https://www.amazon.com/filament-dryer/s?k=filament+dryer
A filament dryer is important for 3D printing if you want to achieve better results. Most 3D filament dryers can only dry one or two spools of filament, which does not meet the needs of Bambulab AMS.
for the ams itself i dont need a filament dryer…from my AMS i print PLA, PETG , ABS…and AMF gets heated because it stand on my X1C and i use the additional silica boxes from the hydra ams project+ the silica spool weights. so humidity in the AMS is around 13-15% and around 35°C
I supported the KS Filament dryer and will use it for CF or Nylon…or to dry older filament over night before i load it in the AMS ( PC for example) As CF Filaments dont AMS anyway.
Here is a Test of different Dryer
I’ve been using the SUNLU filament dryer for some months now. It’s built well, is quiet, and does the job well. SUNLU in general makes nice 3D printer accessories.
I use Sunlu S2 for my filament’s to dry it and i printed abrasive filaments directly from it. From my AMS system i print PLA, PETG
I’m also using the Sunlu dryer with no issues.
I’ve been using this method for over a year, works flawlessly and is super cheap price-wise vs the amount you can dry at once. Plus once it’s finished, you can store them in there and put a small tub of damp rid in there and it will keep it dry. Amazing use of combo Damprid and Dryer.
After much research I chose the EIBOS 3D Series X: Easdry.
I had problems with new filament right out of the vacuum sealed bag and did not believe it could be a moisture problem. After about six hours in the dryer that filament prints perfectly.
The dryer does not have a temp sensor. It just has a knob with labels for filament types so I put a thermometer in it and set the knob to get the temp I wanted. Because I am only using PLA, I just leave the temp knob in the one spot and use the on/off switch to operate it.
I went with one of these myself to dry out filament. Works well and you can do many at the same time.
A Drybox is no replacement for a dryer. Drybox just slows_down the intake of moisture, it doesn’t even stop it. AMS is no exception. Some materials (Nylon) need to be printed directly from a dryer, not even drybox is sufficient if humidity is high.
And not all materials are the same - for example BL PAHT-CF seems less suspectible to moisture than Polymaker CoPA. I also have several brands of PETG, some don’t care about moisture at all, others (Devil Design, Extrudr) hate moisture and will foam if left out of the drybox just overnight. PLA is mostly resistant, except when it has some sort of fill, like fibers or CF (though again - BL PLA-CF seems to be pretty resistant). Verbatim PETG claims “hygroscopic”, which is absolutely not true but drybox with some dessicant bags works fine.
It will mostly depend on what your humidity is. The room where my printer and filaments are is pretty humid (50-70%), after the rain or if I clean and forget to open the windows, it gets even higher. Someone with a dry room with 30% humidity might get away with not drying PETG but will still have to take care of PA/Nylon.
I am pretty happy with Sunlu S2, though for effective drying I have to open the box a few time during a cycle to let it vent a bit. Some sort of timed fan would help here. I also refresh the dessicant in my dryboxes regularly and redry filaments in an oven.
Oh, and if you put a moist spool in your drybox, it’s not a drybox anymore, no matter how much dessicant you put in there.
I use a Sunlu S2 but I’m on the edge about recommending it. It works great, if you mange it. Personally, I would suggest buying one that can dry at temps up to 70C, however 80C would be best for some nylons and PCs, but 70C is serviceable. Another feature I think is needed is the ability to evacuate the moisture it pulls out of the filament. This is where the Sunlu S2 comes up short. I have to constantly open the lid, or use a small prop to lift the cover by a few mm’s.
Other features that come in handy are automatic timers and presets for different filament drying. One other thing I think the Sunlu comes up short in is the angle of the print opening for drying while printing. The port is just in a weird position. Its just not good for brittle filaments because the awkward angle. This is pretty easy to eyeball if you are looking for it. As referenced below, the red shows the approximate odd angle for full rolls (which isn’t too bad for low rolls). I got around this problem by using a piece of PTFE tube in the port (which appears to be exactly the right size for that, so they likely intended this, but didn’t tell the buyers). This tube allows the filament to bend at a more friendly radius.
So long story short, the Sunlu S2 dryer is good, but requires more user input than it should.
I bought this cabinet back in September to try out. It was only about $3K back then. So far it has worked flawlessly and we have had zero issues with our filaments. It measures 46" wide X 25" deep and 65" tall.
I too chose the Easdry and for the same reasons. And that it just fits on the tool cart I’m using as a printer stand. A food thermometer fits in one of the filament ports to give me the exact temperature but knowing that isn’t really necessary.
Since I can’t leave well enough alone, I did “calibrate” mine. At the division between PLA (40°C-45°C) and TPU (45°C-50°C), mine was 8-10° low. There is an adjustment pot under the left cover. I found that the tinyest bump CCW brought it to ~45°C with the knob right on the line. By tinyest, I mean maybe the width of the slot in the pot. If you do this, be aware that there is mains voltage on that PCB and that you will need to wait at least an hour with the dryer fully assembled with a spool in it to see the results of each adjustment. I went from somewhere in the high 20 watt range to about 32 watts at 45°C.
I thought about leaving the thermometer in mine and putting marks around the knob for the temps that I use.
I headed down that path but my OCD plus desire to know how everything works got the better of me. 
Given the knob does not have high quality calibration marks, how to did you make sure you can reset to the same temp later?
I do not understand why you thought having the filament in the dryer was necessary to calibrate the temp. What am I missing?
Now I want to fiddle with mine. 
I tend to print PLA for the most part. I didn’t want to run the risk of over heating it so I wanted the PLA range to have the best calibration and I made the assumption that a cheap plastic box wouldn’t be insulated well enough to have the upper ranges be too hot due to heat loss since it’s only a 45 watt heater. Since there appears to be no temperature feedback to the controller, I made the assumption that the output is PWM and that the unit was designed to be able to dry a full spool. Based on this plan and the “chart” that is at the bottom of this page, I set the knob to what I felt was the division between PLA and TPU and adjusted the temperature to the PLA maximum.
Now no matter where I set it, as long as it’s inside the PLA range, it won’t be too hot for PLA. As for why a full spool, my thinking is that I’d want it calibrated for the highest heat load. Something I picked up when doing temperature uniformity surveys of heat treat furnaces in the mid 80’s. It may or may not be true in this case but it makes me happy 
