Influences of sheet-like and rod-shaped support structures on horizontal overhang fabrication in SLM: a comparative study

Different types of support structures are usually added in selective laser melting (SLM) to address the challenge of fabricating horizontal overhang structures. This challenge comes from the powder bed’s weak thermal conductivity, which causes temperature retention in the overhang region and further induces residual stress and deformation of the formed part, and the support structures work by assisting in heat dissipation and limiting deformation. To provide necessary guidance for their selection and design, this study summarily classified all the support structures in SLM into two main types, sheet-like and rod-shaped, and then compared their effects on the fabrication of the horizontal overhang through finite element simulation and SLM experiments. The results show that due to the weak thermal conductivity of the powder bed, direct laser irradiation of the material on it is prone to temperature retention. Compared to rod-shaped supports, interconnected sheet-like supports exhibit superior thermal conductivity, accelerating temperature homogenization in the overhang. Higher temperature gradients and residual stresses occur as a result. However, due to its higher structural rigidity, after the third layer was completed, the maximum deformation of the overhang with sheet-like supports is 13.5 μm, which was much smaller than that of 30.7 μm with rod-shaped supports. Subsequent SLM experimental results also confirmed similar conclusions.