We've created a weather-proof and water resistant enclosure to test the limits of 3D printing and to help inform future designs. The current design is about 150x100x60 mm and is "waterproof" for up to 10 minutes fully submerged. The box has latches and hinges using M3 15mm nuts and bolts and 6mm diameter silicone aquarium tubing for the seal.
We're back to the drawing board. After a 12 hour test using the silicone aquarium tubing as a seal and without any water entering the case while fully submerged, we tried a 24 hour test.
The results were disappointing. A small amount of water had leaked in. Worse still is that a second test at just 1-2 hours showed similar results. So unless the tubing is just right, water will get in. This is hardly a solution for what should be a reliable system especially if we're going to make new boxes in the future or if anyone else wants to make these.
So we're back to trying 3M silicone sealant. This time we very carefully laid it down, ensuring it fully fills the groove. We will give it a full 3 days or maybe even a week to cure before testing. We're also looking into other types of silicone sealant, making the groove wider/deeper to accept more silicone sealant, and testing some other lid-ridge designs to interface with the silicone seal.
In the meantime we're designing an updated version of this case that will be further optimized for actual use (rather than a testbed for waterproofing). It includes a tray to further divide the internal volume and external braces to primarily reduce the amount of surface area in direct contact with the ground or objects placed on top of it. This helps create friction and reduce slipping especially when placed on wet, smooth surfaces like a kitchen or bathroom counter.
The original seal used 6mm diameter silicone aquarium tubing. It would keep the box water-free for up to 10 minutes fully submerged. But tests of 1-2 hours would see a little bit of water eventually make it in.
Then the tubing was replaced by 3M transparent silicone sealant. After curing for 24 hours the box was submerged for 10 minutes, 1 hour, and 2 hours. Even after just a few seconds water somehow made it in.
2 more lid designs were made with different sized and shaped ridges to press down into the silicone seal and none of them worked.
But because the tubing had worked better, I wanted to see if the new lids would work better with the tubing than the original lid design. Turns out the rounded 2.5mm ridge kept water out at 10 minutes, 1 hour, and even 2 hours. Not a drop of water made it in.
Last step then is to find a way to permanently glue the tubing into the groove (hot glue has not worked) and a permanent way to seal the ends of the tubing where they meet.
We learned a lot from the first couple of tries and completely reworked the design not only to make it more water resistant but also more functional. Printing at 100% takes a long time and it would be nice to have a case that is actually useful when it's done.
The walls on this version are 3mm vs 2mm in the previous version. We also used 45 degree angles instead of curves and kept all the overhang for the seals to the outside rather than interior of the case.
The hinges are sturdier and the latches are redesigned (but not sure yet if they are better). We also added in a hook system and gummy rubber bands to turn the lid's interior volume into a separate storage area. On the exterior there are little loops for straps or handles.
Looking at the cross section shows how the seal is created. The 6mm aquarium tubing is placed in the U-channel on the bottom half of the case. The top lid has a triangular ridge that presses into the tubing hopefully creating a seal.
We're using silicone tubing and using a slightly smaller diameter section of tube to connect the cut ends of the tube.
It is important to stress that this is water resistant and not "waterproof." The difference is that this case can sit in the rain or take a dunk and keep water out but if you submerge it for more than 10 minutes or so moisture might start making its way in. It's a poor man's Pelican case. Pelican cases are made of molded plastic which, unlike 3D printed plastic, have no gaps between layers for water to enter. The seals are also professionally designed and manufactured.