I’ve heard some people advise to dry your filament until the weight no longer changes. I think that may actually never happen within any practical timeframe. For sure the rate of loss will slow down, but actually stop entirely? No, I’ve never seen that. I have a spool of Sunlu PLA drying right now that’s been drying for over 2 days at 60C. That’s 60C with plenty of make-up air. Not just a sealed chamber or something. I checked it today twice, and over a 4 hour interval it lost another 0.11g. I bet I could dry it for a week and it would still be losing weight–more slowly for sure, but still losing a measurable amount given a long enough time interval.
Which is too bad, because I was wanting to setup a test specimen that was fully 100% dry by conventional means, and then see if I could dry it more using desiccated air in the dryer. So, I guess the way to do it will be to keep track of the rate of moisture loss while drying, and then see if that rate accelerates markedly when I switch to drying with desiccated air. I don’t see any other way to do the test.
I did a similar test and the results are I think what you would expect - and the test was I think your idea too. I let a spool use ambient air while drying using that printed spacer to hold the top part of the filament dryer open. I only went until the weight change got pretty small and the humidity and the drying chamber pretty much stalled. When I started adding dry air, the weight loss jumped and the RH started dropping again.
Looking back at my notes, the last hour without dry air, the RH dropped 1% from 38% to 37% in the Sunlu while the spool only lost 0.04g by my scale. I started the dry air immediately after getting those numbers and in the next hour, the RH dropped from 37% to 28% and the spool lost 0.17g in weight.
RH with ambient air was still dropping but very slow. Same for spool weight. But both spiked in amount of change after starting the dry air. That test and then just pumping room air straight into the drying chamber (which behaved very much like drying with the hatch on the filament dryer propped open but was actually slightly worse) indicated it’s not just air exchange that helps drying.
Air exchange does help drying - but only to a point. The door props actually do help. And just pumping ambient air in does help. But both of those are limited by ambient humidity and it will largely stop the humidity from dropping at some point in the filament dryer. Dry air removes that floor in RH and both dries filament faster and to a lower water content.
One or two grams of moisture in a spool of filament makes no difference in my prints ( PLA PETG TPU ASA PC), so I don’t see a need to measure tenths of grams. My shop scale only indicates full grams and I consider a spool effectively “dry” when the weight has not changed in the past hour. Coincidentally, that is also about one hour after my Eibos Easdry indicates interior humidity of 10%, the lower limit of the hygrometer.
I guess it depends on where your spools are moisture-wise compared to where you see water effects. If you are well away from seeing those effects, parts of a gram won’t matter. But if you are close they can.
But good point. I wanted the extra resolution because I was weighing spools hourly and so needed to be able to see smaller changes. I really think, though, that if using dry air in a filament dryer it could be that weighing only confirms weight loss one already knows happened. As I was running spools through the drying process here, I stopped weighing them after about the 20th spool because without exception I was seeing good weight losses. When I did the PETG-HF, I went back to weighing since it was different. Weighing confirmed weight loss, but kind of just became a formality.
No difference that I can see, with the materials I’ve used. It’s possible that more than 2 grams of moisture in a full spool might not matter for some filament types, but I arbitrarily set that as my threshold for re-drying. New spools are always dried to establish a baseline. Something like PA might be less tolerant of moisture, but I’ve not used that yet.
Interesting. Definitely see the utility plus it’s a record of use. I like it!
Also it’s interesting the differences into and out of box. They all tend to show increases where they appear which is similar to what I was seeing when I was putting away spools overnight - there was generally a slight increase. This was before I made the spool/hygrometer stands and put desiccant packs in the cereal containers. Haven’t done the in/out recording since but might just to get a handle on how things are going.
I took the arid air model private. It’s because I came up with a better way to attach the bottle. It’s obvious but I missed it. I can really simplify the build by just printing the bottle threads and forgetting about drilling holes and other fiddly stuff. Just print it all.
Should be able to revise and repost this weekend. Only three downloads so far so if you hold off printing the base, it’ll be better and easier. Actually, hold off printing everything.
Ironicly, the same day I posted this the ambient dewpoint rose. Even though I continued to “dry” the filament, its weight increased slightly soon after the rise in ambient dewpoint. It’s the first time I’ve ever observed this happening because in the past ambient dewpoint changed little, if at all, during a drying cycle. In any case, solid proof that the make-up air limits the degree to which filament can be dried.
Hey Electro, that’s basically how it is now. It works well but adds a lot of steps and is a little fiddly. This other way will be precise and straightforward and removes a trouble spot.
That’s ok. It worked and worked well but to get there took multiple steps that would sabotage the print if not done right. That bugged me and I kept thinking how it could be better. You’ll see.
No more drilling holes, punching holes, gluing gaskets, or possibilities to cause leaks that can ruin the model. I should have done it different but was too busy with all the other aspects to realize. Anyway, it’ll be back and much better for it.
Added - The only silicone seal now is mounting the hygrometers and sealing the wires. Got extremely lucky on the printed bottle threads - the bottle company used standard threads and Fusion had them so it was easy to update. And it also worked out with no gluing now for the bottle mounting, no drilling, no fiddling with the straw. Nothing critical now. Cut the straw to length and glue on the end fitting. It no longer gets glued to the base so it all comes apart if needed for anything.
There’s even a bottle tester now that is just the subset of the model that is the bottle threads so you don’t have to print the whole thing to test a bottle.
The new version is up but I need to finish printing a full real one so there’s photos and need to update the instructions for the changes. And it is much better. The previous version nagged at me. No purchased part changes, either. That’s all the same.
The new base printed beautiful last night so will get photos, amend the instructions, and post it back again.
Whoever downloaded the old version, I apologize - especially if you wasted any filament. I didn’t know how to do the bottle threads so was cheating by gluing in the cap for the bottle and using their plastic threads. It worked but now all that is built in too. The old version works fine.
The base still needs sealing and the hygrometers still need to be bedded in silicone, but the bottle parts don’t. They drop into or slide into place and the bottle seals them and holds them in place. So much better than gluing with silicone seal and crossing your fingers. Instead of the gasket in the bamboo cap, there’s a simple gasket in the plastic bottle cap that is also supplied with the drinking water bottle. We use that simple gasket now without glue.
It will make more sense when I get it posted back up again.
Arid Air is back up with improved and simplified bottle mounting built in. It’s much easier to build now with everything critical constrained by design that can be. Here’s the new bottle mount, bead filter disk, and straw mount. No drilling, no drill guide, even gluing the bottle mount pieces isn’t really needed now. It just drops or slides into place. No guesswork.
If anyone printed the old version, pm a photo and we can sort some way to reimburse you. It was a good but flawed design. It works great. It’s just more difficult and fiddly to build.
It was just too much explaining and chances for trouble to glue the water bottle lid in and get the straw properly positioned. And like I said I really didn’t think Fusion would have the bottle threads. It seemed fairly overwhelming. But once I had some breathing room and started looking into doing the mount differently, it all just fell into place. About 4-5 hours to get it done.
And yep - the exact same bottle. You need the plastic straw and the gasket out of the black plastic lid the bottle comes with. That bamboo lid and its gasket aren’t used any more. Same for the metal straw - now not even used to punch holes in a gasket.
In the 3mf file I included the part of the model with the bottle threads as its own part so people can test bottles if they want. Easy to carry into a store and see if the threads fit.
