… And after all that chat, this is what I ended up doing!
Two spools fit into an IKEA 10.6L bin. I made a small stand to put a cheap hygrometer in each, and to tidy up a couple of desiccant canisters, and they all fit neatly into two banks of my printed bookshelves which serve as bedside tables in our spare bedroom.
I can mostly keep humidity in the boxes around 20% which is about bone dry for around here. Bearing in mind that as the temperature goes above 25° the silica gel loses its efficiency too, and today’s minimum is 24!
It’s complicated and I’ve oversimplified it, and why you don’t just take the word of some random person on some random forum post! - The Calcium Chloride promoters will tell you how inefficient it is - I have found through two years of observation that the oversimplification is fair!
I am now using 200 gms of Silica per 10l container, which is a lot more than most companies recommend for packaging - BUT the RH varies between 16-24 in the sealed containers! None of that is a problem because the reason I’m doing it is to prevent absorption in the filament and at those levels absorption is close enough to zero - measured by weighing the filament before and after 2-3 hours in a food dehydrator.
Without storing like this I have removed as much as 3grams (ml) from 700gms of PLA.
I spent some time trying to understand the science, now I just go with the results!
What?!? I had to get a dehumidifier in here last spring. Sitting here I am at 46%RH, we hit 70 at one point, that machine was pulling tons of water out of the air. 13%, is crazy, do you all carry chapstick in your pocket?
I go through about a spool a day on each machine so I don’t bother but the few rolls I do store are in a dry box with heaps of dry packs from all the daily spools. So far they are still good years later.
I have a big ziplock tub with a couple rechargeable desiccant boxes in it. Modified a chepo food dehydrator to dry the spools before they go in the box.
It usually takes me a little while to go through a roll of filament.
I recently picked up one of the commercial drying boxes. It’s working well so far. I’m thinking I should mount a hygrometer inside the 3d printer to see what the humidity is inside the chamber while it’s printing. I think it’d be interesting.
I live in a fairly humid environment as well. We hit 90% Sunday morning. I grew up in Houston. Down there your sweat has sweat. You wake up each morning with condensation on all the windows on the house from the AC running during the night.
I finally got tired of the hassle of the old food dehydrator - It works well, but it’s a day to dry the silica gel and then a day to get two spools of filament down to say 20% in the dry boxes and then by the end of the week we’re back to 30% (which seems to be where it stays once it settles).
So the dry boxes stay, but I’ve done enough research of filament dryers to earn a PhD I think.
My thesis is:
Most people won’t want or need the extreme that I’m working to. Most people aren’t as fussy about the end finish as I tend to be, and they live in a much more printing conductive climate.
I could easily build one that works (a filament dryer not a dry cupboard) but the cost of doing so is more than a medium priced commercial dryer (say a Sovol two spool job)
Ironically the lower priced and medium priced ones mostly don’t actually work as well as the food dehydrator, because they don’t exhaust wet air (they do improve RH but not to the extent I want if I’m spending that sort of money, and they can be modified to be quite efficient. None the less, most peak out temps at somewhere below 60°c which is not quite enough for drying the filaments that most need it>. Remember once again I live in a very humid environment and anecdotally they work well enough in less than extreme conditions.
I’ve bitten the bullet on a Eibos Cyclopes - which is stupidly expensive for what it is (just like Prusa’s stuff! ) but unlike Prusa’s stuff still needs modifying because it’s too hot! It has a 150W heater and can heat the thing to stupid hotativity, but does have a propensity to melt filament and spools when it does if they aren’t moving. There are a couple of nice mods including one that puts a little motor on board to make a sort of rotissery, so watch this space.
When it’s sorted, I’ll be able to dry two spools and their associated silica gel while printing. So finally I should have string free PETG, and Flex and ASA that actually work for more than about an hour!
I haven’t fully tested my filament dryer yet. Today’s humidity is only 57%, but I thought I’d run the dryer on some TPU. I also tossed some dessicant in the bottom of the dryer. I figure I’ll let the dryer dry the dessicant out and then see how well it holds the humidity inside the dryer.
Here’s where the temp/humidity was a few minutes after I turned it on. (24c/57% when I first turned it on)
Yesterday was a very low humidity day for us (57%) and a very chilly 19° C (brrrrr).
I keep all filament in dry boxes when not in use, and mostly unload it at the end of the day. From previous “scientific” experiments, I’ve removed between zero and 1 gram of moisture from older PLA when drying.
I have formed a view some time ago that the benefits of “drying” PLA is mostly “conditioning” it but there’s no chemistry behind that. I am not dismissing drying out of hand, and am hoping to actually be able to print ASA in our climate with my fancy new dryer. HOWEVER -
My dry boxes tend to keep a constant relative humidity between 20 and 30% depending on ambient temperature and the state of the silica gel.
In the following photograph the box on the right was opened to the air for one hour, with 120 grams of silica gel slightly discoloured (some humidity in it) The blue filament has been in use for two years, the yellow probably about 18 months. No drying.
The box on the left has newish filament, 180 grams of freshly dried silica gel and the filament had been dried to 16% RH(4 hrs @45°) before sealing.
The photo was taken twelve hours after sealing the boxes and even allowing for a small discrepancy between the two hygrometers I would describe my drying efforts as disappointing!
I live in a very moderate climate though.
Think of all the shipping costs you don’t have to pay to Prusa as well.
