端銑刀側銑切削之動態應力分析

Dynamic Stress Analysis of End Mill in Peripheral Milling

陳佑安(Yo-An Chen)

指導教授 ： 蔡哲雄

國立臺北科技大學/機電學院/製造科技研究所/碩士(2011年)

https://doi.org/10.6841/NTUT.2011.00153

摘要

本文應用有限元素分析套裝軟體分析端銑刀側銑切削過程之應力及位移變化。假設刀具為線性彈性材料。採用動態分析模式觀察銑刀斷續切削承受衝擊力過程有無振動行為及不穩定切削。由於端銑刀切刃為螺旋刃，並且隨著刀具的轉動角度位置而切削厚度(切削負荷)不同，使得模擬切削過程之刀具受力邊界條件設定複雜。因此本文採用疊加法原理(Principle of superposition)。將刀具在軸向切深中的螺旋刃沿軸向分成若干短刃(Short edge)，就單一短刃切削過程的受力條件對刀具進行動態分析，然後再將各短刃的分析數值結果進行疊加，以獲得刀具實際切削過程的動態行為。
應用本文方法模擬直徑D = 6 mm之碳化鎢端銑刀切削鋁合金材料，徑向切深0.267 D，軸向切深為1.167 D，每刃進給0.04 mm，刀具轉速 600 rpm的中輕切削條件。分析結果顯示，切削過程在端銑刀軸向切深中沿螺旋刃邊緣的應力集中明顯，最大約900 MPa；而在刀端刀尖處的應力最高更高達約1450 MPa，值得注意。端銑刀順銑切削過程的位移響應以刀端刀尖點為例，分析結果顯示刀尖在刀具進給方向的撓曲位移最大到0.0095 mm左右；而刀尖在垂直進給方向的撓曲位移最大則到0.01 mm左右。顯示刀具切削時為彈離工件方向，此撓曲方向將造成讓切的尺寸誤差(Undercut)；另外，刀尖在刀軸方向的位移最大則僅-0.003 mm左右，表示刀具切削過程沿刀軸方向有相當微小被拉長的情形。因此本切削條件對切削面之尺寸精度影響不大。在本模擬分析實例中，由位移響應情形可見整個的切削過程並無明顯的刀具振動現象，而在實際切削實驗中亦顯示切削穩定。本文主要是應用疊加法建構端銑刀切削之動態應力及位移分析模式，未來可進一步考量各種切削條件的穩定性分析等。

關鍵字

端銑刀 ； 側銑切削 ； 動態應力分析 ； 疊加法 ； 有限元素分析

並列摘要

In this paper, an algorithm for analyzing dynamic stress and displacement of end mill cutter during peripheral milling process was developed. The cutter was idealized as a linear elastic material. Using dynamic analysis modeling can observe whether the tool chattering take place or not in the interrupted cutting of the end mill. Because of the cutting edge of the end mill is designed as a helical type, the chip load (or cutting force) of the cutting edge varied according to the tool rotation angle and axial position of cutting edge. In present study the principle of superposition was adopted to deal with the complicated load boundary conditions on helical cutting edge in peripheral milling. The helical cutting edge of the end mill was divided into several short edges for performing dynamic stress analysis of the end mill with only one short edge in load condition during one revolution of the tool. After performing the analysis of each load condition of short edge, the responses of end mill stress and displacement can be obtained by superposition.
Use present method to analyze stress and displacement responses of carbide end mill (with two flutes and diameter D = 6 mm) in cutting aluminum alloy. The cutting conditions are: radial depth of cut = 0.267D, axial depth of cut = 1.167D, feed per revolution per tooth = 0.04 mm and the tool rotation speed = 600 rpm. The results show that the serious stress concentration toward the cutting edge, which the maximum equivalent stress is up to 900 MPa. Worth to pay attention, particularly, at the end corner of the cutting edge, the maximum equivalent stress is up to about 1450 MPa. The analyzed results of the end mill displacement responses show that the maximum deflection at the corner of cutting edge is up to 0.0095 mm in the feed direction, and up to 0.01 mm in the direction perpendicular to feed direction. The latter deflection (perpendicular to feed direction) may cause dimensional error of the machined surface. Moreover; with present positive deflection will give an undercut dimensional error of the milling surface. In addition, the displacement of the end mill in tool-axis direction is only -0.003 mm (at the corner of cutting edge) for the maximal value during cutting. It reveals the end mill has very little extension during peripheral milling in present case study. The displacement response results reveal the peripheral milling which has a stable milling process in present cutting conditions and agrees with actual milling experiment.

並列關鍵字

End mill ； Peripheral Milling ； Dynamic stress analysis ； Principle of superposition ； Finite element analysis

參考文獻

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