Filament breaking in unused tools. Common?  

RE:

Just my two cents about the UV/moisture discussion:

Extruded filament on spools is not the same as printed filament. I have used temporary PLA parts outside and was more than once very surprised how well they lasted. If anything, they warp from heat. I learned from fooling around at work that the Xray diffraction patterns of extruded filament, cast material, rolled material, milled material and printed material differ enough that you can probably tell the manufacturing technique from it. This was PEI though, not PLA. In layman's terms, you can see the difference in strain.
My theory (and it's really just that) is that PLA filament has a) relatively little cross-linking (low melting point, high thermal stability) and b) the molecules like to align somehow (-> we know it can be tempered in the oven for more stability). So what if the polymer molecules are preferentially aligned to be parallel in the filament? When it's spooled it's still hot/soft, so the molecules could align along the curvature. In the PTFE you bend it against it's alignment and introduce strain. Do that too long and it will yield, very normal behaviour actually.
I'm quite sure there are some papers out there at least touching the subject. Maybe I'll go searching if I have a boring lunch break.

RE:

OK, it seems I am on the right track. First article I quickly skimmed, but there is a shit-ton of literature about this:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7450648/   (doi: 10.1021/acsomega.0c02330)
"Constrained Amorphous Interphase in Poly(l-lactic acid): Estimation of the Tensile Elastic Modulus"
These should be open-access, but I cannot check from my network.

The materials they studied wouldn't be the exact same formulations we use for 3D-printing, so not everything in the paper might apply. But bottom-line, there is a surprisingly high number of crystalline and amorphous phases involved, with different stabilities in the melt and solid and at different temperatures. They can slowly interconvert at room temperature, which would change the local strain levels. Maybe bending it even partly induces these transformations.

EDIT: Above, by "high thermal stability" I meant chemical stability, not mechanical. Sorry, comes with the job.

RE: Filament breaking in unused tools. Common?

All the above matches online discussions years ago.
Simple bottom line; spooled pla goes stale fast.
Optimal solution; use some other material.

RE: Filament breaking in unused tools. Common?

Optimal solution; use some other material.

What is a good replacement for PLA that prints close to the same?

RE: Filament breaking in unused tools. Common?

PETG is my main material for functional items and clients. PLA I use only for burn out molds (for Clients) and for full contact supports(which I now do as a rule for all use cases). I can do all the multi color objects in PETG just as well as pla. I don’t see the brittleness problem at all for PLA silks. There’s also PLAPHA although I  don’t see many suppliers of it lately.

I’m sure there’s folks here who will say they have to use PLA… for them there’s a viable solution; add to the end gcode a script so that when a print is done all extruders retract all the way out. Then remove the pla from the printer and store it in a bag with charged desiccant and place that in dark storage. Cause if you don’t do that… well… have you had a strand of pla break all along the guide tube yet? Sometimes getting that cleared takes removal of the guide tube from the machine and using it like a whip!

RE: Filament breaking in unused tools. Common?

Other than fewer color choices,  PETG is going to do most anything that PLA can.   I find I tend to take my PLA out and throw it in the dryer after every print and then in a bag with desiccant packets so it's ready to go next time around.  I definitely don't leave filament loaded for any extended period of time if I'm not actively printing with it.  Probably the longest is over night.   And I've only seen the snapping thing happen maybe twice.  For functional parts definitely PETG.   And depending on the brand and sales it's usually not much more expensive than PLA.  It also has the advantage over something like abs that you don't need to be particularly worried about fumes.

RE: Filament breaking in unused tools. Common?

Not to mention that petg has better temp tolerance for the final product.   Leave your PLA printed stuff in a hot car lol  PETG gives you roughlyanother 20C to work with (~85C vs ~65C)

RE: Filament breaking in unused tools. Common?

Posted by: @ssill2

Not to mention that petg has better temp tolerance for the final product.   Leave your PLA printed stuff in a hot car lol  PETG gives you roughlyanother 20C to work with (~85C vs ~65C)

The one and only main downside I could see is that PETG is significantly more flexible than PLA for a given geometry.  If someone needs the stiffest part and that's the biggest/only consideration, then PETG wouldn't fit the bill.  I'm not sure what would, aside from maybe ABS?

RE:

ASA. Prints much easier than ABS in my opinion and stiffness seems similar to ABS. Also very good for outside use, with way better UV/weathering resistance than ABS. The downside is it's similar chemically to ABS (in fact I think many filaments are ASA/ABS copolymer blends), so you get the same toxic fumes. I very much like its haptics, it feels like high quality car plastic.

RE: Filament breaking in unused tools. Common?

I agree, The few times I've printed with ASA, it prints easily and has a nice feel to it.  I don't have any permanent ventilation hooked up yet so I must move my printers near the window and put the vent tube outside, which limits when I can print ASA/ABS.

Posted by: @ntdesign

ASA. Prints much easier than ABS in my opinion and stiffness seems similar to ABS. Also very good for outside use, with way better UV/weathering resistance than ABS. The downside is it's similar chemically to ABS (in fact I think many filaments are ASA/ABS copolymer blends), so you get the same toxic fumes. I very much like its haptics, it feels like high quality car plastic.

RE: Filament breaking in unused tools. Common?

The bottom surface of ASA prints often has whitish markings/discoloring. These are not actually stains, but signs of strain buildup when it cools down (local crystallization possibly, but just guessing). The same sometimes happens where supports touch the print and when you drill/cut into it.

I found you can just quickly wave a heatgun (200°C or so) over them and they magically disappear.

RE: Filament breaking in unused tools. Common?

I'm familiar with these PTFE couplers and use them with my MMU printer.  Where would you recommend they be installed along the length of  PTFE of the XL?

RE: Filament breaking in unused tools. Common?

Then there is also PC, PC+ and PCCF. All are about as rigid as we can get, but you pay for rigidity with brittleness. I buy all my PC stuff from Snolabs.