Keywords
Citation
(1998), "Rapid prototyping method", Assembly Automation, Vol. 18 No. 3. https://doi.org/10.1108/aa.1998.03318caf.008
Publisher
:Emerald Group Publishing Limited
Copyright © 1998, MCB UP Limited
Rapid prototyping method
Rapid prototyping method
Keywords Fabrication, Rapid prototyping
A rapid prototyping technique called contour crafting allows faster fabrication of large parts, and the products require less final finishing than other methods, reports the University of Southern California, Los Angeles, USA. Most current processes involve building three-dimensional objects one layer at a time, which results in rough edges. Thick layers produce a "laddering" effect, instead of a smooth surface, causing the prototype to look like a stack of discrete strips. Thinner layers minimize the effect, but increase the time and cost to build the prototype. Furthermore, conventional processes are limited to a volume of about 1.3yd3. In the contour crafting process, a material such as plastic is extruded through a nozzle under computer control, to build up layers. A pair of movable, flat, trowel-like control surfaces located above and at the side of the nozzle shape the extruded material before it sets, creating a thin, strong shell. A separate mechanism pours bulk material into the shell, layer by layer. Three additional parameters (two trowel orientations and the nozzle flow rate) must be specified, together with three spatial co-ordinates. This makes programming the system more complex, but its advantages outweigh its limitations. For example, a wide variety of materials may be chosen, including polyethylene, ABS, nylon, and other synthetic and specialized plastics that harden under UV light, fibre reinforced composites; plaster concrete; and powder metals in a binder. Large parts may be fabricated in about 10 per cent of the time required for other processes. The technique even has the potential to become a manufacturing process, says researcher Dr Behrokh Khoshnevis.
For further information contact: Eric Mankin, University of Southern California, 3620 South Vermont Ave, Los Angeles, California, 90089-2538. Tel: +44 (1) 213 740 9344.