積層製造為近年新興之製程之一，與傳統加工方式相比，採用加法製造原理，將材料沉積於指定位置後以雷射熔融凝固形成產品。此製程具節省材料、縮短加工週期與成形複雜幾何等優點，主要技術包含：定向能量沉積與選擇性雷射熔融。
為提升沉積品質，以田口灰關聯分析方法作為實驗設計工具，進行多品質製程因子組合之優化實驗。由分析結果可得五項控制因子：雷射功率、重疊程度、供粉量、掃描速度及雷射頭抬升高度對三項品質：沉積效率、沉積速率及孔隙率皆具有顯著影響，據此決定出能兼顧各品質需求之最佳因子組合。接著，利用實驗數據進行變異數分析，以辨識對各品質影響最顯著之因子，並透過一次一因子實驗進一步微調最佳化製程參數組合。為驗證該最佳參數組合對沉積品質之影響，本研究進行拉伸試驗，結果顯示沉積試片之抗拉強度僅較原始材料下降約10%，證實所建立之最佳製程參數具備良好可行性。
此外，為進一步提升DED在損壞工件修補中的適用性，本研究結合3D掃描與逆向工程建立損壞工件之精確STL模型，並以U-shaped boundary(UB)與Convex-hull boundary(CHB)兩種演算法界定清創範圍。透過沿y軸0.5 mm之切片，可有效辨識損傷區域並規劃清創路徑，確保加工後具備足夠沉積空間。UB方法搭配固定Z-offset之沉積路徑完成實作驗證，結果顯示界面熔接緊密且堆疊品質良好；CHB方法則提出適用於平板型損傷邊界之分區與路徑規劃策略，作為後續推廣至更高幾何變異修補場景之基礎。
將最佳參數應用於工件修補中，首先於Mastercam進行路徑規劃，並結合後處理器設定與雷射系統專用M碼生成可於設備上執行之NC程式。於UB方法界定之修補區域內，本研究以Z-offset 45%搭配逐層交替方向、錯開層間起點及順逆銑交替掃描等策略進行沉積，以避免局部熱累積並改善供粉不均造成的表面凹凸，使堆疊形貌更為穩定一致。至於CHB方法，由於邊界幾何較為複雜，本研究提出底部螺旋路徑平整凹陷並以之字形路徑填補之策略；惟此路徑僅於軟體環境規劃，尚未實際驗證。
最終，針對UB實作修補區域所進行之橫截面分析顯示，沉積層與基材之間形成緊密且均勻的冶金結合，界面完整且未見孔洞或未熔合缺陷，充分驗證本研究所建立之DED修補流程具備高度可行性與可靠性，並展現其於實際工件修補應用之潛力。

Additive manufacturing (AM) has emerged as a promising technology, building components layer by layer by depositing material, melting it with a laser, and allowing it to solidify. Compared with conventional subtractive machining, AM offers reduced material waste, shorter processing cycles, and the ability to fabricate complex geometries. Two major AM methods dominate industrial applications: Directed Energy Deposition (DED) and Selective Laser Melting (SLM).
To improve deposition quality, the Taguchi method combined with Grey Relational Analysis (GRA) was employed to optimize multiple quality characteristics simultaneously. Five process parameters, namely laser power, overlap ratio, powder feed rate, scanning speed, and Z-offset, were investigated with respect to three quality responses: cladding efficiency, deposition rate, and porosity. Analysis results indicated that all five parameters significantly influenced the selected quality characteristics, and an optimal parameter combination was identified to achieve balanced performance. Subsequently, analysis of variance (ANOVA) was conducted to determine the significance of each factor, followed by one-factor-at-a-time (OFAT) experiments for further parameter refinement. Tensile testing was performed to validate the optimized parameter set, and the results showed that the ultimate tensile strength of the deposited specimens was only approximately 10% lower than that of commercial SS316L, demonstrating the feasibility of the optimized process parameters.
To further enhance the applicability of DED for damaged component repair, this study integrated 3D scanning and reverse engineering techniques to reconstruct an accurate STL model of a damaged workpiece. Two defect enclosure strategies, namely U-shaped Boundary (UB) and Convex-Hull Boundary (CHB), were proposed to define the debridement region. By slicing the model along the y-axis at intervals of 0.5 mm, damaged regions could be accurately identified and machining toolpaths generated to ensure sufficient deposition space after debridement. The UB method was experimentally validated using a fixed Z-offset deposition strategy, and the results demonstrated good interfacial bonding and stable deposition quality. In contrast, the CHB method was developed as a repair planning strategy for plate-type damaged regions, incorporating partition-based and toolpath-planning concepts for future applications involving more geometrically complex repair scenarios.
The optimized parameters were applied to repair processes. For the UB-based repair region, a combination of 45% Z-offset, alternating scanning directions, staggered starting points, and bidirectional scanning was employed to reduce thermal accumulation and improve surface uniformity. For the CHB method, a spiral toolpath was used to level the bottom region, followed by a zigzag strategy for material deposition, although this approach was only validated in simulation. Cross-sectional observations confirmed that the UB-based repair achieved sound metallurgical bonding without defects such as porosity or lack of fusion.
Overall, this study establishes an integrated DED repair framework combining reverse engineering, algorithm-assisted boundary design, Taguchi–GRA optimization, and path-planning strategies, demonstrating strong potential for practical repair of high-value metallic components.

[1]ASTM International, “ISO/ASTM52900-21 Standard Terminology for Additive Manufacturing-General Principles-Terminology,” ASTM International, West Conshohocken, PA, 2021.
[2]A. Gaikwad, S. Y. Choquette, T. A. Jobe, P. Wang, and S. S. Babu, “Multi Phenomena Melt Pool Sensor Data Fusion for Enhanced Process Monitoring of Laser Powder Bed Fusion Additive Manufacturing,” Materials & Design, Vol. 221, p. 110919, 2022.
[3]A. P. Chiriță, N. Țălu, R. Udroiu, and C. Oprean, “Leveraging Additive Manufacturing and Reverse Engineering for Circular Economy-Driven Remanufacturing of Hydraulic Drive System Components,” Applied Sciences, Vol. 13, No. 22, p. 12192, 2023.
[4]K. Chaudhary, and A. Govil, “Application of 3D Scanning for Reverse Manufacturing and Inspection of Mechanical Components,” Proceedings of the International Conference on Industrial and Manufacturing Systems (CIMS-2020): Optimization in Industrial and Manufacturing Systems and Applications, pp. 61-76, 2021.
[5]E. Piperi, I. Bodi, and A. Hoxha, “From 3D Scanning, Reverse Engineering to Real Part Production of Personalized Car Parts,” Machines. Technologies. Materials, Vol. 18, No. 3, pp. 97-99, 2024.
[6]X.-C. Zhang, W.-Y. Cui, W. Li, and F. Liou, “A Hybrid Process Integrating Reverse Engineering, Pre-Repair Processing, Additive Manufacturing, and Material Testing for Component Remanufacturing,” Materials, Vol. 12, p. 1501, 2019.
[7]P.-Y. Lin, F.-C. Shen, K.-T. Wu, S.-J. Hwang, and H.-H. Lee, “Process optimization for directed energy deposition of SS316L components,” The International Journal of Advanced Manufacturing Technology, Vol. 111, pp. 1387-1400, 2020.
[8]P.-Y. Lin, Analysis of Process Optimization and Microstructure Characterization of the SS316L in Direct Energy Deposition, Master Thesis, Department of Engineering Science, National Cheng Kung University, 2018.
[9]T. Kuriya, R. Koike, T. Mori, and Y. Kakinuma, “Relationship between Solidification Time and Porosity with Directed Energy Deposition of Inconel 718,” Journal of Advanced Mechanical Design, Systems, and Manufacturing, Vol. 12, pp. 104-114, 2018.
[10]W.-Y. Gao, S.-S. Zhao, F.-L. Liu, Y.-B. Wang, C.-Y. Zhou, and X.-C. Lin, “Effect of defocus manner on laser cladding of Fe-based alloy powder,” Surface & Coatings Technology, Vol. 248, pp. 54-62, 2014.
[11]C.-L. Zhong, T. Biermann, A. Gasser, and R. Poprawe, “Experimental Study of Effects of Main Process Parameters on Porosity, Track Geometry, Deposition Rate, and Powder Efficiency for High Deposition Rate Laser Metal Deposition,” Journal of Laser Applications, Vol. 27, No. 2, p. 022003, 2015.
[12]B. Zheng, J.C. Haley, N. Yang, J. Yee, K.W. Terrassa, Y. Zhou, E.J. Lavernia, and J.M. Schoenung, “On the Evolution of Microstructure and Defect Control in 316L SS Components Fabricated via Directed Energy Deposition,” Materials Science & Engineering A, Vol. 764, p.138243, 2019.
[13]A. Asghar, A. A. A. Raman, and W. M. A. W. Daud, “A Comparison of Central Composite Design and Taguchi Method for Optimizing Fenton Process,” The Scientific World Journal, Vol. 2014, p. 869120, 2014.
[14]Y.-T. Jou, W.-T. Lin, W.-C. Lee, and T.-M. Yeh, “Integrating the Taguchi Method and Response Surface Methodology for Process Parameter Optimization of the Injection Molding,” Applied Mathematics & Information Sciences, Vol. 3, pp. 1277-1285, 2014.
[15]L.-K. Pan, C.-C. Wang, S.-L. Wei, and H.-F. Sher, “Optimizing Multiple Quality Characteristics via Taguchi Method-Based Grey Analysis,” Journal of Materials Processing Technology, Vol. 182, pp. 107-116, 2007.
[16]G.-F. Lian, H. Zhang, Y. Zhang, M. L. Tanaka, C.-R. Chen, and J.-B. Jiang, “Optimizing Processing Parameters for Multi-Track Laser Cladding Utilizing Multi-Response Grey Relational Analysis,” Coatings, Vol. 9, pp. 356-368, 2019.
[17]G. K. L. Ng, A. E. W. Jarfors, G. Bi, and H. Y. Zheng, “Porosity Formation and Gas Bubble Retention in Laser Metal Deposition,” Applied Physics A, Vol. 97, pp. 641-649, 2009.
[18]H. Qi, M. Azer, and P. Singh, “Adaptive Toolpath Deposition Method for Laser Net Shape Manufacturing and Repair of Turbine Compressor Airfoils,” International Journal of Advanced Manufacturing Technology, Vol. 48, pp. 121-131, 2010.
[19]M. Ansari, A. Mohamadizadeh, Y. Huang, V. Paserin, and E. Toyserkani, “Laser Directed Energy Deposition of Water-atomized Iron Powder: Process Optimization and Microstructure of Single-tracks,” Optics and Laser Technology, Vol. 112, pp. 485-493, 2019.
[20]Y.-Y. Chang, J.-R. Qiu, S.-J. Hwang, “Multi-objective Optimization of Directed Energy Deposition Process by Using Taguchi-Grey Relational Analysis,” The International Journal of Advanced Manufacturing Technology, Vol. 120, No. 11-12, pp. 7547-7563, 2022.
[21]J.-R. Qiu, Y.-X. Chen, Y.-K. Hwang, W.-L. Chang, S.-J. Hwang, “Directed Energy Deposition Process Optimization and Factors Interaction Analysis by Response Surface Methodology,” The International Journal of Advanced Manufacturing Technology, Vol. 132, No. 11-12, pp. 5239-5350, 2024.
[22]Y.-X. Chen, J.-R. Qiu, W.-L. Chang, Y.-K. Hwang, S.-J. Hwang, “Process Optimization and Mechanical Properties Analysis of Inconel 718/Stainless Steel 316L Multi-material via Direct Energy Deposition,” Scientific Reports, Vol. 14, p. 28927, 2024.
[23]H.-L. Wei, F.-Q. Liu, W.-H. Liao, and T.-T. Liu, “Prediction of Spatiotemporal Variations of Deposit Profiles and Inter-Track Voids during Laser Directed Energy Deposition,” Additive Manufacturing, Vol. 34, p. 101278, 2020.
[24]A. Calleja, I. Tabernero, A. Fernández, A. Celaya, A. Lamikiz, and L.N. López de Lacalle, “Improvement of Strategies and Parameters for Multi-Axis Laser Cladding Operations,” Optics and Lasers in Engineering, Vol. 56, pp. 113-120, 2014.
[25]J. Flores, I. Garmendia, and J. Pujana, “Toolpath Generation for the Manufacture of Metallic Components by Means of the Laser Metal Deposition Technique,” International Journal of Advanced Manufacturing Technology, Vol. 101, pp. 2111-2120, 2019.
[26]M. Biegler, A. Marko, B. Graf, and M. Rethmeier, “Finite Element Analysis of In-Situ Distortion and Bulging for an Arbitrarily Curved Additive Manufacturing Directed Energy Deposition Geometry,” Additive Manufacturing, Vol. 24, pp. 264-272, 2018.
[27]Q.-C. Tang, S.-H. Yin, Y. Zhang, and J.-Z. Wu, “A tool vector control for laser additive manufacturing in five-axis configuration,” The International Journal of Advanced Manufacturing Technology, Vol. 98, pp. 1671-1684, 2018.
[28]T. Ünal-Saewe, L. Gahn, J. Kittel, A. Gasser, and J. H. Schleifenbaum, “Process Development for Tip Repair of Complex Shaped Turbine Blades with IN718,” Procedia Manufacturing, Vol. 47, pp.1050-1057, 2020.
[29]M. K. Keshavarz, A. Gontcharov, P. Lowden, A. Chan, D. Kulkarni, and M. Brochu, “Turbine Blade Tip Repair by Directed Energy Deposition Additive Manufacturing Using a Rene 142-MERL 72 Powder Blend,” Journal of Manufacturing and Materials Processing, Vol. 5, No. 1, pp.21, 2021.
[30]A. Saboori, A. Aversa, G. Marchese, S. Biamino, M. Lombardi, and P. Fino, “Application of Directed Energy Deposition-Based Additive Manufacturing in Repair,” Applied Sciences, Vol. 9, No. 16, pp. 3316, 2019.
[31]張守進，劉醇星與姬梁文，「半導體雷射」，科學發展，第349期，第14-21頁，2002。
[32]翁俊仁，許巍耀，施至柔與黃升龍，「綜觀高功率光纖雷射及其相關技術」，科儀新知，第158期，第13-23頁，2007。
[33]佚名，雷射技術讀本，台灣基恩斯股份有限公司，2015。
[34]L. Li, X.-C. Zhang and F. Liou, “Experimental and Numerical Investigation in Directed Energy Deposition for Component Repair,” Materials, Vol. 14, No. 11, p. 2999, 2021.
[35]T. Cailloux, W. Pacquentin, S. Narasimalu, F. Belnou, F. Schuster, H. Maskrot, C.-C. Wang, K. Zhou, and F. Balbaud-Celerier, “Influence of Trapezoidal Groove Geometry on the Microstructure and Mechanical Properties of Stainless Steel 316L Parts Repaired by Laser Metal Deposition,” Materials Science and Engineering A, Vol. 859, p. 144238, 2022.
[36]H. Kahya, H. Gurun, and G. Kucukturk, “Experimental and Analytical Investigation of the Re-Melting Effect in the Manufacturing of 316L by Direct Energy Deposition (DED) Method,” Metals, Vol. 13, No. 6, p. 1043, 2023.
[37]A. Ascari, G. Berselli, L. Fortunato, and L. Orazi, “Laser Directed Energy Deposition of Bulk 316L Stainless Steel,” Lasers in Manufacturing and Materials Processing, Vol. 7, No. 4, pp. 426-448, 2020.
[38]李輝煌，田口方法：品質設計的原理與實務，高立圖書有限公司出版，2011。
[39]蘇朝墩，「專訪世界品質大師：田口玄一博士」，品質月刊，第3期，第30-32頁，2004。
[40]溫坤禮，張簡士琨，葉鎮愷，王建文與林慧姍，MATLAB在灰色系統理論的應用，全華圖書股份有限公司，2006。
[41]E. Kivirasi, J. Martikainen, T. Mäntylä, and A. Mikkola, “Detecting Spattering Phenomena by Using High Speed Imaging in L-PBF of 316L,” Procedia CIRP, Vol. 94, pp. 398-403, 2020.
[42]A. Saboori, A. Aversa, G. Marchese, S. Biamino, M. Lombardi, and P. Fino, “Microstructure and mechanical properties of AISI 316L produced by directed energy deposition-based additive manufacturing: A review,” Applied Sciences, Vol. 10, No. 9, p. 3310, 2020.
[43]T. DebRoy, H.-L. Wei, J.S. Zuback, T. Mukherjee, J.W. Elmer, J.O. Milewski, A.H. Beese, A. Wilson-Heid, A. De, and W. Zhang, “Additive manufacturing of metallic components – Process, structure and properties,” Progress in materials science, Vol. 92, pp. 112-224, 2018.
[44]A.W. Hashmi, H.S. Mali, A. Meena, K.K. Saxena, A.P. Valerga, U.S. Rao, D. Buddhi, and K.A. Mohammed, “Design and modeling of abrasive flow finishing of freeform surfaces of FDM printed femoral component of knee implant pattern,” International Journal on Interactive Design and Manufacturing, Vol. 17, No. 1, pp. 445-457, 2022.