I’ve been trying to print some things in TPU, using a fairly soft 85A TPU, and I keep having under extrusion.
I’ve already reduced speeds to max 25mm/s, and reduced retraction. My printer uses a direct drive extruder, and as far as I can tell, it’s grabbing the filament just fine. I’m printing at 240°C, using my default 0.4mm volcano CHT brass nozzle.
Make sure your filament roller doesn’t have too much resistance as well. Since TPU stretches linearly way more than any other filament if it does have a lot of resistance then the extruder won’t be able to pull more filament until it overcomes that resistance and the stretch and it ends up physically thinning out the filament. Just a thought, hope it helps!
Yeah i noticed that right away, it’s sitting on a roller with bearings, not sure I can give it any less resistance without actively unwinding filament as it’s used.
Great tip! I spent a long time chasing issues with TPU only to realize the spool to extruder section was the culprit. Bypassed the runout sensor and put the spool on bearings to fix the issue.
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Make sure your filament roller doesn’t have too much resistance as well. Since TPU stretches linearly way more than any other filament if it does have a lot of resistance then the extruder won’t be able to pull more filament until it overcomes that resistance and the stretch and it ends up physically thinning out the filament. Just a thought, hope it helps!
Yeah i noticed that right away, it’s sitting on a roller with bearings, not sure I can give it any less resistance without actively unwinding filament as it’s used.
Great tip! I spent a long time chasing issues with TPU only to realize the spool to extruder section was the culprit. Bypassed the runout sensor and put the spool on bearings to fix the issue.