臺灣博碩士論文加值系統

銑削加工為機械加工中常見之重要方法。在銑削加工過程中工件與刀具之間會產生相對的振動，此振動會影響工件切削厚度，並使銑削力產生不穩定振盪，進而造成銑削加工的不穩定。此種在銑削過程中由自身引起的自激振動，稱之為顫振(Chatter)。為了避免顫振現象的發生，一般的銑削加工會參考切削穩定耳垂圖設定加工參數。然而切削穩定耳垂圖的準確性會受到切削常數、刀具模耗及製程阻尼等因素影響，使得最佳的加工參數不易取得，且目前並無一個有效的方法判斷切削穩定耳垂圖是否正確。
由於銑削系統受前次切削行為影響，為一具有漸進式混沌特性(route-to-chaos)之非線性系統，因此一般分析顫振所使用的傅立葉頻譜並無法直接反應此非線性的切削行為。本研究首先透過敲擊測試及材料參數試驗，建構切削穩定耳垂圖，並使用切削力量理論建構出一套可預估切削力之動力學模型，且藉由主軸轉速與切深的變化來探討顫振現象。為了驗證此模型的正確性，將會搭配平板型力量計來擷取實際切削之力量訊號，並以時頻分析法觀察切削力在時間域及頻率域隨加工穩定性及製程的變化。

Milling has played an important role in the machining process. During the milling operation, the tool and the workpiece generate relative oscillations which affect the cutting depth, render unsettled cutting force and make the milling dynamics unstable. This kind of self-generating vibration called “chatter” has an intimate correlation with certain machining parameters such as spindle speed, feed rate, radial and axial depth of cut, and workpiece material. Chatter is often accompanied by the deviation of cutting depth, incomplete surface finish and high-pitch noise. To prevent the onset of machining chatter, people usually resort to the stability lobe diagram to setup machining parameters. However, the accuracy of the stability lobe diagram depends on several factors like cutting coefficients, tool wear, process damping and so on, rendering optimized machining parameters unavailable, and currently there are no efficient solutions to verify the accuracy of the stability lobe diagram.
This study first developed a stability lobe diagram by conducting the impact test, followed by constructing a milling dynamic model to predict the cutting force. Multiple combinations of spindle speed and depth of cut were investigated to discuss milling chatter. In order to validate the dynamic model, a force sensor was mounted to measure the cutting force, and the time-frequency analysis method was used to observe the cutting vibration in time- and frequency-domain. As a result the difference of the cutting force generated by the simulation and the milling experiment was verified.

摘要 I
ABSTRACT II
誌謝 III
目錄 IV
表索引 VII
圖索引 IX
符號表 XVI
第一章 緒論 1
1.1 研究背景與動機 1
1.2 研究目的與方法 2
1.3 文獻回顧 3
1.4 論文架構 5
第二章 穩定耳垂圖與銑削模型 7
2.1 模態分析 7
2.2 一維穩定耳垂圖 11
2.3 二維穩定耳垂圖 19
2.4 銑削力量及位移模擬 29
第三章 實驗設置及架構 33
3.1 實驗儀器、工具 33
3.2 實驗架構 33
3.2.1 敲擊測試 34
3.2.2 切削常數實驗 39
3.2.3 實際切削實驗 47
3.3 時頻分析方法 51
3.3.1 Root Mean Square (RMS) 51
3.3.2 Fast Fourier Transform (FFT) 51
3.3.3 Short-time Fourier Transform (STFT) 52
3.3.4 Hilbert-Huang Transform (HHT) 52
3.3.5 Lyapunov Exponent 54
第四章 數值模擬結果分析 56
4.1 時間域訊號分析方法 57
4.2 頻率域訊號分析方法 59
4.3 時頻域訊號觀察方法 62
4.4 不穩定切削之訊號表現 64
4.5 穩定切削與顫振切削比較 71
A.轉速1500rpm，切深1.0mm vs. 1.4mm之比較 72
B.轉速5250rpm，切深0.6mm vs. 1.2mm之比較 76
C.切深1.0mm，轉速1200rpm vs. 2250rpm之比較 80
D.切深1.2mm，轉速4500rpm vs. 6000rpm之比較 84
4.6 模擬訊號之穩定性探討 88
第五章 實驗結果分析 90
5.1 模擬與實際切削訊號比較 90
5.2 穩定切削與顫振切削比較 93
A.轉速3000rpm下，不同切深之切削訊號比較 94
B.相同切深1.2mm下，不同轉速之條件 98
5.3 實際切削訊號之穩定性探討 102
第六章 結論 106
6.1 銑削顫振特性與時頻響應 106
6.2 銑削力量模擬與實際切削之差異 107
6.3 研究貢獻 110
6.4 未來目標與展望 110
參考文獻 111

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