Solid freeform fabrication of ceramics

Abstract

troversially that some processes may be materials speci c. It seems that the taxonomy of manufacturing Solid freeforming is a genus of manufacturing processes is not well organised from the student's processes in which three-dimensional objects are assembled by point, line or planar addition of point of view and awaits completion. In the casting material. Confining surfaces, such as mould or die category, which embraces sand casting, die casting, walls, are absent. The shape is built by adding injection moulding, solvent casting, slip casting and rather than subtracting material. Solid freeforming microcasting methods such as LIGA (Lithogra ehas come to be computer controlled over the past Galvanoformung-Abformung), a change of state two decades in parallel with the expansion of the occurs against con ning surfaces that de ne the shape. data handling capacity of personal computers. It The range of state change methods includes phase can be used for rapid prototyping but also offers change, solvent evaporation, chemical reaction and mass production pathways in which individuation phase separation. In deformation methods, dies, rolls is possible. It is of particular interest for the and formers are used for compaction, drawing, creation, inter alia, of prosthetics that can be individually built from modified X-ray computed forging, rolling and spinning. Most of these processes tomographic data. Some routes offer the are now enhanced by computer control. Machining additional capability to control, from the computer, operations include carving, turning, milling, electronot just the shape but also the composition discharge machining, laser machining and etching, throughout a component. Thus, three-dimensional while joining methods such as welding, soldering, functional gradients in multiphase ordered brazing, adhesive bonding and the use of fasteners composites become possible. The concept of allow prefabricated components to be assembled to 'design' now embraces the integration of the achieve a higher level of complexity. spatial variation of composition, microstructure Some processes are missing from this list. The and hence of properties together with the shape creation of a coiled pot from clay can be dated to the parameters for multifunctional materials. This is a vast and expanding field in which the first 5th millennium BC.7 It does not t these categories textbooks are emerging. A review of this type must but is the historical antecedent of a solid freeforming necessarily be focused. The emphasis here process known as 'fused deposition modelling' (q.v.) therefore is placed on ceramic processing. This in which the computer controlled travel of an extruder review attempts to set out the taxonomy of solid nozzle builds a shape from linear extrudate.8 It is also freeforming in an historical context, disentangling not quite so easy to classify brickwork. Houses are the multiplicity of process names that have arisen not made by building a large block of masonry and over the past two decades. Special emphasis is machi...

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