The Fraunhofer Institute for Laser Technology ILT presented its results of the analysis of mechanical properties of generated aluminium components by selective laser melting at the international conference ICAA11 on 25 September 2008 in Aachen.
Aluminium alloys are largely used in all kind of industries, for example in the car industry, mechanical engineering and aerospace industry. For some applications the additive manufacturing technology represents an economical alternative to the various types of mould casting. For serial-identical functional prototypes, one-off parts or short-run batches, the selective laser melting (SLM) process enables to react faster to the customer's demand than by conventional processes. In close cooperation with industrial partner Festo, the Fraunhofer ILT has now demonstrated how it could reduce production times by SLM processes.
The additive process of SLM is used in the direct manufacturing of metallic functional components in various branches of industry. The SLM process fabricates metallic components – layer by layer – directly from 3D-CAD data. The primary objective when qualifying a material for SLM is to obtain a component density approaching 100 per cent without any cracks or fusion defects. This involves evaluating the required process parameters, especially scanning velocity and laser output power. Also an optional preheating process of the parts to decrease residual stresses and so to minimise crack building is analysed. The results of the research cooperation with industrial partners are promising. With a laser power of already 150W and a scanning velocity of 100mm/s densities approaching 100 per cent are achieved with AlSi10Mg parts.
At a laser power of 250W, the scanning velocity can be increased to 500m/s which consequently increases the build rate. Also various parts can be simultaneously manufactured layer by layer in the SLM plant. The results of tension and fatigue tests demonstrate that the mechanical properties are at least equivalent to the strength parameters of series-produced components made of die-cast AlSi10Mg according to EN 1706 specifications.