this post was submitted on 27 Mar 2024
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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).

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[–] [email protected] 20 points 7 months ago (2 children)

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.

[–] [email protected] 6 points 7 months ago

That adds up. All the spots it broke are where the filament bends pretty substantially. Thanks.

[–] [email protected] 5 points 7 months ago

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.

[–] [email protected] 10 points 7 months ago

This is one reason I'm switching away from pla+ back to normal pla. The esun pla+ really seems to get brittle when held under stress. This is an issue with printed parts as well. I've had parts suddenly crack in half where they were stressed over a few months.

Also it's really annoying when little bits of filament get stuck in your filament guide tube :(

[–] [email protected] 8 points 7 months ago* (last edited 7 months ago)

That happens to my filament as well, i assumed it was drying out to much. Your humidity is way lower then mine, i'm typically around 50%. Not sure that this is the reason though

[–] [email protected] 4 points 7 months ago (1 children)
[–] [email protected] 3 points 7 months ago

More likely humidity. Mine is in a windowless room and gets brittle like that after sitting.