Waterproof/watertight 3D prints

[moose_grunt]

So I know that ABS and possibly PETG are the recommended materials for underwater use, but has anyone been consistently successful in making waterproof/watertight parts? For example, printing a blank lid for an old can light canister to use as dry storage for epirb/phone/money during dives. Anyone found something that works? 100% infill with multiple shells? Vapor-smoothed ABS? ABS with XTC-3D or some other 2-part epoxy? PETG with ...?

Thanks,
Jim

 

[emoreira]

I've been printing BCD flanges and second stage parts for several months with ABS and now with PETG with 100 % infill, 0,12 mm layer height and 5 perimeter shells.
For BCD and Second stage use they are enough water and air tight. I cannot be 100 % sure if they would be water tight enough for a battery canister or some electric/electronic device that will be inside the print.
PETG seems to have better layer adhesion that ABS.
I would print the canister, and dive with it, just empty with a blue napkin to see if water comes in.

 

[James79]

I'm doing BCD flanges and elbows in ABS, vapor smoothing the elbows. 95-100% infill with 3 perimeters. I second @emoreira , try it with napkin or toilet paper as the payload to be sure.

 

[moose_grunt]

Thanks for the starting points. I'm especially interested to see if vapor smoothing, or using something like the epoxy smoother (XTC-3D) actually seals the surfaces to the point of being watertight at pressure.

Jim

 

[James79]

If you haven't yet, look into room temp vapor smoothing. I've been using a mason jar for small parts, super simple and way lower risk than the heated acetone methods. Just takes a bit longer. (An elbow for a BCD usually takes about 30 minutes before I pull it out of the jar)

 

[SeaWarden]

Any one know where I can get custom O-rings in Singapore for the custom parts that I print?

 

[CuriousRambler]

Any one know where I can get custom O-rings in Singapore for the custom parts that I print?

Custom orings aren't likely to be easy to find. You can buy an oring vulcanizer to essentially weld cut orings to the length (diameter) you need, but you're still relying on readily available cross sections. Is what you're doing really so specific you can't design it to fit a standard oring? That's what the pros all do, because custom ones ain't easy.

 

[SeaWarden]

Yeah.. my video camera housing is a bit back dated.. so they no longer sell orings for it.

 

[CuriousRambler]

Yeah.. my video camera housing is a bit back dated.. so they no longer sell orings for it.

You could try something like this. A proper vulcanizer is probably more than a new housing.

 

[OTF]

It depends on how watertight you need the parts to be, how much pressure they need to hold, and what kind of 3D printer you have. FDM parts, even at 100% infill are inherently porous. Almost like dense wood. They will absorb some water if you don't do any post-processing. Meaning they're fine for things like brackets and knobs but not so good for things like housings.

Ways to improve waterproofness:
- SLA/SLS printers can make more solid parts.
- On an FDM, print hot and slow to reduce porosity. 100% infill.
- Coat the finished parts with epoxy or some other finish. I've tried this, but found the coatings tend to crack or flake off the plastic in heavily-used parts.
- Vapor smooth using acetone. Room temperature works fine, using heat works better. If you go the heated route do it outside and take fire/explosion precautions. You can also carefully brush/dab liquid acetone on the part to melt the outer layers. Or make a gel of dissolved filament in acetone and paint it on with a brush. All of these options work, but the "seal" only comes from a thin coating and a scratch or abrasion could allow water to seep in. I wouldn't trust it to hold ocean pressure out of a critical, heavily used housing long term. Good for most other parts like brackets/adapters/mounts though.
- Soaking the printed parts in a sealant (especially using a vacuum or pressure pot to draw it deeper into the parts) probably has great potential. I haven't gotten around to trying this, but it would probably make very waterproof parts. Messy though.

As for O-rings: O-ring suppliers have nearly every size oring imaginable. (Mcmaster, Apple Rubber, Parker, allorings, etc. - not sure who would ship to Singapore). The old camera housing almost certainly does use a standard size, you just have to measure and figure out what it is. You may have to order a few sizes that are close and see which one fits best. It's okay because orings are cheap and useful for lots of things.

As for custom part orings, you should be able to design any custom parts to use off-the-shelf orings. It will make it cheaper and easier to replace in the future. There are some handy tools online to help you design the grooves properly.