Solid freeform fabrication of ceramics

Abstract

Solid freeforming is a genus of manufacturing processes in which three-dimensional objects are assembled by point, line or planar addition of material. Confining surfaces, such as mould or die walls, are absent. The shape is built by adding rather than subtracting material. Solid freeforming has come to be computer controlled over the past two decades in parallel with the expansion of the data handling capacity of personal computers. It can be used for rapid prototyping but also offers mass production pathways in which individuation is possible. It is of particular interest for the creation, inter alia, of prosthetics that can be individually built from modified X-ray computed tomographic data. Some routes offer the additional capability to control, from the computer, not just the shape but also the composition throughout a component. Thus, three-dimensional functional gradients in multiphase ordered composites become possible. The concept of 'design' now embraces the integration of the spatial variation of composition, microstructure and hence of properties together with the shape parameters for multifunctional materials. This is a vast and expanding field in which the first textbooks are emerging. A review of this type must necessarily be focused. The emphasis here therefore is placed on ceramic processing. This review attempts to set out the taxonomy of solid freeforming in an historical context, disentangling the multiplicity of process names that have arisen over the past two decades. Special emphasis is placed on multilayer printing methods, because they have tended to be neglected in popular reviews, and upon applications in the medical arena, because they, among all possible applications, demand the individuation that solid freeforming can offer.