螺旋模仁在流體研磨加工機制的研究

A study of abrasive flowing machining mechanism with a helical mold core

鄭根全(Ken-Chuan Cheng)

指導教授 ： 陳冠宇 ； 王阿成

中原大學/工學院/機械工程研究所/博士(2013年)

https://doi.org/10.6840/cycu201300723

摘要

相較於其他研磨加工方法，流體研磨加工(AFM)是一種操作簡單、快速、低成本且有效率的拋光方法。然而現有的AFM仍存在一些缺點，例如：受限於單一垂直方向作動加工機制的影響，研磨後，圓形孔洞軸向的表面粗糙度會有不均勻分佈的現象；此外，對於多邊形或複雜形狀孔洞的拋光，會因孔洞間的距離不同，造成徑向的表面粗糙度會有不均勻分佈的現象。因此，本文提出在孔洞內部放置螺旋模仁的方法，透過內部螺旋流場新增一切線研磨分力，如此可增加孔洞表面研磨的面積與總切削力，來改善前述缺點。首先，本研究利用計算流體力學軟體(CFD-ACE+)進行模擬分析，結果顯示內置螺旋模仁在圓形與多邊形孔洞軸向的流速分佈，可呈現多方向均佈的運動路徑，且在孔洞徑向的剪應變率變化量較小，應可有效減少拋光的表面粗糙度及增加其均勻性。其次，經由一系列的單因子實驗及田口實驗方法發現，模仁螺旋的設計在槽數為4槽、槽寬0.5 mm、間距為0.5 mm及螺旋圈數為1圈為最佳化條件。最後，相較於無模仁AFM方法，內置螺旋模仁的拋光加工實驗結果，驗證在圓形孔洞拋光後的表面粗糙度，改善率可達到76%，高於無模仁流體研磨加工後的表面粗糙度改善率60%。在多邊形與梅花異形放置螺旋模仁的研拋結果，也顯示類似表面粗糙度改善的效果。另對圓形孔洞軸向表面粗糙度均勻性的改善效果，螺旋模仁表面粗糙度的偏差值是0.035 m (Ra)，與無模仁流體研磨加工後的偏差值0.104 m (Ra)比較，有很大的改善效果。另在多邊形孔洞放置螺旋模仁，對表面粗糙度均勻性，則以四邊形的改善效果最好。而在梅花異形放置螺旋模仁，表面粗糙度的偏差值是0.0782 m (Ra)，與無模仁流體研磨加工後的偏差值0.1513 m (Ra)比較，改善率可以達到48%，綜合以上結果可知，孔洞放置螺旋模仁明顯可改善表面粗糙度與其均勻性。

關鍵字

多邊形孔洞 ； 田口實驗法 ； 表面粗糙度 ； 圓形孔洞 ； 螺旋流場 ； 流體研磨加工

並列摘要

The abrasive flow machining (AFM) is a simple and efficient method to polish workpiece surface compared to other polishing methods. However, conventional AFM method has difficulty achieving uniform roughness of an axial distribution in circular holes polishing since one-way motion of abrasive media. Besides, it is also difficult to reach the uniform roughness of radial distribution in polygon holes polishing, due to the polygon holes width is not symmetry and the abrasive force is non-uniform in the corner edges. Therefore, a novel mechanism with a helical passageway is developed by modifying AFM set-up in this paper. The helical motion of abrasive media leads to a new item of tangential force to increase the abrasive area and cutting force. In this study, numerical results simulated by CFD-ACE+ software indicate that the motion of a helical passageway significantly affected the abrasive medium in the channels with multiple flowing paths of velocity. Next, after conducted a series of one factorial experiment and the Taguchi experimental method, an optimal design of the helical mold core including for a four-helix groove, a 0.5 mm gap, a 0.5 mm slot thickness and a one helical turn was obtained. In the end, the experimental results indicate that the helical passageway is superior to circular passageway in reducing roughness improvement rate (RIR) by roughly 76% compared with RIR 60% for the circular passageway. Additionally, the experiments of polygon and complex passageways inserting with a helical core are obtained the similar results. Moreover, roughness deviation of the helical passageway of approximately 0.035 μm (Ra) is significantly better than those on a circular passageway of around 0.104 μm (Ra). According to the measuring results, the square passageway with a helical core performs the best improvement of the roughness uniformity. On the other hand, the surface roughness deviation of the helical passageway for approximately 0.0782 μm (Ra) is also better than those on an original complex passageway for around 0.1513 μm (Ra). Thus, this research demonstrates an excellent solution that the helical passageway performed significantly better in reducing surface roughness and increasing the roughness uniformity than those on the original passageways.

並列關鍵字

Surface roughness ； Abrasive flow machining ； Polygon holes. Taguchi experimental method ； Circle holes ； Helical passageway

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