Nop, I did not had any free time to work on this more, but still in my todo
I would love to collaborate with you on this. I am almost ready to switch to Capricorn tubes and give the experiment a try with 4 different color TPUs at the same time. I’m am trying to use 100a or 65d TPUs to start with and then try to dial down to 98a if everything goes well. I keep telling my self this has to be possible some how and we only need to do the work. Also, not sure if Varioshore TPU from Colorfabb would be ideal. It is a 92a TPU but colorfabb claims that it is as easy to print as PLA because they use an additive that makes the TPU expand when heated and makes it soft. So I wonder if when the TPU is cold it is stiff enough to bypass any of the tube, ams, and filament buffer issues that can cause the TPU to jam.
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Hehe 
I have tried to put a filament to fridge to see if it help, just to know, spoiler alert, it does not really works and filament pulled from the spool get back to room temperature very quickly. But to be true this was just for the love of science, never thought that it may be a real solution, but I just wanted to know.
Anyway you are welcome to post all your ideas here or PM me, I am pretty sure that the main problem does come from between AMS spool feeder and AMS output motor.
My main idea from the start is to make some kind of buffer between those two motors (spools feeders motor and AMS output motor)
EDIT : I already have a first design that I will test this WE if I get enought free time.
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is it possible to slow down AMS speeds when TPU is used
I think that the problem when using TPU is too fast feed speeds and the wire is pushed too strongly into the hot end. therefore the TPU twists and gets stuck.
can we adjust the AMS operation? as far as I know we don’t.
You probably right, and this is probably something like this which is happening, the output motor pushing too hard and twisting the filament (I have posted a picture of the internal of the ouput motor unit somewhere upper in this thread that show this problem)
No there is in my knowledge no access to the AMS controller software, but we have access to the data bus and to some other parts and connectors on the AMS board. I have not that many time to work on this, but I work on it a little regulary each week, actually, I am looking for a solution that would not imply too much works or cost, I dont want to re-build a full AMS :).
The next try I will do, will probably to use an external extruder at the output of the AMS, if I can not get it working with a more simple solution.
In my case, with TPU, I never had any problem other than in the AMS motor ouput unit, so I am concentrated on this unit and how can it be modified.
EDIT :
Below is my last attempt, the idea is to enable some kind of buffer between AMS spool motors and AMS output motor, spoiler alert “this does not correct the problem” but I think that in some way it help as it enable to better handle a wrong synchronisation between different motors (spools and output motors), I have to try such buffer after the ouput of the AMS to avoid TPU filament (or any other filament) to be pushed with force when it have no more space in the PTFE tube, this little system couppled with a spring or elastic is intended to let some free space/simulate an extendable PTFE tube (to avoid permanent deformation of the filament).
Some news,
I just ordered that on Aliexpress :
I am convinced that the AMS output motor is not strong enought, it is audible that as soon as the spool feeder motor stop, the AMS output motor is forcing a lot too much and filament is moving too slowly IMO (I have tested with two different AMS and three diffrent AMS output motors units), it is even more noticable with TPU filaments (also spring tensioning of this extruder is too strong for TPU, this may also explain the problem).
When unplugging the tachometer of the AMS output motor everything works better as the spool feeder motor does not stop and both motors are working together, but then problem is that the AMS get crazy and indefinitly load & unload the filament.
There are many ways to improve the printer, but you can use a new material developed by our company Moisture-Activated Filament to make the part you want, made of both solid and soft plastic. Printing with this material is easy, just print it as PLA.
I wont call that a solution in any case but at least it is interesting to know you make filament of blended PLA and TPU.
That’s odd - it’s bunching up so you want to push on it harder? Ah, that is the final output motor?
Thanks for posting the picture of the filament jam. I’ve never had one with TPU, but at least I can see where it happened. It seems like the spring-mechanism on the back of the printer perhaps wasn’t taking the TPU as fast as it could have? That or maybe a filament sensor didn’t trigger?
@ marko.pietikainen Yeah, that’s a good point, on the MMU feeding slower could help, and it’s reasonable here, given what he’s seeing.
I did some short print, I think a squeegee, with probably 15 changes and it worked fine, but even just for material handling I’d like to see switching work.
The lack of TPU support is really annoying. I want to print a hybrid PETG/TPU part (mixed layers) and without the AMS I don’t see how it’s possible.
I can’t practically change the filament manually throughout the entire print. Are there any other approaches I might not have considered?
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Bambu never put a blanket ban on just any TPU: Their wiki says the printers can handle 80A/30D or harder, and the AMS can handle 55D/98A or harder.
There are some reddit threads where people have listed brands/types that worked or not. I’ve been meaning to experiment with it but haven’t had the time yet. I noted from some such thread that I might want to try Overture High Speed TPU 95A, Extrudr Flex Hard TPU 58D and/or Priline black.
My use case is printing seals in place. I do have some CC3D TPU 98A but didn’t try it in the AMS, I might do so but to me it feels just as soft as Bambu’s 95A.
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Has anyone had success using 2 different external filaments and switching manually at the required layers?
I have never tried it, I am far too concerned about messing something up in the AMS and while the rear spool holder is not near as convenient it works for me. With that being said, a friend of mine has had no problems using Bambu’s own TPU (95A) in his AMS. He said he used a mod to extend the tube I think it was this one (AMS Saver V5 by madizmo - MakerWorld) but I am not 100% sure.
I haven’t tried it but I noted that you can’t insert a “filament change” at a layer for this. Their “filament change G-code” is made for AMS only so if using external spool it’s just a no-op and the printer will chug along with the old, now wrong, filament after no pause at all. It should be easy enough to amend that code with some conditional for when external spool is used so it works for both cases - in fact it may have been discussed semi recently on this very forum?
So what we currently need to do, is insert a pause instead. Very unintuitive design but as long as you know that, shouldn’t be a problem at all. It pauses, you switch the external spool and then you resume.
Taking it a step further, IMHO we should be able to switch between AMS and external spool back and forth at will, within a print. Even within a layer, not just between layers. I made a GitHub feature request for that but I’m not holding my breath.
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Thanks for the tip, I actually overlooked that and it’s an absolute top link!
Since the information are about the AMS and the AMS lite, the information seems to be really up to date so there should by nothing dusty that has been overlooked or not updated.
The follow-up information are also absolutely great too, Thanks!
By the way, I’ve been over it with Orca - at least the slicer doesn’t cause any problems with TPU/ASA mix with the AMS - but I haven’t sent anything to the printer yet (the printer will be working for another 2-3 days before I get a free plate to try this out 
Shore 55D would be a very helpful start - I really have to try this out, especially for the adhesion of the first layer on certain parts. 95A are applications that I would very rarely need - I use 55D far more. Splitting properties and chemical resistance as well as UV resistance - although pigments can also change color when reacting to the environment. Whatever the case, AMS mit 55D would be already a huge step forward. Thanks!
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I’ve not tried with TPU, but I’ve manually changed colors without an AMS using PLA, PETG, and ASA.
Simply adding a Pause at a layer used to cause a slight layer shift, but that may have been fixed. I’ve not risked it with recent firmware/software. Instead, I Add Custom G-code, which does not create a shift:
M400 U1 ;pause
G28 X ;home
With the printer Paused on my X1C, I don’t have access to the screen controls (Resume or Cancel are the only options), so I use Studio or Handy to make the manual filament change, and then Resume.
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Wow that is a ridiculous bug, and a very valuable piece of information - thanks!
Hmm okay so a working option thanks Ikraus. It would be nice to have a hub option like the tie in for multiple ams, instead for an external spool and your ams, then u can have tpu externally and still ams filaments.
One of thw issues is the hub in the ams. It has magnets in hall sensora and tpu may not be rough enough to lift the magnets, it would get tgere and start gathering up. Also if it dose make it through the ams the hub on the back of the machine will cause issues with tpu. Tpu is just way to flexible to work properly in the ams
Now I had time. That works with Orca - but only in Orca itself.
But TPU can not by used in my firmware (Printer 01.06.05.01 / AMS 00.00.06.40) since you can select TPU in the Fillament settings on the printer but the Pinter will not accept the Filament typ TPU for AMS.
@BambuLabWikiTeam your Wikipost TPU printing guide | Bambu Lab Wiki is wrong. May it works (TPU 75D or harder in practice) but is not supported/blocked by the Bambulab Software as well as not on the Firmware of the hardware. If it’s due to the firmware I use, kindly add the usable printing firmwear version to the wiki.