One sculptor has learned technology so well that he’s able to put it to use for his sculptures, selecting the right process for the right piece.
by Terry Persun, Technology Journalist
William F. Duffy is a professional sculptor known for his public and private works. He has been in the forefront of the foundry industry, casting high-temperature metals for more than thirty years. Mr. Duffy has also been a consultant for the CAD/CAM industry and has taught 3D computational graphics at the college level. So when he decides to use a particular technology, he knows what he’s doing.
Some of his more recent works include a few highly complex structures, including mathematical models. His work investigates 3D computational graphics to define and represent the underlying forms in nature. This has also led Duffy to produce pieces concerning the Anthrosphere, in which he melds traditional practices with his new mathematical models. According to his website, “Hyperbolically, the process of physical creation of the Anthrosphere epitomizes contemporary manufacturing technologies such as rapid prototyping and exemplifies the merging realms of information and nanotechnologies with fine art.
Along these lines, Duffy uses Stereolithography (SLA) models from Solid Concepts Inc. (Valencia, CA) as part of the QuickCast™ investment casting process. The QuickCast investment casting process includes the company’s in-house photopolymer created specifically for investment casting, and unique SLA build style. The company’s proprietary material features low water absorption to mitigate in-vat swelling and post cure distortion, high green strength for accuracy and to minimize the mass of the final patter, and low and stable viscosity to assure consistent drainage results and to keep costs down. Together, these benefits provide a material for investment casting patterns that works well with foundry processes to cast metal pieces.
QuickCast style patterns are designed on a 3D CAD system and saved to an STL file for use with SLA equipment. Solid Concepts creates a proprietary honeycomb pattern in the part geometry and the final design is uploaded to the company’s SLA machines where it is produced in a matter of hours.
Solid Concepts’ combination of a proprietary QuickCast build style, SC 1000 photopolymer material, and their clear coating process provides superior investment casting patterns for foundries, allowing customers to produce functional metal prototypes without producing hard tooling. This can typically be done at a third of the cost and in 10% of the time of traditional methods, such as using wax or wood patterns.
Quickcast patterns are up to 35% lighter than conventional SLA patterns, which translates to higher yield in the casting process. When those patterns are made from SC 1000 they also provide proportionately less ash and minimal thermal expansion forces during flash firing.
“I occasionally use the SLA part without casting, as well,” Duffy said. “Some of those sculptures get a quick lacquer coating, are spray painted, and put on display, like my Anthrosphere.” But much of the time, Duffy uses the SLA model as a step in using QuickCast in order to cast his sculptures into bronze.
When asked about post production work, Duffy explained, “I like to show the signature of the process on the surface of the work itself, so I don’t do any sanding or post prep except for the light lacquer coating mentioned earlier. I look at the striations in the built piece like a human fingerprint, only of the mechanical process. Sometimes you can actually see the polygon, the virtual structure of the geometry.”
Duffy also produces art projects using clay or plaster, just as he’s always done. “But there are some things you can’t do by hand,” he points out. “For example, the uniformity of a mathematical shape like my Compound of 5 Cubes sculpture. In rapid prototyping you can do things you can’t do by hand.”
Duffy’s latest Anthrosphere of human figures, is about 18-inches in diameter. “The beauty of SLA is that you can go big if you want to, and still keep the bulk and weight of the product down. Solid Concepts’ process also retains the accuracy of the CAD model. “That’s the beauty of working with Solid Concepts,” Duffy said. “I can receive a gigantic box from UPS that weighs so little that it feels empty. I know that I can go as big as I like without costs rising enormously. Plus, I get the sculpture fast, in only a matter of days.” He explains that each section of a larger sculpture is resolution independent—similar to digital photography only in three dimensions. The larger the piece, the more you have to consider making it hollow, to reduce the chances of shrinkage of a solid piece.
Duffy used to create several versions of a design on his CAD system before producing a part, but has now learned what the computer can do and seldom makes a prototype. He goes straight from the design table to production with full confidence in the technologies. “I can even make sculptures watertight if I want to,” he said.
Solid Concepts Inc.