마이크로 방전가공을 이용한 흑연전극의 성형 및 금속표면 가공 = Shaping of graphite electrode and machining of metal surface using micro electric discharge machining

다국어 초록 (Multilingual Abstract)

The graphite electrode has been using as the most common material in electric discharge machining(EDM), but it was mainly used for large-scale electrode such as a die-cast. However, with the advances in C-MEMS(Carbon-Micro electro mechanical system) technology, it has become possible to fabricate multi-electrode with several tens of microns. Therefore, this study aims to study the machining characteristics of graphite multi-electrode in μ-EDM. In this study, three types of EDM methods were used such as EDM, R-EDM, and WEDM, to fabricate the micro-scale graphite multi-electrode.
The graphite electrode which has an even surface can be precisely machined with the coordinates returned by using the occurrence of short circuit in RC circuit, and geometrical methods. The result of surface roughness and machining time depends on the variation in capacitance. As the capacitance increases, the machining time is reduced and surface roughness tends to be better results, but no further improvement has been made over a certain capacitance. As the capacitance increases, the single discharge energy increases, as well as the wear rate of the graphite electrode increases. As the wear rate of the graphite electrodes increases, the travel distance becomes relatively long, as a result, the machining time is not significantly reduced. In addition, if the single discharge energy becomes too large compared to the discharging area, the surface roughness becomes worse. Therefore, the use of the appropriate capacitance in μ-EDM is an important factor to get better machining quality.
Based on the results of this study, it is expected that more in-depth research about graphite electrode fabricated by C-MEMS will be possible.

목차 (Table of Contents)

• 1. 서론 1
• 2. 이론적 배경 4
• 2.1. 방전가공의 기본원리 및 가공특성 4
• 2.1.1 방전가공의 기본원리 4
• 2.1.2 방전가공의 가공특성 6
• 2.2 단발성 방전 에너지와 방전가공 단계 7
• 2.3 정밀 좌표 설정법 9
• 2.4 흑연전극 황삭(Rough Grinding)의 필요성 11
• 3. 실험 장치 제작 및 절차 12
• 3.1 실험장치 구성 12
• 3.1.1 EDM-WEDM 복합 방전가공기 구성 및 제작 12
• 3.1.2 와이어 가이드 설치 17
• 3.2 실험절차 및 조건 18
• 3.2.1 와이어 방전(WEDM)을 이용한 흑연전극 황삭 가공 절차 및 조건 18
• 3.2.2 역방전(R-EDM)을 이용한 흑연전극 황삭가공 절차 및 조건 19
• 3.2.3 흑연전극의 성형(Shaping) 조건 22
• 3.2.4 기하학적 계산을 이용한 흑연전극 성형 23
• 3.2.5 성형된 흑연전극의 형조방전 조건 27
• 4. 실험결과 및 고찰 28
• 4.1. WEDM과 R-EDM을 이용한 흑연전극 황삭가공 결과 28
• 4.2. WEDM을 이용한 흑연전극 성형 33
• 4.2.1. 축전용량에 따른 가공특성 33
• 4.2.2. WEDM을 이용한 사각기둥 형상의 다중전극 제작 36
• 4.2.3. 다중전극의 가공표면 관찰 39
• 4.3 흑연 다중전극의 금속표면 형조방전 41
• 4.3.1 형조방전시 표면조도 개선 41
• 4.3.2 형조방전시 가공시간, 표면조도, 전극 소모비 비교 44
• 5. 결론 47
• 6. 참고문헌 50