In the AMS a fan at least won’t be a negative, but molecules are tiny little things and much smaller than even surface roughness of filament. There’s not totally free movement but even on a perfectly-wound spool, there will be huge (to a water molecule) gaps between wraps.
And down in the atomic/molecular world, you’d be surprised how much motion there is. I really wasn’t expecting to find a micrograph of filament but just like how silica gel beads have a huge surface area, it looks like at least some PLA does too which explains a bit about how hygroscopic filaments can be so hygroscopic.
If you look close at the image of the PLA filament, those pores are 100-250 micrometers across. Water molecules are about 27nm across so the pores are 7,000 times or so the size of a water molecule. A little more torturous but water molecules are tiny.
A fan will get you to equilibrium faster, though, but the water getting out of the spool will be the slow step that a fan can’t help so much with.
I don’t understand what this has to do with the discussion.
What I was referring to was those graphs that relate humidity to moisture content. The measurements to make those graphs are not made in free air and ambient humidity isn’t a factor.
I get your point but just for example, no fan and that water molecule is going to take probably 10 times as long to make 1 circuit of the AMS. The more motion the better.
Do you want natural convection to take 3 days to cool your house or have a robust fan that can cool it down in 2 hours.
A fan may help in the AMS but you can think of a water molecule leaving filament and getting grabbed by desiccant as a series of steps that each has a time/probability associated with it. Slow steps will dominate the chain while fast steps will happen basically as fast as water is available. If you’ve ever looked at multiple resistors of different values in series, it’s kind of the same thing.
If water is leaving the filament at a rate called X but diffuses to the desiccant at 2X, you’ll still get water out no faster than X. Adding a fan to make 2X into 20X will still take at least X to get to desiccant. There is some benefit but not much.
I’ve been exploring regenerating silica gel beads and they can hold a lot of water and it takes a long time to come off. I’ve decided a microwave pretreatment can really speed things up but I have other reasons to finish them in my filament dryer.
Sorry for my earlier flippant remark, as I just didn’t have time yesterday to post a proper follow-up.
So, yes, you are 100% right. The experiment is done, and I an confirm it:
I thought I had posted it earlier on this thread (which is the reason for my obscure Inception reference), but apparently I hadn’t.
So, now that we’re all on the same page, welcome aboard! The more the merrier.
At the moment I’m waiting on a shipment from China of a very precise differential pressure gauge that I’ll use to more accurately set the minimum pressure needed to maintain positive pressure without wasting dry air flow.
NBD. I’ve been asking questions on forums for a long time and it comes with the territory.
I’m ordering parts to build a dedicated air dryer as I type to just keep a little positive air pressure in the AMS so the more humid room air can’t get it in. It doesn’t require much pressure. It’s not like I’m going to put an air hose quick disconnect on the AMS.
All I want is for AMS to be just a tad above ambient pressure. You might not even be able to feel it seeping (certainly not blowing) out of the hood. As long as dry air is seeping out, wet air can’t seep in. There are two parts, 1)drying what you’ve got and 2) keeping it dry;
Right now I have the AMS and a Sunlu S4 and initially may take some rotating in and out of S4 & AMS to do part 1 but my end goal is to maintain 8 bone dry spools between the two containers.
So far, I’ve been shuffling and printing PLA from a bookcase so probably my 8 dry spools won’t be PLA but you all got me straight on the PETG so it’s home will be among those 8 spools
Are there any universally liked/recommended filament dryers out there? Every time I search which one I should buy, I feel like I find conflicting opinions everywhere. Half of the people wholeheartedly recommend Sunlu dryers, while the other half claim they’re horrible. Just found some recommendations on the Eibos dryers this morning, but now I’m also seeing a ton of posts saying they’re ■■■■ as well. All I want is something simple to dry out the occasional roll (probably PETG or TPU) to use with my A1 Mini and AMS lite.
I think, nearly each cheap filament dryer (for around 50 bucks) should fullfill your requirements. The only one I really found is, it should have a fan inside to move the air. PLA, PETG and TPU doesn’t need really high temperatures and so they should dry even if the dryer is not reaching it’s own specified temperatures. Because you want t use it ‘occasionally’ - in my opinion - you don’t need a professional or perfect dryer.
I have a very cheap dryer (eSUN eBox lite) and use it for PLA, PETG, TPU and ASA and it works for me. Sometimes I dry the spool for 24 hours, but mostly around 12 hours. Since then I never had problems with wet filament again.
I have both a Sunlu S2 and Creality Dry Box 2.0. They both seem to do the job they were made for. What is interesting to me, the lowest humidity level I can get is 15% for either one and that’s both PLA and PETG.
For PLA, I’m typically getting 7%-9% RH, if the PLA is put in a sealed box after drying with just an TH meter and no desiccant. That’s after a thorough drying, which very few people are doing, in a blast oven but still with ambient make-up air during the drying process. And where I live it’s pretty humid much of the time.
