Rapid-injection molding delivered complex prototypes to Tensys Medical Inc., San Diego, (tensys.com) in six days to support product-development programs. The company designed T-Line, an unusual beat-to-beat blood pressure sensor that would be difficult to manufacture. But a quick turnaround on the RP parts gave the team more time to test the design and make it easier to assemble. Rapid prototyper Protomold Co., Maple Plain, Minn., (protomold.com) used proprietary software and high-speed NC machining to make injection-molded parts in production materials.

Protomold's online ProtoQuote also guided Tensys engineers in working within the specs for rapid injection-molding, highlighted where wall thickness was significantly greater or less than nominal, and pinpointed where draft was less than three degrees, making it impossible to add textures. Tensys submitted an order for 25 revised sensor-frame prototypes. “Protomold shipped parts while a tool maker struggled to produce a workable mold,” says Tensys senior engineer Russ Hempstead.

The design's unusual geometry posed a challenge for Tensys' traditional prototyping and manufacturing techniques. “Large wall-thickness variations and sharp transitions make the sensor frame difficult to mold,” says Hempstead.

Although urethane castings provided a conceptual design check, limited material selection and short tool life became design constraints. What's more, the design's unconventional geometries kept Tensys' tool vendor from constructing the tool properly. As a result, the tool created lots of flash — excess material that “leaks” into parting surfaces. “Flash means manually trimming each part,” says Hempstead. “That's unacceptable.”

“Simply uploading a CAD file to the site and adding a few detailed notes easily cut 50% off the time I typically spend on quotes,” says Hempstead. “A different molder would have meant dealing with CAD compatibility or 2D drawing requirements,” he says.