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I want to make some prints of pressure resistants. I am currently trying to print a simple cylinder to find the best parameters to make my prints airtight (by airtight I mean, it needs to resist to 10 bar).

Here is the test model that I have made for this:

Screenshot of a model for a pressure resistant

Here are the parameters that I have changed in Cura:

  • layer height: 0.1 mm
  • infill : 100 %
  • print temp: 250 °C (high temp to make the layers stick between them)
  • wall line count: 5
  • infill overlap: 40 %
  • flow: 115 %

But all these changes in Cura don't give good results for ABS. It's not even airtight at 2.5 bar:

Photo of pressure resistant under water producing bubbles; not airtight

And here is a mid-cut of the print :

Photo of pressure resistant cut in two to show internal structure

Do you have any ideas/suggestions to have better results? Can it be from the ABS itself? There is a sort of white powder between the layers, is this normal for ABS? Should I try using PETG? What could I change in my parameters?

agarza
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Zylar
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3 Answers3

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It's very difficult to get accurate internal sizing with 3D printing for this sort of application. It's also difficult to get it airtight without some sort of post-processing. My group wrote a paper on the flow dynamics of pressure restrictors made with 3D printing. In short, I'd suggest you use a drill or mill to produce such parts. We were using pressures < 0.1bar and still struggled to get them to seal without post-processing.

fifteenforty
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This is going to be hard. Even holding a vacuum is hard (I've tried it and not succeeded). I'm not sure what the mechanism of air molecules getting thru the print is - whether it's defects in inter-layer bonding, defects at seams, imperfect mating with the fitting, or even permeability of the plastic itself. It might not actually be existing flaws in the print, but rather the high pressure being a stronger force than the bonded layers can withstand, essentially ripping the layers apart from the weakest point until the pressure can discharge through the opening produced.

If using ABS, you might try an acetone bath followed by a long period of trying or use of vacuum chamber to quickly remove the solvent, if you can stand some possible part deformation. This would tend to fill any gaps. Coating with low-viscosity CA glue (Loctite 420 or equivalent) might be a better version of this approach, as the solvent will both attack the ABS and deliver fill material.

In principle PET (maybe also PETG, but PET is preferable anyway if you can get it) should be a suitable material for pressure vessels, as it's what's used for soda bottles at comparable pressure, but those are blown from a single piece, not fused together with seams.

At some point I will attempt this again, and will update my answer if I have any findings that contribute to your question.

R.. GitHub STOP HELPING ICE
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Not without postprocessing

FDM is pretty much welding plastic to plastic. Many many layers. Each of them is a potential breaking point, a corner for stress to arise and break the print.

Easy with a hollow body

Printing a hollow item that can be filled with resin is comparatively easy. Once filled with a monolithic curing resin (epoxy), that will take the pressure much better and seal it fully.

Trish
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