Like a fingerprint, an individual's ear canal is entirely unique in size and shape. For this reason, the fitting of a hearing aid has to be customized and shaped to precision. For years, this was a highly inexact science and extraordinarily time-consuming.

But that's not the case anymore. Today, the contours of a patient's ear can be digitized in CAD/CAM software within minutes. In just a few hours, a custom-fitted hearing aid shell can then be created from liquid photopolymer. All this is made possible by advances in rapid prototyping.

As a technology, rapid prototyping has been around for 25 years. Initially, it served as a breakthrough to speed up product development, allowing engineers to see and hold a physical representation of a design. What's changed is that engineers aren't the only ones using rapid prototyping. Nor is it limited to just prototypes.

A prototype of automotive car headlights produced from 3D Systems' Accura 25 Plastic is ready for functional testing.

The technology has now crossed the barrier into rapid production as a result of improvements in accuracy, repeatability and predictability, according to Abe Reichental, CEO of 3D Systems Inc., a maker of three-dimensional imaging and rapid prototyping systems. Equally important, rapid prototyping can now produce with a wider array of materials.

"You're seeing it in the production of hearing aids because the technology offers a freedom of creation," says Reichental. "Its ability to accommodate biomechanical materials makes it uniquely suited for hearing aid devices. You're also seeing its use in dental applications for crowns and bridges."

Rapid prototyping can help manufacturers produce several thousand parts at a time in short turnaround, bridging the gap between when a part design is finished and when it goes into production.

Rapid prototyping broke through commercially in the automotive industry in the late 1980s. In recent years, it's found a wider audience and broader application. Medical companies, for instance, are able to produce patient-specific knee replacements using CT scan data. The technology has been used to manufacture air ducts, conduits and a variety of panels and dashboards for the commercial and military aircraft industries.

Perhaps the most significant advantage of rapid prototyping evolving into rapid manufacturing is that it can help bridge the gap between when a part design is finished and when the part goes into production. If, for example, a company needs several thousand parts molded while waiting for tooling to be made, production parts can be rapidly manufactured to jump-start the process.

Both rapid prototyping and manufacturing use additive manufacturing, a process of creating a physical object through selective fusion, sintering, or polymerization of a material. A design is created using a CAD program which controls the building of a part layer by layer with powdered material.

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