| 摘要: | 近年來，金屬積層製造技術在醫療、航空等各大領域皆有使用的需求。醫療業中，由於鈦金屬具有良好的生物相容性，利用積層製造技術以鈦合金代替骨頭植入人體，以利於支撐和固定肌肉組織。航空業則選擇積層製造技術製作複雜零件，通過拓撲優化減少零件重量，達到輕量化等目的。然而，金屬積層製造存在技術上的挑戰需要克服。
選擇性雷射熔融(Selective Laser Melting, SLM)為金屬積層製造技術之一。製作過程中，金屬粉末在高溫下被完全熔融，隨後冷卻固化。這一過程中，零件在不斷重複的加熱和冷卻狀態下成形，因此會有複雜的熱歷史。倘若過程中溫度梯度過大，金屬零件內部會累積相當程度的殘留應力，這可能在SLM過程中導致翹曲或其他缺陷的產生。因此，需要對過大的溫度梯度進行處理，以減少殘留應力的影響。
針對SLM製程中的翹曲問題，研究人員一般會調整雷射掃描參數，例如：雷射功率、掃描速度，並將其應用於實驗中。近年來，也有研究著重於掃描路徑來有效控制製程中零件之冷卻速率，進而影響零件之溫度梯度，或著重在掃描路徑設計，常見的調整方式包括改變掃描長度，或是採用區塊(方格)式的掃描，但這種方式在單層外型為特殊狹長面積時還是會造成溫度梯度過大。
本研究嘗試考量區域溫度的平穩性，藉由跳躍式的島式分割區域掃描方式，讓整層溫度能趨於平衡從而降低溫度梯度並改善翹曲。並利用橋曲率法驗證此策略製造之Ti-6Al-4V零件能否改善翹曲所造成的掃描瑕疵，以及利用X射線繞射(X-ray Diffraction, XRD)量測內部殘留應力。經由實驗顯示，本研究提出之策略所列印的樣本零件比起一般水平短路徑策略(由左掃描至右邊比起一般掃描，長度較短)平均翹曲角度從2.27度下降至1.5度，減少約33%，並且本研究所提出策略之樣本裂痕明顯少於一般水平短路徑策略之樣本，但經由XRD檢測樣本殘留應力兩件樣本皆在誤差範圍內
;In recent years, metal additive manufacturing has gained widespread adoption in key industries such as medicine and aerospace. In the medical field, titanium is highly valued for its excellent biocompatibility, allowing for the fabrication of titanium alloy implants that can replace bone structures and provide essential support and stabilization for surrounding muscle tissues. In the aerospace industry, additive manufacturing enables the production of complex components, leveraging topology optimization techniques to reduce weight and achieve lightweight design objectives. Despite these advancements, several technical challenges remain to be addressed in metal additive manufacturing.
Selective Laser Melting (SLM) is a widely adopted metal additive manufacturing technique in which a high-energy laser fully melts metal powder, followed by rapid solidification upon cooling. The fabrication process involves repeated heating and cooling cycles, leading to a complex thermal history. When the temperature gradient becomes excessively steep, significant residual stresses may develop within the component, potentially causing warping or other fabrication defects. Therefore, controlling temperature gradients is critical to minimizing residual stress and ensuring the structural integrity of the manufactured part.
To mitigate warping during the SLM process, researchers have optimized laser scanning parameters—such as laser power and scan speed—and validated these adjustments through experimental studies. In recent years, increasing attention has been directed toward the design of scanning path strategies. By optimizing these paths, temperature gradients can be more effectively controlled, thereby reducing the formation of residual stresses. Scanning strategies influence the part’s cooling rate, which directly affects the thermal gradient. Common approaches include modifying scan lengths or adopting grid-based (block) scanning methods. However, when dealing with layers characterized by narrow and elongated geometries, these strategies may still result in significant temperature gradients.
This study proposes a jumping island-based scanning strategy designed to improve regional temperature uniformity in the SLM process. By alternating scan locations across segmented sub-areas in a non-sequential manner, the strategy aims to balance the temperature distribution within each layer, thereby reducing temperature gradients and minimizing warpage. The effectiveness of this decision-making approach is evaluated using the bridge curvature method, which determines whether the fabricated Ti-6Al-4V parts exhibit reduced scan-induced warpage. Additionally, X-ray diffraction (XRD) is employed to measure the internal residual stresses within the printed components.
Experimental results demonstrate that the average warping angle of parts fabricated using the proposed strategy decreased from 2.27°to 1.5°, representing an approximate 33% reduction compared to the conventional horizontal short-path scanning strategy. Additionally, parts produced with the proposed method exhibited significantly fewer cracks. However, XRD measurements revealed that the residual stress levels in both sample types remained within the experimental margin of error. Finally, this study discusses potential improvements to the proposed strategy, providing a foundation for future refinement and development |
