.8mm nozzle layer problems

I'm printing TPU with .8 mm nozzle and having troubles with the first layer. There are gaps between the layer lines and it looks pretty bumpy.

I'm printing with .3 mm layer height and my print speeds are at 20 mm/s.

Any idea what I could do to improve the first layer?

4 comments

Looks like wet filament to me, TPU really loves moisture so storing it in a dry box is necessary.

If you do go to dry your filament use a dehydrator (food or filament) not your oven.

But something I'd check as well is the distance between the bed and the nozzle, just to be sure.
- I think you're right! It's extremely humid right now and when I print I'm hearing snaps and crackles. I'm guessing that is the moisture from the filament?
  
  Thanks for the help!
  
  If you can already hear it during normal printing, then yes, it's most likely wet filament. The water trapped inside almost instantly turns into steam inside the nozzle and expands, causing the molten filament to bubble up as the steam escapes.
Hm, not sure if it's (just) the grainy photos, but the skirt line looks pretty uneven. Is that a fresh roll of TPU, or if not, how did you store it? TPU is hygroscopic (attracts moisture), so if you left it outside a drybox it probably got wet. A quick test to confirm that would be to just extrude some in thin air. If you see/hear any sizzling/bubbling, that's the trapped water turning into steam.

General tips for printing TPU: print it slow and with as little retractions as possible (if you're on a bowden setup). You could also try slightly increasing the extrusion multiplier.