Drying Fresh (new) filament

I know the box says dry before use, and I’ve seen opposite opinions in here, what is the consensus on needing to dry freshly opened filament like TPU or PAHT? They are vacuum sealed with dessicant so shouldn’t they be good right out of the bag? I put a spool of PAHT in my AMS (which has a ton of desiccant boxes) and the hygrometer didn’t change from the 10% it’s always at, after 24 hours, can I assume it’s dry and safe to print, or does heating it drive out extra moisture?

I have a sunlu S2 drier, but lately I’ve just been using it as a spool holder since when I use it, the RH never goes below 25%, whether I crack it open or not, so it seems like just putting spools in the very dessicated AMS would actually dry them more and keep them dry.

I will say that I for one was a very severe sceptic with regards to some of the hype I’ve heard about filament drying. Truth is, I can’t honestly say it gave me much trouble but then again, I also had to admit that I wasn’t as scrutinizing as a I should have been.

I have been doing a bakeoff between the Sunlu S2(2 weeks now) and the Creality Space Pi this week. So far the S2 is on the losing end but I’ll save that for another post. One of those two will be going back to Amazon at the end of the week.

On the subject of drying filament. If you’re just drying it and hoping for the best, you can’t really say whether it’s working or not. Do you weigh your filament before and after? Also, as was recently pointed out to me, if you have a cardboard spool, weight will be really thrown off but for a plastic spool, it’s reliable. Just remember, 1g=1cc=1ml of H20. So it’s really easy to calculate the moisture content of the filament after it’s been dried to see if there is an impact.

One of the two more hydroscopic filaments I frequently use is PC and PETG. PC is notoriously hydroscopic, some say even looking at it and it absorbs moisture. Well… last week I did a before and after with a benchy and the Sunlu S2 dryer. Although there was only 1.2% moisture content, take a look at these two benchies and tell me what you make of the quality. Pay close attention to the smoke stack.

The one on the left is before and the one on the right is after drying the spool of PC. This was right out of the box and vacuum packed with desiccant. I deliberately opened a new spool just to conduct this experiment.

This one of the smoke stacks side by side is really telling. Look at the clarity of the right hand one after drying and the stringing of the one on the left before drying.

Just to be clear, I also ran a temperature tower as well as other tests and they all showed similar improvements when dry.


Thank you for doing this test as it’s something I have also been wondering about. I’ve just been opening fresh Bambu filaments and putting them directly into the AMS and printing right away.

Looking at your results I think I should start using the drying function on the X1C before putting new filament into the AMS.

I would throw a word of caution at that practice. I have ruined filaments by overcooking them and making them stick to one another or making them too brittle to print. So it’s always wiser to weigh your spools first. Write the weight onto the spool label so you don’t forget.

In my case, I keep blank spools around and write the weight of the empty spool on the label or spool if it’s cardboard. Then I weigh the new one for comparison before I decide whether it needs drying. Spool weights out of the factory normally don’t deviate more than 10g I’ve found.

I’ve also gone the way of using just the benchy roof in order to print the smoke stack since it is a quick print that reveals any sins lurking in that filament.

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Thanks for the great advice. I’m still pretty new to 3D printing so this is all great stuff to learn about :slight_smile:

I dry every new filament I buy and most have been Bambu filament. They lose between 2 and 6 grams of water and a few lost as much as 9 grams.

The best one for dryness I have tested was Flashforge PLA Pro. They lose between 0 and 1 gram of water.

I also dry every roll of filament that I use. I only use Polymaker products. ABS, ASA and PC-ABS.

The one thing I have never considered was the cardboard spool that Polymaker uses. I also tear off the spools from Polymaker then use the Bambu Lab split spools for AMS use. As well in my Qidi.

Now before drying I will remove the cardboard spools for the Bambu Lab spool before I dry the filament.

I dry till the weight stops going down. For Polymaker and the cardboard spools, it was between 3 and 9 grams when drying up to seven hours.

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6 years of 3D printing and i only dried filament maybe 5 times but only after it gave me problems. I would guess 3 times were with my now also 6 year old TPU spool that i maybe use once
every 2 years :smile: And the other one PETG.

I like knowing that if my print is not good, I can rule out moisture and just look for other reasons for the problem. I also calibrate every new filament at least for flow rate and dynamics.

Since you’re actively in the market, what’s your take on the sunlu s4, now that it’s finally available?

For my “Personal” use-case, it would be like buying a truck when all I need is a car. So the S4 is not on my radar.

However, Sunlu’s performance so far, along with their false claims and false advertising on their product, as well as the radio silence I received from Tech Support, puts them on my blacklist of bad manufacturers—at least for hardware. My review will cover my findings once I’m convinced I’ve done all the measurements correctly. I’m expecting delivery of a more accurate thermometer, and I am calibrating five hygrometers I have to gauge their accuracy so that I can at least say I measured both dryers fairly.

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Thanks for all the info.

All of that being said, do you think after a full drying session and right into the fully dessicated AMS, that they should not require any more drying as long as they stay in the AMS for their lifespan? One spool in my AMS (PAHT) I only print from once a week or two, and it would be semi annoying to have to pull it out and dry it every time I want to use it.

I hear you. On the other hand, if a truck can fully restore old spools of filament that a car can’t, then the truck may actually more than pay for itself. I say that purely hypothetically, because if it turns out that the car can perform that task just as well anyway, then there may be little left to be gained by using the truck other than, say, drying in parallel or something like that which may not matter to you at all.

I can’t speak to the AMS but I can speak to the principles of humidity absorption and what I am about to describe should work everywhere.

If you’re a disciplined user who keeps a digital hygrometer in your drybox or AMS, it will only provide the humidity at that moment, not the humidity absorbed over time. This is where humidity cards come in handy. You can attach them to the spool, and as they absorb moisture over time, they change color, mimicking the filament’s experience. The advantage is that with recoverable cards, once you return the spool to the dryer, the card returns to its original color, indicating a known state for both the spool and likely the filament. However, note that the cards dry much faster, so don’t rely on them solely to determine if your spool is dry; for that, you need to check the weight.

For Amazon search, use the keywords reusable Humidity Indicator Cards. Make sure you test these cards by exposing them to a steam bath. I’ve found a number of counterfeit cards on Amazon. In fact, Amolen’s filament storage bags come with these cards that are fakes. They do not change color at all. So buyer beware.

This is the one I purchased twice that work real well. But any of them will do the trick if you test them to be sure.

I completely agree. However, in my case, two factors are at play. Since I don’t use an AMS, I only need one spool at a time. Now that I’ve established a reliable dry storage system, as mentioned in the other thread, there’s little justification for the additional expense of accommodating a second spool.

Moreover, the space taken up by the larger dryer also influences my decision. Single spool dryers are compact, whereas the S4 takes up more than twice the space and costs twice as much. Even if I needed the capacity for two spools, I’d prefer to buy a second single spool dryer rather than one large one. This way, I could have one next to the printer while the other stays out of my way.

Again, I wouldn’t fault anyone for purchasing a larger dryer; I understand its utility. However, if one does their research, I would question choosing Sunlu as a preferred supplier. As I’ll elaborate in my review, they demonstrate themselves as a low-quality enterprise seeking quick profits, rather than someone aiming to enhance their brand with a great product. Yet again, we’re discussing a company adhering to the Chinese business philosophy of Chabuduo, so no surprise there.

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The way I’m looking at larger space is as a kind of buffer that, together with good air circulation, reduces the chances of hot spots. Maybe there’s a better way, though, like maybe the rotisserie method, which can be more compact and maybe still avoid hot spots. I still think that would likely be less ideal than just a uniform temperature field, like a blast oven would have. Blast ovens seem to be the gold standard against which to measure all else, at least on performance.

A thermal camera would surely help check for hot spots, but maybe an IR gun would be good enough to find the high and low temps on the spool.

I agree with your skepticism about sunlu dryer quality though. I purchased the original sunlu filament dryer (no fan) when it first came out, but returned it after determining it didn’t seem to help at all.

Most of the compact driers seem to have a stunted temperature range, maybe to avoid getting too hot of a hotspot.