MoldsThese various molds have complex structures resembling three-dimen-sional puzzles. They are movable to allow the resin poured into the mold to be removed once it solidifies.Toshiaki OzawaMechanical Design and R&D Group, R&D Department, R&D Center. Joined Rion in 2014 after completing his studies in mechanical engineering at university. He began in the Sales Department, training at the Rionet Center Shinjuku and the Tokyo Sales Office, and later worked in Medical Instruments Section 3 and at the Sendai Sales Office before moving to his current role in 2021.Shinichi MurakamiMechanical Design R&D Group, R&D Department, R&D Center. Joined Rion in 2000. He is a highly experienced engineer who has been engaged in mold design and processing since joining the company. His sharp eyes, cultivated through years of experience, support the quality of Rion’s products.Takumi MurataMechanical Design R&D Group, R&D Department, R&DCenter. Joined Rion in 2018. Since then, assigned to the Production Engineering Section, he’s engaged in the design and manufacture of molds for resin parts. He studied mechanical engineering at university.Small resin partsThese black resin parts will be attached to the end of the tube in a hearing aid. They have lotus root-like holes and slits on the external surface. You can see how small they are compared to the edge of a one-yen coin. Molds exist even for parts as small as this.The role of molds in producing high-quality resin partsThe most rigorous precision: smoothness within 0.02-mm“It’s like making the iron plate of a waffle maker used to bake taiyaki (fish-shaped pancakes),” explains Ozawa.Murakami adds, however, that designing and manufacturing molds for hearing aids requires far more time and steps as they are more complex than one might imagine. “After confirming the product specifications, we go through every step repeatedly, from mold design through adjustments with the mechanical design engineers to mold manufacture. Finally, we even finish the molds by hand to achieve the micron-level preci-sion required. For example, polishing the mold for a hearing aid housing case to a mirror-like smoothness can take up to 30 hours.”The size of the parts produced from a single mold can be as small as 1 mm. For example, for a donut-shaped part with a diameter of 1 mm, which is about the size of a sesame seed, its wall should be extremely thin, just 0.5 mm thick at most. The outer part of BTE hearing aids is formed by joining the left and right halves together, like making a taiyaki waffle. If there is any unevenness of 0.02 mm or more at the joint, users will feel it and experience discomfort. Hearing aids, like eyeglasses, are worn from the moment one wakes up until bedtime, so comfort for extended periods matters. In other words, even the slightest unevenness is unacceptable.One of Rion’s main products is hearing aids. The main types are “in-the-ear (ITE),” “behind-the-ear (BTE),” and “body-worn” models. All parts of a hearing aid—except for the shell (outer casing) of custom-made ITE hearing aids, which fit the ear canal of individual users, and the electronic components inside—are made of resin (plastic). For example, in the case of BTE hearing aids, about 10 parts are used per unit, such as the housing case that comes into contact with the outer ear, the battery holder, and the switch. These parts are assembled like a plastic model, with the hearing aid’s acoustic and electronic components tucked inside.Virtually all plastic products—not just hearing aids—are made by pouring resin into metal molds, cooling it, and letting it solidify. In other words, each component of a hearing aid has its own mold. In the development of new hearing aids, a product designer formulates the design based on mechanisms created by the mechanical designer. Factors such as functionality, aesthetic appeal, ease of use, size, total weight, comfort when worn, and price range are taken into consideration during this process. Then, it’s the task of Shinichi Murakami, Takumi Murata, and Toshiaki Ozawa of the Mechanical Design R&D Group to design and cre-ate the molds for producing the resin components. At Rion, this trio is currently engaged in the design and manufacture of molds for the resin components used in hearing aids.7
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