I’ve been storing spools in sealed boxes with desiccant, and I keep an eye on the hygrometer. But I’m not sure what numbers actually matter.
Mine sits around 20-25% RH now. Is that “dry enough”? Or do I need to get it lower? What’s the threshold where moisture starts causing problems?
Also, does the reading inside the box actually reflect what’s going on inside the spool? Or is it just the environment around it?
Just curious what numbers people actually target.
That’s not a black-and-white question. Humidity matters as a function of relative humidity, exposure time, temperature, and the specific filament.
For example, PLA is only moderately hygroscopic, so leaving it at >50% RH for some period of time may not produce any noticeable change in print quality. PETG is more moisture-sensitive and can absorb enough moisture to affect printing more readily.
Time is the other major factor. If I start with a very dry spool of PETG and print the entire spool during an 8-hour period, even in relatively high humidity, it may not absorb enough moisture during that time to produce a noticeable difference in the print.
So RH by itself is not a universal pass/fail number. The material, starting moisture level, temperature, and duration of exposure all matter.
Since I asked nearly an identical question, and got no definitive answers, I target the lowest I can get.
I’m presently with a dry cabinet that is doing well to hold 24-25%RH. Then I additionally dry in one of my AMS2 Pro’s from which the filaments are served to my P2S printer.
I have ordered up a Sunlu S4 to use as my “go-between” because I like the specs on it, and because it can handle 4 spools of filament.
So the Sunlu S4 will hold exactly the same number of spools as one of my AMS’s. How novel. My plan is to be able to put 4 spools in one of my (2) AMS2 Pro’s and run through the jungle.
So no matter what, I’ll have done my best to feed dry filament. Presently, my AMS2’s are doing great holding <10% including desiccant holders I printed for them. When my RH creeps up to ~20% I do a drying cycle and regenerate my desiccant from the holders.
So my answer is to do what you can and are comfortable with to provide dry filaments to your printer(s). I find I need to service my AMS’s about weekly with my RH% hovering between the 30"s and mid-40’s ambient, so far.
Hope that helps. I can say I don’t have any problems I can relate to wet filament. So I’m happy. I don’t run much exotic or specialized filaments. Mostly PLA, PET-G, ABS, and TPS.
Bottom line from me would be <10% to ~20%. Other people’s milage may vary.