Study on the Application of Electrode Control Aided Electrochemical Discharge Drilling Method in Transparent Brittle Materials

基於電極操控輔助電化學放電鑽孔加工法於透明硬脆材料之研究

何昭慶(Chao-Ching Ho) ； 林祐安(Yu-An Lin)

《中國機械工程學刊》 41卷6期 (2020/12) Pp. 763-772

摘要

The Electrochemical Discharge Machining is a kind of innovative machining method newly developed for processing the non-conductive brittle materials. To enhance the machining efficiency and optimize the drilling depth, normally the voltage or the electrolyte concentration increasing method is applied. However, excessively high voltage and electrolyte concentration are the main reasons causing the overcutting, heat-affected area expansion and cavities as to degrade the quality. Therefore, the graphic and current monitoring approaches are used in the online-aided machining system during the research to achieve the parameter-based real-time feedback and adjustment effect. To support the glazing system, the cumulative extent of bubbles and the electrode features are observed to determine the appropriate timing for performing the polarity switching; further, the current values are also controlled to minimize the glass shattering effect when passing through the conveying hole. The polarity switching result indicated that this research can reduce 22.84% of front-side cavity overcut and 36.73% of through-hole overcut. In heat-affected area, 41.99% can be reduced for part of front-side heat-affected area; whereas, 24.4% can be reduced for the through-hole heat-affected area. Regarding the sapphire machining, the current-responsive inching control method was applied that the electrolyte at the electrolyte tip can be renewed as to minimize the influence resulting from electrolyte degradation while limiting the discharge of current. In view of this, the machining work can be performed under higher level of voltage without damaging the electrode. Furthermore, multiple pieces of electrodes are also used in this research for easier replacement as to stabilize the electrode material. Finally, during the composite control aided machining, we have achieved 184.06 μm maximum depth which represents 61.67% more of drilling depth when compared to the uncontrolled machining result.

關鍵字

electrochemical discharge machining ； transparent hard and brittle material ； Polarity reverse machining ； digital image processing

並列摘要

電化學放電加工是一種針對非導電硬脆材料之非傳統加工法，為了提高加工效率和鑽孔的最大深度，通常使用增加電壓或電解液濃度的方式，然而過高的電壓與電解液濃度是造成過切、熱影響區擴大和孔洞品質降低的主要原因。本研究提出了一種線上輔助加工系統，此系統利用圖像和電流監測來實現參數化的即時反饋和調整，在輔助對玻璃加工的系統上，本論文觀察氣泡的堆積的程度和電極特徵以決定進行極性切換的時機，並且使用控制電流數值來降低通孔時的玻璃碎裂。根據極性切換結果，本研究可以降低22.84%的正面孔洞過切與36.73%的通孔過切，在熱影響區的部份正面熱影響區降低了41.99%，而通孔熱影響區降低了24.4%。在加工藍寶石方面，本研究使用了根據電流響應的寸動控制法，使得電極尖端部分的電解液得以更新，降低電解液鈍化的影響，並且限制電流進行放電之控制，因而本研究可以在較高電壓下進行加工，而不使電極損毀；研究另外使用了多支電極加工中進行更換來確保電極材質穩定。最後在採複合控制輔助加工中，可得到最大深度184.06 μm，對比未進行控制的加工結果提升了61.67%的鑽孔深度。