Printing TPU had been problematic for me, the filament often got stuck mid way through a 3-hour print which was frustrating. Tried many different settings but nothing seemed to work. In the end I had to change out the tube which made a huge, immediate difference!
The original tube is made of some sort of rubbery material (on the left in the following picture). TPU also has a rubbery texture, so I suppose when the filament passes through the tube, it create friction. The friction is probably great enough to somehow restricts the filament’s movement, and eventually clog up the print head.
The new tube I bought is made of PTFE (on the right in the above picture). it’s less flexible than the original tube, but has a more slippery surface and much easier for the filament to pass through. The tube I picked up also has a bigger inner diameter (4mm) which might also help.
I printed a couple of these GoPro Session Mounts for my drone, which took 3 hours each and no jamming. Quality also looks nicer than before.
The tube I picked up is designed for 3mm Filament with 4mm ID and 6mm OD.
I found these for 1.75mm filament, but I haven’t tested them:
These settings are for the Ultimaker 2+
- Temperature: 220C
- Bed Temp: 60C
- Flow: 105%
- Fan Speed: 80%
Printing slower helps. I use 40mm/s which works well (I use 70mm/s for PLA).
If you are still having trouble, the other advice I was given is to put a drop of sewing machine oil on the filament before it enters the tube. This would make it even easier for the filament to pass through the tube and avoid getting stuck.
However I haven’t had an issue since replacing the tube so I haven’t had to try this yet.