Case Study / Hot Runners Filters for hearing aids — Bringing the world to life with sound

Editor: Steffen Donath

Toolcraft details its steps to a finished automated production of hearing aids, enabling people who suffer from some form of hearing impairment to enjoy “a world full of sound”.

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The mass storage unit housing additional filters makes it possible to fit the hearing aids with an initial filter on Sonova’s assembly line.
The mass storage unit housing additional filters makes it possible to fit the hearing aids with an initial filter on Sonova’s assembly line.
(Source: Toolcraft)

Sonova, headquartered in Stäfa, Switzerland, is a provider of hearing-care solutions. The company pursues the simple vision of creating a world in which there is a solution for every type of hearing loss, making it possible for people to equally enjoy the delight of hearing. Sonova uses a complete solution from Toolcraft to manufacture and package a cerumen filter protection device for hearing aids. Experts from injection moulding, mould-making and robotics work together closely to produce the complete dispenser system, which includes eight filters.

“The dispenser system comprises three external parts (bottom, top and label), with the filters inserted into the bottom. There is also a mass storage unit housing additional filters so that the hearing aids can be fitted with an initial filter on Sonova’s assembly line,” says Thomas Lender, head of injection moulding at Toolcraft. The filter can be changed by the hearing-aid wearer independently. This increases the durability of the hearing aid, improves its performance and makes it easier to use. The initial design of the cerumen filters and the dispenser system had to be revised in close co-operation with the client in terms of its manufacturing feasibility and ability to be produced automatically. Aside from the fully automated production process, discussions focused on economic efficiency. During the design and construction of the systems, particular attention was paid to the high accuracy and precision of the individual components.

Ensuring it was possible to manufacture the mould and to handle the filters during production proved to be the greatest challenge. “The development of an automated process was particularly tricky when determining how the parts could be picked up and handled. Inspecting the parts using a camera and laser micrometer technology as well as lasering the packaging components in the predetermined cycle time demanded extensive knowledge of process development and camera and laser technology,” explains Markus Bengel, deputy head of engineering and robotics at Toolcraft.

After the project team, consisting of mould-making, robotics and injection-moulding experts, had been assembled, the focus turned to the feasibility study examining the plastic components in terms of moulds, injection moulding, gripping technology and separation during the automation process. This was followed by design coordination with the customer and optimisation of the geometry. After the conceptual development of processes for manufacturing, removing and handling the components, the moulds were designed and at the same time the construction of the automation started. Finally, the individual components were brought together and the systems commissioned. Random CT measurements of the parts also ensured continuous quality assurance.

The tight time constraints meant that the second system had to be planned and put into series production at the same time as the first. Thanks to its network of suppliers and expertise in automated injection moulding, Toolcraft was able to successfully complete the project. The filter systems have been rolling off the fully automated production line ever since and are used in the new hearing aids to ensure wearers can enjoy a world full of sound.

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