It’s not that quantitative a process. There’s no way to read the humidity of the filament itself, so what dryers report is the RH of the air inside the dryer. As the dryer heats up, the reported RH goes down. But that’s not a measure of the filament, it’s a measure of the air. The “humidity time constant” of the filament itself is much, much longer.
The process I use for very hydroscopic filaments (ABS/ASA, Nylon, PETG, etc) is - load 'em in the dryer, watch the RH go down, wait for it to bottom out, then start the drying clock for 24 hours.
But there is a lower limit for how dry the filament can get with heat alone, which is dependent on the ambient conditions. So if you’re in a tropical location with very high relative humidity and hotter ambient temperatures, a dryer won’t get the filament as dry as the same filament and dryer in a less tropical environment. Maybe, it won’t get it dry enough no matter what. In that situation, you will need a vacuum dryer, heat alone won’t be enough.
My approach to drying filaments is to weight them every hour while drying. When the falling weight levels off for 3 hours, I figure I have done as much as I can. Seems logical, but I have no way to prove it works!
My AMS goes down to RH<10% @ room temperatures with the extra containers you can print filled with dessicant.
This is how we do it when drying wood before using a stabilizing resin for turning. Weigh the wood, dry it for a few hours in a convection oven on low, weigh the wood again. Rinse and repeat until the wood weight doesn’t change or change much.
My AMS are usually at 10% humidity with additional desiccant containers in them (unless I just opened it).
@RocketSled , @Bobbo , @freeformz many thanks for your replies! I think the approach to weight the spool makes a lot of sense and is a very practical tip!
Does AMS at ~ 10% RH at normal room temperatures work if you store PAHT/similar in them? I guess it is optimal to only temporarily unpack the PAHT/nylons and print but leaving it in the AMS is obviously very practical
In my experience, no, the AMS has a long, sloooow humidity time constant but filament print quality still degrades after some time in the AMS, requiring the filament to be re-dried.
But that’s the “stock” AMS. There are plenty of project files to print that allow you to significantly increase the amount of desiccant that can be loaded inside, and those tweaks might address the stock configuration’s slightly-less-than-ideal performance.
