Task
Multi-material components are composite materials which consist of areas of different, polymeric materials with different properties. For realization, the laser beam melting as additive manufacturing technology is used which enables to build parts from thermoplastic powder materials with arbitrary geometry without using additional tools. Currently, however, parts can only be built out of a single material. The fabrication of multi-material components would open up new application, but requires creative solutions for further development of the technology.

Approach
In order to generate multi-material components, new powder layer preparation methods and exposure strategies are investigated. The powder preparation methods shall enable the flexible deposition of heterogeneous powder layers (e. g. different thermoplastics) with clearly defined interfaces between the different powder materials. Processing of these layers requires locally differing heating temperatures as well as an energy deposition which are adapted to the respective materials. This can be realized by a simultaneous, intensity-selective exposure strategy in which a micro-mirror array is applied in order to realize the required spatial-temporal optical power density.

Results
Promising results were achieved by using a vibrating nozzle setup for the deposition of very small powder quantities with high selectivity. Moreover, an experimental setup was built up which enables the investigation of electro-photographic powder layer preparation. The laser energy deposition into the powder bed is mainly defined by the absorption properties of the powder materials. Hence, an integrating sphere setup was used to determine the optical properties of different powders at a wavelength of 10.6 μm (CO₂ laser). By this a more efficient qualification of new powder materials for the laser beam melting process is possible due to the adaption of the processing parameters to the optical material characteristics.