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tomnagel

Moisture content of filament

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In shini.com/ep_edm/en/contect.php?e_id=18&ID=246&flag=1 I read that the moisture content of PLA must be kept low.

From work, I know that plastic granulate used for injection moulding must be kept dry. I think the equipment manufacturer that wrote the page mentioned above is referring to the use of PLA for injection moulding.

But has anyone experimented with dry or not-dry PLA for a 3D printer? Does it matter? On thingiverse, I found someone who made a special box from which the PLA goes into the printer. (http://www.thingiverse.com/thing:52873). Would that do any good?

And dear forum member: how do you store your PLA rolls?

 

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I've been starting to run TGA to analytically determine the moisture content of different filaments and propose different bakeout profiles. I ran some Taulman nylon that was reported to be too saturated to work with.

It contained about 1-2% water by weight. By about 2hrs at 93C, it was nearly entirely baked out, but not quite asymptotic. If anyone has any particularly difficult filament that they think is causing problems because of moisture content, consider sending it to me for some testing. I only need ~1cm to test.

I'm doing this using equipment at work on my own time, so no promises on exactly when I can get the results back to you :oops:

 

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It matters if your filament has absorbed water.

PLA with too much water in it generates uglier prints. It does print, but you kinda get an ugly finish. (took us a while to figure out that this was the problem with some of our prints) printing hotter sometimes helps a bit, but you're always left with a bad finish.

 

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The "ultimaker HQ" way of getting the moisture out of a roll of PLA is to print all of it and use a new roll :-)

But storing it dry with the silica gel should be enough. (Ultimaker PLA should come packed sealed with 1 package of silica)

The effect is minor, but looks like a skin condition. I think it's caused because the moister in the PLA boils and causes micro-bubbles in the print.

 

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Standard practice in industry prior to melt processing polymers for high quality applications is to bake it out somehow. I made the mistake of trying to bake out some PLA at the lowest temperature my convection oven would go, 200F/93C. It all stuck together. Don't do that :oops:

I'm insanely busy at work right now and have a sample of ABS I had promised someone I would test for them, but I will try some PLA when things calm down. I can toss it into our accelerated aging temperature at 55C/ 90%RH to force it to be saturated to do a worst case condition, but I'd love to actually test some that someone suspects has a moisture problem.

Any particular colors that seem to be worse than others? Additives can definitely affect moisture adsorption. I have ultimaker black and natural as well as matterhackers red, blue, and orange, as well as some sainsmart yellow that I could try,

 

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I just received Nylon from Taulman. I was very disappointed to open the box and find unsealed thin and torn polyethylene plastic bags. There were desiccant packs in each bag but they and the Nylon must be saturated after a trip from Missouri to Massachusetts in a USPS truck if not before shipping. I posted a complaint on Taulman's store web form, so far no response after 5 days.

Best, Bill

 

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