A1 mini tpu-cf filament

[user_3537834475]

I’m trying to print Spectrum S-Flex Carbon TPU-CF, 90A Shore with 20% carbon fiber, on a Bambu Lab A1 Mini with a 0.6 mm hardened nozzle.

The print starts well and the first layers look good, but after several layers, often around layer 10, the printer stops extruding and continues air-printing. If I manually push the filament into the extruder, it starts extruding again. The nozzle does not seem clogged: if I heat it to about 240-245 C, I can manually extrude filament, and the filament unloads without visible deformation.

What I have tried:

• Brand new 0.6 mm nozzle

• Filament dried before printing

• Direct external feed, no AMS Lite

• Tried with and without PTFE tube; PTFE made it worse

• Very slow TPU profiles

• 0 retraction, low acceleration, low volumetric flow

• Higher nozzle temps up to 245 C

• Fan reduced/off in early layers

• 1 wall, 10% gyroid infill

• Other TPU filaments like 95A, 96A, and 20D print fine on the same printer

Has anyone tried printing this filament and have any idea why it stops printing? The first layers it print are printed perfectly

[Bullocks]

I used TPU-GF from sirayatech, which is likely similar to TPU-CF for printability. I needed .6 nozzle and slow profiles [4 mm3/s]. But it sounds like your issue is the extruder isn’t able to push, grip, or pull consistantly.

Definitely no PTFE

Try to mount the spool both on a bearing-based roller, and above the printer, so it is plucked off effortlessly

Perhaps even look at the tensioning of the extruder but beware of dragons and start writing down your steps if you need to retrace, like if it starts crushing PLA too strongly

[user_3537834475]

Yeah, it seems to be related to the extruder gears. I opened it up and aligned the gears properly, but I didn’t adjust the tension. It’s printing fine now, but I currently have the print head fully open. It might be getting misaligned again when I put the covers back on, so I’m not sure how to fix that.