利用超音波刀把輔助高速銑削曲面對表面粗糙度影響之探討

本研究的目的是針對S45C中碳鋼以超音波輔助刀把夾持端銑刀進行曲面之高速銑削，探討有無超音波輔助加工及各加工參數對於加工曲面表面粗糙度之影響。利用田口法L9(34)直交表規劃切削加工參數，所選擇的三個加工參數分別為：主軸轉速(A)、進給率(B)及切削深度(C)。共規劃9組參數組合，並分別以一般刀把及超音波輔助刀把進行實驗，同時量測加工後之表面粗糙度值。實驗由結果顯示影響粗糙度程度之因子排序，對使用一般刀把而言為切削深度(C)、主軸轉速(A)、進給率(B)。對使用超音波輔助刀把而言為切削深度(C)、進給率(B)、主軸轉速(A)。一般刀把之最佳參數組合為主軸轉速A1 (3200 rpm)、進給率B1 (320 mm/min)、切削深度C1 (0.05 mm)。超音波輔助刀把之最佳參數組合為主軸轉速A1 (3200 rpm)、進給率B3(480 mm/min)、切削深度C1 (0.05 mm)。由最佳參數組合可以觀察到兩者的主軸轉速及切削深度相同，唯獨進給率不同，超音波輔助刀把的進給率(480 mm/min)較一般刀把的進給率(320 mm/min)高33%，因此可得知超音波輔助刀把能提升切削的效率。一般刀把靜點切削處的量測數據平均值為4.468μm，比非靜點切削處的量測數據平均值0.603μm、0.634μm高86.50%及85.82%。超音波輔助刀把之靜點切削處量測數據平均值為1.657μm，比非靜點切削處量測數據平均值0.337μm、0.376μm高79.66%及77.31%。不管是否使用超音波輔助加工因球刀之幾何外型，造成靜點切削時切削能力孱弱使得表面粗糙度不佳。使用一般刀把靜點切削處量測數據最高值為5.748μm，非靜點切削處量測數據最低值0.2μm。使用超音波輔助刀把之靜點切削處量測數據最高值為3.098μm，非靜點切削處量測數據最低值0.249μm。比較同組加工參數下有無使用超音波輔助加工之表面粗糙度改善率最高的為第9組76.20%，而最低為第5組也還有34.35%。由此可以得知超音波輔助加工確實能改善加工之表面粗糙度品質。從有無使用超音波輔助加工之靜點切削量測數據最低值，可以推斷因為S45C碳鋼材料富有延展性，雖然使用超音波輔助加工能提高其品質的穩定度，但也因為超音波本身的振動特性，使得最小表面粗糙度無法達到更佳之效果。由顯微放大圖結果─超音波輔助刀把加工使刀具路徑的分隔沒有如此明顯。而使用一般刀把之加工表面，兩刀具路徑間的分隔十分的明顯，可以知道超音波輔助刀把能有效降低表面粗糙度。但因為超音波震動的關係，所以超音波輔助刀把加工之表面不像一般刀把加工之表面來的平滑，反而很多震動之痕跡。本研究的成果可供使用超音波刀把輔助切削相關產業之參考。

關鍵字

超音波振動輔助加工；高速銑削；表面粗糙度；田口方法

並列摘要

The objective of the research is to explore the impact of existence of ultrasonic auxiliary process and parameters of other means of processing on the curved surface coarseness by the high speed milling of S45C carbon steel ultrasonic auxiliary blade with milling cutter. Using the L9(34) vertical array of the Taguchi method to plan three parameters of the milling: main axial rotational speed (A), feed rate (B), and cutting depth (C). A total of 9 processing parameter combinations were planned, each of which uses a normal blade and ultrasonic auxiliary blade while measuring the surface coarseness value after processing. The result of the experiment is exhibited by the order of degree of coarseness. For normal blade, the order is the cutting depth (C), main axial rotational speed (A), feed rate (B). The best parameter combination for normal blade is main axial rotational speed A1 of 3200 rpm, feed rate B1 of 320 mm/min, and cutting depth C1 of 0.05mm. The best parameter combination for ultrasonic auxiliary blade is main axial rotational speed A1 of 3200 rpm, feed rate B3 of 480 mm/min, and cutting depth C1 of 0.05mm. From the best parameter combinations, the main axial rotational speed and the cutting depth are the same. The only difference is in the feed rate where the feed rate of ultrasonic auxiliary blade of 480 mm/min is 33% higher than that of the normal blade of 320 mm/min. The cutting efficiency with the ultrasonic auxiliary blade can be enhanced. The average cutting measurement value of 4.468μm at the still point of the normal blade is 86.50% and 85.82% higher than the 0.603μm and 0.634μm respectively than that of measured values at the non-still point. The average cutting measurement value of 1.657μm at the still point of the ultrasonic auxiliary blade is 79.66% and 77.31% higher than the 0.337μm and 0.376μm respectively than that of measured values at the non-still point. Whether or not the ultrasonic auxiliary blade is used, the weakened cutting capability at the still point resulted in bad surface coarseness. The highest measured value at the still point using the normal blade is 5.748μm while that of the lowest measured value at the non-still point is 0.2μm. The highest measured value at the still point using the ultrasonic auxiliary blade is 3.098μm while that of the lowest measured value at the non-still point is 0.249μm. By comparing the improvement rate of surface coarseness of using and not using the ultrasonic auxiliary blade in the same set of processing parameters, the ninth set with 76.20% has the best rate while the lowest of the fifth set still has a rate of 34.35%. It can be derived that using ultrasonic auxiliary blade can definitely improve the quality of surface coarseness. From the lowest values measured at the still point of using and not using the ultrasonic auxiliary blade, because S45C carbon steel has malleability, it can be deduced that even though using the ultrasonic auxiliary processing may enhance the stability of the quality, but due to the vibrational characteristic of the ultrasonic waves, the best result of smallest surface coarseness will also not be achieved. Using the ultrasonic auxiliary blade processing will render the division of blade tracks to be not as conspicuous from looking at the enlarged microscope picture. The surface processed by using the normal blade, the division of the blade tracks are quite conspicuous. It can be derived that using ultrasonic auxiliary blade can effectively reduce the surface coarseness. However, due to the vibration of the ultrasonic waves, the processed surface of having used the ultrasonic auxiliary blade is not as smooth as that of using the normal blade, rather, many marks as a result of the vibrations appear. The result of the research can be used to provide reference for ultrasonic auxiliary cutting related industry.