As part of an R&D Project, PolyMerge GmbH, TIWARI Scientific Instruments GmbH and Fraunhofer IKTS (the Fraunhofer Institute for Ceramic Technologies and Systems Dresden) have developed a process for additive manufacturing (AM) of multimaterial ceramic components – which can be heated up to 1400°C – for the contactless welding of plastic components through infrared heating. The AM process using electrically conductive ceramics was shown for complex heating elements.
In contrast to the state-of-the-art technologies, utilizing quartz glass or metal foil emitters, this new technology offers a much greater geometrical freedom and manufacturing flexibility thanks to 3D-Printing fabrication. The development goal of PolyMerge GmbH, Germany, a manufacturer of machines for plastic welding, was to develop complex emitters for contactless heating and joining of plastic components in short cycle times. A team from Fraunhofer IKTS, Germany, supported the development with its process and material know-how together with the 3D-Printing expertise of TIWARI Scientific Instruments GmbH
In the project, fused filament fabrication for ceramics (CerAM FFF) was used to produce customized emitters. The 3D printing of the various structures was carried out at a moderate temperature of 160°C, at a speed of 25 mm/s, and with a layer height of 150 μm. TIWARI Scientific Instruments GmbH, an ESA-supported startup in Germany, used a commercial 3D printer with a modified print head to additively manufacture the parts. Precise extrusion of the filament and very good adhesion with the print bed allowed the parts to be produced with high detail and no distortion. The applied manufacturing process allows a multi-component design. In this way, a combination of electrically conductive and electrically insulating ceramic material was used to produce the sophisticated heater structure.
The base material used for the AM of electrically conductive ceramics to produce the heating elements was silicon nitride (Si3N4), which was blended with electrically conductive molybdenum disilicide (MoSi2). This electrically conducting ceramic composite material has excellent high-temperature strength and withstands high structural loads even during heating. The second material of similar composition, but with a lower MoSi2 content, was developed to provide electrical insulation or to stiffen filigree structures of the conductive component. The electrically conductive and the electrically insulating material were combined into a two-component part by means of multi-material manufacturing. The challenge here was to ensure approximately equal thermal expansion and shrinkage of the two materials during the mandatory heat treatment up to 1800°C (debinding and sintering)
Another advantage of the selected ceramic composite and the fabricated multimaterial part is corrosion resistance. The electrically insulating material can also be used to protect the conductive component against corrosion, preventing oxidation and increasing cycle stability.
Besides applications related to contactless welding at PolyMerge, the technology and process shall also enable the manufacturing of components for aerospace applications, such as lightweight autoignition injectors and other similar applications in Propulsion subsystems.