Bubbly Filament Works Better Than You Think

Normally bubbles appearing in your extruded filament would be considered a bad sign, but it turns out you can now buy filament that has been specifically formulated to foam. [Stefan] from CNC Kitchen has doing some experiments with these bubbly filaments, and the results have been very interesting.

The filaments in question are VARIOSHORE TPU and LW-PLA, both by ColorFabb. Both filaments have a blowing agent added to the formulation, which releases gas as the temperature is increased. This causes bubbles to form, creating a cellular structure, which decreases the density and increases the flexibility of the printed part. This isn’t the first time that foaming is sold as a feature, but previously it was only done for aesthetic purposes in Polymaker’s Polywood filament.

Before putting the materials through his excellent test procedures, [Stefan] first goes through the process of tuning the print settings. This can be tricky because of the foaming, which increases the effective volume of the plastic, requiring careful adjustment of the extrusion rate. Foaming in the PLA filament reached its maximum foaming at 250 C, at which its density was 44% of the unfoamed filament.

In testing the physical properties, [Stefan] found that the tensile strength and stiffness of printed parts are reduced as foaming increases, but the impact strength is improved. He concludes that the lightweight PLA can have some interesting applications because of the reduced weight and increased impact strength, with 3D printed RC aircraft being an excellent example of this. It should also be possible to change the between layers, effectively sandwiching the foamed layers between solid skins.

[Stefan]’s videos are an excellent resource for those looking to master the finer points of 3D printing with different materials. He has reinforced prints with carbon fiber, played with extrusion widths and developed an ingenious gradient infill technique.

21 thoughts on “Bubbly Filament Works Better Than You Think

    1. Would certainly give you a good key in the print for glue joints to other structural parts.. Trying to stablise it could prove tricky though, and might not result in much more than the resin used for material properties. But that would be so hugely dependent on geometry its hard to predict, still ‘lightweight’ filling core for resin use could be very cool for many things.. Going to have to get some to test at some point.

    2. As foldi one said it would entirely be dependent on geometry, and really would make 0 sense. 9/10 times would be quicker, easier stronger, to just do up w a fiber and resin. All my homies HATE 3D printing

    3. Perhaps they could be made like bird bones with a little tweaking.

      I wonder if you could remove the additives and cool the filament under pressure upon production. So it becomes carbonated like a soft drink. That might make it stronger.

  1. He’s on the verge of something very good here, both with his project and his love for metrology: Viscoelastic materials are very commonly used for vibration damping and shock absorption, and these are often foamed. Everything from your next electronics big-box to motorcycle engines may use some variant of this.

    So the next (anonymous) internet challenge would be to start looking into the mechanical frequency response/resonance characteristics using these materials as they’re formed into different shapes and densities.

    Why bother? Everything from very lightweight mounts to make drone videos more vibration-stabilized to vibration-absorbing power-tool grips might be done from home.

  2. Whats the finished texture like? I’d imagine it’s rough but could it be sanded easily, primed and painted for a nicer texture and maybe a more solid looking finish but still maintain a light and relatively solid internal structure.

    1. As the whole filament should be bubbled all the way through the finish wont’ be hugely improved once you get rid of the very outer fluff. It might even get worse as the core of the filament will stay hot longer so bubbles nearer the middle might well be bigger and less regular.

      A filler Primer should do alright on it with a few coats though, as the bubbles even at their biggest are relatively small and shallow.

      If it will stand up to it well enough (which it should I would think – even if you use very high temp softening sheets keep them thin and they won’t have the thermal mass to cause issues) vac forming over the top of the print (geometry permitting) is probably the easiest way to get a solid shell finish. Though if you were using a 3d print for vac forming you could not captive form and just have the vacuum formed shell as your finished part I think this has merit for making forms that are about as light as possible but have the depth (in the printed part) to deal with mounting hardware.

    1. I believe this is closed cell sponge, so not really, but it’s worth trying, maybe there could be some process where cell openness is increased, like printing in very thin layers…

  3. I really like how methodical the guys is and appreciate the level of detail in the information he shares so I dropped a valuable hint into the youtube comments for that video, let us see if he notices and makes his fortune from it, because somebody else will if he doesn’t. :-)

    “You don’t need the extruder to control the foaming, that is just required for controlling the melting and deposition rate, the foaming could be modulated with a laser. Engineer that correctly and have CAD that lets you expressly design with the resulting metamaterial properties then you will have outstanding results.”

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