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Drying out PLA to reduce dribbling

Posted by fdavies 
Drying out PLA to reduce dribbling
December 23, 2010 10:05PM
I have some PLA 3mm filament that has been sitting around for some months. I tried printing with it and discovered that the extruder was dribbling. By this I mean that when the stepper stopped, the PLA kept coming out. When the stepper started again there was a significant delay, presumably as the void created by dribbling was filled. I would occasionally see the tip blow a bubble with a tiny puff of what looked like steam.

I discovered that if I took a small amount of filament (a dozen or so coils) and put it on a piece of aluminum foil in an oven heated to 170F for an hour. This cured the dribbling and greatly improved print quality. The filament in the oven is floppy, but sticks to itself only slightly. It is not too hot to touch (low thermal conductivity, I suspect) and flexing the coils unsticks them from each other. I suspect that heating a large spool might not be a good idea, though. I can see a weight change after baking. One coil went from 120.5 grams to 120.0 grams (almost 1/2%).

I have read various data sheets on PLA that say that it picks up water from the air, and that heating (with dry air) can be used to remove moisture.

Re: Drying out PLA to reduce dribbling
December 13, 2011 05:40AM
I am thinking about putting whole reel, in a airtight bag with only a small hole for the PLA down to the extruder.
Does anyone know how much moisture/if any , a abig well baked silica gel can absorb from PLA ? - will it get the moisture at all without adding heat ?

Another idea I had: what about adding a "baking" chamber, where the PLA is heated for about 10cm before getting to the extruder. - but it should not get too hot... - not sure how much good it would do.
Re: Drying out PLA to reduce dribbling
December 13, 2011 08:18AM
You can store it in rice to draw out moisture.
Re: Drying out PLA to reduce dribbling
December 13, 2011 11:55AM
I had a rather big coil of natural PLA which was useless due to it bubbling when extruding. I put it (together with other PLA) in an airtight container and dropped in a few silica gel bags and a dehumidifying egg. After a couple of months it had turned milky white, and it now extrudes perfectly.

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