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I'm currently printing several cases for electronics, one for a Raspberry Pi 4 and two for smaller electronics, using ABS. These cases will be attached to a drone which might be exposed to rain. The cases itself should handle a little water, but I'm looking for a way to seal the seams where the cases are put together.

As mentioned, the cases must endure light to medium rain. Also, they might be frequently dis- and reassembled, which should work without the sealing being destroyed. The edges of the case parts are normally very thin, so gluing rubber bands or o-rings to them would be very complicated. And if I apply a sealant coating, how to open the cases again?

I was hoping that maybe there was some kind of viscous liquid that is applied to the edges with a brush (or by dipping the edges into it) and then hardens to a rubber like texture that sticks to the part it was applied to. Other Ideas are welcome too, of course.

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    $\begingroup$ Not sure if shopping questions are on-topic here. Have you looked at automotive stuff like gasket sealants? $\endgroup$
    – fectin
    Dec 10, 2022 at 15:03

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I've tried gasket sealant, as mentioned by @fectin, and the result seems to be working. You spread it on the edges of the printed part and evenly flatten it (it helps to print a tool for that purpose that flattens and removes the overhanging sealant at the side of the edge). Now let it sit for about one day. The sealant will harden out and stick to the part. The edges can also be pressed to the edges of an opposite part without the sealant sticking to the opposite edges (so far as I have tested, at least), so a reopening is possible. Aside from that, I'll simply have to use overhangs whenever necessary.

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Plastidip is a spray-on rubber-like material that strengthens and waterproofs your 3D print.

Other than that I would make sure that your model is splash-proof by overlaying structures, so that rain rolls off without entering the body and anything that enters the body can seep out.

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Many ways lead to Rome!

There are many ways that lead to Rome in this case, and I want to propose two:

cut gasket sheet

The most simple solution is a gasket, upon which pressure is applied evenly on all sides. This gasket can be made from any rubbery or foam material and then squished between the halves. A typical construction for a gasket would look akin to this stack: a pipe with holes in the flange at its end, then the gasket, then the endcap. The sealant is deformed against the plates on either side and the pressure is applied by having bolts pass through the faces and the gasket. You'll find this mechanism often where flat surfaces are mating. The thickness of the gasket and its flexibility (some are really stiff, others are super soft) are dependent on the use case. They rely on being tensioned evenly. enter image description here

Among the household solutions that can work like this are 2mm closed-pore foam sheets and faux leather. The latter usually is a PVC foam, at times fiber reinforced. Industrial gaskets are at times papery in make but rely on precision machined surfaces then (motorhead gaskets!)

molded gasket by the sealant grove in situ

In this case, you use a flexible rubber material, such as acyl, silicone, or a Polyurethane sealant, and add it to a groove or onto a surface. In this position, it cures into a staying gasket and when brought in contact with the mating surface, it provides sealing surfaces by deforming in the fashion limited by the channel provided for it. The upside is, that you can have very complex mating surfaces. The downside is, that often the seal might not be replaceable easily and will need to be destroyed to get a replacement done.

In the example shown below, I designed the receptacle for the sealant in the shape of a grove, allowing you to easily shape it with a coin or wet finger and press it into all crevices of the channel. This will result in a well-curing and maximum-adhering shape.

enter image description here

A slight refinement on the design would be an undercut on the receiving side, preventing one from pulling the gasket from the channel if the inside of the vessel had a lower pressure than the outside and the mating surface sticks to the seal. However, this makes replacing the sealant harder if it ages over time.

enter image description here

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How about rubber cement from a stationery store?

Thinly coat both surfaces, let it dry for a while, then press and hold firmly together.

Depending upon the strength of the object, you might be able to simply pry it apart when needed, or use a knife to cut the cement.

Warning: be sure to test the cement on a sample of the printed material first to ensure that its solvent won't react with the print.

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  • $\begingroup$ Thanks, I never heard of that. But the warning is important here, as some rubber cement products seem to contain acetone as thinner, which is basically the arch enemy of ABS prints. $\endgroup$ Jan 8, 2023 at 8:58

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