All FDM 3D printing filaments are hygroscopic. That’s a fancy way of saying that the material likes to absorb moisture.
This hygroscopicity can wreak havoc on 3D printing filaments. As plastic polymers, they’re made of chains of molecules strung together. Moisture introduces water molecules that break up these chains, ruining the plastic and causing a whole slew of problems while printing.
But don’t fret. “Wet” spools of filament are easily saved, and proper storage can prevent future mishaps.
In the following, we look at how to identify wet filament, how to dry it, and finally, how to store the moisture-free result.
Different filaments absorb moisture at different rates, but there are a few common signs that you’ve got a wet spool:
If you’re seeing any of the above symptoms, it’s probably a good idea to dry out your filament. With especially hygroscopic materials like nylon, PETG, PVA, and flexibles, symptoms may appear after just one night left out in the open.
Dry out wet filament as soon as you identify it to preserve print strength and quality.
Probably the easiest and most common way of drying filament is throwing it in the oven. Just set the temperature to right below the glass transition temperature of the plastic, and leave it in there for 4-6 hours for the moisture to cook out. The longer you leave it, the more drying you’ll get.
Important note: Wait until your oven reaches the target temperature before placing the spool in. All ovens slightly overshoot the target temperature when heating up, so placing your spool in early may soften the plastic and fuse parts of the filament together.
You also want to make sure that your oven is capable of accurately holding the temperatures listed above. If not, you run the risk of melting all the plastic and fusing your entire spool together.
Food dehydrators are also great tools for drying out filament, especially if you don’t have a nice oven. Originally designed for drying fruit, dehydrators are designed to operate at lower temperatures than ovens and are therefore easily repurposed for drying filament.
At low prices, they can be found all over the Internet. Usually, they come with removable layers and meshing that you can add or remove to fit your spools.
Now that your filament is dry, you’ll want to keep it that way for as long as possible. To do that, store dry spools in a humidity-controlled environment. This can range anywhere from an airtight box with desiccant packs to dedicated commercial solutions. Usually, the former is more than enough, but use what suits your needs.
Just keep in mind that proper storage can’t dry filament for you — it can only preserve it. If your filament becomes wet again, you’ll have to re-dry it with the methods described above.
Hopefully, this guide was helpful for learning how to identify and dry wet filament. It’s great knowledge to have, especially when printing expensive, specialty materials. And, in general, it should help to drastically reduce print failures.
License: The text of "How to Dry Filament: PLA, ABS and Nylon" by All3DP is licensed under a Creative Commons Attribution 4.0 International License.
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