Synchronized Two-Beam Strategies for Selective Laser Melting

Additive Manufacturing, and selective laser melting in particular, are currently in the focus of various industrial sectors. The processes offer a far higher freedom of design than conventional manufacturing technologies which are already used in industry for decades or even centuries. The additive manufacturing technologies don't even need part specific tools to offer these benefits. Yet, porosity, anisotropy, evaporation and spattering, surface roughness as well as distortion and cracking are inherent problems which are holding the processes back from being used to a larger extent. The presented thesis is taking part in the search for a promising strategy to get rid of those inherent problems within the selective laser melting process by investigating innovative irradiation strategies. These strategies are defined by the use of two synchronized laser beams which are focused to the same scan field. This can be used to change the effective intensity profile within the vicinity of the melt pool or to implement completely new strategies like a point-wise heating strategy. Since no common machine offers the use of these strategies, the concept and use of a self-developed and built up laboratory machine is presented in before. The experimental investigation of these strategies is supported by the use of a numerical model which is covering the temperature and fluid flow simulation on melt pool scale. In before the use of the numerical model it is validated. The validation shows a good accordance of the model with experimental results which can be accounted to the implementation of the absorption model that allows the differentiation of various material configurations while working on a quite coarse grid. The experimental investigation of synchronized two-beam strategies shows that when using a defined offset of a melting beam to a heating beam it is possible to reduce spattering if the heating beam is moving in front of the melting beam. In case the heating beam is following in a certain offset a in-situ smoothing of the surface can be realized. In contrast, when using a point-wise heating strategy global effects can be induced to the part that can be used to reduce distortion and cracking