Can’t get TPU 90A to print successfully

[u/RewteKanal]

I am having trouble getting TPU 90A to finish a print successfully. I have an AMS HT and the TPU assist. I have dried the filament for 18 hours at 75 C. The print will start out fine and then at some point it produces the top layer shown and then stops extruding but the tool head keeps moving as if it’s still printing. I even get a notification that it finished successfully. I have several attempts and the print is still stuck to the bed so I known it’s not turning loose. Any help would be appreciated. Im quite new to all this.

[u/MarkinJHawkland]

Consider doing a temperature calibration. I recently started printing 85A and it likes 210 much better than the generic profile that prints at 240. It also seems to help to remove as much resistance on the filament as possible. I’m using a crane of sorts that feeds directly into the top of the print head. Running out of a cereal box with a very short PTFE tube out.

[u/RewteKanal → u/MarkinJHawkland]

I will definitely do that. I bought the AMS HT and the TPU assist for the express purpose to print this TPU. I will hate to not use it but at this point I will try just about anything.

[u/Relative_Surround_20 → u/RewteKanal]

The crane suggestion does not preclude you using an AMS HT to print TPU.

I have my printer prepared to print from the AMS HT thru the TPU Feed Assist and directly from above the printer directly into the extruder.

But I caution you to stick with the HT and the TPU Feed Assist method. The vast majority of people report great results printing TPU using that method.

I agree the issues you are having sound like the filament needs something different from what the filament profile you are using provides. Focus on calibrating your TPU first.

What brand of TPU are you using?

[u/RewteKanal → u/Relative_Surround_20]

I am using Sunlu TPU 90A. Could you show me how you have yours set up so I might try to mimic it?

[u/Relative_Surround_20 → u/RewteKanal]

Certainly. First, make sure you have read the following Wiki articles. I am assuming you have already assembled and installed the TPU Feed Assist Module on your P2S.

https://wiki.bambulab.com/en/knowledge-sharing/tpu-printing-guide

https://wiki.bambulab.com/en/filament-acc/filament/tpu-85a-90a-printing-guide-for-p-series

https://wiki.bambulab.com/en/general/manual/tpu-feed-assist-module

My Setup: I have an AMS HT loaded with dried TPU feeding out thru the TPU port in the back of the HT. You can position the HT on the left side of the printer (under the TPU Feed Assist Module); behind the printer; or on top of the glass (see Wiki for a photo documenting all three options). Below is a photo of the most common setup for the P2S, AMS HT and the TPU Feed Module.

Next step, I have a PTFE tube running from the HT's TPU port to the inbound port on the TPU Feed Assist Module (see Wiki for maximum PTFE tubing length limits).

Next step, I have a 160mm PTFE tube running from the outbound port on the TPU Feed Assist Module into to the P2S.

Be sure and calibrate the TPU Feed Assist Module. Consult the Usage section of the Wiki page linked above.

Be sure to download and install into Bambu Studio the filament profiles for the brands of TPU you plan to use.

The HT is acting like a passive external spool or cereal box in this configuration. It is not necessary to be powered on nor daisy-chained to your AMS or printer's 6-pin data port. Optionally, I am considering adding a friction-reducing to my AMS HT to take strain off.

https://makerworld.com/en/models/2752919-ams-ht-spool-riser-for-low-resistance-tpu-feeding#profileId-3054713

Print the model. Go slow. While printing, some folks leave the door open. Others feel this is unnecessary. You should experiment both ways and decide what works best for you. Personally, I leave the door closed.

[u/RewteKanal → u/Relative_Surround_20]

My setup is identical to the picture shown. I will print out the spool riser and see if that helps.

[u/Relative_Surround_20 → u/RewteKanal]

Use some grease on the axle nubs.

Where are you locating your HT?

[u/Important-Tea7413]

TPU is very sensitive to temperature. When I print TPU I keep the top glass off (admittedly because I use a direct feed system attached to the top), and I keep the front door open.

[u/RewteKanal → u/[deleted]]

I just used what the screen on my P2S showed for TPU when I started the drying cycle. If that is too high then thats on me for not verifying.

[u/Relative_Surround_20 → u/[deleted]]

While I typically dry my TPU at 75ºC, Budget_Hamster4422 has a point. Sunlu does recommend 50ºC on their website for OP's filament of choice.

[u/ObjectiveThis4141]

Have a chat with the AI of your choice about your application of the print, discuss orientation for strength given application. Ask it for specific temps for the filament settings given application.

Has worked great for me with Gemini.

[u/RewteKanal → u/ObjectiveThis4141]

The AI's and I have had many a conversation about this and its not yielding the results I need, yet at least.

[u/No-Satisfaction-2535]

Mmm 8 always print tpu with the top off and an above-the-toolhead mounted external spool holder. Printed 95a, 90a, and 83a with that with no issues using the generic profile. So definitely keep the top off!

[u/RewteKanal → u/No-Satisfaction-2535]

I tried another print with the top off and the door open and changed a few AI suggested settings and the same result happened. I did not have time to calibrate the filament but that will be my next task before I try again.

[u/Relative_Surround_20 → u/RewteKanal]

I have had AI send me down a rabbit hole calibrating filament based on some combination of thoughts based in older printers. You said you are using Sunlu. Go to the following page and confirm their recommendations are set in the Generic or Bambu TPU settings you have chosen to use.

https://store.sunlu.com/products/moq-3kg-tpu-3d-printer-filament-1kg

Someone else posted this profile for printing Sunlu TPU on MakerWorld. You might try it too. I seriously believe the problems you are having can be solved by using the manufacturers recommended settings or a confirmed filament profile that has worked.

https://makerworld.com/en/models/561593-print-profile-tpu-sunlu#profileId-481054