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  • 學位論文

工具機新機種開發結構剛性強化過程之研究

Study on Structure Stiffness Strengthen during the New Machine-Tool Development Processes

指導教授 : 林盛勇
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摘要


當今切削技術蓬勃發展,再加上科技的蒸蒸日上,促使產品精密度的要求亦日益嚴苛,伴隨高性能刀具與高精度工具機的需求也相對提升。業界為了追求工具機的高性能、高生產效能及低經濟成本,普遍朝向高速化與輕量化的目標發展。然而工具機之加工精度與其結構振動問題相互牽引,為了得到較好的刀具研磨品質與切削加工精度,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。結構剛性的改善亦是工具機廠商時常面臨到的問題,如何針對真正有問題的部位進行修改及如何設計才能節省開發的成本,一直都是廠商非常注重的問題。 本文分別以刀具修磨機及多刀同步車床兩種工具機作為雛型載具。首先利用有限元素法針對結構進行數值模態分析,求得其結構的自然頻率、阻尼比與模態振型等模態參數。接著,對工具機進行實驗模態分析,探討工具機結構模態特性,並與數值模態分析結果相互搭配驗證。藉由數值模態分析與實驗模態分析來求得各個部件與整機系統的結構特性,並可由分析結果所得到之模態振型與結構因共振所產生之最大變形量發生處,將判定為單部件與整機結構剛性較不足的部位,並針對這些結構較為脆弱的部位予以補強。透過增加部件之補強肋數量、改變部件之幾何尺寸、變更孔洞的位置等方式對結構較脆弱處進行設計改善。設計變更後再度修正數值模擬分析之模型,並重複上述之數值模態分析,藉由雛形機與改善機模態參數之比對,以確認結構較脆弱之處是否得到改善。透過此二個案例的研究探討中發現,對於新機種結構剛性改善過程中輔以模態分析法的交叉使用是可行的。

並列摘要


The modern cutting technique coupled with the science/technology developments are flourishing day by day. It has resulted in the increased demand for precision and excellent products more stringently. The needs for high quality cutting-tool and machine-tool have also correspondingly increased. The machine-tool industry is in a pursuit of making high performance, high production efficiency and low cost machine tools. In addition, the functions of high speed machining and light weight structure are also usually set as a development goal. However, there is a conflict between machining precision and structure vibration. In order to get the good grinding quality for cutting-tool and better precision for machining, more analyses regarding rigidity and dynamic characteristic of the machine-tool structure itself should be performed in advance. And it would be helpful in designing and manufacturing of a better machine-tool as well as structure strengthening, which the occurrence of structure resonance may be avoided. Machine-tool manufacturers often face the problems of stiffness improvements for structure and how to find out what part should be modified exactly is the major concern. Furthermore, how to create a design rule that will minimize the development costs has also been a matter of great importance to the manufacturers. A cutting-tool grinding machine and a simultaneous turning lathe with multiple cutting-tool were used as the analysis objects in this study. First of all, the numerical modal analyses were performed for these objects by finite element method, and the natural frequency, damping ratio and mode shape of the structures are obtained consequently. Next, the experimental modal analyses were conducted to investigate the modal characteristics of these machine-tool structures and to verify the results obtained from the numerical modal analyses. The structure modal parameters of the major sub-system and whole system of these machine tools can all be obtained from the above modal analyses. The weaker zones within the structures may be pointed out and located also from the investigations both on the results of mode shape and maximum deformation due to resonant vibration of the structure. These insufficient stiffness locations in the structures are the improvement reference for structure strengthening. By increasing the number of reinforcement ribs, changing the geometrical dimensions in the parts and changing the locations of some holes distributed in the machine-tool structure design, the stiffness on those weaker zones may be improved accordingly. Finally, the numerical analysis models are modified based on these design changes and the numerical modal analyses are performed repeatedly once again, and the stiffness improvement results of the structure can be further identified from the comparison between the modified results at that time and original prototype results. Through these two case studies it was concluded that the numerical and experimental modal analyses applied crossly on the improvement processes of the structure modal parameters for those new development machine tools is feasible.

參考文獻


[39]王柏村、黃俞憲、李昆達,2009,應用實驗模態分析與操作模態分析於平台模型驗證之探討,機械技師學刊,第2卷,第1期,32-37頁。
[1]B. Luo, et al., 2015, A method to predict position-dependent structural natural frequencies of machine tool, International Journal of Machine Tools & Manufacture, Vol.92, pp.72-84.
[2]Walunj Prashant S., V.N. Chougule, Anirban C. Mitra, 2015, Investigation on Modal Parameters of Rectangular Cantilever Beam Using Experimental Modal Analysis, Materials Today: Proceedings, Vol.2, pp.2121-2130.
[3]S.J. Idehara and M.D. Junior, 2015, Modal analysis of structures under non-stationary excitation, Engineering Structures, Vol.99, pp.56-62.
[4]A. Devin, P.J. Fanning and A. Pavic, 2015, Modelling effect of non-structural partitions on floor modal properties, Engineering Structures, Vol.91, pp.58-69.

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