I have 4 AMS 2 Pro’s connected to my A1, each with its own power supply.
On one of them (the A unit, if that matters), I have two rolls of Bambu Lab PLA Basic loaded. The humidity on the screen was showing as 20%. I unloaded the filament and secured it to the spools. I ran a drying cycle with the defaults (12 hours 45 degrees C). I enabled spool rotation. During the drying cycle, I spot checked the humidity and temperature, using the Bambu Handy app or the screen. They seemed to be constant at 45 degrees and 26 % RH. The drying cycle completed overnight. In the morning, the RH was 22%. This doesn’t make sense as it is higher than when it started. Is this normal? I have extra desiccant installed - 16 10 gram packets that have been dried.
Also, I noticed that the LED’s by the filament loaders will still pulsing like they did during the drying cycle, even though the screen shows that it isn’t drying. None of the LED’s on the other AMS’s are lit or pulsing.
Another question. Is a drying cycle of the AMS 2 Pro enough to recharge the desiccant? For my dry storage boxes, I recharge the desiccant in an oven at 100° C (210 °F), but the AMS drying temp for PLA is only 45° C.
Shouldn’t desiccant be removed from the AMS before running a drying cycle? As it warms up it will serve as a source of moisture, will it not?
I’ve been experimenting with an AMS-HT. What seems to work is to load a spool of filament, remove all desiccant from the unit, run a drying cycle, let it cool to room temperature and THEN load it with fresh desiccant and keep it sealed. Doing this, the humidity fell until it stabilized at 10% (the minimum it can display) on one of the little round hygrometers I placed inside that I’ve come to trust (the readings it gives matches readings of other hygrometers that I’ve compared it to across a range of conditions) and has stayed there for over a week. The HT display itself has stayed within one or two per cent of 16% over the same time frame. I suspect the HT humidity sensor is being exposed to air leaking into the case from outside and the 16% reading is a balance of the dry air inside the filament chamber and humid air coming in from outside. It will be interesting to see how this changes as we go into winter. RH in my house is generally in the 60-70% range in the summer but falls to about 35% in the winter.
I think there is a basic flaw in the HT (and AMS 2 Pro as well) ventilation scheme. It sounds good on paper with opening and closing vents and a fan to circulate air, but all it does is draw in humid air from outside the enclosure. It should have been designed to pull in outside air through a charge of desiccant before being released into the case. Another experiment I’d like to do is to seal the AMS HT itself in a big plastic bag with a good charge of desiccant to see how the HT humidity display behaves.
Anyway, thank you for reading until the end. Like and subscribe!
Don’t know about air leakage or other stuff, but desiccant in any container will overwhelm any relation between humidity and filament. Actual desiccant is a much much stronger influence on humidity in any container than filament is. Any humidity measurements made with desiccant present are really only speaking to the condition of the desiccant.
Easy to verify. Get a thick wall plastic container that seals well and stick a hygrometer in with a spool of filament. Let it sit until the hygrometer stabilizes. With only filament in there you are measuring the humidity caused by water content in the filament.
In a container that’s just bigger than a spool, the amount of air in it is tiny and the amount of water in that air is tinier still. The filament overwhelms the air because it has lots more water and you are indirectly reading the filament moisture. Bet it reads somewhere between 10% and 30% but the actual value doesn’t especially matter.
After it has stabilized, crack the lid and drop in a known-dry sack of silica gel. I use 50g sacks in my filament storage. Watch the humidity. The humidity will scream down to where the hygrometer stops reading with the actual humidity somewhere below. If it doesn’t, your silica gel isn’t as dry as you think it is.
The reason is just like with filament holding much more water than air can only this time it’s the capacity to hold water by the silica gel is much higher than filament.