I’ll do that, but the stock desiccant beads turned green in about a week, so that wasn’t a good sign.
ah, indeed.
have you run a drying cycle yet in the days since you mentioned not having done so?
No. All four spools of filament were fresh, sealed Bambu PLA basic. I’m running a drying cycle now to see what happens. It seems counterintuitive to dry, then open the AMS and reload the filament. I guess if the filament is dry the desiccant should lower and maintain the RH inside the AMS despite being opened recently?
Welcome to water. 
Filament fresh from a factory bag can be wet even with a desiccant pack in there with it.
Desiccant can both absorb water or release water depending on the ambient humidity it’s in. Silica gel beads are sold in various water contents to use to set and control humidity in archive/storage/museum applications. If they get put in an environment “dryer” than they are they give up water to raise humidity. If wetter, they absorb water to lower the humidity.
If your desiccant is “wet”, it can give up water to filament and that can look like a leak. Desiccant has defined moisture vs humidity curves. If you put desiccant in an air tight container with a hygrometer, you’ll get a reading that will tell you how much water the desiccant is holding. If you can’t get to a low enough reading, you need to regenerate or get new desiccant.
Thanks for these insights, guys. I’m almost halfway through an 8-hour drying cycle and the RH now shows 13%, so things are going in the right direction.
A few hours after opening the AMS Pro 2 and reloading all four spools of filament, the RH has again fallen to 14% and is dropping slowly. The lowest I saw was 13% so hopefully no air leaking is occurring.
RH sensors tend to slow down how fast they settle when at lower humidity. Response time gets longer.
AMS units shouldn’t really leak much. They do leak a little but the way in/out is through the PTFE tubing but the lengths make that slow compared to the lid being open.
With freshly-dried filament I also see humidity drop in the AMS. When they start showing “2” on humidity, if I put in a dried spool the humidity will drop back to “1”.
1 Like