PETG can be rediclous, i’ve had rolls that had to dry for like 40 hours before they stopped giving off wet.
TPU is worse in my experience, but this particular roll had been torn open sitting on top of a rubber horse stall mat just sucking up the moisture for 3 weeks before I got to it.
There’s a photo showing the sensor location here: AMS HT - How to keep it dry - #8 by user_251696923
Also some user(s?) found the sensor covered by film from the original component packaging… 
There are cracks and gaps around the various connectors on the back and the seam around the entire bottom edge.
Interesting… I’ll need to examine mine more closely! I’m not sold on the lid seal theory either. For all I know one of the plastics in the housing could be more porous than it should be.
-Max
Many people make the mistake of saying they’ve dried their filament to 6, 8, or 10% humidity.
No, you haven’t. You’ve only dried the surrounding air down to that level. Definitely not the filament itself.
Of course, it’s important to remember that filament continues to release moisture over time. And this moisture is naturally distributed more evenly in a large AMS than in a small one.
I don’t really have any problems with this. Once the filament is completely dry, the moisture level in the AMS increases by 1 to a maximum of 2% per week.
So I can’t complain.
If it increases more than that, regardless of the IMS, the filament simply wasn’t 100% dry and still contained some residual moisture.
After another drying cycle, I’m back down to my 1 to 2%.
I agree with Micha.S, if you dry it proberly it stays in low humidity.
I dried TPU and it is still at 10% after 3 days.
Those putting silica gel beads in filament dryers or AMS units need to understand that they only help when they are themselves kept dryer than the filament.
If the beads aren’t kept more dry than the filament, the beads will be able to give up water to the filament and slow/stop/reduce the effectiveness of the dry.
Beads in dryers can help but they need to be dried frequently to keep them helping rather than hurting the drying process.
Also, relative humidity is highly dependent on temperature and whenever quoting a relative humidity value it’s important to mention the temperature of the air along with the humidity.
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What do you guys think of this?
If you want to dry your filament, do it, if you don’t want to, don’t and accept whatever consequences come as a result.
The opinion of one guy from one company doesn’t have any impact on that calculus.
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I think the title is misleading and sensational. They don’t ever discuss your dryer lying to you. They discuss limitations in dryers. And yep, dryers that don’t exchange air with the outside world don’t do the best job. It’s probably why there are door props for many dryers on MakerWorld.
The plant manager does a really good job of explaining things but if you listen close to what is actually being said, he is really saying they don’t use fillers and such to where the filament just doesn’t absorb as much water to begin with. No idea if that’s true or not but it is what he says - that their filament doesn’t need drying.
The stuff about annealing is interesting but similar to his discussion on filament taking a “set” after a long time on a spool, the effects of annealing probably would last as long as it takes to take a set for the molecules to get out of that “relaxed” shape. The issue is they say at one point that it’s not drying that improves prints but annealing. That doesn’t explain how after drying a spool can be left out and start printing poorly again. But this gets back to what filaments people use. He’s addressing his filaments in large part.
I think it’s possible his filament doesn’t pick up much water and therefore doesn’t need to be dried but have not used it yet to know. You have to be careful when listening to what is being said if he’s talking about his filaments or filament in general.
And the part where they did talk about drying was pretty basic. In desiccated or purged dryers, that trapped moisture can be removed and it can really help with drying over closed “dryers” that rely on the filament pass-through holes to let air out. Only caveat is beads in a dryer need to be kept really dry or else they can add to the water load.
But they never said you don’t need to dry other filaments. Just the PLA his company makes which may or may not be true. He claims it so maybe? Other filaments may have fillers, etc. They allowed that other filaments may need drying.
Listen close. Some good information but a little bit of misdirection and definitely a misleading title. And it felt like a big dose of “buy my filament”. It may be good filament but no experience with it.
I have a partial spool of Push PETG that I’ve had kicking around for years, it’s about as “not dry” as possible, and can attest it’s absolute garbage to print with right now.
I really should do a before and after just to show how much of a difference drying actually does make.
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I’m in a sort-of similar basket. I’ve been working with the dry air purge stuff with mostly PLA and PETG and it makes a difference and made a Sunlu S2+ into a stellar dryer. I tried it stock and if it was just heat, it still should have improved prints and it did a little.
I was plotting chamber humidity and it did fall after spiking and without a door prop. When it stopped changing the spool printed better than undried but nothing like how it printed after drying with the air purge but at same temperature. And purging with room air was similar to drying in the stock dryer until the humidity stopped changing except it reached the terminal humidity significantly faster. Purging even with room air helps.
All that points squarely at moisture and how good drying can fix things. Maybe annealing is involved somehow too, but what I know is drying makes a big difference for me. In the humid times of the year I couldn’t print without some kinds of issues. May have been ‘good enough” but I could still see a big difference after I started drying and then after going to a dry air purge.
They key point I took from it was hydrolysis is non reversible. So once your filament is “wet” as in damaged on a molecular level theirs nothing you can do anyway. It makes so much sense that people have stringing then they dry it and ALL BETTER… or is that because you have annealed it so it works better at the temps you were using?
Something interesting to think about.
How did you find out the gasket was pinched? My ams ht’s humidity climbs really fast. After drying at 45 degree for 12 hours with no filaments (totally empty ht with 2 humidity meters inside), the humidity meters shows 18% only, and it climbs back to 30% in a few hours.
Long story but it started with a cockeyed AMS 2 Pro due to the inside tray not being installed right and the lid didnt sit flat. This led me down a path of inspecting all of my AMSs and I noticed two HTs lids didn’t close right and it was the gasket not sealing good/obstructing. I had gotten into the habit of shaking the lid side to side once it was down before latching and I haven’t had the issue since.
I noticed the temp/time you posted just now, I see the same thing on empty AMSs and even an empty storage box when closed will stay in the 30s. That little desiccant slot is very small and I dont think it has enough surface area when idle to really do much to keep things dry. I use desiccant spool inserts which likely helps more than anything.
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