在 積 層 製 造 (Additive Manufacturing, AM) 領域中， 定向能量沉積技術(Directed Energy Deposition, DED)使用粉末噴塗(Powder-Fed)的方式加工產品，此技術已廣泛應用在各領域製造各種高自由度外型的零件，但技術方面仍須克服許多挑戰，如產品的機械強度、尺寸精度、製程參數的選擇等。
本研究利用ANSYS Fluent 數值分析軟體建立三維暫態DED 加工不鏽鋼
316L 數值模型，由工業技術研究院的DED 機台實驗驗證數值模型，與實驗數據比較證明模擬結果具有準確性。後續探討雷射功率及雷射速率對金屬薄層幾何尺寸影響，並依兩個自定義參數，分別從節省能源及節省製程時間的角度比較各種製程參數組合的優劣，獲取最佳製程參數。最後選用最佳製程參數進行比較基板預熱、金屬粉末預熱及保護氣體預熱對金屬薄層的冷卻速率及幾何尺寸的影響性。
研究顯示雷射功率為影響金屬薄層高度的重要參數占73.7 %貢獻率，而雷
射速率相對較小占22.1 %；雷射功率亦為影響金屬薄層寬度的重要參數占68.7%貢獻率，而雷射速率占28.4 %。依兩個自定義參數比較模擬的數據，雷射功率1600 W、雷射速率10 mm/s 最能夠節省能源及製程時間。基板預熱能增加金屬薄層幾何尺寸，但降低基板溫度梯度效果有限；金屬粉末預熱能夠顯著的降低冷卻速率同時也增加金屬薄層的堆疊高度；最後保護氣體預熱無法有效降低冷卻速率也無法增加金屬薄層的幾何尺寸。

In this study, a numerical model of Directed Energy Deposition (DED) process for stainless steel 316L is developed to investigate the thermal effects of process
parameter. According to the results, laser power has the major effect on both height and width of the metal thing layer; however laser speed has the minor effect on both
height and width of the metal thing layer. By Taguchi Methods, analysis shows that laser power has 73.7 % effectiveness on height and 68.7 % on width respectively,
and laser speed has 22.1 % effectiveness on height and 28.4 % on width. Further, the parameters, laser power 1600 W and laser speed 10 mm/s, are found to suitably reduce manufacturing time and save laser energy.
To improve DED process, three different preheating methods were implemented to reduce temperature gradient, reduce cooling rate and increase size of the metal thing layer. Preheated substrate has the limited result on reducing temperature gradient, but it can increase both height and width of the metal thing layer. In aerospace applications, the columnar grains dominant products have more creep
resistance on high temperature. One of the key factor to develop columnar grains is to reduce cooling rate during solidification. Preheated metal powder can not only reduce cooling rate effectively but increase height of the metal thing layer. Because shielding gas is a poor thermal conductor, preheated shielding gas has little effect on
reducing cooling and size of the metal thing layer.

1. I. Gibson, D. Rosen, and B. Stucker, “Additive
Manufacturing Technologies 3D Printing, Rapid
Prototyping, and Direct Digital Manufacturing Second
Edition,”Springer, 2010.
2. C.Y. Yap, C.K. Chua, Z.L. Dong, Z.H. Liu, D.Q. Zhang,
L.E. Loh, and S.L. Sing,“Review of selective laser
melting: Materials and applications,” Applied Physics
Reviews, Vol. 2, 041101, 2015.
3. G.K. Lewis and E. Schlienger, “Practical considerations
and capabilities for laser assisted direct metal
deposition,” Materials & Design, Vol. 21, pp. 417-423,
2000.
4. P. Michaleris, “Modeling metal deposition in heat
transfer analyses of additive
manufacturing processes,” Finite Elements in Analysis
and Design, Vol. 86, pp.51-60, 2014.
5. L. Wang, S. Felicelli, Y. Gooroochurn, P.T. Wang, and
M.F. Horstemeyer, “Optimization of the LENS® process
for steady molten pool size,” Materials Science and
Engineering A, Vol. 474, pp. 148-156, 2008.
6. R. Ye, J.E. Smugeresky, B. Zheng, Y. Zhou, and E.J.
Lavernia, “Numerical modeling of the thermal behavior
during the LENS® process,” Materials Science and
Engineering A, Vol. 428, pp. 47-53, 2006.
7. W.F. Smith and J. Hashemi, “Foundations of materials
science and engineering,” McGraw-Hill, pp. 424-428,
2007.
8. 謝之駿, “不銹鋼材料,” 國立中興大學。
9. M.V. Boniardi and A. Casaroli, “Stainless steels,”
Lucefin S.p.A., 2014
10. W.D. Callister and D.G. Rethwisch, “Fundamentals of
Materials Science and Engineering: An Integrated
Approach, 4th edition, 2012.
11. L. Wang and S. Felicelli, “Process Modeling in Laser
Deposition of Multilayer SS410 Steel,” Journal of
Manufacturing Science and Engineering, Vol. 129, pp.
1028-1034, 2007.
12. P. Peyre, P. Aubry, R. Fabbro, R. Neveu, and A.
Longuet, “Analytical and numerical modelling of the
direct metal deposition laser process,” Journal of
Physics D: Applied Physics, Vol. 41, Number 2, 2008.
13. J.C. Heigel, P. Michaleris, and E.W. Reutzel, “Thermo-
mechanical model development and validation of
directed energy deposition additive manufacturing
of Ti–6Al–4V,” Additive Manufacturing, Vol. 5, pp. 9-
19, 2015.
14. R. Klein, “Laser Welding of Plastics ,” Wiley-VCH,
2011.
15. 楊隆昌, “雷射發展的趨勢與應用”, September, 2014.
16. 張守進、劉醇星、姬梁文, “半導體雷射, 科學發展”, 349,
January, 2002.
17. D. Schwartz,“Head and optics innovations key to laser
cutting growth, ” The Fabricator, April, 2016.
18. S. Louhenkilpi and F. Imre, “ A lézersugár
jellemzése,” Anyagtudományi folyamatszimuláció -
Hőkezelés modellezése, 2011.
19. “Gaussian Beam Optics,” Available:
http://www.cvimellesgriot.com/.1919–1928, August 1997.
20. K.C. Mills,“Recommended values of thermophysical
properties for selected commercial alloy,” Woodhead
Publishing, 2002.
21. D. Hu and R. Kovacevic,“Modelling and measuring the
thermal behaviour of the molten pool in closed-loop
controlled laser-based additive manufacturing,”
Proceedings of the Institution of Mechanical
Engineers, Part B:Journal ofEngineering Manufacture,
2003.
22. L.X. Yang, X.F. Peng, and B.X. Wang,“Numerical
modeling and experimental investigation on the
characteristics of molten pool during laser
processing,” International Journal of Heat and Mass
Transfer, Vol. 44, Issue 23, pp.4465-4473, 2001.
23. E. Toyserkani, A. Khajepour, and S. Corbin,“3-D finite
element modeling of laser cladding by powder
injection: effects of laser pulse shaping on the
process,”Optics and Lasers in Engineering, Vol. 41,
Issue 6, pp. 849–867, 2004.
24. L. Wang and S. Felicelli,“Analysis of thermal
phenomena in LENS™ deposition,” Materials Science and
Engineering: A, Vol. 435–436, pp.625-631, 2006.
25. 朱紅鈞,“FLUENT 15.0 流場分析實戰指南,” 人民郵電出版社,
2015.
26. 隋洪濤, 李鵬飛, 馬世虎, 馬富銀, 胡穎, 人民郵電出版社,
2013.
27. Y.A. Cengel,“Heat and Mass Transfer: A Practical
Approach,” McGraw-Hill, pp.20, 2006.
28. E.W. Lemmon and R.T. Jacobsen, “ Viscosity and Thermal
Conductivity Equations for Nitrogen, Oxygen, Argon,
and Air,” International Journal of Thermophysics, Vol.
25, pp 21-69, 2004