工具機及主軸系統結構分析與振動量測實務

Analysis and Vibration Measurement Practice for Machine Tool and Spindle Structure

張鎔崴(R. W. Chang)

指導教授 ： 林盛勇

國立虎尾科技大學/工程學院/機械與機電工程研究所/碩士(2009年)

https://doi.org/10.6827/NFU.2009.00037

摘要

本文針對業界常見之工具機主軸及磨床工具機進行結構數值模擬分析及振動響應量測。主軸性能直接影響其切削加工時之加工能力與加工精度，在工具機中扮演著重要的角色，磨削加工在精密加工業的運用相當廣泛，各種機械或電子元件的製造均朝著精密化的方向發展。故本文選擇了旋轉式進給平面磨床工具機與工具機主軸進行結構數值模擬分析及振動響應量測分析與診斷評估。
於數值模擬分析方面利用有限元素分析軟體針對工具機主軸及磨床工具機進行模態分析及結構勁度分析。求得磨床工具機各大組合部件及整體結構自然頻率與所對應之振動模態及結構勁度，並建立主軸-軸承系統有限元素模型以模擬軸承於不同預壓時主軸勁度的變動情形。在軸承預壓求取主軸勁度實驗驗證方面，使用砝碼施以不同大小作用力，並以千分錶量測力作用方向之變形位移。選定輕預壓、中預壓及重預壓等各種不同預壓力分析其對軸勁度之影響。同時分析因製造上的幾何公差或瑕疵形成間隔環左右兩側平行度的誤差，探討不同程度平行度誤差量在軸承預壓過程中，影響主軸勁度的情形。於振動量測實驗方面，於主軸與床台各部件及磨床整體結構黏貼加速度規，利用敲擊鎚在不同位置進行多點敲擊，進行靜態敲擊響應實驗，藉由加速度規擷振動訊號並搭配頻譜分析儀之分析可得知磨床工具機整體結構及各部件自然頻率，並可暸解主軸軸承不同預壓狀況其頻率響應之特性以及主軸勁度與頻率響應特性之關係，並量測磨床砂輪主軸及旋轉磁盤於運轉時之迴轉振動響應，透過靜態敲擊響應實驗及迴轉振動量測與數值模擬分析做搭配驗證。於進行加工時避開機台結構自然頻率以免於共振的引發，提高加工可靠性。此量測、分析與診斷流程之建立，對未來工具機結構於設計上具有一定的參考性。

關鍵字

軸承預壓 ； 結構分析 ； 振動量測 ； 頻譜分析

並列摘要

A numerical model and frequency response measurement of the machine tool spindles and grinding machine tool structures commonly utilized in industry are analyzed in this study. The performance of the spindle directly affect the machining productivity and finish quality of the workpieces, plays a significant role of the machine tools. Grinding have been widely used in precision processing industry. The manufacture of each machine or electronical components all toward precision development trend. Therefore, the rotary table surface grinding machine structure and machine tool spindles are selected as the objects for the numerical simulation, frequency response measurement, analysis, diagnosis and assessment in this study.
The static stiffness and vibration mode shapes of the machine tool spindles and grinding machine were analyzed by using a commercial finite element analysis software in order to determine the natural frequency and vibration modes. Moreover, the finite element model for spindle-bearing system is established enabling the variation of spindle stiffness calculations under different bearing preloads. On the other hand, the spindle stiffness may also be obtained from the experiment and its result may be utilized to validate the theoretical calculations. The load is acted by weights at different directions and orientations, and their corresponding deformations are measured through dial indicator. Three bearing preload conditions, i.e. light, medium and heavy preloads are selected, which are imposed on the bearing to investigate the spindle stiffness variation, respectively. In addition, the effects of the geometrical parallelism error at the end surfaces of spacer due to the manufacturing tolerance or some imperfection on the spindle rotational stiffness are studied. The impact test on the machine tool spindle, grinding machine tool structures , grinding machine tool components such as the bed, saddle, ribbed column, rotary table and headstock is performed by hammer and the corresponding vibration signal on the surfaces is acquired by accelerometer, the natural frequency of the machine tool spindle and grinding machine structures were measured experimentally, the spindle stiffness may be reflected in the other manner through the signals processing by spectrum analysis. The relationship between spindle stiffness and frequency response may be obtained consequently. The dynamic behaviors of grinding machine’s spindle and rotary table were examined. From comparison of the numerical simulation calculated results with experimental results, it can avoid the resonance vibration when the machine operate, enhance reliability of machining process. A build up response measurement, analysis, diagnosis and assessment is benefit for design new structures of machine tool in the future.

並列關鍵字

bearing preload ； structural analysis ； vibration measurement ； spectrum analysis

參考文獻

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