Since about 2 days I havent been able to print with my TPU 85A (bambu) on the P1S.
I got the TPU Assist module roughly half a month ago, have printing with it just fine, and was relying on it since 85A is too soft to use when not directly mounted above the toolhead.
I confirmed that the Assist module still works perfectly fine, and took a small piece that I cut from the spool and fed it in directly.
But in both cases, the TPU gets grabbed by the extruder gears, pulled in a good amount, but then hardly makes it through the nozzle (0.4 hardened steel bambu).
For the test with the cut filament piece, I heated the nozzle to 220°C and manually made the printer pull in the material.
I took apart the extruder assembly checked that it was in good condition, as well as completely replacing my hotend for a new one (same type) to make sure there wasnt any chance of cloging in the nozzle, after already having done ~5 cold pulls.
Im essentially out of ideas what to do.
The filament gets pulled in and then doesnt actually get pushed out.
Here is a small (poorly made) demo video of the issue: Demonstration of extrusion issue
What did you most recently print with? If you have a chunk of something reasonably high temperature sticking out of the top of the hotend, the TPU isn’t going to be stiff enough to push it through, no matter how long the extruder gear runs.
Also, check the spring tension on the extruder idler, it should be turned up all the way.
Another thing you can do is unscrew the hotend and let it hang, and try feeding the filament through again to see if it’s getting through the feeder successfully.
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I believe TPU 85 requires a 0.6mm hotend.
Also, the TPU Feed Assist module was not needed here, and indeed didn’t print properly when it was installed. Removing it and feeding the TPU directly in to the Bowden tube on the back (where the AMS connects) fixed that problem. I also have a 0.6mm hotend.
Feed the 85A filament directly from the assist module to the hotend, bypassing the AMS PTFE tube.
Also 0.4mm nozzle is not compatible with 85A, according to the TPU printing guide.
Yes, but I will say it’s very possible to print with 85A and a 0.4mm nozzle if you have a well optimized setup.
In my opinion, a bed slinger is better suit for TPU printing because the hotend is only moving on the X-axis and less pulling on the soft filament.
I am considering getting an A2L for TPU and also for the possible occasional future need of a larger build volume and some cutting jobs, probably at the end of the year or next spring (due to my self-imposed 6-month waiting period 
But does an extruder moving in two axes pull on the filament more?
I’m going to say it doesn’t - the PTFE tube length is essentially unchanged regardless of position, so the TPU length shouldn’t be changing either.
I think it does. The PTFE tube in a coreXY is long and winding by necessity to accommodate the wide area that the hotend has to travel.
