Quality Applications

Rapid Prototyping Benefits Produces visual models and functional prototypes quickly Streamlines the design-and-development process Can process a wide variety of materials for assorted applications www.acceltechinc.com

Rapid Prototyping Helps Snowshoe Maker Refine Design
Rapid Prototyping

When Spring Brook Manufacturing of Grand Junction, Colorado, was ready to finalize the design concept of its new Saguache snowshoe, the company chose Accelerated Technologies Inc.'s (ATI's) rapid prototyping services to streamline the development process and meet tight marketing deadlines. Rapid prototyping helped Spring Brook create and produce the Saguache in only nine months, allowing the snowshoe to enter the market a full year earlier than it would have been able to otherwise.

 Spring Brook began the development process by sketching and then refining the snowshoe's design in AutoCAD and SolidWorks (a solid modeling tool that allows the creation of flowing, nonplanar surfaces). The company took the photorealistic design images to L.L. Bean, which agreed to jointly develop and market the Saguache. Spring Brook then contacted ATI and, three days later, received two selective laser sintering (SLS) prototypes (built from Spring Brook's 3-D CAD data) of the snowshoe deck.

 SLS is a thermal process that uses a laser to sinter (fuse) layers of powdered thermoplastic materials to form solid objects. The major advantage of using SLS instead of other rapid prototyping methods is that it can process a much wider variety of prototyping materials, including investment casting wax, polycarbonate, standard and fine nylon, and a powdered metal material for prototype injection mold production. Additionally, SLS produces a highly functional model--in this case, one that could actually be tested on snow. Spring Brook used these prototypes for the design review with L.L. Bean and displayed them at the first industry trade show of the season.

 After the successful show, Spring Brook produced and tested functional models of the complete assembly and then turned its attention to the bindings. For this application, the company used rapid prototyping in conjunction with room-temperature vulcanization (RTV) tooling, a fast and economical solution for prototype quantities of up to 100 parts. RTV tooling can produce as many as 50 parts per mold at a rate of three urethane castings to 40 urethane castings per day, taking as little as two weeks to move from CAD data to completed project. Cast urethane materials can mimic production parts in material properties, thermal properties, color and surface texture. ATI produced Saguache prototypes both for testing and for a complete design review that included an evaluation of the aesthetic appeal. Using the existing SLS prototypes, ATI fabricated an RTV mold for the snowshoe deck. The rigid urethane castings were produced in translucent green.

 Stereolithography (SLA) was used to build a master pattern with which to create an RTV rubber mold for the bindings. SLA uses photopolymer resins, cured in a vat through the application of ultraviolet laser energy, to produce solid objects. It creates complex 3-D models by successively "laser curing" cross-sections of liquid resin using data from surface or solid-modeling CAD systems. The liquid photopolymer hardens in the specific areas where it interacts with the ultraviolet laser beam, and the model is built layer by layer without tooling, programming or machining. It takes only a matter of hours for a design to move from CAD data to physical part, and the final prototypes offer a superior surface finish, small feature definition (capturing features as small as 0.010 in.) and high dimensional accuracy (±0.005 in. across critical part dimensions). The first urethane prototypes were cast in a Shore A 80 material that mimics the soft-touch, low-durometer production bindings, but they lacked the desired stiffness. A second set, cast in Shore A 90, was just right.

 Because it allows such a thorough design analysis, rapid prototyping eliminated the anxiety Spring Brook inspectors used to experience while awaiting first article. "Rapid prototyping greatly reduces the chances of error caused by human interpretation of the CAD file and blueprint," says Todd Grimm, ATI's director of marketing. "One of its primary benefits is that it produces an exact interpretation of what you designed." In Spring Brook's case, when the first shots came back, reviewers had only one surprise: The chevron pattern of the traction ribs was highly visible through the translucent Lexan. The reviewers were delighted; the silhouetted ribs lent the snowshoe the modern, high-tech look for which the manufacturer had been striving.

 To offer the snowshoe in its fall catalog, L.L. Bean required product photos in May 1999. Spring Brook didn't yet have production bindings, but L.L. Bean agreed that an SLA-created prototype binding was so detailed that it could be paired with the production deck for an attractive catalog display.

 Without rapid prototyping technology, Saguache's development process and market introduction would have been delayed by at least six months, which would have stalled the snowshoe's catalog debut by a year. "With respect to the time frame, rapid prototyping was critical," Grimm says.