碳化鎢具有高硬度、耐磨耗等特性，因而可用於製作微小元件，但也因此而難以使用傳統加工方法加工。放電加工法特別適用於高強度、高硬度材料之加工，而微細放電加工法適合於製作精微模具。因此，本研究以WEDG法與EDG法製作直徑為100μm微細電極，並利用微細放電加工機對KG5碳化鎢進行深寬比為10之盲孔加工。並藉由本實驗，探討不同放電加工參數（放電電壓、放電電流、放電持續時間、放電休止時間）對於碳化鎢之擴孔量、電極消耗、加工深度與表面缺陷之影響。

在微孔放電鑽孔加工中，由於電極對孔壁的放電與電極尖端消耗的關係，使得盲孔形狀趨於尖錐形。在本實驗中，當放電電流小於1.5A時可以藉由放電電壓的縮小以及放電休止時間的增加，有效的降低擴孔量的大小，但也容易造成電極消耗加劇、加工深度下降及因為加工時間過長造成孔底變形的情況。而當放電電流過大時會由於電極消耗劇烈，造成加工深度不足便結束加工，因此孔底的變形情況並不明顯。

碳化鎢的表面經微細放電後，其表面充滿了放電痕與放電加工表面的缺陷。在本實驗中，放電痕的大小受到放電電壓與放電電流的影響，且所有參數都會發現裂紋的存在。放電表面的裂紋大多沿著放電痕產生，在氣孔與空孔的附近尤其容易發現。氣孔與空孔延伸出來的裂紋，可利用降低Duty Factor的方式抑制空孔的產生，進而降低裂紋的發生。碳化鎢經微細放電後加工面會形成一層重鑄層，其厚度小於1μm，當放電能量大時才容易被發現之，且分佈相當不均勻。此外也會在孔壁的碳化鎢晶粒上發現因急熱遽冷影響而產生的熱裂紋。

Tungsten carbide (WC) is widely used in producing micro tools and components due to its high hardness and excellent resistance to wear, but it is also hard to machine by conventional ways. Micro-EDM is a process suitable for machining materials with high strength and toughness, and it is particularly useful to produce micro molds. Therefore, in this study, micro electrodes manufactured by EDG and WEDG are used to drill blind holes with aspect ratio of 10 on KG5 tungsten carbide. Effect of EDM parameters upon process characteristics and surface integrity, such as hole enlargement, electrode wear, hole machining depth, etc., are discussed.

During micro-EDM process, blind holes tend to cone-shape due to discharge machining at hole wall and extremely wearing at electrode tip. Decreasing pulse voltage and increasing pulse-off duration lead to decrease hole enlargement but increase both electrode wearing and process duration. A large pulse current causes extreme wearing of electrode and decrease the working depth, but the bottom of the blind hole is flat due to its short process time.

EDMed surface of WC is filled with discharge craters and surface defects. This study reveals that the size of discharge crater is affected by both pulse voltage and pulse current. On the working surface, cracks are found around discharge craters and porosities. Decreasing duty factor can reduce porosities and crack formation. The study also reveals the recast layer on working surface has been observed when discharge energy is large. The thickness of recast layer is smaller than 1μm. In addition, thermal cracks are observed in WC grains at hole wall.

1.N. Taniguchi, "Current status in, and future trends of, ultraprecision machining and ultrafine materials processing.", Annals of the CIRP, Vol. 32, No. 2, pp. 573–582., 1983.
2.R. Snoeys, F. Staelens, W. Dekeyser, "Current trends in non-conventional material removal processes." Annals of the CIRP, Vol. 35, No. 2, pp. 467–480., 1986.
3.董光雄, "放電加工", 復文書局, 中華民國, 1988.
4.L. C. Lim, L. C. Lee, Y. S. Wong and H. H. Lu, "Solidification microstructure of electrodischarge machined surfaces of tool steels", Materials Science and Technology, Vol. 7, No. 3, pp. 239-248., 1991.
5.D. M. Allen, A. Lecheheb, "Micro electro-doscharge machining of ink jet nozzles: optimum selection of material and machining parameters.", Journal of Materials Processing Technology 58, pp. 53–66., 1996.
6.T. Masuzawa, "Micro-EDM", Proceedings of the 13th International Symposium for Electromaching ( ISEM XIII ), vol.1, pp. 3-19, 2001.
7.戴子堯, "放電加工之電極尺寸與加工參數對工具鋼表層特性之研究", 國立成功大學機械工程研究所博士論文, 2004.
8.童文煥, "放電加工鑽孔白層與引進殘留應力之關連性研究", 成功大學機械工程研究所碩士論文, 1998.
9.戴子堯, "利用放電加工鑽孔法量測硬度層表面殘留應力", 成功大學機械工程研究所碩士論文, 1999.
10.R. A. Mahdavinejad, A. Mahdavinejad, "ED machining of WC-Co", Journal of Materials Processing Technology, Vol. 162–163, pp. 637–643, 2005.
11.仁雄, "放電加工技術之現狀與將來", 機械技術, vol. 161, pp. 220-226, 1998.
12.A. G. Mamalis, G. C. Vosniakos and N. M. Vaxevanidis, "Macroscope and microscopic phenomena of electro-discharge machined steel surface: an experimental investigation", Journal of Mechanical Working Technology, Vol. 15, pp.335-356, 1987.
13.N. F. Petrofes and A. M. Gadalla, "Processing aspects of shaping advanced materials by electrical discharge machining", Materials and Manufacturing Process, Vol. 3, No.1, pp.127-157,1988.
14.Bormann, R., "Understanding die-sinking EDM surface integrity", Carbide and Tool Journal, Vol. 20, No. 6, pp. 12-16, 1988.
15.M. A. E. -R. Merdan and R. D. Arnell, "The surface integrity of a die steel after elelctrodischarge machining:(I) structure,composition,and hardness", Surface Engineering, Vol. 5, No. 2 , pp 158-164., 1989.
16.M. A. E. -R. Merdan and R. D. Arnell, "Surface integrity of a die steel after electrodischarge machining: (II) Residual stress distribution", Surface Engineering, Vol. 7, No. 2, pp. 154-158., 1991.
17.L. C. Lee, L. C. Lim, Y. S. Wong and H. S. Fong, "Crack susceptibility of electro-discharge machined surface", Journal of Materials Processing Technology, Vol. 29, pp. 213-221., 1992.
18.L. C. Lee, L. C. Lim, Y. S. Wong and H. S. Fong, "Toward crack minimization of EDMed surface", Journal of Materials Processing Technology, Vol.32, pp. 45-54., 1992.
19.Y. S. Wong, L. C. Lim and L. C. Lee, "Effect of flushing on electro-discharge machined surface", Journal of Materials Processing Technology, Vol. 48, pp.299-305., 1995.
20.J. P. Kruth, L. Stevens, L. Froyen, B. Lauwers, "Study of the white layer of a surface machined by die-sinking electro-discharge machining," Annals of CIRP, Vol. 44, No. 1, pp. 169-172, 1995.
21.莊永旺、顏瑞宏, "放電加工對SKD61熱間工具鋼表面性質之影響", 中國機械工程學會第十三屆學術研討會, pp. 437-444., 1996.
22.J. S. Soni, G. Chakraverti, "Experimental investigation on migration of material during EDM of die steel", Journal of Materials Processing Technology, Vol. 56, pp. 439-451., 1996.
23.J. C. Rebelo, A. Morao Dias and J. L. Lebrun, "Influence of EDM pulse energy on the surface integrity of matensitic steels", Journal of Materials Processing Technology, Vol.84, pp. 90-96, 1998.
24.C. Van Osenbruggen, "Micro spark erosion", Philips Technisch Tijdschrift, Vol. 20, pp. 200-213., 1969.
25.T. Masuzawa, M. Fujino and K. Kobayashi, "Wire electro-discharge grinding for micro-machining", Annals of the CIRP, Vol. 34, No. 1, pp. 431-434, 1985.
26.T. Masuzawa, J. Tsukamoto, and M. Fujino, "Drilling of deep microholes at EDM," Annals of the CIRP, Vol. 38, No. 1, pp. 195-198, 1989.
27.T. Masuzawa, "Micro EDM," Journal of Japan Society Precision Engineering, Vol. 57, pp. 963-967., 1991.
28.T. Masuzawa, C. L. Kuo and M. Fujino, "A combined electrical machining process for micronozzle fabrication", Annals of the CIRP, Vol. 43, No. 1, pp. 189-192., 1994.
29.Z. Y. Yu, T. Masuzawa, M. Fujino, "Micro-EDM for three dimensional cavities-development of uniform wear method", Annals of the CIRP, Vol. 47, No. 1, pp. 169-172., 1998.
30.P. H. Heeren, D. Reynaerts, H. Van Brussel, C. Beuret, O. Larsson, A. Bertholds, "Microstructuring of silicon by electro-discharge machining (EDM) – Part II: Applications," Sensors and Actuators A, Vol. 61, No. 1-3, pp. 379-386., 1997.
31.C. L. Kuo, J. D. Huang, H. Y. Liang, "Precise micro-assembly through an integration of micro-EDM and Nd-YAG," International Journal of Advanced Manufacturing Technology, Vol. 20, No. 6, pp. 454-458., 2002.
32.Z.Y. Yu, K.P. Rajurkar and H. Shen, "High-Aspect Ratio and Complex Shaped Blind Micro Holes by Micro EDM", Annals of the CIRP, Vol. 51, No. 1, pp. 359–362., 2002.
33.T. Tamura, Y. Kobayashi., "Measurement of impulsive forces and crater formation in impulse discharge.", Journal of Materials Processing Technology, 149, pp. 212-216, 2004.
34.Y. T. Kim, S. J. Park and S. J. Lee, "Micro/Meso-scale shapes machining by micro EDM process," International Journal of Precision Engineering and Manufacturing, Vol. 6, No. 2, pp. 5-11, 2005.
35.J. H. Lim, S. U. Je, S. H. Ryu and C. N. Chu, "Distortion of the Bottom Surface in Micro Cavity Machining Using MEDM", International Journal of Precision Engineering and Manufacturing, Vol. 6, No. 4, pp. 44-48, 2005.
36.Z. Katz and C.J. Tibbles, "Analysis of micro-scale EDM process", International Journal of Advanced Manufacturing Technology , Vol. 25, pp. 923–928., 2005.
37.S. Dhanik and S. S. Joshi, "Modeling of a single resistance capacitance pulse discharge in micro-electro discharge machining", Journal of Manufacturing Science and Engineering, Transactions of the ASME 127 , pp. 759–767, 2005.
38.S. M. Pandle and K. P. Rajurkar, "Analyzing electro discharge machining of cemented carbide", Annals of the CIRP, Vol. 30, No. 1, pp. 111–116., 1982.
39.W. J. Tomlinson and J. R. Adkin, "Microstructure and Properties of Electrodischarge Machined Surfaces," Surface Engineering, Vol. 8, No. 4, pp. 283-288., 1992.
40.S. H. Lee, X. P. Li, "Study of the effect of machining parameters on the machining characteristics in electrical discharge machining of tungsten carbide", Journal of Materials Processing Technology, Vol.115, pp. 344-358., 2001.
41.I. Puertas and C. J. Luis, Proceedings of the International Conference on Advances in Materials and Processing Technologies (AMPT’03), Vol. II Dublin, Ireland (2003), pp. 877–880., 2003.
42.S. H. Lee and Xiaoping Li, "Study of the surface integrity of the machined workpiece in the EDM of tungsten carbide", Journal of Materials Processing Technology, Vol.139, pp. 315-321., 2001.
43.T. Kawakami, T. Kunieda, "Study on factors determining limits of minimum machinable size in micro EDM", Annals of the CIRP, Vol. 54, No. 1, pp. 167-170., 2005.
44.邴兆齊, "放電加工鑽孔法量測殘留應力之可行性分析," 成功大學機械工程研究所碩士論文, 1994.
45.葉麗雅, "放電加工鑽孔法量測殘留應力之應用研究," 成功大學機械工程研究所碩士論文, 1995.
46.楊永名, "放電加工參數與加工表面特性對量測殘留應力之影響評估," 成功大學機械工程研究所碩士論文, 1996.
47.李驊登、于劍平, "碳化鎢放電加工之研究", 中華民國第十七屆機械工程研討會, pp.239-246., 2000.
48.許多, "SKD11工具鋼殘留應力之放電工加工鑽孔量測法研究," 國立成功大學機械工程研究所碩士論文, 2001.
49.于劍平, "放電加工表面特性之研究," 國立成功大學機械工程研究所博士論文, 2002.
50.陳柏瑋, "尺寸效應對放電加工表面粗糙度及表面裂縫的影響," 國立成功大學機械工程研究所碩士論文, 2003.
51.陳玉華, "放電加工之表面裂紋敏感性研究," 國立成功大學機械工程研究所碩士論文, 2003.
52.劉全、李驊登、許富銓、謝銘倫, "測量鋼鐵材料殘留應力新技術", 中華民國第九屆破壞科學研討會, 2008.
53.R. Bormann, "Getting Those Better EDM'd Surfaces", Modern Machine Shop, Vol.63, NO.9, pp. 56-66., 1991.
54.黃瑞鐘編譯, 最新放電加工技術, 全華科技圖書股份有限公司, 1987.
55.井上潔原著, 黃錦鐘譯, 放電加工, 高立圖書有限公司, 1998.
56.林楠盛, "放電加工之應用技術", 機械工業雜誌, 82卷, pp.203~215., 1990.
57.D. T. Pham, S. S. Dimov, S. Bigot, A. Ivanov, K. Popov, "Micro-EDM recent developments and research issues", Journal of Materials Processing Technology 149, pp. 50-57., 2004.
58.葉思武譯, "微細放電加工的現狀", 機械雜誌月刊, pp. 118-112, 2000.
59.林培欽, "放電加工鑽孔引進殘留應力之研究", 成功大學機械工程研究所碩士論文, 1998.
60.F. Roethel, "Surface properties in electric discharge machining", NASA Technical Translation (NASA TT), 20243, 1988.
61.Y. Youshen, Y. Mukoyama, H. Kato and T. Hanaoka, "Analysis of crack generative region in crater machined by impulse electrical discharge", Journal of the Japan Society of Precision Engineering, Vol. 60, No. 3, pp. 388-392., 1994.
62.李驊登, "不同放電加工條件下工件表面之缺陷分析", 中華民國第四屆破壞科學研討會論文集, pp. 411-416., 1996.
63.Y. Y. Tsai, "Electrode Wear in Micro-EDM", Ph.D Dissertation, The University of Tokyo., 2002
64.Fuzhu Han, Y. Yamada, T. Kawakami and M. Kunieda, "Experimental attempts of sub-micrometer order size machining using micro-EDM", Precision Engineering, Vol. 30, pp. 123–131., 2006.
65.春保鎢鋼網站資料，http://www.cbcarbide.com/big/products4_0.asp
66.H. Xia, M. Kunieda, N. Nishiwaki, "Removal Amount Difference between Anode and Cathode in EDM Process", IJEM, Vol.1, pp. 45-52., 1996.
67.T. Masuzawa, M. Fujino, K. Kobayashi, T. Suzuki, "Study on micro-hole drilling by EDM – automatic electrode forming with traveling wire", Bulletin of Japan Society of Precision Engineering, Vol. 20, No. 2, pp. 117-120., 1986.
68.T. Masuzawa, "State-of-the-art on Micromachining", Annals of the CIRP, 49, Vol. 2, pp. 473-488., 2000.
69.劉祥年，"超硬合金模具應用常見的幾個問題"，機械月刊，第25卷，第9期，pp. 405-415., 1994.
70.European Coal and Steel Community., "De ferri metallographia.", 1983.