As a matter of fact, I do! First of all, I’m going to credit these observations to a youtuber named “Lost in Tech” who has done the most thorough youtube investigation of printing tpu on different printers that I know of.
- All the bowden printers are a generally a bad match for printing TPU.
- In his experience, the best printers were ones with a double pinch direct drive extruder.
Although I think #1 is widely known, I never heard him voice any direct criticism toward reverse bowden. However, like you, my thinking is getting rid of the ptfe tube entirely should make for a more uniform feed, without random stiction possibly interfering. But TPU can be so droopy that it can’t self support, and that leads us to your picture.
I think the solution is position the TPU filament spool well above the printer so that the TPU is pulled in nearly a straight line into the printhead. In the case of the X1C, this will mean removing the lid. In my case, I chose to buy an inexpensive refurbished double-pinch extruder printer (in this instance, a Creality CR10 XE) and dedicate that to printing TPU, and so here’s a link to a couple of pictures showing how that looks:
I think in retrospect I didn’t really need to buy this extra printer, but at the time I was inexperienced and was afraid TPU would jam up my X1C, which I wanted to keep “at the ready” for printing more regular filaments. Anyway, it was so inexpensive that I considered it cheap insurance.
Worthy of note: I didn’t want any drag at all (or, failing that, the least amount possible) as the TPU emerged from the drybox, so the filament comes off the spool and goes through a somewhat large hole that I drilled into the drybox for this purpose. To keep the filament dry, I pump desiccated air into it to maintain a positive pressure using an aquarium pump. I run that 24/7, and because so little positive pressure is required, it can go for weeks before I need to change out the desiccant.