Discontinuity of overhanging melt track in selective laser melting process

• Main Authors: Le, Kim Quy, Wong, Chee How, Chua, Gregory Kok Hong, Tang, Chao, Du, Hejun
• Other Authors: School of Mechanical and Aerospace Engineering
• Format: Article
• Language: English
• Published: 2020
• Subjects: Engineering::Mechanical engineering; Additive Manufacturing; Selective Laser Melting
• Online Access: https://hdl.handle.net/10356/143562
• Institution: Nanyang Technological University

This study shares a side-by-side numerical and experimental examination on the features of overhanging structure in the SLM process. The simulation model was achieved by incorporating Fresnel reflections in the laser beam through the ray-tracing model. The CFD model was employed to investigate different overhanging situations, including perpendicular and parallel overhanging melt tracks on a cuboid block, as well as parallel melt tracks on an inclined block. The process parameters are found to strongly affect the surface morphologies of the overhanging melt track where voids caused by interfacial instability and geometrical defects namely discontinuities were observed. The subsequent defects caused by the discontinuity have also been investigated in both simulation and experiment. In the range of this study, it found that high laser power alleviates the discontinuity phenomenon of the overhanging melt track. However, by applying high laser power at high energy density, the high value of melt pool depth was formed, causing warpage to the overhanging printed part. Nevertheless, employing high laser power while maintaining low energy density can eliminate phenomenon such as irregular pores, partially-melted powder, deep melt pool formation and geometrical inaccuracy.