The effect of scan path on thermal gradient during selective laser melting

High thermal gradients during selective laser melting (SLM) can generate residual stresses due to uneven volumetric expansion, which can lead to weak or cracked parts. In SLM, scan path refers to the route the laser takes during a single layer of solidification, and has a direct impact on thermal gradient, and by association residual stress. This work uses a finite element model to compare the thermal gradients generated by nine different scan paths, six of which have been tested and discussed in literature, and three of which are proposed in this document. This study found that scan paths which subdivide powder layers into smaller areas were found to produce fewer areas of high thermal gradient, as well as a lower total average gradient when compared to paths that scan the full layer without subdivision. One of the new scan path concepts, named the “subsectioned spiral method”, produced the most favorable results. Of the six non-transient data categories retrieved, the subsectioned spiral scan path outperformed all eight other paths, with improvements ranging between 6 and 44% compared with the baseline path.