The Fraunhofer-Center HTL develops and manufactures components made of ceramics, metal and metal-ceramic composites using additive manufacturing, commonly referred to as 3D-printing. Standard materials are e.g. aluminum oxide, zirconium oxide as well as silicon carbide and steel. The technology field of additive manufacturing includes the development of new material systems and manufacturing processes, the production of prototypes and small series as well as the quality management of additively manufactured components.
The development of new material systems includes the formulation and synthesis of feedstocks for 3D-printing. The aim is to adapt the processing properties of the feedstocks for the 3D-printing process used so that components can be manufactured with high quality and at the same time the material properties desired by the customer are achieved. Examples of this include setting the pourability of powder batches or adjusting the flow properties of slurries for additive manufacturing.
Quality management in additive manufacturing is of crucial importance for the later use of the processes in industrial production. The Fraunhofer Center HTL develops processes for in-situ control of the individual process steps during 3D printing. One focus of quality management is to achieve the most homogeneous and defect-free structure possible in the green body and in the sintered component, as well as the control of the heat treatment processes.
The Fraunhofer Center HTL produces prototypes and small series on behalf of customers. The customer inquiries are first checked for feasibility. Upon customer request, recommendations for the construction of components can also be made. For the 3D printing of the components, two complementary, modern, additive manufacturing processes are available in the form of a stereolithography printer and a powder bed printer (see Nachum, S.; Vogt, J.; Raether, F.: Additive Manufacturing of Ceramics: Stereolithography versus Binder Jetting). In addition, HTL is developing new additive manufacturing processes that promise particularly high material quality.
In both of the 3D printing processes for ceramics, metals and metal-ceramic composites that have been used at the HTL center so far, the heat treatment is deliberately separated from the molding process. This avoids some known difficulties of other additive manufacturing processes such as thermal stress and warpage e.g. in selective laser melting. This procedure also opens up additional possibilities for material synthesis. The open-pore preforms after the 3D printing process can then be infiltrated with molten metal, for example. In addition, the separation of shaping and heat treatment allows a cost-effective parallelization of the partially. time-consuming heat treatment for large batches. The heat treatment processes can be carried out in different furnace atmospheres and optimized using the ThermoOptical measuring devices (TOM) available at the HTL (see Thermal processes). After the heat treatment, the functional surfaces are finished using a 5-axis machining center. In addition, the 3D-printed components can be integrated into larger systems using special joining processes.