Printing TPU had been problematic for me in the past year. The filament often got stuck mid way through a 3-hour print which was frustrating. I tried many different things and nothing seemed to work. The solution was simple, I only had to change out the tube which costed me only $5!
The original tube in the Ultimaker 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 creates 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.
It also works well with PLA and ABS which I have personally tested over 10+ print hours each.
Buying PTFE Tube
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:
My Printer Settings for TPU
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).
Still Having Problems?
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. It won’t affect print quality and just seem to disappear. 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 trick yet.