A half dozen full spools of PLA was discovered in the garage, and they were all out of sealed packaging. Here in the Pacific Northwest, that is no good for hygroscopic filament like PLA and PETG. When printed, it was an inconsistent stringy mess. It had a tell-tale popping like crispy bacon as it extruded, and it refused to adhere correctly. The popping and adhesion problems I had with my tripod printer may have been caused by water-logged filament. Clearly this is a chronic problem. I'd read about filament dryers, but the cheapest were over $40. Rather than splurge, I went the DIY route with the jank turned up to 11.
OfferUp had a few used food dehydrators, and I picked a Nesco model with a few trays for $20. The simplest models are not much more than a hair dryer blowing into a big chamber made up of a bunch of trays. In my case, I wanted a single big changer into which I could put the filament spool(s). After seeing people make plexiglass versions online, I landed on an even simpler solution: $2 posterboard, doubled over and taped together into a cylinder. This gave me a big comfortable chamber in which to dry several spools if I wanted. Now to test it.
I reused the thermostat from my sous vide for clove tincture in a Huckleberry cocktail. Placing the probe into the bottom of the chamber, I tested that an empty dryer would hold the right temp (based on this fantastic article about from Prusa). And I ran it for about an hour while I tweaked the alignment and tape seals with one spool. The improvised chamber wall held, luckily, and the green tape I used does not lose stickiness at these lower temps of up to 45C/115F. I'll update this post if the PETG drying at 55C/131F has a different result.
If this system were to break in any place, it would be on the on/off duty cycle I added to maintain a constant temp. Dehydrators are meant to run for hours without stopping. Getting the fan and heating element up cranked up takes work and wears parts out, and the constant-on model I purchased second-hand was probably not designed for this. The fan was a lot noisier than the rice cooker as it cycled on and off every 30 seconds as well, so it was very annoying. By playing with the thermostat settings, I was able to change the temperature range in which it would trigger the relay while still keeping the chamber between 40-45C/104-115F. This meant it took longer breaks and cycled less often. A win for longevity.
With the preliminary tests done, the only thing left to do was run it all night. As this thing was noisy, we put it in the farthest reaches of the house, but the center of the garage would probably have been smarter. An unknown appliance procured second-hand should be run supervised or in a fire-proof area in case it decides to melt down or short. Nothing happened, but it had me up all night checking it. In the morning, it had run for 8 hours, and I caught it at a cooling cycle at 43C/109F. The filament itself was pliable and felt much lighter. It had a rough texture like a dry sponge.It printed nicely as well with less stringing and no popping. The $20 dryer has hopefully saved more than a hundred dollars in filament from the garbage dump. A resounding success!
I'll weigh the next spool before and after to see how much water we're really taking off. And I'll hopefully be able to test it with PETG as well.
