AMS HT Rants

[hotellonely]

Among all of the Bambu Lab products, AMS Lite and AMS HT might be my worst picks. While AMS Lite is terrible for filament storage, it’s at least featuring fast color swaps. But AMS HT, after use of a couple weeks, all I felt is total frustration.

1. The filament can only reach 70C when the heating was set to 85C.

I don’t care what’s the excuse, but yes this is what you get from 16C room temperature in Sydney’s not so cold winters.

The branded “85C” was only achieved from the hot air vent. Not from the otherside of the chamber like most other filament dryers. Even the cheap cheap Creality Space Pi is doing it right. And the AMS HT is barely reaching a higher temp if not equal, when the Space Pi is set to 70C.

2. The bypass outlet design is TERRIBLE in every possible way

First, it’s on the lid, where it moves with the lid when you open and close it.
While it might not be an issue alone for TPU, it would be an issue for PPA-CF or other strong but brittle engineering filaments. Yes, there is no way to use the outlet without breaking the very brittle filament, because when you’re closing the lid, bang, the filament snaps.

Second, it has a terrible designed outlet angle, introducing more friction when feeding TPU. So it’s not good at TPU as well.

Any other sensible drybox/dryer manufacturer is at least putting the some of the outlets on fixed positions. Why it has to be fixed? Because you would not introduce unnecessary filament breakages.

Creality X4 for example

Sunlu S4 for example again

Both also have outlets on the lids, but that’s not the ONLY option they have.

And did I forget to mention how much easier it is to feed TPU smoothly from these dryers to the printer?

3. Tiny dessicant space to keep the internal space dry, while the sealing isn’t the best notch.

Without extra modification you can expect the internal RH to raise by 1% everyday. With extra modification to add extra dessicants, you can expect it to raise by 1% every two or three days. But still the sealing/the ability to keep the chamber dry is terrible compared with OG AMS or AMS 2.

So, save yourself some money, if you’re not already fully maxed out with your current AMS OG or AMS 2 Pro setups. The AMS HT is really not worth it for what it is.

[The-Ollivator]

Thanks for your post! I really like how you described it and the effort you put into it. Unfortunately, I’m a little disappointed, especially considering the price. Why can other manufacturers do it so well in such a short time, but bambu lab unfortunately can’t?

[KMiller]

Very informative post. I already have an AMS HT but I bought mine for a slightly different use case. I really just wanted something to automatically feed the left extruder and I don’t have the space for another AMS 2. I primarily print in PLA/PETG at the moment. I’m primarily a hobbyist and I just decided to jump in on the H2D. I can agree that my AMS HT RH does drop faster than my AMS PRO 2, however, given the materials I use it’s really not an issue for me personally. I also use Activated Alumina and a model I found on makerworld for the desiccant system and that seems to work much better than the included desiccant. You’ve definitely given me something to consider as I learn to use more advanced materials and I thank you for your earnest review.

[hotellonely]

To be fair, the drying function of the AMS 2 Pro is “okay” to me, as it’s only branded to 65C so it’s good enough for anything below nylon and PVA. But everything for AMS HT makes me feel like they really didn’t think through this, or throughly tested for what it should be aiming for (printing extra soft or extra hard/brittle filaments).

[Luke.S]

the difference between the AMS HT and the Creality Space Pi is that, the Space Pi doesnt rotate the spool while drying, so i guess the constant temperature in the chamber is needed. While in AMS HT the spool is rotated, so every part of the spool will get heated to 85°C anyway.

AMS HT reminds me alot of EIBOS polyphemus, it’s only really hot at the base where the heater is.

Did you measure the temperature in the Creality Space pi? Would be interesting to know this as well.

[hotellonely]

The original Space Pi (single spool) can reach 65C on spool… when set to 70C. And the heating element area can go beyond 85C.

[StreetSports]

I wonder what the temp is directly in front of the heater. Maybe it cools as it spins away. I imagine, to have the intake and exhaust ports, and spin the roll, the heater air would have to be much higher to keep the other side of the roll 85c. Melting the filament in front of the heater. The ports are a positive and a negative.

The filament outlet in the lid is a very bad design. Agree 100%.

With old style dryers, I opened them once every couple hours to let moist air out. I believe the ams ports stay open alot, so youre losing air and heat constantly. Makes reaching equilibrium impossible until the ports close. But I guess people wanted this?

Its because people assumed the roll would soak the moisture back in while sitting in non vented, heated air. My thought was always that thats not how it works. It would need to cool in that same moist air, to reabsorbe the mosture from it. The vents could open for a minute every hour or two and probably achieve the same outcome, more efficiently and reach equilibrium(actual 85c through the whole chamber) for longer periods of time.

We need more settings for everything. Time settings for the vents can be added to the list. This minimalist, locked down system will always have these issues. We need a cleaned up version of klipper settings/possibilities. Like a klipper config file mated with a pretty GUI. Macros ftw

[just4memike]

I didn’t have the same issues with mine. When checking the spool temp at 75C it was around 70C (71C - 73C but I didn’t write it down). Haven’t tried going to 85C yet. Same with the super brittle filaments, haven’t tried it yet.

Looking at your screen shot of the temps, I see brighter areas on the face on the filament, so it doesn’t seem as though you are measuring the hottest points. Were you more interested in the median or average temps?

I’m running a short cycle now to see if my memory is right, but I’m almost sure it will be closer than +25C off.

[hotellonely]

It’s winter here in australia, so the temperature difference would be larger. But it also highlights why it’s not very good idea to regulate the temperature by putting the temperature sensor near the heating element. It should be put to somewhere further away down the air flow path, so that it can get a better understanding of the actual chamber temperature.

I have tried to get the max temp but it’s still 70 ish. Thermocouple measurement proved it as well.

[just4memike]

After around an hour of drying at 75C, mine maxed out on the spool and filament at 66C but had an average of around 60C (with the spool spinning). The air and housing at the bottom near the entry was in the 68-70C. Definitely under the stated value, but reasonable, IMO. I didn’t run it to 85C to check the temps there, but I can see why someone would feel underwhelmed.

However, I do feel like these are the best dryers (AMS 2 Pro and HT) I’ve used, so I’m not unhappy.

[Leif3D]

More important is the temperature where the heating element is the closest to the spool.

The last thing you want is that the spool or material gets too hot at the bottom just to reach a higher temperature at the top. Sunlu had that issue for example with some of their recent dryer prototypes (think it was the E2).

The turning mechanism will compensate for the colder temperatures at the top.

[hotellonely]

hahahahhaha

@Leif3D

More important is the temperature where the heating element is the closest to the spool.

The last thing you want is that the spool or material gets too hot at the bottom just to reach a higher temperature at the top. Sunlu had that issue for example with some of their recent dryer prototypes (think it was the E2).

It’s always gonna be non uniform. But the problem is you can always lower the temp when you target a higher temp at design. Not the other way around. It’s very easy for sunlu to simply lower the temperature for 5 degrees, but it’s very hard for bambu to dry nylon efficiently

[APEX86]

What are you laughing about? That is true.

If you set the dryer to 85c, no part of the filament should get significantly hotter than 85c. That basic laws of heat transfer say that unless the entire unit is extremely well insulated, there will be a large temperature gradient from the heater outlet, to the far side of the dryer.

Have you actually failed to dry filament that should fully dry at 85c?

If you are so particular about drying, I assume you have a 0.1g accurate scale that you can check spool weights before and after. Take a before measurement, run a full 85c drying cycle. Measure again. Then, but it in your oven at 85c for a couple more hours and see if the weight decreases any more.

Your thermal images of the open dryer aren’t evidence of lack of drying performance.

[L0rdS474n]

One thing I’ve noticed is that my old, trusty EIBOS dryer — the one that actually spins the spool like it means it — keeps everything nice and evenly heated. What the AMS HT does exactly? Honestly, I’m not quite sure. Every filament I dry in the AMS HT or AMS 2 Pro ends up brittle in record time and loves to snap inside the PTFE tubes like it’s trying to escape. I’ve never had to clear so many tubes in my life.

I suspect it’s because the AMS units don’t rotate the spools consistently — they just sort of… do it when the mood strikes. If they spun every 5 seconds or so, maybe we’d be friends.

On top of that, both units grip the filament like a bulldog. If you have “detect when unit is on” enabled, all the back-and-forth movement ends up chewing up the filament until it eventually breaks in the tube. Not ideal.

That said, the motors are strong. One time the cutter failed, and the AMS yanked the filament back in with such force that it cleared the tube without even cutting it. Big bang, little panic — but hey, it worked!

[hotellonely]

@APEX86

What are you laughing about? That is true.

Editor bug, was replying to another post.

@APEX86

If you set the dryer to 85c, no part of the filament should get significantly hotter than 85c. That basic laws of heat transfer say that unless the entire unit is extremely well insulated, there will be a large temperature gradient from the heater outlet, to the far side of the dryer.

Problem is there’s almost only a few kinds of filament that is actually optimal at 85C for drying. It’s either lower than 70C, or actually asking for significantly higher temps.

According to Bambu, these are the filaments suggested for 75-85C drying. You can see that most of them are already taking a quite long drying time. Especially for PAs.

Then for the range of PPA/PPS, 85C is already on a very low stretch for those filaments.

The so called overheating issue of Sunlu E2 can be easily fixed by reducing the temperature but it’s very hard to increase the temperature for AMS HT.

I’m not talking about “failed to dry”. I am talking about drying efficiency. As long as you give it long enough time, it would still be able to dry the filament. And my other major complaint is the terrible bypass outlet design. It’s just quite inconvenient and overpriced for what it is.

[hotellonely]

@APEX86

Your thermal images of the open dryer aren’t evidence of lack of drying performance.

Well. I actually also measured it with thermocouple. Near the AMS inlet side of the spool, the air temperature is only 70-72C ish. The only thing that might save the grace is the ability to roll the spool over the process, but it’s apparently not dry and hot enough to let the inner rolls of a saturated spool dry out.

Yes we can say it “works” as a dryer, but for its price, its terrible design of outlets, I wouldn’t really call it a good investment. Because other dryers can do more and better in this price range.

[Paul_B]

Completely agree with you. I am very disappointed with mine. I bought it for TPU and Nylon. The sealing is my biggest gripe. First even after three or four 12 hour cycles the humidity only get s down to 15% and after sitting for a week it’s back approaching 30% again. I’m in the UK summer and the humidity has been above 50% most days but the Pro2 sat next to it takes the humidity down to 3 or 4% and stays below 10% for weeks. It is impossible to print PA6-CF through the bypass as the angle is terrible. I’ve been forced to make a dry box with rollers in and lots of desiccant to be able to feed TPU and PA6-CF after drying in the HT.
It is absolutely not worth the money. I spent a long time thinking I had a bad unit but it seems not.

[just4memike]

@Paul_B

…humidity only gets down to 15% and after sitting for a week it’s back approaching 30% again.

This is the only issue I have. Mine was 19% when it was done and cooled down yesterday after a short cycle, but now, it currently sits at 26%. Personally I don’t like printing TPU over 30%, so I’ll likely have to start another cycle when I want to print it.

@L0rdS474n

I suspect it’s because the AMS units don’t rotate the spools consistently

When I checked it yesterday, I only saw 6C difference from the furthest to the closest to the element. IMO, that is solid. It doesn’t move like a rotisserie, but it appears to be effective.

All said, I can understand the disappointment in it not reaching the stated temps. I checked mine when it was mid cycle and the heater was running (likely harder than normal, because the door was open and temps going down) where the air and plastic panel was still 6-10C under the stated temp. Personally, it has worked well, and dried everything I’ve thrown at it in a reasonable time, so I’m not disappointed… but I can understand.

[illien]

I’m not upset about it as the price is still okay, it beats out cardboard on the heatbed for those with no other options so finally anyone can print dried PETG lol. But I never did and never will use their drying features. If you check Bambu’s own recommended drying time the HT/AMS2 Pro is terribly inefficient for a number of reasons, but most importantly the complete lack of active air flows to move heat + moisture around & out.

Nothing beats a dumb blast oven w/ big fans, dirt cheap too (at least for my place) compared to dedicated plastic ‘dryers’ marketed at FDM hobbyist, imo all those ‘smart’ features are worth neither the performance sacrifice nor absurd price tag. A decently sized one can dry 3 rolls at once and bonus point, 105C to regenerate silicon desiccants… safer too.

[L0rdS474n]

Something seems to differ, as I consistently end up with damaged filament when drying in my AMS HT and AMS2 Pro, compared to my EIBOS dryer, which continuously rotates the spools.

The only thing I’m not entirely satisfied with on the new AMS units is their tendency to “chew up” the filament, causing it to break inside the PTFE tube.

In addition, none of my AMS HT units allow the spool to rotate freely, which makes it very difficult to print with TPU — which was actually my main reason for purchasing them in the first place.