I ended up doing a bunch of research because the idea that water is incapable of escaping filament regardless of the humidity felt off to me since its not like we’re drying at the temps where the water would literally boil off. Turns out it is one of those “true, but …” sort of things, as desiccant drying is likely how the plastic was dried before it got turned into filament. Here’s what I learned
- Water will always exit plastic more efficiently at higher temperatures
- Desiccants become less efficient as you heat them
- Silica gel is less effective at low humidity, and thus can’t be relied on to continue to remove moisture under about 10-15% humidity
- You can not effectively or efficiently use desiccants for water removal without air movement.
- Desiccants produce heat as they absorb water.
- The actual volume of water found in plastic – even plastic we’d call extremely wet filament – is tiny, both in terms of the total volume of the plastic and the total amount of water it could potential hold.
At room temperature, drying requires humidity levels near 0%. Drying with only a desiccant requires using a desiccant other than silica gel, having enough of it to drop the humidity to extremely low, keeping the desiccant cool, and moving high volumes of air.
It goes something like this:
- Have two connected chambers, one containing enough of a desiccant that works well in extremely low humidity to lower the humidity to near 0 and the other containing
- Dry air by blowing it through the desiccant, causing it to heat up. Fan must be sufficiently forceful to make contact with all of the desiccant rather than to find paths around it.
- Blow that warmed air over the plastic
- Have a large enough return for the air that by the time it gets to the desiccant it has cooled somewhat
- Repeat until the filament dries
As you can imagine, this is difficult to do at home in the small footprint most people are looking for in a filament dryer.
However for everyone who is having issues with keeping filament dry, look into zeolite!