Yes, you can dry filament with just a dry box

Bambu Filament and Accesories Filament
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So, new to 3D printing and wanted to try the PETG hotness. I heard PETG can be “challenging,” but I never really knew what that meant, until I started using it.

Excited to print with PETG, I printed something on day one, and then another couple of things a few days later and then, by the end of the week, I had my first massive print failure with PETG.

I did what every new person does with their first failed print, I scoured the Internet, and ultimately chalked it up to wet filament. Everything was going so well and I was hoping not to have to make another investment in a filament dryer.

So, I decided to try what most people say won’t work. I figured if it didn’t work, I’d have to do this anyway, I’d just go ahead and buy a purpose-built filament dryer.

I bought a quality dry box, a hygrometer and likely more desiccant than I need. I put the filament in the dry box along with the hygrometer and the desiccant and, within several hours, the hygrometer showed 0% humidity. I kept the dry box sealed for almost 2 weeks.

Today I opened the dry box, connected the PETG filament and proceeded to print a simple model that failed spectacularly last time; it was as close to perfection as I can expect.

Pullcord_PETG
Pullcord_PETG1920×2550 865 KB

While I can’t say this will work for everyone, I can say this has definitively worked for me. It’s possible this is related to my specific environment, which usually hovers a bit under 40% humidity, but I did make this post because I wanted to reiterate that this does work. I don’t know if I would have had the same results if I removed the PETG from the dry box within a few days or week instead of almost 2 weeks, but maybe someone else can chime in.

If you want a quick run down of what I use and how I use it, I took my first stab at designing a simple hygrometer holder for my needs and documented this and related at Hygrometer Bracket Ezy Storage 32L 33.8qt Dry Box by Bink3D - MakerWorld.

Cheers!

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What kind of desiccant did you use?

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At this time I’m using a molecular sieve.

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I’d expect the hygrometer to read 0 continuously then, independent of the dryness of the filament, it really isn’t an indicator of anything except the desiccant being depleted or the box leaking.

So yes, given enough time, you can suck moisture out of filament given a low enough ambient dew point. You might even be able to completely dry it in a few months. It’s unfortunate you didn’t weigh the spool and determine how much moisture you removed.

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I concur regarding the hygrometer. As for a scale, it’s one of my next purchases.

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I’m still saving my bucks to get one. :wink:

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Not to take away from your enthusiasm, but your approach lacks key elements of the scientific method. What proof do you have that moisture was actually present in the filament? Did you weigh it before and after drying to confirm moisture loss?

It seems like you assumed moisture was the culprit simply because of a failed print. Maybe it was, maybe it wasn’t. What did the failures look like, and what other troubleshooting steps did you take to rule out other causes?

Also, two weeks in a dry box isn’t a controlled test or a practical solution. Who would wait two weeks for a spool to dry. In addition, how do you know the conditions between your initial prints and the later test were the same? Without a more rigorous method, your conclusion is anecdotal at best.

Here’s a more practical and scientifically sound approach:

  1. Take two identical filament spools suspected of containing moisture. Weigh and label both.
  2. Keep one spool sealed in its original bag without desiccant as a control—it won’t absorb or release significant moisture.
  3. Place the second spool in a dry box with desiccant. Weigh the desiccant as well to track moisture absorption.
  4. After two weeks, weigh both spools and the desiccant to determine actual moisture loss.

Ideally, the desiccant should have absorbed the same amount of moisture that the spool released. However, cardboard spools can also retain a significant amount of moisture. Remember: 1g = 1ml = 1cc of water. I’ve measured up to 5g of moisture in a single cardboard spool, so it’s worth noting the spool material in your test.

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Highly respect your content here @Olias.

My approach is not scientific and is purely anecdotal.

Who would wait two weeks for a spool to dry.

Me. I’m not in a rush/I don’t do this for a living and I imagine others are in a similar boat.

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In a very low humidity environment filament will give up water but it’s a slow process. Since your prints went from working to failing and that’s when you tried this, your filament was just wet enough to cause trouble so didn’t have so far to go to get back to printing successfully.

Actually, what you did was very similar to storing filament in poly cereal containers with packets of fresh desiccant.

If you have a fairly wet spool, it may take much longer to get printable filament again. Heat really speeds the process up.

But good information and thanks!

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I suspect you could also eventually dry your filament by throwing it in the freezer and waiting for freezer burn to dry it. You’ve maybe experienced this before happening to food that you’ve left in there for too long. But “too long” is the operative condition. It may well take quite a long time.

Also, maybe think of filament moisture as roughly too different types: deep rooted moisture and surface moisture. The surface moisture seems to come off a lot faster and easier than the deep rooted moisture. I’d wager that in your example you got rid of your surface moisture, and there wasn’t much deep rooted moisture. Heat helps a lot in expunging the deep rooted moisture.

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You might be on point here, but I will say I am still rather pleased with the current solution and it’s still working well for me.

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I think this is very true. Water molecules deeper in cracks and pores are more surrounded by the plastic they are sticking to so can be more tightly held by that attraction. It’s like holding onto a hand or arm vs a bear hug.

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I’ll buy that. Right now I have two competing mental models to represent what’s going on, and that’s one of them. So, by that theory, not only would adding heating help energize the water molecules and give them more breakaway energy, but possibly through thermal expansion also open up those deep microscopic cracks and ravines in the filament, so their random walk has a clearer exit path with less likelihood of bouncing back into the filament, only to give up energy and get held again.

It’s a little like the theory of how long does it take for light which originates in the sun’s core to reach the earth. Well, it’s a lot longer than 9 minutes:

how long does it take for light to escape from the center of the sun to the surface of the sun?

ChatGPT said:

The time it takes for light (or more accurately, energy in the form of photons) to travel from the core of the Sun to its surface is surprisingly long due to the highly dense plasma in the Sun’s interior. This process occurs in two main phases:

  1. Random Walk Process in the Radiative Zone (~100,000 to 200,000 years)
  • In the Sun’s core, nuclear fusion generates high-energy gamma-ray photons.
  • These photons undergo a random walk—they are repeatedly absorbed and re-emitted by electrons and ions, changing direction with each interaction.
  • Because of this scattering, a photon might take a highly indirect path rather than traveling straight to the surface.
  1. Convective Zone Transport (~1 week to 1 month)
  • Once photons reach the convective zone (outer 30% of the Sun’s radius), the energy is carried by convection currents rather than photon diffusion.
  • Hot plasma rises, releases energy, and cooler plasma sinks in large convection cells.

Total Time Estimate:

  • 100,000 to 200,000 years (random walk in the radiative zone)
  • 1 week to 1 month (convective zone transport)

After reaching the surface, the light escapes freely and takes about 8 minutes and 20 seconds to travel to Earth.

This means that the sunlight we see today originated from nuclear reactions that happened at least 100,000 years ago deep in the Sun’s core!

Me again: of course, all of this is qualitative, but I find it’s helpful to have at least some kind of framework for thinking about “What’s going on here?” On this theory, either the freezer or room temperature can still work–just slower–because relative to absolute zero either one is still pretty hot.

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Could well be a factor. Photomicrographs of filaments show lots of cracks, pits, and surface roughness.