Any fix for PLA prints getting more brittle over time?

  • I've been printing small quantities from a PLA filament spool on a Craftbot printer for about two months now. Recently the printed objects have been coming out very brittle. Some structures that printed fine two months ago are now difficult to re-print. The print head gets clogged easily, and when the object does print, it's quite brittle and 1/4" to 1/8" rods will easily snap off if not handled gently.

    I'll admit to not following the precautions for storage of PLA. It's much easier to just leave the filament installed rather than trying to remove it after each print, so this one spool has just been sitting on the back of the printer for all these weeks now. I'm sure it's been humid some of the days, we've had some rain here.

    Has the spool of PLA been damaged just by leaving it exposed to room air for two months? Could that be the sole cause of the brittle prints, or are there other possible causes? Is there any way to fix the spool or future prints from this spool, or do I have to scrap it and get a new spool?

    Have you tried drying the filament (eg in an oven on "warm")?

    Haven't tried anything yet. What temp is "warm"? Less than 400F I would guess :)

    Yeah, you don't want to overly soften the filament or it will go out of round and jam. Maybe 120F / 50C for a couple hours.

    I had this as an answer, but the question was about PRINTS, not FILAMENT. There is no question that PLA filament grows brittle with age. It grows so brittle that it will spontaneously break when subjected to stress. I experience this as PLA breaking along the path between the spool and the printer when left untouched for a few hours. This happens even during the depth of a New England winter when the humidity is very low. Part of this problem comes when the PLA is tightly coiled onto a spool with a small hub. ...

    The PLA seems to anneal the strain induced by winding so that when the filament is unwound the filament is again strained. The strain may open tiny cracks, which develop into larger cracks and breakage. I have not had this problem with newer spools where the diameter of the hub is larger. Recently I threw out 4 spools that were 80% used because the remaining 20% broke several times during printing. I don't see this with open but less used rolls of filament I bought around the same time. I do not have hard data on when I bought each spool. Now, I avoid spools with small hubs.

    Use an electric oven. A gas oven generates combustion products that I think include water vapor.

  • Increase nozzle temperature. When the filament is new it will print easier, requiring less heat to print well. So if you didn't store your filament properly to begin with, increasing print temperature will make it jam less and increase layer bonding.

    The reason for this is because the moisture that accumulates in the filament will absorb heat and evaporate when printed, meaning that the filament itself isn't getting the same amount of heating as it used to.

    That being said, the storage suggestions mentioned by tbm should be your first priority. I personally put my filament in Zip Lock plastic bags and store these in a dry location not exposed to sun or temperature changes.

    Awesome tip! And yes I've been taking better care of my PLA these days, getting it off the printer and storing in a ZipLoc bag etc. But cranking up the temp seems to help a lot.

    Throw some silica gel moisture absorber packs into the ziplocs.

    I save all of the little desiccant packages I get for exactly this reason!

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Content dated before 7/24/2021 11:53 AM