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I am wondering if making an hermetic box is feasible using 3D printer. The box would be a cube with a front face removable, with screw and sealing joint to close it.
I searched for different materials, however, none talks about hermiticity. (However, I found a product that seems to improve water resistance of 3D printed items here, which might be a starting point)

Does anyone have experienced to make hermetic things ? I am specially interested in carbon fiber reinforced materials.

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  • $\begingroup$ What sort of printer do you have that can use carbon fiber? $\endgroup$ – Carl Witthoft Oct 4 '16 at 16:02
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    $\begingroup$ @CarlWitthoft Carbon-fiber filled filament are somewhat common. It's not pure carbon fiber, though. Same deal as the "metal" and "wood" filaments. $\endgroup$ – Tom van der Zanden Oct 4 '16 at 19:18
  • $\begingroup$ I' go on a professionnal company for doing that, but as Tom said, it seems that more and more carbon reinforced-filaments become available, and compatible with more hobbyist printers. $\endgroup$ – dudu721 Oct 5 '16 at 11:29
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    $\begingroup$ Over extrude. It will look a mess but it will squeeze its way into all holes, then sand it down. $\endgroup$ – Trotski94 Oct 5 '16 at 14:07
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A few thoughts that might help...

Material:

  • ABS can be vapor smoothed with Acetone which results in the layers sort of "melting" together to form a smoother, and less porous surface.
  • Other plastics can be smoothed with compatible solvents, but I've not tried solvent smoothing with anything other than ABS. Be careful if you try.

Print Method:

  • Consider slightly higher print temps to increase layer adhesion. You'll likely have to compensate with extra retraction to avoid excessive stringing.
  • Consider more perimeter layers and more top/bottom layers.
  • The CF materials are stiffened with chopped CF strands...I think it's a stretch to call them "reinforced" unless you happen to have a Markforged printer or similar.

Sealants: This is probably your best bet.

  • Epoxy: Generally considered effective for producing hermetically sealed containers. Dip or brush on. Mind your VOC's and pay attention to working time.
  • Plasti-dip or similar sealants: These may be good enough for your application and result in a rubbery coating over your part. Good for water sealing, and may be close enough to hermetically sealed for your needs.

Design:

  • To mechanically seal the opening, there are many options depending on your requirements. O-rings, gaskets, etc. If you use a rubberized dip, you may be able to skip the gasket. You could install a few threaded inserts around the perimeter of the opening, put in the screws, then dip. After drying, you slice around the screw and remove it (this just keeps the coating out of your threads) Dip the cover as well. Then when you screw on the cover, it will provide a water-tight seal. To help make a good seal, apply a silicone grease to the mating surface.

I hope this helps. :-)

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I have very little experience printing waterproof stuff.

I printed a flower pot in ABS some time ago. Right after print it was leaking water. Then I processed the pot with acetone vapour to create a layer of melted ABS on the surface of the pot and then it became water-proof.

As another option for non-solvable in acetone materials like PLA I would rub in some sealant paste to the surface, but I never have actually tried that.

Another thing to consider: you should think carefully about your design and may be even conduct few experiments to verify printed part meets your mechanical criteria. Unlike injection molding, FDM prints are breaking more easily in some directions.

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  • $\begingroup$ Thanks for the advices. The water leaks shows that it's probably porous. I wonder if the process and the paste are reliable. Have you been using your pot since ? $\endgroup$ – dudu721 Oct 5 '16 at 11:28
  • $\begingroup$ I never tried paste. Only acetone. Pot was water-tight until the end of life. $\endgroup$ – fukanchik Oct 5 '16 at 13:14
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I'm currently working on a project where a kind of box has to stay underwater, and until now, the best hermetic system I found is using coatings.

The best of them until now is PVC glue that I use on ABS as a coating with a little trowel. What I find nice is that's quick and that looks smoother and resistant. A disadvantage is that you need some practice to make something quite esthetic...

An other option I've tried is a very fluid mastic call "Creeping crack cure" which is perfect for 3D print since the part literally drinks it. Then, when it's dry, it also acts like a glue and can reinforce the part. A disadvantage I have however is that the mastic becomes no more transparent when the part stays in water.

Still not the perfect solution, but at least, no water goes through my parts :)

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I believe this can be achieved using o-rings. That's what they use for scuba diving lights. The component doesn't need to be circular, but the o-ring needs to be slightly smaller than the component so that it is held in place via tension. Additionally, you'll want to create a groove for the o-ring to set it in and make sure that the o-ring protrudes slightly so that it applies pressure and creates a tiny amount of friction when it's coupled with its counterpart. Apply some type of lubricant to prevent the o-ring from sliding out of place and to keep it from drying out and cracking.

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  • $\begingroup$ Ok, thanks for your answer. I am also wondering about the printed material itself, is it dense / hermetic itself ? While printing, I imagine plastic melting, could it include air bubbles in plastic making it somehow porous ? $\endgroup$ – dudu721 Oct 3 '16 at 15:35
  • $\begingroup$ There are rectangular gaskets (aka "square o-rings") so if the box in question has a standard size gland, those can be used as well as a circular o-ring. $\endgroup$ – Carl Witthoft Oct 4 '16 at 16:03

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