One-sentence answer: An electric toothbrush is exposed to water flow and foam every time it is used. The brush head shaft seal ring, silicone buttons, cordless charging area and bottom cover are the main water ingress paths. Using the CTS Sentinel C28WE (C28) leak detector to perform an air tightness test on the complete unit by vacuum decay can intercept the risk of water ingress short circuits before shipment.
The point where the motor shaft passes through the housing must satisfy both rotation and sealing. Seal ring compression and shaft coaxiality deviation can both cause water seepage, making this the most typical leak point for such products.
The handle is slender and the internal pressurizable volume is small, so readings are sensitive to temperature and plugging cavity changes. The large length-to-diameter ratio also makes fixture positioning and clamping more difficult.
Users rinse the product in running water and toothpaste foam every day. Water ingress often first permeates slowly at weak sealing points, and the failure appears weeks later, which is a typical delayed failure.
Sealing locations: the seal ring between the brush head and the handle shaft, the silicone buttons and the housing mating surface, the cordless charging coil area, the bottom cover O-ring and seam, and the openings for the indicator light and display.Consequences of leakage: after moisture enters, the motor bearings and coils corrode, causing increased noise, reduced speed or shutdown; the battery being damp carries risks of swelling and short circuit; water ingress in the charging area causes wireless charging failure, and after-sales service often determines this as human-caused water ingress and denies warranty.
During complete unit testing, the shaft hole must be reliably plugged, and the plugging part needs a guiding structure to avoid pushing the shaft off-center. If the shaft seal needs to be evaluated separately, a local plugging method can be used to cover the shaft hole area, and the result can be compared with the complete unit result to confirm its contribution.
Yes. Although the cordless charging area has no metal opening, the housing here is usually thinner. Water seepage through the potting or sealing layer between the coil module and the housing can also cause charging failure, so it should be included in the plugging and judgment scope during testing.
Reduce the additional volume of the plugging cavity, fix the clamping force, and keep the ambient temperature stable. The C28's ambient drift correction and absolute pressure sensor can offset ambient fluctuations, but the fixture design should still make the plugging cavity fit the handle contour.
It cannot fully represent it, but it is sufficient as a factory gate. During operation, motor vibration and high-speed shaft rotation put the seal ring under alternating stress, and static testing cannot reproduce this working condition; however, static testing can intercept dimensional deviations, improper assembly and seal ring defects. Dynamic conditions can be supplemented during type verification with immersion or spray tests under operating conditions, while the production line still relies mainly on 100% inspection by air tightness test.
The difficulties of electric toothbrush air tightness are dynamic sealing of the rotating shaft, slender small cavities, and high-frequency water exposure scenarios. The CTS C28WE uses vacuum decay, ambient drift correction and 32 programs to adapt to multi-model mixed-line testing. Together with a guided custom-formed fixture, it forms the front-end guarantee for handle water resistance reliability.
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