Overhanging structure is an inherent geometric process limitation of selective laser melting( SLM), which would easily reduce the shape and dimension accuracy of built parts. To find the causes of defects in building overhanging surface,overhanging structure building experiments were carried out on 316L stainless steel at different inclined angle, scanning length and different speed. The results showed that at smaller inclined angle and the lower scanning speed, more serious warpage would happen, and the theoretical minimum building angle and reliable building angle fit with the experimental results at high and low scanning speed. High-speed scanning can build the overhanging surface with the minimum building angle, while low-speed scanning can only build the overhanging surface with a reliable building angle. Wrap of scanned overhanging surface would be more likely to happen along the long line direction. By control of local processing parametem, the quality of overhanging surface can be significantly improved. The basis for building overhanging surface by SLM was provided from the perspective of process and design, and the preliminary solution was proposed.%悬垂结构是选区激光熔化成型存在的固有几何限制,其容易导致成型件形状与尺寸精度变差.为了掌握悬垂面成型出现缺陷的原因,在自主研发的选区激光熔化成型设备上,采用316L不锈钢粉末,进行了高速与低速条件下成型不同倾斜角度和不同扫描线长度的悬垂结构实验.结果表明,倾斜角越小和扫描速度越小,翘曲变形越严重,理论分析了最小成型角度与可靠成型角度分别与高速扫描、低速扫描的实验结果吻合.高速扫描可成型具有最小成型角度的悬垂面,而低速扫描下只能成型可靠成型角度的悬垂面.悬垂面沿着长线扫描方向更容易发生翘曲变形.通过对悬垂面进行局部成型参量控制,可以明显改善成型质量.本研究从工艺与设计的角度为选区激光熔化技术成型悬垂面提供了依据,并给出了初步解决方法.
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