Emerging Architectural Potentials of Tunable Materiality through Additive Fabrication Technologies
standardization efforts are under way to further expand implementation into industrial and potentially architectural production cycles.8
1.1.2 Application of additive fabrication I: Rapid Prototyping (RP) Rapid Prototyping is a group of technologies that follow the additive fabrication principle of layered material assembly. Common synonyms include: 3D Printing, Freeform Fabrication, Solid Freeform Fabrication, Layered Manufacturing and Stereolithography. Yet most of these are imprecise. The application of RP is generally restricted to representative or model functionality. Medical prototyping can serve as a training and didactic tool for complicated medical operations (Suzuki et al. 2004), (McGurk et al. 1997) and the functional testing of rapid manufactured prostheses through coupling with CT data. Industrial design uses the technology for product development in scale and for basic functional testing (Avrahami and Hudson 2002). The first commercially available rapid prototyping machine, called SLA-1, was developed in 1988 by 3D Systems (Rock Hill, SC). The technology was coined “Stereo Lithographic Apparatus” and operated with local UV laser-based solidification of a liquid photopolymer resin to generate parts. The stereolithographic process was abbreviated SLA and was patented in 1990 by Hull (1990). Today SLA, along with “Selective Laser Sintering” (SLS), represents the most prominent RP technology for high-quality, large-scale objects using a broad spectrum of materials. The concept of a layered assembly of material, based on a digital model, nevertheless already existed long before 3D Systems’ first machine was developed. In 1971 Wynn Kelly Swainson filed a patent for a manufacturing system that contained the key elements of the later SLA technology. His patent was finally approved in 1977 and described a “Method, apparatus and product in which a three-dimensional figure is formed in situ in a medium having two active components by causing two radiation beams to intersect in the media. The dissimilar components are selected to respond to the simultaneous presence of the beam and to either react or to produce reactants which render the intersection of the beams physically sensible or distinguishable. The beams trace surface elements of the figure to be produced.” (Swainson 1977) 1991 saw the arrival of three new additive technologies: Fused Deposition Modelling (FDM), Solid Ground Curing (SGC),9 and Laminated Object Manufacturing (LOM).10 A year later Selective Laser Sintering (SLS) became available on the market. The technology was originally developed at the University of Texas, and patented11 in 1989 by Carl Deckard and commercialized by DTM Corporation, now 3D Systems. The SLS rapid prototyping process uses the heat of a CO2 laser to “sinter” or melt powdered thermoplastic materials at high temperatures, but powdered materials such as ceramics and metals are also feasible in layers of 0.1mm-0.15mm. The CO2 laser is guided across the part bed by a scanning system and “selectively” sinters or melts the material based on cross-sectional slice information from the 3D CAD data file. The parts are built in an atmosphere that controls the thermal distribution and thus requires very little laser power to sinter the material. The powder in the build chamber acts as a support for the part during fabrication and no additional support structure is 8
An unpublished proposal for ISO classification of additive fabrication processes headed by the manufacturer EOS GmbH and
DIN (Deutsche Industrie Norm) can be found here (EOS GmbH/Deutsche Industrie Norm 2010). 9
The SGC process uses photosensitive resin hardened in layers similar to stereolithography. The SGC process is considered a
high-throughput production process as each layer of photosensitive resin is hardened immediately. 10
In the LOM process cross sections from a digital model are cut from paper using a laser. The paper is unwound from a feed
roll onto the stack and first bonded to the previous layer using a heated roller that melts a plastic coating onto the bottom side of the paper. Waste paper is wound on a take-up roll. After a period of technological stagnation, LOM-based manufacturing technology has been further developed recently by Mcor Technologies (2011). 11
Deckard 1989 30