Drying filament under vacuum

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Location: Fullerton CA

Re: Drying filament under vacuum

Postby MDVolle » Tue Feb 18, 2020 3:08 am

I know this is an older post - any additional information on vacuum drying?
I put together a tank and pump and am trying it -

With an empty tank, my pump will pull the chamber down to 30" on the gauge (so calibration might not be spot on) but it goes to 30 and stops - so I'll take that as "full vacuum.

With a spool or two of filament, it drops quickly but NOT to 30 - that takes a variable number of hours before it finally goes to "30" but so far, each time, it does get to that point (eventually)

I read that using the gas ballast valve on a pump can reduce the maximum vacuum pulled BUT allows the moisture to escape without condensing in the oil?

I'm new to the whole vacuum field but I'm four spools in and my oil is still clean and clear using the ballast valve until the very last draw on the tank.

Its slightly disappointing - as the frothy white contaminated oil seems like a sure sign you are doing something! but if using the ballast vale is actually allowing the mositure to escape without being condensed in the oil, that seems like a really good thing and would save folk some time.


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Joined: Fri May 22, 2020 6:52 pm

Re: Drying filament under vacuum

Postby akyle32 » Wed May 27, 2020 9:43 pm

I thought about this but I wasnt sure if its going to work. Its a good thing you did the experiment. Ill buy my own vacuum next month.

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Joined: Sat Oct 21, 2017 2:02 pm

Re: Drying filament under vacuum

Postby zemlin » Thu May 28, 2020 12:09 am

I'm still using the vacuum pump for drying. i haven't tried adding heat as JohnSays suggested. As I mention early on, it isn't as quick as I as hoped, but it works. I recently made a drybox to use during printing with a Rubbermaid 21 cup container.
https://www.amazon.com/Rubbermaid-07169 ... B00NP6T9JE <- Don't by them here - the local grocery/mega-store had them for $7.50. I've only run a few prints with the drybox, but I got the best looking PC parts I've ever printed after vacuum drying and keeping the spool in the drybox for printing. Also made a big difference in print quality with CF EPA filament. While I've never been concerned with moisture in PETG, some small tests I did have me thinking that will be worth drying out as well.

Here's the insert I made for the container.

A bit of 1" PVC pipe for the spool core. The rectangular frame is for one of these:
https://www.amazon.com/gp/product/B07NSZ9XPY - readable through the plastic. I throw a few big dessicant packs in the vacuum pump with the filament and pitch them all in the dry box. I just put a spool of PETG in the vacuum. Took about 36 hours before the spool stopped losing weight. The weight of the spool decreased by about 2 grams. Not a lot compared to other materials, but that's 2ml of water. I also use the vacuum for drying my desiccant packs.

I haven't tried to do anything to eliminate the water in the oil either - I just see it as the nature of the beast. I bought a gallon of oil so I can keep a few oil changes worth in circulation. When the oil level gets above the top of the site glass I do an oil change - just takes a couple minutes. I collect the wet oil in a plastic milk jug. After I have a few changes worth of wet oil I put it in the freezer. When the water is frozen I pour the oil out of the jug. It's shocking how much water is in the used oil. I then use that oil for subsequent oil changes.
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