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Air tight materials

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Posted · Air tight materials

Hi there,

 

We want to print a closing shell. It will be ca 1 meter in diameter, 0,5 meters long and 4mm thick.

 

We will flush this volume with dry air or Nitrogen. I was thinking about printing something with 100% infill.

 

First doing a prototype in our Ultimaker to then go to something big, like a Bigrep.

 

What materials would you recommend that are air tight?

 

thanks

regards

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Posted · Air tight materials

Air tight??? I think it is more related to the settings in the slicer. That being said, I had good result with PP as the layer adhesion is excellent I was able to print water tight objects that are also impact resistant. I would give it a try to test it's ability of being air tight...

 

Good luck!

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Posted · Air tight materials

Most materials should be reasonably airtight if printed *slow*, in *thin layers*, and with good flowrate. So you get good layerbonding, and absolutely no underextrusion (important). A little bit of overextrusion could also help, but might create blobs. Do not use separate support materials (PVA) that dissolve: if they made strings in a print, these will dissolve and become holes.

 

But all models will have tiny "canals" and pores where bacteria can grip and grow. It's just that the water or air won't blow through.

 

For shell thickness, I would use at least 2 lines (=0.8mm for a 0.4mm nozzle), maybe 3.

 

Don't pressurise 3D-prints: they might explode at a much lower pressure than injection moulded models.

 

For huge models (1m), I would rather apply a coating, I think? Maybe even reinforce them with glass fiber mats, and then apply epoxy resin? Do tests if a 3D-print can handle the required loads and temperatures (PLA softens and warps in the sun).

 

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Posted · Air tight materials

Hi there,

 

In the end we will use tough PLA, we got a BASF 2.5kg spool.

 

I always print with the standard options so I am not expert in touching many of the options.

 

 - For this purpose I have changed the infill to 100%, the "wall line count" to 10 (to make sure it the print head goes around 10 times and not the zigzag filling)

 

 - The printing speed is set at 50mm/s by default. Would you recommend to change it?

 

 - Layer height 0.15mm. It takes already 2.5 days. With 0.1mm takes 3.5 days, would you recommend to to to 0.1mm?

 

 - All flow options are at 100%. Which ones would you recommend to change and how much?

 

 - Would you suggest any other changes?

 

The coating idea is very good. We can paint it inside and out. Since we are testing first the small part with the Ultimaker, we will do a leak test, then paint and do it again

 

thanks

 

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Posted · Air tight materials

I just printed a filter for my vacuum pump, to prevent it from sucking up big particles when suddenly applying vacuum. The filter was printed on an UM2, thus in a single material, no supports.

 

I printed the first model at 0.3mm layer height, 25mm/s. This was *not* airtight: when I put tap water on it, maybe 10 tiny jets spurted out of the shell, through tiny holes. The holes were where the layer-changes and take-offs and landings from traveling had occured.

 

The second model was printed at 0.06mm layer height, and 50mm/s. This model is *absolutely watertight*. Yes it took a lot longer, but it works now.

 

This filter is quite small, 30mm diameter, with 8mm, 10mm and 12mm bulbs for attaching tubing. So it has a thin shell. Bigger objects might need a *much thicker* shell to withstand pressure.

 

Major slicer settings:

- 0.06mm layer height,

- 50mm/s (don't go too slow at thin layers, otherwiste the material sits in the nozzle for too long and might decompose),

- shell 0.8mm (=2 lines, 0.4mm nozzle),

- infill 50...60%,

- top and bottom: 0 (=no solid top and bottom layers, so the filter is porous);

 

I could have printed it in one shot, vertically. But this would require custom supports for stability. I did not want it to wobble or fall over. So I preferred to split and print it in two parts, and glue them together with cyanoacrylate glue. And then I sanded it lightly and acetoned it, for a good fitting of the tubing.

 

vacuumfilter4.thumb.jpg.525b5359ffecf6d05ff546b8494a0133.jpg

 

Both parts need to be glued together, bottom to bottom, carefully applying cyanoacrylate around the edge, without gaps, but also without flooding and blocking the filter.

vacuumfilter5.thumb.jpg.476398dcc6d3f1f76a56d1f735626570.jpg

 

Anyway, before doing a large print that takes days, try different settings very carefully on a smaller testmodel. Go from where it sure leaks, and then gradually to where it is surely tight. Then keep a safe margin.

 

Also consider post-processing, acetoning, coating, glueing, whatever,... to make sure it is airtight. A thick varnish, coating or paint might also solve the problems.

 

Print without dissolvable support if you can. Otherwise strings of support through the print would cause holes after dissolving.

 

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Posted · Air tight materials

Hi there,

 

thanks for the extensive information.

 

So you have 0.8mm wall thickness. We have 4mm. I attach some pictures. It's a "box". It will be glued to an aluminium frame (which will be screwed with an o-ring to an aluminium plate).

 

No support, the design was made in a way that it is not needed.

 

I'm thinking about going to 3mm thickness (for structure) and then do the painting/coating (for tightness)

 

thanks

 

 

shell2.PNG

shell1.PNG

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