A Specialized 3D Printer for the Hearing Aid Market

Three of these machines, however, have been positioned to produce one product, hearing aids. In this article we'll focus on the largest of the Perfactory series' hearing aid printers, the Perfactory 4 DSP (Digital Shell Printer) XL.

While hearing aids might seem to be a niche market they represents an excellent opportunity for additive manufacturing (AM). Given that everyone's inner ears are uniquely shaped, AM makes building customized medical devices much easier and less expensive.

Without 3D printing, designing a hearing aid was a laborious task. First, an impression of a patient's inner ear was made from silicon. With a custom silicon mold in hand, a technician would then create a positive of the patient's ear from which the hearing aids external shell would be produced. The entire process could take weeks if not months.

Today, the process for creating hearing aids has been revolutionized as these customized medical devices can be made in as little as a few hours thanks to 3D scanners, CAD software and most importantly 3D printing.

How the Perfactory 4 DSP XL Works:

Enviontec's Perfactory 4 DSP XL uses Texas Instruments' Direct Light Projection (DLP) technology to create models from a shallow pool of resin. Next, the CAD model has to be converted into layers by a pre-processing package. Then the printer can begin building a model layer by layer.

Because of its underlying DSP technology, which uses a stencil of light to cure resin according to a model's layer data, the DSP XL can produce models with remarkable resolution. Unlike other DLP AM systems that hold a reserve vat of resin from which a part emerges, the DSP XL builds its parts upside down. That eliminates the need for a resin bath. This technique reduces the amount of errant resin that binds itself to the outer edges of a print, ensuring that its layers stay as crisp as possible.

When the Perfactory 4 is outfitted with Envisiontec's Enhanced Resolution Module (ERM) it can create x and y steps with a 42 micron (0.017”) resolution (without the ERM layers can be programmed between 50 and 100 micron steps). When it comes to resolution in the z direction, the DSP XL really shines. It can build layers that achieve a 15 micron (0.0006”) resolution.

In addition to its high quality prints, the DSP XL can also build parts extremely quickly. Without any add-ons, the Perfactory will complete an entire tray of parts in 2 to 3 hours. If Envisiontec's high-speed module is added to the machine, the same tray can be printed in an hour or two.

The Perfactory does require some delicate post processing work once a print has finished. The support structures have to be removed by hand, making the last step of each job quite delicate and time consuming.

The Perfactory 4 DSP XL in Action:

GN Resound has been building hearing aids using a Perfactory 4 DSP XL since 2001. However, from 1943 until then the company used manual methods to manufacture hearing aids. Once Russ Schreiner, ReSound's Director of Development Engineering, heard about additive manufacturing, he knew the game had changed.

After trying out a number of systems by other big-name manufacturers, Schreiner and his team at ReSound decided that EnvisionTec's systems were the way to go. According to Schreiner “When EnvisionTEC equipment became available it was clear which choice made the most sense. The 3D printers from EnvisionTEC were just as accurate if not a little bit better than [other] equipment. They ran on less material, they had a smaller footprint and the ease of operation, as far as training operators and technicians on how to use the equipment was simpler as well.”

Today, ReSound operates a fleet (40 machines total) of Perfactory systems that churn out hearing aids on a near constant basis. Not only has AM taken much of manual labor out of building hearing aids, but Schreiner has notice a marked uptick in overall product quality. “Now with all of this digital processing, we've gotten away from all the manual inconsistencies [of the past] .” The bottom line is this, hearing aids are getting better because of 3D printing, and that means that many people's quality of life is also improving thanks to 3D printing tech.”