本研究主要目的在發展電化學放電加工非導電藍寶石極間現象觀察與加工技術，由於電化學放電中氣膜厚度、放電火花情形及液滴滑落頻率都將影響加工品質與加工效率，故本研究採用高速攝影機拍攝與觀察電化學放電時的氣膜厚度以及氣膜包覆情形，以及觀察電化學放電時極間現象，藉由實驗了解氣膜形成現象與加工特性。
本研究規劃與執行藍寶石電化學放電加工參數實驗，同時觀察電化學放電時極間現象，加工參數包含有液面高度、工作電壓、電極轉速及衝擊係數，並分析探討各加工參數對氣膜厚度、電流大小、電極損耗及液滴滑落頻率之影響，期盼能獲得優化之加工參數，克服藍寶石難以加工之困難點。
實驗結果顯示利用高速攝影機拍攝電化學放電時極間現象，能有效觀察氣膜厚度以及氣膜包覆情形，較高的氣泡結合率可以增加加工能力及減少側向放電，所以本實驗藉由觀察分析探討改善氣膜穩定性及加工能力，並能獲得較佳的加工孔深，實驗證明在液面高度700 µm、工作電壓48 V、衝擊係數50 %及工具電極轉速200 rpm之下，可獲得較佳的平均孔深86.7 µm、孔徑129.5µm。

關鍵字：電化學放電加工、氣膜、極間間隙、藍寶石

This study aimed to observe of gap phenomena and develop the electrochemical discharge machining method for sapphire. It was found that the thickness of the gas film, the discharge spark, and the droplet sliding frequency in the electrochemical discharge affected the processing quality and efficiency. This study used a high-speed camera to photograph and observe the bubble formation, gas film coating, and the phenomenon between tool electrode and workpiece during electrochemical discharge processes. The formation mechanism and processing characteristics of the gas film were understood through experiments.
Furthermore, this study executed the sapphire electrochemical discharge machining parameter experiment and observed the electrode gap phenomenon during electrochemical discharge processes. The machining parameters include the liquid level, working voltage, electrode rotational speed, and duty factor. They analyzed and discussed the effect of each machining parameter on the gas film thickness, current value, electrode consumption, and droplet slip frequency. Moreover, this study aimed to obtain optimized processing parameters to overcome the difficulty of processing sapphire.
The results show that a high-speed camera could effectively capture the bubble formation and gas film coating situation during electrochemical discharge processes. In addition, a higher bubble incorporation rate can increase the machining capability and reduce the side discharge phenomenon. Therefore, this study could obtain better processing hole depth through observation and analysis to improve gas film stability and machining capability. Moreover, at liquid level of 700 µm, working voltage of 48 V, duty factor of 50 %, and tool electrode rotational speed of 200 rpm, better average hole depth of 86.7 μm and pore diameter of 129.5 μm could be obtained.

Keywords: electrochemical discharge machining; gas film; electrode gap; sapphire

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