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.
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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.
I’m running two AMS2 Pro’s here and have added the power supplies for optimum drying. One AMS2 Pro came with my printer “package”. and I could immediately see reason to add the 24v power supply, and ordered it. So when I decided to add my second AMS, I ordered up a power supply for it as well.
In real life, I’m glad I did. My P2S has 2 connection points for the cables and it recognized the AMS2 Pro units immediately. Also, I was able to just connect the second unit to the Ext Spool PTFE tubing port so did not need the 4 into 1 PTFEadaptor.
I use the drying cycle in both AMS2’s quite often. Dry is dry, and I like my printers RH indication. Like MZip stated, removal of the desiccant add-ins makes sure the dryer function is’ just trying to dry the chamber and filament. My desiccant gets dried separately while a drying cycle is running. Then I run the cycles while dried desiccant is replaced into the units. Where I differ is I place my hot dried desiccant into some self-sealing Jelly jars while it it hot, screw the lid down, and as it cools it vacuum packs the jelly jar so the detent in the lid goes “pop”. As long as that lid is sealed, I’m confident the desiccant inside it is fresh and dry. I use indicating desiccant so that also assures me the seal is sound.
I’m always trying to improve things. Now, in AMS-B two of my desiccant boxes have dried desiccant in them, and the other 3 are empty. (two small end units, and one with a Hygrometer in it that doesn’t really hold much anyway.) I’m seeing how well it holds the floor RH, and for how long before it begins climbing.
For me the desiccant is a hold-over for when my AMS’s are just storage and not actually in use. Not actively drying, nor feeding filament. Or Static, if you will.
I’m of the opinion that if the AMS is kept dry with active drying, the desiccant will also stay drier as well. Anyway, that’s the direction I’m going presently.
Just to be clear though, if the desiccant is more dry than the ambient air in a cabinet or dryer, it will help by scavenging water and reducing the humidity further. But at some point it makes the active drying part unnecessary since it’s doing all the work.
Where it gets to be a problem is if it is allowed to collect too much water where it becomes wetter than the air in the cabinet or dryer and there it becomes a source and adds water load to whatever drying process is being used.
Not to me it’s not. drying the chamber that the filament lives in along with the filament removes the moisture. Drying the desiccant removes a percentage of the moisture it has absorbed from the chamber as well. Recombining the dried chamber, dried filament, and the dried desiccant, then running the Bambu Labs drying cycle further helps balance the 3 elements at the lowest % the Bambu Labs drier can attain (since it is the only active part of the equation). So everything within the AMS chamber is as dry as the AMS can possibly dehydrate it. Whatever that % may be.
As RH infiltrates the AMS chamber, the desiccant will be the first to absorb it. helping to hold the internal RH and help keeping the filament dryer. Watching the printers read of the AMS’s RH tells me when the desiccant is loading and the chamber is becoming a higher RH. Which tells me to run the drying, or address the desiccant, or both. Personally, I prefer to do both. Pull my desiccant holders and dry the desiccant while the AMS dryer is running to dry that. Then recombining the holders in the dried chamber and run the dryer further to dehydrate the air from me opening the chamber. To me, that is as good as I can do it given what I have to work with. It isn’t my vacuum chamber and vacuum pump.
Presently, AMS-B which was dried and freshly changed desiccant today, then additionally dried, is at 13%RH. The AMS-A which just got opened, and a new roll of Polymaker Gold filament was put in it, is reading 25 RH on the Hygrometer, or 26% on BL AMS chamber Hygrometer. So while not “wet”, it is suffering the change of atmosphere from opening it.
Once the award badge is printed, I plan to run the drying cycle overnight to draw down the RH as much as possible. But both the built-in dryer, and the fresh desiccant should bring the chamber into the mid to low teens. And away we go…
I have to have BL send me a new fan for the newest AMS. The one in there has a bad bearing, IMHO.
I understand what you are sayin MZip. You can’t dry desiccant with the puny dryer built into the AMS or what have you. It requires it be physically delt with. But if precautions are taken to maintain the atmosphere in the chamber, I believe I might lengthen the periods between servicing’s.
Make sense? I just wish my AMS’s could run more automagically. Without major surgery… Well looky there, AMS-A is now down to 19%. So it is headed in the right direction.
It sounds like you’re on your way now! Congrats! The payoff comes in being able to just print without having to troubleshoot things all the time. That’s big! Cheers!
