Non Porous Filament

Hi All

I'm attempting to print parts for a pump to produce a partial vacuum but am encountering porosity. I've reduced porosity a bit by adjusting the Slic3r settings but I need to reduce it further and I'm thinking of changing to a material that's less porous than the PLA that I'm currently using.

Like most filament materials for 3D printers, PLA is hygroscopic (it absorbs moisture from the atmosphere). As water can move through it I suspect that air can also pass through, contributing to porosity. If this is the case then all hygroscopic filaments are probably unsuitable for me. So I’ve been looking for an online guide that will tell me what filament materials are not hygroscopic but I can't find one. Where's a good place to look?

Regards

Dave

My understanding is PETG is not hygroscopic. I'd use this for a part that needs to be water/air tight and print it quite thick with 100% infill and maybe 4-5 solid layers. Maybe even slightly over-extrude, use higher temps so the extrudate is more fluid.

Its incredibly difficult to avoid gaps between extruded filament paths, they are round, they do not tessellate, except by forcing it using the tricks above - any many others I am sure will be proffered after this.

I have read some posts about annealing, apparently doesn't do much for strength but might decrease porosity.

Edited 2 time(s). Last edit at 07/04/2016 10:48AM by DjDemonD.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

Hi,
i think you mix things up here. Absorbtion will not make your printed parts leak or pass through any noticable amount of liquid. It would require seriously high pressure to force absorbed water out of plastic, i doubt a pump made of said plastic would be anywhere stable enough for this.
It is much more likely that your print is simply not watertight. Use a large number of shells and high infill, then try to post process the surface to seal it. With ABS i had good results with using aceton to make parts watertight under low pressure.
An alternative would be to use low infill and fill up the empty volume with resin.

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Quote
Srek
An alternative would be to use low infill and fill up the empty volume with resin.

That's a clever idea. Great way to work with the material/process properties instead of fighting against them.

Thanks Guys

The odd thing is that I thought I saw a reply to this thread that suggested using Colorfabb's nGen, which is what I have tried and can now get such low leakage that I had to upgrade my leakage test rig. With quite a wide range of Slic3r settings the leakage is so low that it can't be distinguished from the residual leaks in the rig.

Regards

Dave