Rapid Prototyping of Ceramic Structures
Rapid prototyping (RP) is a well established technique for the fabrication of polymeric and metallic prototypes. The fabrication of ceramic prototypes is still limited due to the lack of the achieved surface quality and the insufficient mechanical properties of the final ceramic parts.
To increase the solid loading of the green part and in order to avoid pores and cluster formation of powder particles, a slurry based process seems to be inevitable. In the course of this project two different RP-technologies are adapted ,so that a high solid loading (> 50 vol%) can be reached. This leads to parts with a sintered density up to 99,5 %, which is difficult to achieve with techniques which directly process dry powder (e.g. laser sintering, 3D-printing).
One process is based on photosensitive ceramic filled resins, which can directly be cured by a laser scanning system (e.g. stereolithography) or by digital mask projection. Alumina parts with a layer thickness of 25 µm have been produced. It has to be ensured that the light is not absorbed by the ceramic, which can only be guaranteed for oxide ceramics. Another disadvantage is the need for supporting structures for overhangs, which have to be removed mechanically. Internal overhangs are therefore difficult to manufacture.
Gelcasting in combination with RP-processes overcomes these disadvantages, but it is not a direct fabrication process. A negative wax mould is built with a wax-printer (Solidscape’s Benchtop T612) and a low viscosity slurry is filled in the mould and thermally cured. With that process every powder can be used and very high solid loadings (up to 65 vol%) are attainable. In Figure 1 a concept model of a silicon carbide cross flow filters with internal overhangs is shown, Figure 2 depicts an alumina screws for cruciate ligament fixation.