Chemical solid free-form fabrication: Making shapes without molds

Solid free-form fabrication methods are surveyed. This approach of making objects by depositing material layer by layer lends itself to the direct conversion of fluid reactants to a solid part, as opposed to the production of a material and its subsequent processing. Examples are given of the formation of ceramics, metals, thermoplastics, thermosets, and composites. In principle, mobile products can be removed from the layers as they form, allowing a much wider range of reactions to be used. Since the composition may be varied as the object is built up, it is also possible to combine several materials into a monolithic piece.