積層製造中的選擇性雷射熔融在製造複雜的幾何形狀有很大的潛力。然而越是複雜的幾何形狀，其懸浮面也越多。而懸浮面在選擇性雷射燒熔中是最困難的部分。而造成懸浮面極為困難的三大要因為分別是階梯效應、翹曲與殘渣的生成。這些缺陷會導致下表面的粗糙度粗糙和翹曲甚至是斷裂，進而導致實驗的失敗。因此本研究建立一套找出水平懸浮面最佳雷射參數區域的方法。此套方法是根據一個模擬懸浮面的三維熱傳模擬，並考慮粉末和塊材中材料性質與雷射吸收率的差異。透過觀察模擬中熔池的深度、熔池的長度和固體冷卻速率找出最佳的區域。並藉由替代模型預測模擬的結果和減少計算所需的時間。此外本研究還探討在大面積懸浮面中不同掃描策略的結果。而根據實驗的結果，10x10mm2和20x20mm2的懸浮面已經印製完成，而標準參數印製的區域的密度高達99.78%。除了水平懸浮面之外，本研究也探討45度懸浮面的表面粗糙度。下表面的表面粗糙度能夠到達16μm，而且密度保持在99.81%。

Additive manufacturing such selective laser melting has much potential to produce unique parts with complex geometry in a short time. However, there is lots of overhanging surface in complex structure and overhanging structure is the hardest part in selective laser melting. The main defects of overhang surface are staircase effect, warpage and dross formation. They would cause bad surface roughness and crack in overhanging surface. Therefore, a method is created to optimize the laser parameter zone for overhanging surface in this study. A three-dimension heat transfer simulation is built to simulate horizontal overhanging surface. Material properties difference between solid and powder is considered. And the absorptivity difference along depth of powder layer is also considered. The surrogate model is built to predict simulation results to build processing map and thus reduce the computational time. According to the criterion in melt pool depth, melt pool length, and solid cooling rate, the optimal zone in processing map is built for reducing dross formation and improving process ability in overhanging structure. And three different scanning strategies for overhanging strategy are studied. According to experimental results, 10x10mm2 and 20x20mm2 horizontal overhanging structure is built. And the density which is printed by standard parameter can reach 99.78%. Besides, in this study, a 45 degrees inclined surface is studied. The overhanging surface roughness can reach 16μm and density is 99.81%

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