Running on Trac

Urethane parts help exercise equipment manufacturer meet prototype production deadlines

Often the long turnaround times from vendors — not design time — are what postpones final test, production and shipping. As speed to market critically affects sales, when Star Trac, Irvine, CA, found the shipping of their Elliptical EDGE jogging trainer was waiting for three essential rubber components — footpads and grommets — they had to move quickly. Hard tooling for the footpads was under way, but the normal 16-week turnaround for tooling was going to take much longer. An alternative method had to be found for the equipment to make it to market on time. Because fitness centers buy equipment for look as well as function, the foot pads had to have the right texture, feel comfortable to the user, offer the appropriate wear characteristics, and provide a consistent look from one machine to another. 

Solid Concepts, a rapid prototyping service in Valencia, CA, was called in to provide quick turnaround for the small quantities needed. They recommended cast urethane parts created from silicone rubber tooling to provide the look and feel of injection-molded parts. According to Dave Cawley, engineering manager at Solid Concepts, “Quickly producing hundreds of urethane castings with the quality and consistency of injection-molded parts requires a level of sophistication well beyond what is usually needed for one or two urethane castings.” 

The grommet, a flanged L-shaped component, was difficult to work with because of its complexity. The footpads, on the other hand, were the most visible components needed, so aesthetics were important. The final texture and color of each 13- x 6–in. footpad had to be identical for each machine so that when lined up on a fitness room floor there would be no evident difference between them. Repeatability and consistency of the production parts was a must, but in order to meet the production schedules, multiple patterns and multiple silicone molds were required. “In a production environment, only very high-volume parts are produced from multiple molds, so repeatability and consistency is not as difficult to achieve,” said Cawley. Nonetheless, Cawley found that new urethane materials formulations, special equipment and procedures would enable Solid Concepts to meet performance and quality specifications, while still getting the first 400 prototype machines off the shipping floor in time.

—SG

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