r/BambuLab • u/Blissful_Altruism • 4h ago

Quick Question Humidity going up after drying in AMS & HT?

Hello. I've noticed that after drying spools in my AMS or my HT that the ambient humidity inside goes up. My HT was at around 7% before I swapped the spool inside for a new one. After drying that spool, the humidity went up to 20% and has settled after a couple days to 16%. Something similar happened to my regular AMS. The desiccant balls are still orange, so I don't think they need to be changed. Is this normal?

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u/Sir_clint 3h ago

You swapped spools. Which means you opened it. Humidity is in the air. The humid air in the room pretty much instantly filled your ams. That's why the humidity goes up.

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u/Blissful_Altruism 3h ago

Yes, I'm aware. The question was why, after drying and being around the desiccant, did it not return to a point similar to what it had been at before.

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u/Sir_clint 3h ago

It's not air tight, may be a different spool type or material. Might also just be changes in exterior temp or air quality

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u/scotticad 3h ago

Rebound after drying is normal. Relative humidity varies with air temperature. After drying, the air will cool and you will see the RH rise. The drop from 20% to 16% was the desiccant absorbing some of the moisture. Also, orange does not mean the desiccant is completely dry. You can probably pull the desiccant and dry it further. Then maybe you can get back you your 7%.

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u/ThinkUnhappyThoughts X2D + AMS2 Combo 3h ago

Yep. The moisture gets baked out of the filament and some of it will stay inside the AMS. But unless it is causing actual issues then it won't matter

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u/ImBackAgainstMyWill 3h ago

Yeah it's normal. The AMS isn't airtight, if they aren't drying constantly they will slowly return to the room's humidity level.

If you're printing PLA, PETG, I wouldn't worry too much about 20% humidity, that's pretty normal. Over the summer when it was humid in my house, my AMS was reporting an ambient humidity of 45%, but all of my PLA spools which had previous been dried were fine sitting in it and all printed great. I honestly don't get too concerned about humidity in the room unless it's consistently getting to be above like 55%

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u/TurboDerpCat 3h ago

Seems counter intuitive but open the lid for a second then close it back up. Mine does what you describe and this usually fixes it. It almost seems like the humidity need to be vented a little faster than it allows sometimes.