Storing 3D Printing Filament & Restoring Wet Material
All 3D printing filament is hygroscopic (a material property describing that material’s propensity to absorb moisture) to some degree. An exposed Nylon spool can be moisture-laden in as little as 15 minutes, rendering it utterly useless for printing. In contrast, PLA absorbs moisture far slower – sometimes taking months, even in a humid environment. Markforged mitigated the risk for moisture absorption by printing their spools from a sealed dry box. However, this dry box only stores one spool. Since most of us have applications that require different materials, we likely aren’t consuming entire spools before switching over. Therefore, how should we store partial spools?
Here’s our solution. EZY Storage 19 quart bins from Home Depot with rechargeable desiccant packs and a cheap hygrometer. This bin size stores four standard (~1 kg) spools compactly and without risk of moisture absorption because these bins are IP67 rated. For rechargeable desiccant packs, it is recommended to avoid the color changing beads; those are known to have some hazardous chemicals. Instead of relying on a visual cue, use a hygrometer! Our bins stay closed almost all the time and they’ve been holding 10-12% RH for months. Once your hygrometer starts reading above 30%, you can consider recharging the desiccant – see instructions on packaging.
In case you were wondering, fresh spools should be stored in their packaging. Spools are shipped in sealed bags with desiccant all contained in a small cardboard box.
For storing Metal X spools, full or partial, always keep the spools upright. Spools stored on their circular face will result in broken filament (Metal X filament is much more delicate than plastic filament). Also, partial Metal X spools do not require any special dry box for storage.
Now, what happens if your spool has absorbed moisture? First, you will know it has by the poor print quality (stringing) along with seeing steam and hearing crackling during printing.
If you are experiencing these, then there’s no need to panic. It is possible to restore a moisture-laden spool back to working order. Although there are several ways to do this, using a food dehydrator is among the most popular.
Food dehydrators are typically cylindrical and feature stacks of plastic mesh discs for placing thin strips of food. Hot, dry air is blown inside at temperatures between 95oF and 165oF which is low enough to avoid softening or even melting a spool (most ovens cannot reach the temperature that low and if they can, there will be considerable fluctuations). To dry spools, these dehydrators will need to be modified.
COSORI manufacturers a high quality, thermally consistent food dehydrator. The 5 discs included are thick plastic – some recommend cutting the mesh out, but there is a less destructive method, especially if you desire to salvage this for its intended purpose. We place one disc on the food dehydrator for stacking spools and use a printed adapter and corrugated plastic to increase the dehydrator’s volume. With this configuration, we can fit 4 spools!
This spool of Onyx was left out of the dry box for 12 days. Here’s how it printed:
Markforged’s built-in test print, Onyx Pillars Test Print, helps diagnose print issues. The close-knit array of pillars requires multiple retractions which will produce heavy stringing from wet filament.
We set our dehydrator to 165oF (no risk of softening Nylon-6) for 2-hour increments. The spool was flipped over and ran for another 2 hours for a total of four hours.
The spool was close to empty:
After the drying cycle was completed, the spool was loaded into the dry box for our Mark Two desktop printer. Here’s how it printed:
Although there is still some stringing present, it is a noticeable improvement. Since Onyx is a dense, carbon fiber-infused material, it requires longer drying times at higher temperatures to restore compared to PLA. Leaving it in the dehydrator for a few more hours would’ve restored it properly.
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