On the numerical simulation of the thermal behavior during the selective laser melting process

In the selective laser melting (SLM), components are manufactured layer by layer using an additive process. A laser beam is used as a heat source to fuse fine metal powder. The occurring temperatures during the process have a decisive influence on the manufacturing process itself and the consequential mechanical and technological properties. By varying process parameters such as the laser power, it is possible to influence the temperature level as well as the geometrical extent of the melting zone. A big issue of the selective laser melting technology is thermal distortion resulting in residual stresses that can lead to a fracture of the component. In this study the heat balance during the selective laser melting production process in terms of resultant stresses is analyzed using the Finite Element Method. For this purpose, the melting zones of one single layer are investigated numerically for an initial aluminium alloy process. Afterwards, the geometric extend of the zones are validated using microsections of manufactured components in order to optimize the thermal boundary conditions of the simulation model. The main features here are the path width, the layer thickness and the resulting overlapping zones of the individual melt pools. These preliminary identified findings are used to create a model to investigate the occurring residual stresses. With this analysis, on the one hand the qualitative correctness of the representation of the numerical stresses could be shown. On the other hand, the influence of laser-power and laser-spot-velocity on the component accuracy and so the formation of stresses are investigated by applying a parameter study.