Just purchased a Sunlu S1 Plus Filament Dryer. After looking at its design, the chemical engineer in me was quite disappointed. It has a heating element with temperature control, a timer, and a humidity sensor. No forced convection and no means for removing moist air from the enclosure.
I use a food dehydrator to dry filament and then print it from either a dry box or something like that Sunlu. None of those “filament dryers” are any good from what I have seen. My favorite dehydrator is one of these due to the combination of a large volume without modification and low noise level: https://a.co/d/hDwHiTZ
I like this one, personally. Rosewill Countertop Portable Electric Food Fruit Dehydrator Machine with Adjustable Thermostat, BPA-Free 5-Tray RHFD-15001 Amazon.com
I pair it with a 5 gallon bucket with the bottom cut out of it. Pull all of the shelves out of the dehydrator, put the bucket upside down and then put the dehydrator lid on top. I can fit at least 4-5 rolls in!
I think I may have the same one as you, and I also have a food dehydrator which I think works better but does not seem to quite reach the temperatures it says on the readout. With the Sunlu I tend to run the filament in there for a long time (like an entire 24 hours), opening up the case periodically and spinning the spool on the bearings to refresh the air in there. By doing this, I can get the RH% to go down over time. Before doing so, the RH% seemed to plateau.
I also bought a big bag of larger sized dessicant + decent quality vacuum storage bags the spools fit into. I put each spool + a large dessicant into a bag, and then I store those in a large sealed tote that has it’s own very large box of dessicant in it. There’s a lot of humidity in my locale (Seattle area), and before I started drying filament even my PLA would go bad (brittle) fairly fast.
One thing to try with brittle PLA: Go higher temp than recommended (like 65C) for a few hours and then dial it back to more like 50C. I’ve had brittle unprintable PLA go back to being pliable and printable by refreshing it like this.
We’ve purchased multiple over the years including the original PrintDry, the Sunlu ones, etc. My current favorite is from EIBOS. It lets you print directly from it, it doesn’t have a timer you have to constantly reset, has a fan to move air around and it keeps the humidity down to about 10% (the lowest the monitor can read) inside the box.
I had to make mine… My shop is un-heated and un-cooled when I’m not in it. And, in Houston, of course Unfortunately, normal dessicant beads RELEASE water when you get them Houston hot!
So, I bake my filament and then put it in my custom built enclosure and print right out of it It has a peltier dehumidifier built through one wall, with a drain to take condensed water out of the enclosure. A night light bulb keeps the contents a bit warmer than the shop ambient for extra goodness.
Most likely anything nylon based though PETG stored in the open for long enough could also be a use case. I’ve never needed to dry PLA and I’ve used several year old rolls stored open on a classroom shelf. My experience is limited and anecdotal though. Would love to hear from a someone that’s needed a dehydrator regularly before.