Effect of process parameters on thin-wall distortion in selective laser melting

Selective laser melting (SLM) is one of many 3D additive manufacturing (AM) techniques that uses a laser beam to fuse and melt powder materials together in the creation of metal parts. Although SLM offers greater design flexibility as compared to conventional manufacturing methods, fabrication of fine features and thin-wall structures is still challenging. This is because the rapid heating and cooling cycles inherent to the SLM process tend to generate large residual stresses, which may lead to severe plastic deformation in the part. The degree of distortion may be alleviated by tuning the processes, but there is a limit to how much the process parameters can be adjusted before the part density and/or integrity are compromised. In this research, we investigated the effect of four major process parameters – laser power, scan speed, hatch spacing, and layer thickness on thin-wall distortion. The amount of distortion in the thin wall was measured and analyzed against the original flat rectangular wall. Results showed that similar wavy and symmetrical thin walls were formed due to the buckling deformation, despite having the volumetric energy density varied between 25% and 200% of the optimal value for the material in this study. In addition, simulations on the thin-wall distortion were performed using the finite element analysis (FEA) and the outcomes were in good agreement with the experimental results. Finally, a design rule was proposed in order to mitigate thin-wall distortion problem in SLM process.