PLA filament snapping randomly

[Oliveros 11]

Hey everyone,

 

I had a bit of an issue yesterday when trying to print with PLA filaments that aren't necessarily too old, only a month or so, They are Monoprice filaments, wood and black PLA and both would snap randomly when trying to feed it into the printer, but when bent in certain places it wouldn't snap. So when I printed with it, the wood filament snapped 3 or 4 times and I had to redo the prints (i've disabled the filament runout sensor).

 

The PLA isn't stored anywhere special, in an air conditioned room, under the printer, no dessicant packs in the box and it's just sitting in the box. 

I've stored PLA like that for several months with no issues, but now it seems to be a problem? My Nylon 6, Nylon 12, ABS, PETG and Armadillo are all printing fine, was it a bad batch of PLA or what?

[geert_2 525]

If you bend PLA and then keep it bent under stress, then microcracks may grow, and they may keep growing until it snaps. This can happen when it is sitting in the feeding traject for a longer time. So it is best to unload it after printing, and store it under no load. As it gets older, it can become harder and brittle too. Moisture also degrades PLA, it breaks down the molecules, so that could also speed up the brittling-effect. But I haven't had it snapping while printing or while in the feeding traject yet. So, in your case, it could be a bad batch or bad brand too. Wood, stone, carbon, or metal-filled filaments are also more brittle.

 

These are microcracks after I bent the filament in the opposite direction for a few seconds, and then released it again (=removed stress), to make bending radius less tight and reduce friction in the bowden tube and nozzle.

 

Idem, seen through a microscope

 

These are cracks growing in a keychain carabiner hook, due to repeatedly opening the hook. A few times more, and it would totally snap.

 

 

[Oliveros 11]

Interesting, Okay cool, so I'll email Monoprice and ask them about it.

 

Just wanted to make sure it wasn't me storing it or doing something wrong with it.

[Oliveros 11]

Well, who would've thought, Monoprice is replacing the filaments free of charge.

 

I love companies that stand behind their stuff.