偵測磨削過程動態響應訊號，以瞭解小型平面磨床於實際磨削過程的動態行為。結果顯示，由實驗模態分析結果得知，大型龍門平面磨床在可能發生共振的頻率範圍內計有兩個模態容易引發結構共振，小型平面磨床計有三個模態容易引發結構共振，由磨削實驗結果得知，當進給速度越快與磨削深度越深時，振動訊號越大，表面粗造度越差。

關鍵字

平面磨床 ； 結構剛性 ； 模態參數 ； 動態行為

並列摘要

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.

並列關鍵字

surface grinding machine-tool ； structural stiffness ； modal parameter ； dynamic behavior

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