Using modern 3D printers, Fraunhofer-Center HTL designs and manufactures custom-specific components from various materials. The 3D printing at the Fraunhofer-Center HTL aims not only at the rapid and cost-effective production of prototypes and small series, but it also focuses on the development of new design opportunities for ceramic, metal and metal-ceramic composites. For this purpose, two complementary, modern additive processes are available with a stereolithography printer and a powder bed printer (see Nachum, S.; Vogt, J.; Raether, F.: Additive Manufacturing of Ceramics: Stereolithography versus Binder Jetting).
Using stereolithography, very high green densities are achieved, which leads to a high strength of the produced components. The spatial resolution of the method is very high due to the small primary particle size (<1 µm) and the homogeneity of the applied slurries. The process is limited to light transmitting slurries and therefore not suitable for the 3D printing of metals.
On the other hand using the powder bed process, metallic components can be produced. Since fluid powders (> 10 µm) are required, the microstructures are coarser than with the stereolithography process. The green density is significantly lower, which increases the requirements on the subsequent heat treatment process. The 3D printing version used at the Fraunhofer-Center HTL binds the powder particles through the binder-jetting process. An advantage of the powder bed process is the greater flexibility in the applied raw materials in comparison to the stereolithography process. A further advantage is the larger installation space of the powder bed printer.
Regarding both 3D printing methods used at the Fraunhofer-Center HTL, the heat treatment is intentionally separated from the molding process. This avoids some of the known problems of other 3D printing processes - for example, thermal stresses and distortion in Selective Laser Melting. It opens up new possibilities for materials synthesis. Preforms with large pores produced in the powder bed process can be subsequently infiltrated with molten metal. In addition, the separation of forming and heat treatment allows an economic parallelization of the time-consuming heat treatment for large batches. The heat treatment process can be performed in different furnace atmospheres. It is optimized using the thermoOptical Measuring devices (TOM) available at the HTL (see Thermal Processes).