I’m printing Paramount TPU 92 and I have dialed in most settings to get a decent print with it. But there is one thing I haven’t been able to fix and that’s bits or small blobs at the start or end of a layer. The issue is somewhat better with a little bit of retraction (0.6mm with zhop 0.4mm) but everything I’ve read says to not use retraction at all for flexible filaments, so I’m reluctant to keep messing around with retraction.
I’ve tried different seam positions and different line functions (outer/inner vs inner/outer). I suppose I could reduce the flow ratio a bit?
Ignore the no retraction for flexibles, that’s an old one from crappy old printers that’s not had a place in printing TPU for probably the last 8 years or more, retraction is fine, I run 1.8mm on my P1S.
I run with 1.2mm retraction length. Increasing it did the trick for clean prints.
And I know it’s becoming a meme, but make sure your filament is absolutely dry. TPU is very runny and any bubbles will make it much worse. Also because TPU prints slower I decreased the seam gap to 3% and made it random and it turns out pretty good (also to make it more watertight which helps with the TPU feel when squishing stuff :))
Yeah thanks for the replies. After I posted this question I increased the retraction by just 0.4mm (to 1.6mm) and also raised the print temp by 5C and that made a HUGE difference. The inner walls are smooth now. Completely different result!