At the beginning of this millennium, Sonova was one of the first companies in the world to employ innovative 3D printing technology for production. Today, 3D printing has long been the standard at Sonova: All the shells for custom in-the-ear hearing aids as well as various custom earpieces for behind-the-ear and receiver-in-canal hearing aids are produced using 3D printers. This enables the shape of the shell to be tailored optimally to the wearer’s individual ear canal and degree of hearing loss.

Mass-produced custom-made products 

Sonova has been advancing the industrial use of 3D technology for many years. At the beginning of the millennium, Sonova was one of the very first companies to start digitally producing shells for custom in-the-ear hearing aids, followed by custom earpieces for behind-the-ear and receiver-in-canal hearing aids. At the time, this pioneering technology represented a breakthrough in the modernization and digitalization of hearing-aid manufacturing. Previously, production had been the sole preserve of modelers who finished each unique piece by hand in a time-consuming and costly process. Digital manufacturing of custom in-the-ear hearing aids started in 2001/2002. Engineers developed the necessary tools – scanner, software, and printer – and then these were adapted to Sonova’s specific requirements. In the years following, the technology was continuously improved and refined, and increasingly also employed to model the earpieces for behind-the-ear hearing aids. Since 2001, RSM (Rapid Shell Modelling) software developed in collaboration with Sonova’s partnerMaterialiseensures that computer-aided modeling can be done even more easily and efficiently.

Layer by layer from nothing

First, silicone impressions of the ear canal (which are still taken by hand) are scanned into the computer using laser technology. Further processing is then carried out digitally on-screen. Once a hearing aid shell has been finished on the computer, the file with the three-dimensional structure is stored in a central database and transmitted to the 3D printers at the production site. The actual printing is a fascinating process to watch: Layer upon layer of light-curing acrylic resin appears to be built up from nothing to form the new hearing aid shell.

Harnessing this technology, Sonova is able to mass-produce hundreds of thousands of custom-made products every year. Despite the high quantities involved, each product differs in its shape and is tailored to suit the individual needs of each wearer. This is the most impressive demonstration of the huge potential of 3D printing.

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Taking an ear impression at the hearing care professional’s office is the first step in manufacturing a custom-made hearing aid shell.
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Scanning the ear impression
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During the scanning process, a laser optically measures the impression.
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Using proprietary 3D modeling software, specialists turn the digital scan of the impression into a virtual shell, optimally fitting the ear canal of the customer and reflecting all the ordered options.
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Printing the shell : From the virtual 3D model, a 3D printer creates the shell, layer by layer.
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Printing the shell: Many shells…
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Printing the shell: … and even different colors can be printed on a single platform.
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Printing the shell: Trained technicians keep a close eye on each stage of the process.
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Serializing shells (number, type, brand): After some post-processing, a laser engraves the serial number and product name onto the shell…
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Serializing shells (number, type, brand): …and a technician fills the engraved letters with white color.
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Laser cutting the faceplate: Similarly, a laser cuts the faceplate – the cover plate with the battery door and other hearing aid components – based on the contour of the shell.
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Final assembly of a custom product : After assembly of the shell with the faceplate and all other components…
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Final assembly of a custom product: …the hearing aid is first tested for correct functioning.
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Grinding and buffing : The roughly pre-cut faceplate, already glued to the shell, is fully cut out, then ground and buffed to fit the shell smoothly.
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Lacquering : The shell is lacquered to protect it and provide a perfect finish …
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UV light-curing: …and the lacquer is hardened, or cured, using UV light.
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Quality inspection: Careful final quality control comprises visual and manual inspection and a listening test…
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Pre-programming and electroacoustic testing: …as well as electroacoustic testing, ensuring that the hearing aid will function correctly. The device is preprogrammed to address the individual hearing loss of the end user – one of Sonova’s unique customer services.
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Quickly delivered to customers

The use of 3D printing technology means that the hearing aid shells produced by Sonova across the world meet the same high standards of quality. The entire digital production chain can be closely controlled, giving Sonova a competitive advantage. Once an order is placed, it takes just a few days for the finished product to be delivered, and the customer receives a hearing aid with optimal fit.

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