Simple question, how the bloody hell have people successfully managed to dry PET-CF/PAHT-CF?

So far only printed PLA, which has been very straight forward. Looking to print under the hood car parts, which requires one of the higher end manufacturing filaments (heat/strength). According to the Bambu these both require drying @ 80°C for 8-12 hours

My current setup is a P1S, no AMS. As I understand, after days of going into this rabbit hole, there are a few options:

  • Oven; doesn’t seem like a great option. Potentially harmful to cook food in after. Temp can vary too much, and not match what is set. Not necessarily a consistent temperature throughout the chamber.
  • Food dehydrator; seems somewhat popular, but getting one that goes up to 80°C (usually they go up to 70), is tricky and gets more expensive. Also as I don’t have an AMS, would then need to also buy/create a dry box to store and feed from.
  • Dedicated filament dryer box; leaning towards this option as it allows me to dry, store, and feed. Options include SUNLU Dryer Box FilaDryer S2 (up to 70°C), EIBOS EASDRY (up to 65°C), or EIBOS Dryer CYCLOPES (up to 70°C). Big kink is none seem to go to 70°C. Aware the S2 has some issues, but seem to be easily fixable.
  • Using the printer itself; seems feasible, but concerns around burning through the elements, and prevents printing during this process.

My preference is the filament dryer box, but given they don’t reach the desired temperature, will they work, maybe running them for longer? What have you had success with? Help!


Edit @ 2023-08-28T19:40:00Z: Attempting to summarise the information in the thread, will update in the future based on further info.


  • Selfishly I’m tailoring this info for humidity conditions in the UK (70-92%)

Key points (do not take this as gospel/fact):

  • The reason most driers and food dehydrators tend to not go higher is that 70ºC is the max temp something can reach without requiring protections against the user being burned. UL says below 70ºC only needs a “HOT” warning. Above 70º and you fail UL testing unless you add extra insulation (which raises the cost of your product) - @RocketSled

  • Although Bambu states drying for PET-CF/PAHT-CF requires 80ºC for 8-12 hours, members have had success with dryers with stated max temp 70ºC

  • Results will vary based on your own environment (temp/humidity)

  • Lower temperatures should still work, but will probably require longer drying times

  • Driers without a fan, will work but will take longer. Fanless Sunlu S2 is estimated to require 30-50% longer, than the fan equipped version of the Sunlu S2.

  • “The thing about filament drying that many people miss is that the RH reported by the dryer is the air not the filament. Just because the dryer is reporting 10% RH doesn’t mean the filament is dry. Proper drying requires getting the RH to a low value and keeping it there long enough for the moisture in the filament to diffuse out of the plastic. It takes time. I don’t think many people have the patience to wait 24 to 48 hours after the dryer’s RH has bottomed out.” @RocketSled

  • Vacuum drying is the fastest and most consistent, but more pricey @RocketSled


Name State temp range (°C) Max temp Tested with PET-CF / PAHT-CF / equivalent† Removed water after 30’ Removed water after 1h T, RH during test
eSun eBox* 60 46°C @vladimir.minkov what filaments did you test with? 34.7% 73.2% 22°C, 50%
eBox Lite* 40-55 48°C 48.0% 90.3% 22°C, 50%
Sunlu S1* 35-55 42°C 18.8% 36.3% 22°C, 50%
Sovol* 40-50 50°C 22.3% 56.1% 22°C, 50%
Creality* 40-50 51°C 39.9% 69.9% 22°C, 50%
Eibos Cyclopes* Up to 70 63°C 75.8% 99.9% 22°C, 50%
Sunlu S2 Up to 70 50°C / 64 (tested by @Lemming :white_check_mark: with PA (@RocketSled @just4memike), with PET-CF (@Ceppetoswerkstatt), see key points ††. 23% 48.8% 23°C, 50%*
Eibos Easdry 40-65 57°C 45.2% 91.1% 22°C, 51%
Eryone Snail 40-55 55°C 32.6% 74.5% 23°C, 52%
Fixdry 45-70 45.1 @Lemming Mixed info, not advised N/A N/A N/A
Print Dry Pro 3 35-85 N/A @freeformz what filaments did you test with? N/A N/A N/A

† Based on information provided by Bambu Lab found in drying filaments on the printer. PA / PA-CF / PAHT-CF / PET-CF / PC / ABS / ASA require same drying requirements and are considered equivalents.
†† Available in fanless and fan version. Both should work, but fanless will require longer. Fan version does not seem to be available in the UK.

Baseline information MyTechFun. Other sources referenced in table.

Hope that helps:
i am using esun drier lite with small bag of silica and printed silica container in the middle of the roll, it has 3 settings on the highest the heat plate is around 100C+ in the box is only 50C and the keep it for around 15 hours and rotating the roll a few times, some times more than 15 hours ,
As my silica changes color i have one container in the air and put it together for drying and keep the roll at least until silica shows me that lost all moisture and more
Then move it to container with lots of silica 500g and keep it there if not using

I got extra drier and these days i print from the drier directly and leave it running on setting 1 or 2 all the time even when print. From the humidity meter custom print and cheap one from aliexpress < 2$ . If i turn it off for more than 12 hours it starts getting moisture

Also used 2 times the printer , but takes out of print time so not using it , and by the way inside the printer chamber is also difficult to get above 60C at 110C plate

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Heat only quickens the process, if you plan your filament use of the more hydroscopic filaments just use desiccant in a vaccumed bag, it does exactly the same thing without the heat. Again if you live in moisture rich environment though and need both a drying system and heating system the AMS gets that hot sitting on the glass ceiling of the system I live in Florida and my houses humidity is about 50-65% but my AMS never gets above 20% with the desiccant beads as long as it is closed and sealed

I use the Bambu wiki as guide to drying filament in the printer. ( I see it has been updated to included the P1S.) Because it is less efficient, the times in the chart are a bit longer, and the bed temperatures are a bit higher, than the suggested air temperatures Bambu suggests using in a dedicated filament dryer.

Drying the filaments you mentioned calls for 90-100º C bed temperature for 12 hours, flipping the spool after 6 hours.

The times given in the chart work well in my X1C. I do use a small digital scale from the kitchen to monitor the weight of my spool. If the weight stops dropping for an hour or two I will stop the drying early.

I’m not concerned about burning out the heating elements, but being unable to print while drying is a nuisance. I only print occasionally, so I’m willing to tolerate the delay for now.

Big thank you for the replies.

@william.e.lewis464 playing devil’s advocate, not my opinion as I’m pretty uninformed. However, whenever I’ve seen this suggestion the common response is that the dessicant only absorbs moisture in the air, and requires heat to actually force the moisture out of the filament.

Additionally, should’ve mentioned I’m in London, UK. Humidity is between 70-92, and for months can be closer to the top end.

@vladimir.minkov, @lkraus - both very helpful. Based on this I’m thinking of getting the SUNLU S2, currently available for £50, and following a similar process to Vladimir. Saves me having to create appropriate storage for the spool once de-moistured (?). Only planning to have one roll in use, so I’ll probably keep it in the drier and feed from there - I don’t have the AMS.

Make sure you get the latest 2023 edition of the S2 which includes a little fan to recirculate the air inside the enclosure.

Wasn’t aware there was a version with a fan. Plan was to keep the lid ajar whilst drying, then close in with dessicant when dry. Had a look, but can’t seem to find any in the UK with the fan upgrade. Can get the EIBOS EASDRY which has a fan, however it only gets up to 65 deg C.

Edit: About filament dryers Useful link on performance of filament dryers. His methodology seems sound, see YouTube video links on page. Based on this Eibos Easdry (£60) / Cyclopes (£98), seem the way to go.

I had no issue ordering the fan-equipped S2 from Amazon Germany but noticed that this version is not available on Amazon UK right now. :thinking: Da§#%* Brexit… :grimacing:

It actually is quite hard to distinguish the old S2 from the upgraded version with the fan. They look completely identical on the outside and there is no hint whatsoever on the packaging or the device itself. Only when switched on you can hear the fan running. As it is hidden below the lower hearing element, you cannot even see it.

I have both versions and noticed a significant performance increase from the fan. I use a little spacer to keep the lid slightly open and allow moisture to escape. This does not affect the temperature at all as I could confirm with a calibrated laboratory thermometer. The spacer I got from Printables even includes threading for a PTFE tube fitting, allowing me to print directly from the dryer.

All in all the new S2 is the only of the three dryers I had here for testing that (almost) reaches the promised temperatures and delivers the expected performance, considering weight loss as well as print performance of the filament after drying. The old fan-less version of the S2 worked as well but much slower, and a very similar device from a competitor stayed almost 20 °C below the set temperatures and did not retrieve a single gram of water from some quite moist filament… :roll_eyes:

I bought a Print Dry Pro 3. Pricey, but goes up to 85°.

UPDATE: see further tests below, I returned the fixdry unit…

I got a fixdry (https://www.amazon.com/dp/B0BWYKLWDX) and it has definitely made a difference. Also only 70C max, but as far as I know that mainly means longer drying times are required. Given your environment if you venture outside of PLA you will have to print out of a dry box or AMS with plenty of dessicant packs.

I’ve got 4x S2s and they all work just fine.

The thing about filament drying that many people miss is that the RH reported by the dryer is the air not the filament. Just because the dryer is reporting 10% RH doesn’t mean the filament is dry. Proper drying requires getting the RH to a low value and keeping it there long enough for the moisture in the filament to diffuse out of the plastic. It takes time. I don’t think many people have the patience to wait 24 to 48 hours after the dryer’s RH has bottomed out. The ambient environmental conditions speed up or slow down the process in a way that’s not easily quantified.

If you want fast and consistent drying, vacuum dryers are the way to go. Vacuum reduces the “vapor pressure” for the moisture in the filament. It “cooks off” really quickly. An hour of vacuum is probably the equivalent of a couple of days of heat drying in a high humidity ambient environment.

There is no “magic” temp. The upper limit for the dryer is the glass reflow temp of the filament. Go higher than that and the filament will start to bond to itself on the roll. PA dries just fine at 70ºC. The reason the dryers tend to not go higher is that 70ºC is the max temp something can reach without requiring protections against the user being burned. UL says below 70º only needs a “HOT” warning. Above 70º and you fail UL testing unless you add extra insulation (which raises the cost of your product). So the 70ºC max is just fine.


+1 on the 70C dryers. They work fine. I use a Sunlu S2 (no fan) which has a maximum of 70C and it works fine. Never had to do a second cycle, generally within printing parameters within a single 8 hour dry cycle. I normally keep it on while printing though. PA sucks in moisture like nothing else. One to two hour prints will be fine, but much more than that, and you might have a problem mid print. In an AMS, I imagine you can print fairly long prints, but I prefer the peace of mind in the dryer.

I dry my PET-CF with my Sunlu S2 dryer for 12 hours at 70 Grad Celsius

That’s the one that did not work here at all. This is after running the device for more than seven hours:

The upper value is from a probe resting in free air inside the enclusure (cross-checked at various spots with only very minor variations), the lower one comes from a probe nested between the filament strands and, hence, measuring the actual temperature of the material. After having the moist PETG in there for 24 hours, the weight of the spool was exactly the same as before, so no moisture has been extracted at all. Just as expected with such low temperatures.

Immediately thereafter, I transferred the filament to the new, fan-equipped Sunlu S2. Temperature readings after about 6:45 hours:

I weighed the spool upon completion of the 8-hour-cycle and it already lost 3 grams, then one more after a total of 24 hours.

I contacted Fixdry support with this data and asked whether my device is defective. The answer:
„We would like to take this opportunity to explain our filament dryer’s unique features. Our dryer utilizes PTC heating technology and a fan to effectively dry and dehumidify your filaments. The hot air is blown into the dryer from the outlet, and then the fan circulates the air to ensure even distribution of heat. Therefore, due to the temperature difference at different positions inside the dryer, you may notice slight variations in the temperature compared to the set temperature. However, this is a normal occurrence and does not affect the dehumidifying performance of the dryer.“

Well, needless to say that I returned the Fixdry for completely lacking the promised performance and kept the S2 instead… :man_shrugging:t2:

I use the 2023 S2 for actually drying the filament and keep the older, fan-less S2 to be able to print from one pre-dried spool while drying another one in my primary device. Works quite well for me. However, to get back to the original post: I have not attempted to dry any filament requiring higher temperatues than 70 °C yet. Therefore, I cannot make any promises regarding the performance of the S2 with such materials.

Edit: In my experience, the fan-less S2 is perfectly capable of removing just as much moisture as the new edition (provided you keep the lid open by a few millimeters). The difference is merely in the time required to do so. I have not done a thorough test, but I’d estimate it needs about 30 to 50% less time for the same result.


Great stuff. Out of curiousity do you have the measurements/details for the third drier you tried? Thinking of summarising all the available data (from the replies in this thread and external sources) in my original post.

Edit: Updated original post

Thanks for posting your measurements. I went back and tested my unit. Glad I did!

I first inspected the inside and saw that there are no vent grilles or baffles, so it’s not clear what the intended airflow is (the fan is on the bottom of the picture, not visible on the other side of the side-wall). One can see the heating element (I have a probe stuck to it in the photo) and the temperature/humidity sensor basically right next to it. A 1/2 sq in surface of the heating element showed 90C, so it is indeed heating.

I then put two probes inside with filament:

Basically same observations as @Lemming (47C and 39C). This was after several hours and ambient temps >30C, so not in a snow storm ;-).

The unit has a fan and it blows air out. What’s not clear is from where nor where air is supposed to get in. I have the feeling it’s drawing cold air in through the various cracks and blows hot air out given that it’s very close to the fan.

My unit is now on its way back to Amazon… By luck there was a 10% off on the Sunlu S2, I’ll see whether that works any better…

My Sunlu S2 worked for everything so far, even though it tops at 70ºC and doesn’t have a fan. Most rolls dry just fine in 5-6 hours, but I open and vent it briefly when it’s drying to let the saturated air out (not sure it does anything though). I also sometimes dry filaments in bulk in an oven, but there I use a lower than recommended temperature because the temperture varies a lot and there are hotspots in there (your oven might work better). I just drier a bunch of PETG at just 50ºC and it did dry just fine, but I left it in there for almost a day.
I tend to print Nylon straight from the drier, but PAHT-CF prints just fine from the AMS if you have it dry with fresh silica beads, I kept it there for almost a week and it worked fine (that was after drying it because it actually was very moist, so I have a comparison).

The Fixdry did help me drying filament. I had clear moisture issues with PAHT-CF and put the spool in the fixdry for >24hrs at the 70C setting. The spool lost several grams of weight and the prints were substantially better afterwards. So the unit is not completely useless, at least in my dry climate, but the design is very strange (shoddy).

One vote for the food dehydrator, which is cheap, reliable and functional.

I bought the Silvercrest, which is quite affordable (<40€) and has three years of warranty. It goes up to 70ºC and entails a circulating fan and high power (350W).
With a simple cake transport case cover, you can dry two spools and even more with tinkering. And the total investment will stay below the 50€.

I know that premium products have some fancy add-ons and great designs but at unreasonably high costs. The only extra I miss and would pay more is the ability to dry at higher temperatures, which is helpful for more demanding filaments. Yet such equipment (e.g. constant temperature oven) is expensive and overkill for home use.
Note: Besides the silica colour change trick, you may also weigh the filament.


FWIW, Vision Miner recommends drying PET-CF at 90C for 6 to 8 hours:

which is outside the capability of all of the filament dryers listed by the OP.

In addition, they add a very curious footnote: “* These temperatures are intended for a dehumidified hot air dryer, using air with a dew point below -40°C.” What the heck does that even mean? It sounds as though they want any air that’s entering into the dryer to already be that dry, even before it gets heated up?