純水中的電解現象分析與大電流放電加工特性研究; A study of electrolysis and high current Electrical Discharge Machining in pure water

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Title:	純水中的電解現象分析與大電流放電加工特性研究;A study of electrolysis and high current Electrical Discharge Machining in pure water
Authors:	鄭宜峰;Yi-feng Cheng
Contributors:	機械工程研究所
Keywords:	純水;電解;大電流;放電加工;pure water;electrolysis;high current;EDM
Date:	2008-06-20
Issue Date:	2009-09-21 12:01:46 (UTC+8)
Publisher:	國立中央大學圖書館
Abstract:	由於放電加工不受限於工件強度及硬度的影響，只要工件具導電性即可加工，對於加工硬質材料具有極優秀的能力，但缺點是加工速度低，且以煤油為加工液，大能量放電可能有燃燒的危險，且會有環境污染的疑慮。故為了提升加工速度、改善加工環境，因此本實驗以大電流、純水加工液為實驗方向。但採用純水時，會產生電解的現象，影響加工效率及精度。故本研究先探討純水中產生的電解現象，並於純水中進行大電流放電加工，探討其加工特性。經由電解實驗可知，電極椄正極時，受到的電解腐蝕較嚴重。電壓越大及間隙越小時，由於電場強度較大，使得電解越嚴重。並且發現到，電極旋轉及改變電極材料都能有效減低電解的破壞。純水中大電流放電加工實驗中，電極接負極時消耗較多。並且在電流倍數增加時，材料移除率也幾乎以倍數提高，只不過當電極尺寸不夠大時，大電流下放電會使電極消耗過快。實驗也發現，增加脈衝時間與縮小休止時間，都具有減低電極消耗的能力，且適當的工作時間，更可以提升排渣效果及加工速度。此外，當以大電流進行放電加工時，可以得到較為平整的加工面。 Electrical Discharge Machining (EDM) enable to machine high hardness material. However, low machining speed is it’s weakness. So, rising current is an effective method for increasing machining speed. Due to kerosene could be fired in high current; hence pure water is used as dielectric in EDM. Nevertheless, electrolysis will be happened when water is used. Therefore, this research investigates the influence of electrolysis and high current EDM in pure water. In the electrolysis experiment, it is found that electrode is corroded seriously when its polarity is positive. Higher voltage and smaller gap lead to electrolysis corrosion more seriously. Furthermore, rotating electrode and changing electrode’s material can reduce corrosion effectively. In the experiment of high current EDM by water-based dielectric, the higher electrode wear ratio is found during negative polarity machining. It is also confirmed that material removal rate increases with rising current. Beside, longer pulse on time and shorter off time can reduce electrode wear rate. In addition, a proper working duration can improve debris flushing for rising working efficiency. In high current EDM, the surface roughness of workpiece is fine.
Appears in Collections:	[Graduate Institute of Mechanical Engineering] Electronic Thesis & Dissertation

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