Filament breaking in unused tools. Common?  

RE: Filament breaking in unused tools. Common?

I don't have the same problem BUT I had these problems with some PLA filaments brands. Yesterday I was cleaning up my filaments and the vanilla white from Prusa was brittle, the first time I had this with a prusa filament. But a lot of time with other lower quality brands.

So not sure if really a problem of the toolchanger

RE: Filament breaking in unused tools. Common?

I could confirm @ChiSao. Some PLA filaments are so brittle, that they easily break when you want to fasten them on the spool after you used them.

As it absorbs water PLA filament becomes brittle.  If is under stress, constrained to a toolpath for example, it can break without external input.  This can happen with any printer left loaded but with multiple filaments it is more noticeable.

If you use MMU or multi-head XL you must expect to be doing up to five times as much drying.

Cheerio,

RE: Filament breaking in unused tools. Common?

But I am not sure if there is something with structure changing in a heated environment, even if it is only about 10 or 20°C more than ambient. Because some of my brittle filament weren't that brittle initially  but some days later yes (and no it is not moisture)

RE: Filament breaking in unused tools. Common?

Interesting in my case the PLA was dry because stocked in drybox than dryer and then printing.
But who knows maybe some brands have pla which is more hydroscopic than other

in my case the PLA was dry because stocked in drybox than dryer and then printing.

When printing a single filament PLA is usually used up as fast as it spoils so the problem is rare.  With a multi-filament print four are paused at any one time, absorbing atmospheric moisture while just waiting their turn.  If the colours are just decorative it will usually be better to print with a single filament and paint afterwards.  For functional prints - scales, graticules and labels, try and constrain the colour changes to a limited number of layers and don't load until close to the time they will be needed, unloading filaments that have  finished as early as possible.

Cheerio,

RE: Filament breaking in unused tools. Common?

Appreciate the feedback. The filament is eSun so a decent brand of PLA. I think the fact it's contained under tension in the bowden and then subject to movement from the printer when working all contribute to it cracking.  I don't tend to dry PLA but I've realised with the XL this is a consideration I need to make.

RE: Filament breaking in unused tools. Common?

definitely have observed this across a number of brands, esp with the idler tension - stuff just fragments in there, resulting in a lot of tweezing and cleaning...

ugh...  never had this problem with other printers in the past, but then i've never had bowden tubes this long lol

RE: Filament breaking in unused tools. Common?

Never leave PLA (and probably other filaments) just sitting in the tubes was something I learned back in my early MMU2 days. Something about the confined tubes makes PLA get super brittle super fast. Maybe it traps moisture, idk. That's why I always unload the XL after a print unless I've plans to use the same filaments again within a couple days.

RE: Filament breaking in unused tools. Common?

I had to clean out two of the boden tubes last night. The PLA had broken in to multiple pieces. One was a new spool as well. It was a pain to clear the tube but easier if I removed them. Involves detaching from the filament sensor and festo on the extruder, then unclipping from the orange clips. I used some spare filament to push the old stuff out. May help others as I'm sure I wont be alone on this.

RE:

There is a user on here who has stated that brittle PLA is caused primarily by UV exposure more so than moisture, and specifically identified the clear PTFE tubes on his XL-5 as a non-optimal design decision.  A quick test of this theory could be to cover the tubes with opaque cable wrap or sleeves and see if the breakage happens just as quickly.  If you can find a sleeve option that is easy to remove, you'd still be able to uncover them during loading to see where the filament is, if needed.  A pretty simple solution if UV light is confirmed as the culprit.

-J

RE: Filament breaking in unused tools. Common?

well, I can say with some certainly that there is nearly zero UV in the room with my XL

inside corner, away from the only window (which is north facing, and has curtains).

if one googles "does ptfe block uv", the first result is: "PTFE has particularly good UV resistance because of its very strong carbon- fluorine (C-F) bond [almost 30% higher than the carbon-hydrogen (C-H) bond], which is the common side bond that surrounds the carbon (C-C) backbone in a helix and protects it."
so I'm going to say that the PLA inside the Bowden tube is MORE protected than just by sitting in the dark corner 😉
summayr: lol 🙂

RE: Filament breaking in unused tools. Common?

I have had some used low volume spoolsof filament crack at lower temperatures. PLA gets pretty stiff when it is cool and the tight winds towards the end of the spools have cracked on me. They are pretty springy. The cure I found was to put the spools in a drier. It seems to relax and warm the filiment a little. 

I have had this happen with pretty new spools and no they are not kept in the light nor are they kept in a humid environment.

RE: Filament breaking in unused tools. Common?

Filament should not be left in PTFE (e.g. MMU2), as this then becomes brittle. After printing, unload the filament and store it on a cool, dry place. If necessary, dry in a dehydrator before use.

wbr,

Karl

RE: Filament breaking in unused tools. Common?

The breaking is NOT from moisture. Please stop posting incorrect info. The PLA breaking is from UV exposure. Moisture does effect it but it’s not the cause of it going brittle and breaking easy.

Cheerio

and there’s two simple solutions for the OP:

unload and store the filament after use or

https://www.printables.com/model/32368-join-ptfe-tubes-together-magnetically

Er, OK.  But stick in a dryer for a few hours and all the UV goes away.

Cheerio,

RE: Filament breaking in unused tools. Common?

I fully believe enough UV exposure can shatter PLA, but the only light my filament was exposed to at the time was from computer monitors and room lighting LEDs. There's some other factor affecting things. I'm not betting it was moisture - I just don't have any idea what else it could have been. Does PLA chemically react to PTFE over the course of a week? lol ¯\_(ツ)_/¯

RE: Filament breaking in unused tools. Common?

The chemical stability of PTFE is one of the reasons to use it in the first place. I would be very surprised if a week of loose contact at room temperature would have any effect whatsoever - but I'm not a studied chemistry person, so my impression might be false.

RE: Filament breaking in unused tools. Common?

From experience, I can report that filament (PLA, PETG, CPE...) becomes brittle or fragile if it is stored in PTFE for weeks. It subsequently breaks when loaded by the MMU2.

https://3dprinting.stackexchange.com/questions/16765/pla-filament-becomes-brittle-inside-ptfe-tube

wbr,

Karl