An effective and efficient model for temperature and molding appearance analyses for selective laser melting process

The selective laser melting (SLM) process is an additive manufacturing technique that can fabricate three-dimensional workpiece by laser scanning and sintering of designated material in powder form on a preset scanning route along a bed of powders. This process involves a moving laser heating source which causes local transient mass and heat transfer with phase change, i.e., melting and solidifying, in a pool of melted powders. To fully investigate such a complicated transport process with reasonable computation cost, a novel quasi-transient numerical model (hopping model) was proposed and validated experimentally in this study. This approach includes a volumetric heat source defined as an elliptical Gaussian laser spot which hops along the scan path. Inconel 718 (IN718) superalloy powder is selected as the material for demonstration. Thermal analysis was carried out using a number of laser power and scan speeds in the range from 80 W to 120 W and from 80 mm/s to 140 mm/s, respectively. The comparison of molding appearance of the work pieces from the developed hopping model, full transient model, effective-transient model, and experiments illustrates the accuracy and the efficiency of the proposed hopping model. Molding appearance obtained from the quasi-transient model was consistent with experimental results with a relative error of less than 1.71% on the width of the IN718 stripes fabricated by SLM. For the cases analyzed in the current study, the quasi-transient model showed a 99% and a 60% reduction in both the computation time and the amount of computer memory needed compared to the full transient model and the effective-transient model, respectively. This novel quasi-transient simulation technique can be used to rapidly and effectively optimize process parameters for intelligent additive manufacturing.