I left a spool of eSun PLA+ beige in my Prusa MK4 with Prusa enclosure, which has sat idle since my last print about 6 weeks ago. The enclosure has a PTFE filament feed tube that runs the filament from the spool to the extruder.
Today I went to change the filament, and it broke apart in several pieces, right at the ends of the ptfe filament feed tube. The filament on the spool itself - within an inch of where it simply separated from the broken bits - I can fold over 180° tight without breaking it. Even the several ~1" lengths of broken bits are similarly ductile.
Ambient humidity is something like 15% (per my filament dryer) to 30% (per my dehumidifier, which is idle because it’s winter).
Any idea why this happened? I’m curious about maybe interactions with the PETG parts that the broken pieces were close to (that’s the only thing I can come up with, anyway).
PLA stress fractures over time, even just holding it straight like when partially off the roll into the extruder is enough to make it brittle after a few weeks. If you aren’t using your PLA for more than a couple days eject it and roll it back into the spool.
That adds up. All the spots it broke are where the filament bends pretty substantially. Thanks.
Ooohhhhh thanks for explaining, that makes perfect sense. I’ve always wondered why my filament is brittle in the extruder but not on the roll.
Thanks for this. I was worried about how some of my filament was wet in a very dry winter, but this explains why it broke in the spots it broke.
Does this apply to printed parts that are under load as well, then, or are they safer because they don’t get bent/unbent the way filament does (assuming you aren’t trying to do a living hinge or other flexing design)?