A Closer Look at Sonova’s 3D Printed Titanium Hearing Aids

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Most industries have been touched by 3D printing in one way or another, but few have been affected as much as the hearing aid manufacturing industry. The entire industry turned to 3D printing several years ago after global company Phonak began using the technology in the production of its hearing aids. Phonak, owned by Sonova, had such success using 3D printing that the rest of the industry quickly took notice, and before long 3D printing had essentially wiped out all other production methods in the hearing aid world. That’s certainly not something you see every day, and while most industries are integrating 3D printing into their production processes, they’re also finding that it’s a nice complement to other manufacturing methods, rather than a full-out replacement.

The hearing aid industry, therefore, will always stand out as an industry that tried 3D printing, found it to be better than everything else, and committed fully to it – and Phonak and Sonova will always stand out as the companies that shifted an entire industry. This year, Phonak celebrated its 70th anniversary, and reinforced its reputation as a manufacturer of the future with the release of its first custom titanium 3D printed hearing aid. While the introduction of titanium is brand new, the company has been 3D printing hearing aid shells in plastic for 10 years, and according to Patrizia Richner, digital manufacturing engineer at Sonova, they now can’t imagine doing it any other way.

Richner was one of the many speakers to present at the International Conference on Additive Manufacturing and 3D Printing, which 3DPrint.com attended last week in Nottingham, UK. Once Sonova and Phonak discovered the benefits of 3D printing, it was really a no-brainer to continue with it – particularly because of the customization it offers. Hearing aids are tricky devices, and if they’re not sized absolutely perfectly, there are going to be problems, Richner explained.

“If a hearing aid is 100 microns too large, your ear will feel the difference,” she said. “Not only in hearing, but you’ll feel it…if it’s too small, there will be acoustic leakage from the inner ear to the outer ear. The analog process we did before 2007-ish had really big drawbacks; we could not reproduce. If it was wrong, we had to start over at the beginning. With a digital process, we can just reprint the shell.”

Creating a well-fitting, well-functioning hearing aid is all about the specific needs of every individual, and there’s nothing automated about the design process – an actual person creates the model for each ear, placing the components individually and designing the shell.

“For an in-the-ear hearing aid, it needs to be as discreet as possible, so as small as possible — that depends on your ear canal shape,” Richner explained.

Sonova and Phonak have been using EnvisionTEC for their 3D printing needs for the last 10 years, ever since they began working with the technology. A tremendous amount of work went into developing the new titanium hearing aids; as Richner explained, introducing any new material – or even a different color – requires a heavy load of testing and qualification. Mechanical and physical properties are tested, including stiffness and strength, resistance to static and shock, elongation at break, and processability – i.e. how well the material can be bonded, trimmed or polished. Environmental resistance is also assessed, as a good hearing aid should last between three and five years, even while coming into contact with all sorts of factors such as UV rays, sweat, cosmetics such as sunscreen, and cleaning materials like isopropyl alcohol. Then there’s the purity and consistency of the 3D printing material from batch to batch, as well as the printing precision.

That’s a lot of effort for something so small, but according to Richner, it’s precisely because the devices need to be so small that so much effort has to be put in. Sonova has found that people would generally rather not wear a hearing aid at all than wear one that’s visible, so in order to properly correct hearing loss it’s crucial that the devices are small enough to be hidden in the ear canal. That’s tough to do without compromising on electronics, so for hearing aid manufacturers, it’s all about making the walls thinner, which titanium and 3D printing lend themselves well to. The standard thickness of acrylic hearing aid shell walls is 0.6 mm, while Sonova and Phonak’s target thickness is about 0.2 mm. Thinner walls allow for deeper placement in the ear canal, resulting in less visibility. Thinner walls also allow for more available volume for large vent channels, resulting in less occlusion and improved hearing comfort. There’s also more room for the integration of larger or additional components, such as battery receivers.

Phonak is now producing hundreds of the titanium shells every day, with about 60 per batch. With that many shells coming out of the 3D printer, it’s all too easy to get them mixed up, but the company is dedicated to making sure that doesn’t happen – because, again, a few microns can mean the difference between comfort and discomfort, effectiveness and ineffectiveness.

“The worst thing that could happen is sending a hearing aid to a customer when it’s not their shell,” Richner said. “We really have to avoid this and make sure it’s not the right one in 99.5% of the cases; it needs to be 100% of the cases.”

Phonak ensures accuracy by printing a four-character code on the inside of each titanium shell. Every innovation comes with a downside, and with mass customization, the potential for error becomes larger – but Sonova and Phonak are clearly committed to customer comfort and satisfaction, and are willing to put in the time and effort to make sure that every patient gets exactly what he or she needs. You can learn more about Phonak’s titanium hearing aids here. Discuss in the Sonova forum at 3DPB.com.

[All photos: Sarah Goehrke]


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