Drying PLA (New Idea)
July 09, 2013 08:45AM
I had a roll of red PLA that initially printed really well but after a few weeks absorbed some moisture. It's my own fault as I often leave prints going overnight then the roll of PLA ends up sitting out for extended periods of time in my basement. Finally it started to develop the symptoms of having absorbed moisture. I could see and hear steam escaping from the nozzle when I manually fed the filament and when it was printing. The filament was oozing extremley as well as skipping spots when the steam escaped.

I started reading up on ways to dry the PLA in an oven but none that I read seemed to end up being advisable in the end. I came up with the idea of leaving the roll on the seat of my car for a 9 hour work day which was around 90 degrees outside. I figure it easily must have reached 100 with the windows closed. I did just that yesterday and after work I tried a print. It printed every bit as good as it originally did if not better. I didn't come across anyone having done this in my searching and am just wondering if it is something that I missed. I attached a picture of the first print yesterday. It is a spinning top.

Bob
Attachments:
open | download - Top.JPG (497.8 KB)
Re: Drying PLA (New Idea)
July 09, 2013 05:20PM
Problem is that not everyone has a car (or that it isn't always hot outside), I guess.

By the way, I just put the filament into a large plastic container (doesn't have to be 100% airtight, just a plastic lid is enough) together with a bag of room desiccant. Even taulman 618 prints nicely when stored like that.
Total investment: around 10€ or so.
As long as you have the desiccant in a separate, smaller container inside and don't touch it with bare hands (when moist, the desiccant is caustic AFAIK), this is a very safe and tidy solution.
Re: Drying PLA (New Idea)
July 09, 2013 05:36PM
How long does it take for moisture to get into the pla? Is it hours or days. I have been doing some prints that lasted 7+ hours. A couple of those in a row and the pla is exposed for quite a while. It's not a matter of what it costs to store it it's just a matter of getting it stored in time I guess.
Re: Drying PLA (New Idea)
July 09, 2013 07:57PM
1+ for desiccant. if you place it in when pla arrives, there should be no issues. otherwise i would use the oven bake out tricks.
Re: Drying PLA (New Idea)
July 09, 2013 09:06PM
My Filament came sealed in a resealable plastic bag with the desiccant packet. It was stored in the bag with packet when not printing. The filament absorbed the moisture I believe during several back to back several hour long prints.

I was simply sharing sharing something that did work for me.

So far no one was was able to answer my question as to how long out of the bag does it take to absorb moisture?
Re: Drying PLA (New Idea)
July 10, 2013 01:47AM
i don't think I've had bad pla in a while. of course if you soak it in water it will absorb it, or if you are in a coastal city you may have issues. just guesses.

i would think it would take more than a few days.
Re: Drying PLA (New Idea)
July 10, 2013 04:05AM
It probably also depends on the filament supplier. We stored our reprapworld PLA filament out in the open for half a year without any problems although we are pretty coastal. Then again I have heard people like you having problems with moist PLA and do remember that the workshop instructor I am working with mentioned that he had to dry the GRRF filament.
So saying that the filament will take X amount of time to get saturated to Y level with humidity will be rather difficult.
Some differences may also stem from different hot end design. So far, I only have used the GRRF hot end successfully with PLA. By design it has got a very long brass tube (actually not a good design), so heat can creep up. Maybe this preheats the PLA, aiding in evaporating the moisture. In fact, some hot ends are supposed to be more susceptible than others to filament having absorbed air humidity.
Re: Drying PLA (New Idea)
July 10, 2013 07:23AM
Thanks. This was cheap filament and once its used up I will try a know better quality one.
Re: Drying PLA (New Idea)
July 10, 2013 07:53AM
The reprapworld one is also one of the cheaper filaments out there, but it seems to work really well.
Re: Drying PLA (New Idea)
July 11, 2013 01:28AM
Be careful drying filiment with heat alone. The material is extruded and is under a fair amount if internal stress. If you get it too warm when drying, you can cause it to change shape, making it harder to run through your print head.

If you want a better way, you need to make or buy a container big enough to put a spool in it and able to withstand 10-15psi vacuum pressure. You can best dry your filament by heating it to 80-120F while in the vacuum container and hooking it up to a good oil diffusion vacuum pump. Doing so will give you well dried filament in an hour or so, depending on how much moisture it has absorbed. Running undried filament cause excess nozzle drool, gaps in print tracks and rougher finish.

An issue I discovered is that some filament is poorly extruded, with bubbles inside. Test your filament by cutting with a razor blade to get a clean cut and check the exposed ends for hidden bubble cavities. Test several cuts within a foot or so to get a good sample. If you find bubbles, return it to the seller because it will never run right.
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