New developments in the solid freeform fabrication of ceramic components

In the literature, the Solid Freeform Fabrication (SFF) of components is de scribed with a large number of terms and predominantly English abbreviation s. Essentially, the processes can be classed in four categories. Derived fr om stereolithography, in which light-sensitive polymers are polymerized by a laser beam and consequently solidified, 3-D printing was developed. In th is process, a component is built up in layers by the gelation of an aqueous ceramic suspension. A layered structure is also the key characteristic of another freeform fabrication process: the Layer Manufacturing Technique (LM T) uses ceramic tapes to build up components. This technique has been known for decades in advanced ceramics and forms the basis for the production of ceramic substrates and packaging for electronic applications. So far, the tape technique is the only freeform fabrication process to be developed up to the series production stage. In the layered build-up of ceramic componen ts with Shape Deposition Manufacturing (SDM), prototypes are fabricated fro m a mixture of ceramic powders and organic polymers, as also used in inject ion moulding. All techniques mentioned so far have the drawback that the or ganic additives must be burnt out prior to sintering. Very promising signs for a freeform fabrication of complex-shaped prototypes without organic add itives in the starting powders have come from Laser-Assisted Sintering (LAS ). After its design has been drawn up at a CAD workstation, a component is broken down again into individual layers. A directed laser sinters the indi vidual layers, successively building up the component. This method seems pa rticularly suitable for the manufacture of porcelain, but also for the fabr ication of advanced ceramic products. in this review paper, the different t echniques are presented and their applicability for ceramic products is dis cussed.