We’ve been off to a great start this year, working towards getting our tooling perfect and preparing for the earplugs’ mass production.
Since we’re reaching the very final milestones, February is a heads-down-working kind of month. That’s why we want to dedicate all of our time and effort into testing and fine-tuning steps. In this update, as usual, we’ll share with you the details on the R&D and the next steps will conclude the update.
How things have progressed
Mode switching button
As mentioned in the previous updates, the unnecessarily big gap between the button and the actual switch component on PCB made the button feel stiff. The gap between some components and the elastomer was also too small.
We figured out the solution by reducing the gap and adjusting the elastomer in the tooling. The new plastics arrived at the factory and were assembled with other components. The button works well with our latest modifications. Some material was added to the bottom of the button, so it rests closer to the switch component.
You can press the button to change modes if needed. It’s a neat and important addition in this model since it can come in handy if you have small kids. You don’t have to take the earplugs out while taking care of the kids during the night. When travelling by airplane, you can also switch modes to listen to announcements or to communicate with flight attendants.
The mic gasket seals now since the surface of the PCB was made smooth.
In the earlier revision of the PCB, there was a track going across the area where the microphone gasket should seal. A track causes small unevenness to the surface of the PCB. The track has been moved away from the critical area. The height of the microphone gasket made from soft elastomer was also increased. These changes ensure that the gasket seals properly against the PCB.
As it’s very critical to make sure every small step is well verified and tested before the mass production, we have had different builds and been conducting the testing iterations. After each round, we realize issues that can have some certain effects on the performance of the products, so we conduct fixing as we have updated.
At the moment, we have some working products from the work completed at the factory with our partners. We are testing the different assembly methods to find the most reliable one that can be applied for the whole production line.
Ultrasonic welding is employed as the method used in our production line.
It is an industrial technique whereby high-frequency ultrasonic acoustic vibrations are locally applied to workpieces being held together under pressure to create a solid-state weld. It is commonly used for plastics, and especially for joining dissimilar materials. In ultrasonic welding, there are no connective bolts, nails, soldering materials, or adhesives necessary to bind the materials together.
This technology is used to get perfect welding of the components. The process needs to be airtight, durable and does not make any sharp edges.
By using this, we are able to make the devices super small, because it does not need any room for connective mechanics like screws.
This is where the top cover of the earplug will be attached to be welded with the earplug’s body.
The air flow resistance of the pressure release channel was measured before the welding process. 6 pairs were ultrasonic welded at the factory.
At this step, we see that the soft elastomer part in earplug top cover easily melts and gets perforated during ultrasonic welding. On tightly welded samples the ultrasonic energy was too high for the elastomer to handle. We had some parts without any damage in the elastomer but at the same time the welding result of the hard plastic was weak.
In the following week back at the office, the airtightness of the weld and gaskets was measured, and the faulty ones were opened. The welds were analyzed.
Some of the unwelded devices were glued together and functioning earplugs were made.
Solution and fixing time:
Improvements to the welding rib and ledge are ongoing. Suggestions to improve the sonotrode of the ultrasonic welding tool have been proposed to the welding tool supplier. The idea was to modify the shape so it doesn’t touch the elastomer part which could reduce visual defects.
Pressure release channel
The tooling has been improved, yet in the latest plastic samples, there were some inaccuracies in dimensions and defects on the surface quality. This is partly because the tool maker didn’t have enough time to properly finalize the molds, and partly because of the difficult design that requires very small and accurate features.
We have discussed with the plastic maker about the importance of the properties for functionality. The width and depth of the channel were increased slightly for easier manufacturing without compromising the quality.
As mentioned earlier in the update, we keep these iterations till we achieve the perfect quality. The changes in the plastics part and the welding tool take three more weeks extra, yet the April timeline is still attainable.