Machine Design

Online RP comes to CNC parts

Sometimes stereolithography doesn’t cut it for making prototypes. This was the situation for a handheld communicator used by SWAT teams.

“The handheld’s plastic enclosure, which consists of three parts, was a tricky assembly,” says Kroll Associates president David Kroll. The Westerfield, Mass., product-development firm was on a tight schedule and needed to verify fit and function, while at the same time proving-out the electronic packaging. “Typically, we would have used stereolithography at this stage of prototyping,” he says. “But in this case, we needed a stronger part than STL could create.”

Kroll went to online facilities from Proto Labs, Maple Plain, Minn., where he got an automated quote and ordered a set of three machined plastic prototype parts. “The parts were well within fit tolerance of 0.010 in.,” he says. “Better yet, the quality was so good, the parts could have been mistaken for injection-molded components. So we ordered more parts and were pleasantly surprised to receive them in just two days.”

Kroll used the prototypes to get customer reactions. “Based on this feedback, we moved some internal bosses, repositioned a few internal walls, and expanded the case slightly to accommodate new, larger batteries,” says Kroll. “An additional set of prototypes from Proto Labs confirmed we had a finished product.”

Kroll submitted a 3D CAD model of the final part geometry to Proto Labs’ Protomold online-quoting service. As is often the case, design requirements for injection molding varied slightly from those for CNC machining. Protomold suggested several minor design changes regarding wall thickness and draft.

“It took just 30 days from when we ordered the parts to receiving the production, injection-molded components,” says Kroll. “Without Proto Labs, this part of the project could easily have taken six to eight weeks.”

Proto Labs,
Kroll Associates,

TAGS: 3D Printing
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