Drying filament under vacuum

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zemlin
Posts: 326
Joined: Sat Oct 21, 2017 2:02 pm

Drying filament under vacuum

Postby zemlin » Fri Jul 06, 2018 2:06 pm

I really dislike having to dry filament in the kitchen oven for hours and hours. At the day job I work some with vacuum chambers. I poked around the www a bit but didn’t find much information about folks using vacuum chambers to dry filament.

I’m going to give it a shot.

I ordered a 3 gallon vacuum chamber (a pot with a thick acrylic top) from Amazon, and an Inficon QS5 vacuum pump. There are cheaper pumps, but I don’t like to buy junk and reviews indicate they can't reach their rated vacuum level. The Inficon seems to have a decent reputation. I also got a tube of Dow 111 silicone grease to use on the seal on the chamber.

This pump is rated at a vacuum level of 15 microns, and it’s been reported that some will get down below 10 microns. Boiling point of water is about -60C at this pressure so I’m hoping that I can achieve a better level of dryness in less time. It should also work well for drying out my desiccant packets.

It’s a modest investment – about $350US total, and if I decide I need to add heat it could cost me another $100 – but I’m thinking additional heat shouldn’t be necessary at that level of vacuum. The pump shows up today. I already have the tank.

Might also be fun to play with drying fruit without heat.

If anyone out there has messed with vacuum drying at pressure levels like this I’d love to hear about your experiences.

Vice Chief
Posts: 84
Joined: Wed Aug 23, 2017 5:04 am
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Re: Drying filament under vacuum

Postby Vice Chief » Fri Jul 06, 2018 2:10 pm

I've been interested in similar ideas (but ended up with a lab oven instead - randomly found a great deal on one). Very interested in what you learn as I also need a vac setup for casting.

Phife
Posts: 73
Joined: Thu May 12, 2016 3:47 pm

Re: Drying filament under vacuum

Postby Phife » Fri Jul 06, 2018 2:57 pm

I use a vacuum pump and a chamber on a heat plate set to 50c to dry my Nylon, 15micron is more than enough, I only get down to maybe 50,000micron. Works well. I also line the bottom of the chamber with Silica beads so the moisture has somewhere to go. Although I'm not sure how necessary that is.

billbucket
Posts: 35
Joined: Sun Apr 22, 2018 7:41 pm

Re: Drying filament under vacuum

Postby billbucket » Fri Jul 06, 2018 3:20 pm

Interesting idea. I already have a vacuum chamber, but hadn't considered this application. Let us know how it works out.

zemlin
Posts: 326
Joined: Sat Oct 21, 2017 2:02 pm

Re: Drying filament under vacuum

Postby zemlin » Fri Jul 06, 2018 4:20 pm

Phife wrote:I use a vacuum pump and a chamber on a heat plate set to 50c to dry my Nylon, 15micron is more than enough, I only get down to maybe 50,000micron. Works well. I also line the bottom of the chamber with Silica beads so the moisture has somewhere to go. Although I'm not sure how necessary that is.

I'm going to keep the pump running throughout the drying process so that will extract any water vapor - but if you pull your vacuum and then disconnect the desiccant might be helpful.

MaxwellRi
Posts: 1
Joined: Fri Jul 06, 2018 9:38 am

Re: Drying filament under vacuum

Postby MaxwellRi » Fri Jul 13, 2018 2:29 pm

That's a brilliant idea tbh. How long does this process take btw?

zemlin
Posts: 326
Joined: Sat Oct 21, 2017 2:02 pm

Re: Drying filament under vacuum

Postby zemlin » Mon Jul 16, 2018 4:30 pm

I've been working with this a little and it seems it's going to work well, but it's going to take longer to dry the filament than expected. The good news is it seems to get things far drier than cooking them in the oven.

My last test was to put my spool of NinjaFlex in the tank along with about a dozen Silica Gel packets. I tried drawing the vacuum down and then shutting the pump down after an hour - let it sit overnight but the packets with indicator were still pink. So I tried it again, but this time left the pump running overnight. The desiccant and the humidity indicator cards were all blue. I put the filament, a desiccant packet, and a humidity card in a ziplok bag - and put the rest of the packets and humidity cards in another bag for storage.
It's been over a week and the 10% indicator is fully blue on the card in the bag with desiccant packets. I've never seen the 10% dot go blue. Same thing with the filament spool. The humidity card in that bag starts at 30%, but it is dark blue - looking better than I've seen after cooking.

What I've learned is that the water that comes out of the stuff in the chamber ends up in the pump oil - so I'll need to monitor that. A tip I read online was to drain the oil and then freeze it - you can then pour off the oil and the ice stays at the bottom of the bowl - seems like a good way to recycle the oil and keep it clean. I bought a gallon of oil for about $20, and the pump capacity is about 12.5 oz - so it's not a big expense, but I wouldn't want to drain and pitch the oil after every big drying run.

I've been traveling on business a fair bit so I haven't had much play time - but I'll post more when I learn more.


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