For some reason after drying (im pretty sure it wasnt like this before), my 85A TPU became sticky, causing my printer to constantly underextrude, because it could barely pull the filament off the spool.
Is this normal?
It litterally was fixed if I take the connected filament line, and pull an extra amount off the spool to “loosen” it from the stick.
I was using the TPU setting on the AMS 2 Pro to dry the material.
I think it’s more about stretching too thin to extrude with any kind of load on it. I’ve successfully printed TPU 85A but only when I either hand pulled the filament from the spool, creating some slack, or, I ultimately fixed the problem by making a ‘feeder’ where the spool will be turned slowly if the slack ‘tightens’ up.
This worked on a X1C and P1S and manually starting the filament with the AMS feed disconnected.
Manually pulling the filament to create slack is what I was talking about, thats what worked for me.
But still I dont have any other filament (TPU 90 / 95A) that when dried like this becomes sticky.
But could you further explain what you meant by making your own feeder?
I use a Sunlu S4 dryer and keep the filament in one end. I modified the ‘inside’ roller so that I can rotate it with a GT2 belt. On the opposite roller position, I’ve placed a gear motor that drives the belt and also has a tension arm to control the motor on/off.
On setup I pull enough filament off the spool to feed through the tension arm and then out the far filament port in the door and then manually feed it into the printer through a PTFE tube replacing the AMS connection. When printing the only tension on the filament is lifting the lightweight tension arm and the friction of the PTFE tube. As the filament is taken up, the tension arm lifts, trips a switch and turns on the gear motor to drive the spool. The gear motor is only 6 RPM but it’s plenty to keep up with the extrusion.
Could you please explain how you dried it?
Huh, now that I think about it, the AMS 2 Pro does have motorized rollers that turn the Filament for drying when its disconnected from the inlet.
Couldnt that be used in junktion with the gears to push AND pull the pillament at the same time to achieve a similar effect?
It could be done as a hack but good luck getting any documentation from Bambu Labs and for sure it would void your warranty and you’d still need a tension sensor.
Idk, I feel like it wouldnt need it, if you have in G-Code already every step of the extruder gear planned out, you can litterally sync up the motors of the AMS to rotate the spool simultaneously (if not first) to match pace, always ensuring the consistent feeding.
That wouldnt even be a hack, but could simply be firmware backed in to operate during printing, with Studio injecting it into the G-Code, which btw I assume the AMS already does when printing with any filament from it. Except instead of rotating the whole spool, it simply pulls filmanet forward with the gears by the inlet, so if you just add 1 more step in that where you instead of “pull with AMS inlet gears → pull with toolhead extruder” there is now “rotate spool → pull with AMS inlet gears → pull with toolhead extruder”.
The main difference might be how much you have to rotate the spool and the inlet-gears ahead of the extruder, depending on softness of filament, to give adequate amount of slack?
They announced drying while printing as a feature coming in the near future, so I dont think its that far fetched.
I missed this earlier sorry.
I put it in the AMS 2 Pro, set it to default TPU settings of 75° for 18h then tried using it.
Just for confirmation, the TPU isn’t in any AMS for the purpose of printing?
You are using the recommended method, which for most printers involves inserting the filament directly through the print head and not using any other route.
Are you also using the recommended nozzle size?
Yeah I dont use the AMS for printing TPU, I have my own side mounted enclosure that I use for ‘external’ material printing.
I tried using both direct connection to print head and feeding it through the XY’s filament tube that connects out the back of the printer. Both have me the same result.
I also tried printing the material with a .4mm and a .6mm nozzle that came extra with my P1S, both again giving me the same result.
Initially with the .6mm but I wanted to try and see if it was possible to print with the .4mm in the first place, since I noticed no difference it seems possible, and the “not compatible” marketing from Bambu is probably just airing on the side of caution to prevent any issues that are just more likely with that nozzle size.
75 ° is tooo hot for tpu drying.
Well, thats good to know, but ill be honest, the AMS 2 Pro doesnt reach 75°.
Whenever I check on it and how much time remains on the disaply it always reads 65°.
I assume it was a miss-type when they wrote the firmware presets for it, or they simply include a thermostat for the unit that isnt actually capable of measuring past 65° and so will be at that temp no matter how much higher you go (which would be a massive design oversight if your unit is actually capable of higher temps).
I also got confused by this. You’re right, the AMS 2 Pro only dries up to 65°. If you want to go up to 75°, you need an AMS HT.
That could be your problem? I don’t think a lower temperature would cause sticky filament, though. I don’t print TPU, so take this with a grain of salt. Did you turn on “rotate spool while drying”?
I use 70C degrees, probably 12 hours, to dry Siraya Tech TPU 85A and then ‘maintain’ it at 55C.
Yeah rotate spool is on whenever I dry, because why not get the “better performance” mode.
Since it doesnt allow dring mid print anyways, no reason not to imo.
But good thing you mention the HT, maybe the 75° they show in the menu, is in fact a firmware version for both AMS and HT.
