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標題: | CNC銑削顫振預測與抑制系統之研究 Development of an Chatter Predict and Suppress System in CNC Milling Process |
作者: | Yu-Sheng Chen 陳譽升 |
指導教授: | 廖運炫 |
關鍵字: | 銑削加工,再生式顫振,顫振預測,顫振抑制, milling,regenerative chatter,chatter prediction,chatter suppression, |
出版年 : | 2019 |
學位: | 碩士 |
摘要: | 銑削製程由於能製作複雜形狀而被廣泛用於機械製造,然而不適當的切削條件之選用會容易產生加工時的顫振。再生式顫振屬於加工異常振動中最常見的一種,
會降低生產效率、減少加工精度、破壞工件表面、損傷刀具甚至降低工具機的使用壽命。再生式效應切削過程的動態切削力有關,在顫振條件下產生系統不穩定,引發自激式顫振。因為再生式顫振具有特定頻率特性,可以藉由架設感測器的方式,量測切削力或是主軸振動,進行即時頻率分析,做為判斷切削系統穩定狀態的依據。 本文提出一種線上再生式顫振的預測法則,目標為在顫振發生前判斷並且準確辨別顫振頻率。透過線上量測切削訊號並進行頻譜分析,檢查組成中頻譜強度較高的頻率是否屬於穩定切削的範圍,將穩定訊號與異常訊號區隔,並比較異常頻率強度比例是否達到標準,判斷是否屬於再生式顫振。藉由以上流程,當預測出顫振發生時,可以同時識別顫振頻率,以便後續顫振抑制的對策的進行。 為了測試線上顫振預測與抑制的可行性,以電腦程式實作顫振監控模組,實際進行顫振切削測試。不同材料與不同切削條件的測試中,顫振振幅成長時間約為0.3至0.5秒之間,預測程式則可在0.1至0.2秒內偵測到異常,在顫振尚未完全發展前判斷顫振即將發生。根據顫振抑制方法計算穩定主軸轉速進行調整後,有效抑制顫振使振幅收斂,驗證顫振頻率預測與頻率辨別的效果。 Milling has been widely used in manufacturing process due to its versatile machining characteristics; however, applying inappropriate cutting parameters causes chatter problem easily in this type of machining. Regenerative chatter is one of the most common abnormal vibration in machining, which deteriotes material remove rate, surface integrity, tool wear and the machining center. The regenerative chatter is related to dynamic cutting force in the material removal process, where the system distablizes and induced self-excited chatter in specific circumstances. Since there are certain frequency characteristics in the chatter phenomenon, chatter can be distinguished by applying sensors and analyzing freqeuncy simultaneously during machining process. In this thesis, a online regenerative chatter prediction rule is proposed, which targets at predicting the occurance and identifying the frequency of chatter. Applying online cutting signal measurement and spectrum analysis, frequeuncies with higher power would be recognised and checked if it were part of the stable cutting process. After discriminating unstable signals from stable ones, a magnitude ratio threshold test is applied to determine chatter existance. With the process proposed above, chatter frequency can be identified simultaneously as chatter is predicted. This feature allows faster respnose and provides critical information for chatter-suppress operation. In order to test the feasibility of online chatter prediction and suppression with the proposed method, a cutting process surveillance module is built and tested in chatter experiment. Under several different cutting parameters, chatter amplitude rising time stays between 0.3 to 0.5 seconds, when monitoring module identifies chatter 0.2 or 0.3 seconds prior to full vibration development. After applying spindle speed change according to suppression algorithim, chatter vibration is diminished shortly. The results prove the proposed chatter prediction rule effective in machining application. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/73719 |
DOI: | 10.6342/NTU201903923 |
全文授權: | 有償授權 |
顯示於系所單位: | 機械工程學系 |
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