What Are They?
Think of the way in which the top of a wedding cake is built up: the icing is squeezed, like toothpaste, from a gun. Now reduce the scale by a factor of 100, and you have the basis of deposition-based rapid prototyping. The input – as with laser-based prototyping – is a cad file describing in the form of the component; the output is a single realization of the component in polymer or wax. The figure shows one variant of the technology.
In fused deposition modeling (fdm) a fine stream of thermoplastic or wax is deposited by a two-axis heated extrusion head. The semi-liquid polymer or wax is extruded from the heated head and deposited in layers, typically 0.1 mm thick, one layer at a time, starting at the base. Successive layers bond by thermal fusion. The process is well adapted to form abs and nylon and requires no post-curing (making it faster). Overhangs can be created without support because the polymer sets very quickly.
In ballistic particle manufacture (bpm) particles of molten thermoplastic are shot by a piezo-electric jet and freeze when they hit the object. The jet-head scans the surface, creating single layers at each scan, a range of thermoplastics and waxes can be used in the jet. In true three-dimensional printing the thermoplastic is jetted from a print head with up to 96 jets in a linear array, like an ink jet printer. The resolution is like that of the printer – about 300 dpi. The process, which is rapidly evolving, has the potential to build objects both accurately and quickly. All three processes can be adapted to deposit fine powders of metals or ceramics, though commercially available systems that do this are not yet available.
Solid or hollow complex bulk shapes.
Rapid prototyping systems are evolving very rapidly, and are already an essential part of the model-building capability of designers. Their speed and precision will increase and their cost will decrease in the future.
The cost of making an object depends on size and process – $500–$5000 gives an idea. This will decrease as faster systems become available.
Rapid prototyping is widely used in product design to realize a three dimensional model of an evolving concept.
No particular hazards.