I’ve looked and looked, but I’m still left wondering if you can dry your filament too much.
I’m using my AMS 2 Pro with the Bambu Lab 24 volt, 4 amp power supply It defaults to a 12 hour drying time. And I usually run it during printing, as well as when not in use.
But is there a point of too much drying?
It can hurt the filament, dont overdo it.
Best to bring the filament down to an acceptable amount then maintain it.
Overdrying breaks down the structure, makes filament brittle, fades the color, and is overall a waste of energy.
Thank You. I’ll cut back on my fanaticism. 
Filament and printers makers should jointly fund a comprehensive research to have an definitive answer for the good of the industry.
The research should find final answers on the acceptable moisture level for different types of filament, and lay the foundation to develop devices that can measure if a roll of filament needs drying and if needed, stops the drying when it is dry enough for the purpose of 3D printing (vs drying until it can’t be dried anymore).
The vague and generic recommendation to dry the filament before printing, for 8/12 hours, uses a lot of energy and time, some of which are almost certainly unnecessary and a waste of precious resources.
Check this link Filament drying guide for detailed information on drying times and moisture reabsorption for many different types of 3D printing filament. On the Bambu website only pure PLA has a recommended re-drying interval that i can find.
Unless you live in a swamp, PLA can be left out for months (or years) even and it prints fine without having to dry it.
There are some materials like PP that never need to be dried and the other extreme like PA6 that at minimum has to be dried before every print and (for long prints) has to be actively dried while you are printing.
I hate when companies put that kind of information in literature without qualification.
An 18 day redry time is BS that many will likely take as gospel.
It all depends on ambient humidity, storage setup, how people dry, etc. There are so many factors wrapped up in any drying advice like that and it looks like none of the conditions are specified.
Thing is, whether people need to dry or not is subjective. I don’t live in a swamp but for the best print quality I do need to dry. Others may not print demanding models or may be more tolerant of stringing or doughy surfaces, clumping, zits, or whatever water symptom.
But specifying a redry time assumes everyone is starting from the same initial moisture content, subjecting the filament to the same ambient humidity, and the dryers all dry to the same extent. No way that’s happening. A “redry” time is pure hand waving.
Thank You All for your views on drying. Yes, it would be very subjective based on a lot of variables especially where one lives on the RH scale.
My climate is considered on the dry side normally. But to err on the side of dry, I’ve been running my AMS2 Pro’s drying cycle a lot. (For the climate conscious, I’m a Solar producer. So my energy footprint is pretty tiny.) That is until I began wondering if too much could be a detriment to my growing stash of filaments. I am having a blast printing things almost on a daily basis, and about to start making trail badges for a local 4X4 club. So since things are getting more serious and complicated, I was wondering.
Other than that, I could use a second AMS to double my available pallet. And a lot of what I print would be considered toys for the Grandkids and their friends. The P2S is basically a new Grandpa toy.
Thank You all for your thoughts on drying. I haven’t experienced any of the threatened problems with my printer. At least, none I could say Ah-HA, too.
First, getting a second AMS was one of the first things I did after getting my first AMS in a combo. I love having all the colors or different filaments available. Haven’t been able to justify any more for my own needs but I’m still envious of the folks with full house systems.
On drying there are things to keep in mind. You only need filament dry enough to print well but some conversations have me wondering if a target uniform dryness might be even better for better calibrations and tuning. I haven’t seen that need yet and it might be splitting hairs.
There have been other discussions here on if you can dry too much. Plasticizer loss being cited a bit. I don’t know but maybe. The bigger issue discussed has been getting filament too warm to where it changes its molecular structure - both good and bad.
And about printing issues from water, there are discussions here too about seasons changing bringing lots of printing problems posts. Humidity goes up in monsoon or rainy seasons, and lots that haven’t had problems start seeing them as their filament spools start picking up enough water to show issues. That was my experience. I bought my printer on a black Friday sale and it printed great - until spring started sprunging and humidity climbed.
But much depends on what you print too. Overhangs and other printer hero moves get less able to be done well as filament gets wetter. Prints can get slightly worse or catastrophically worse, show issues near doors or fans, or any number of things. If filament is misbehaving it’s frequently the filament. And you can also tune a lot out. Slowing down a print is a common way to get around some issues.
Anyway, if you get results you like you’re golden. Have fun!
Wait a minute, your printer has been threatened with problems? 
. How?
DW, You know the gambit, stringing, clopping, and so forth. I take most of those problems tongue in cheek, with a grain of salt (rock salt). LOL
Some folks are their own worst enemas. While others are just disgruntled turdmisters. I consider untested files a challenge to unravel before moving on. But mind you I’m still under a thousand hours with my printer. So truely a newby. 
Is it difficult to double up on AMS’s? I discovered my local Best Buy today. I think I’m in trouble…
“down to an acceptable amount then maintain it.”
Could you elaborate, Please? What is “an acceptable amount” ?
I do tend to trust the equipment to be more intelligent than me. But I can’t say I’ve experienced any brittleness or fading. As for wasting energy, I’m listed as a Solar Power Plant by my utility, so the only thing I’m wasting is sunlight. (5.88 kwh) Since 2013.
If there is a mean RH% (20% ?) it would be enlightening to know. I have noticed my AMS 2 Pro shutting down when the drying is on and I’m also printing. Maybe it is trying to conserve energy unbeknown to me.? But if I set the AMS to drying when not in use it will usually run all night.
I just haven’t found anything I could use as a target RH% to make me feel like I’m in the ballpark. And I’d bet there are others who could also gain from some target for keeping their filaments in good condition.
It’s actually very easy. There is a 4 to one combiner for the filaments that lets 4 AMS units feed to the printer that you need, and a cable (the AMS units daisy chain electrically).
Way too easy. 
I figuered you are a newbie. But even old-hands can fall into something called old-habits-die-hard and do unnecessary things.
But it looks like you are having fun and that is good. Don’t let all these bad stories/warnings on the forum spoil it. From my perspective, I took up this because I want to have fun, not because I want some more chores to do or more things to worry about :).
Absolutely. That’s why people need to quit giving that poor advice to dry your filament for every question that gets asked.
Except that many times the problem is wet filament. So many posts about how prints worked but now don’t, “new” print issues, or obvious water issues when they post images.
After bunches of new parts the problems are still there, etc.
Wet filament is probably one of the biggest issues especially for new people. That’s why it’s mentioned so many times. Maybe not always correctly but it stands to reason many will offer that advice when so many times it IS the problem.
I think I’ve come to a workable conclusion for me and my particular environment. I have two AMS 2 Pros, I printed desiccant holders that also hold round Hygrometer’s in each one to monitor the RH in them. I’ve watched them carefully and don’t open the AMS’s unless replacing or renewing a spent spool (so keeping the spools in a controlled environment).
I’ve seen the RH indicated slowly rise to 25% indicated on the higher reading one. At that point, I removed the desiccant holders and while drying my desiccant I ran a drying cycle on that AMS with the Hygrometer in it for reference to reduce any humidity in the chamber or filament while the desiccant was being dried. Not a long time, but enough to get the reading to 17%. Then put the dried desiccant back in the holders and put them back in place. I did the same to my second AMS which is setup identically but was reading a lower RF than the first one. Just so they would both be done and out of my worrying for a while.
Today, both are reading 10% after setting overnight static, so I concluded my drying the desiccant and also drying the AMSs has achieved a happy medium for me. I had tried running the AMSs drying cycles with the desiccant still in the chambers but that did not work to dry the desiccants. Doing a drying cycle while also drying the desiccant seems have gotten my filament into desert levels without heating the heck out of it.
My currant RH has been 38-40% indoors, and 45-48% outside. Typical for what the weather people are calling a monsoonal flow. We just called it our summer thunderstorm times since I was a kid.
I’m happy to say my second power supply arrived early today and is working fine as we speak. And that adding a second AMS to my printer was as easy as removing the external spool holder and putting the second AMSs PTFE tube in that port on my P2Ss feeder. Then plugging in the second AMS into the second electrical port on the back of my printer. Mind numbingly simple with my P2S. Nothing else needed. The display shows 2 AMSs and A1 thru A4; and B1 thru B4.
So in closing, I’m happy and printing. I hope my findings might help others when wondering about specifics. Presently most of my printing is with PLA and some PETG. Your RH may vary….
In my case for PLA i never dry filament, and i store in a normal drawer.
I only have 1 month at year with high humidity here, but rest of year is 30-40% humidity ± and i don’t have problems.
TPU i dry it and if is a non important job i don’t dry it (and maybe i have stringing).
If you see stringing, noises of boobles exploding in nozzle and problems printing Dry it, if you see all become well printed don’t dry it (for me i use this common sense 
).
