Recent acquired a A1 Mini and having tons of fun with it. Probably like most new 3D printer owners, kinda going crazy with filaments. probably have ten 1kg spools and ten 0.25kg spools. I’m storing them in 43qt Iris containers. The approximate volume of the containers is 3700 cubic inches (~60l). I live in central Texas where the humidity level runs from about 40% to 60% and higher. I need to know how much desiccant I need to use per container to keep the humidity level in the 15% to 25% level. Right now I have an unknown volume (maybe about a pound?) in one container and the humidity level is in the low 30s to upper 20s. I’d like to keep it a bit lower.
If you start with low humidity filament and air tight storage containers you don’t need much desiccant at all.
You can do the calculations though - there are online humidity calculators that will tell you how much weight of water per volume air at a given RH% and temperature. It gets more complicated as you correct for air displaced by a filament spool and what final RH% you want to hit.
There are curves that give wt% water in silica gel from 0 to 100% RH. Knowing how much water weight you want to remove net from the air and the final humidity you want to hit will tell you how much silica gel you need to hold that water at that humidity.
Add fudge factors for not totally dry silica gel, etc, and you can go with that. I wouldn’t do loose silica gel and weigh it. I’d get packs that are the size bigger than what you figure you need and call it a day.
The trick is drying the filament first. If you don’t dry it or know it’s dry, you can have a second source of water in your container that can throw your calculations off. Plus, at room temperature with no air circulation it will take longer to equilibrate with the silica gel.
If you don’t formally dry your filament, I’d really recommend the silica gel pack and cheap hygrometer route and not even worry about calculations or how dry the filament is. Just swap packs out whenever thr RH% goes above or nears your limit.
Yeah loose silica gel is not a good thing - found out the hard way when one of my silica gel containers accidentally opened up while moving stuff around. What a bloody mess! Bad design and printed in black PETG - opens too easily and can’t easily see the silica gel for color change. Will be reprinting with a new design (suggestions anyone?) and in clear PLA.
I currently don’t have a drying box but I do try to put the filament away as soon as a print is done. Might get a dryer when the budget allows. Been thinking about adding an internal fan to my storage bin for air circulation -might help some. Got hygrometers in each bin to help me keep track of humidity. Right now humidity in the house is around 48%, both bins (which are sealed) are in the upper 20s but I think I could do better.
Thanks for your time and information. I will look at that link to see what other information I can glean.
A fan would help the silica gel pick up water from the filament as long as it’s not saturated at the box RH% but a proper dryer would help a lot. Because of the slow liberation of water from filament at room temperature even in a closed up box, even if the silica gel has more water capacity at the box RH, “drying” will be slow.
Have a look at some of the dryer threads here but IMO, most reasonable cost dryers don’t work well unless you are in a dry environment with the lid propped open. They can even add water on humid days. It’s a long story. I answered because I’ve been deep in desiccants and dryers trying to get things sorted because on some prints I’ve been seeing some humidity effects.
Anyway, what the low cost dryers need is a source of dry air that pushes the moist air out. I’ve got what I hope will be a very functional design almost finished. To give it away (it’s documented in another thread) it’s just an aquarium pump and desiccant that supplies dry air to whatever filament dryer people have. I built a test stand to get a better handle on what was important and what wasn’t so now comes the actual device.
Results are promising and it delivers <=10% RH air to the dryer. I say <=10% because the hygrometers can’t display below 10%. Even 10% is a win but it’s likely much lower. What I’m doing in the next version is going to a simplified and optimized design with the larger pump mentioned in the thread. Apologies if it’s of no interest but I was drying filament while it was raining outside and the doors and a window were open - a spool of “dry” filament lost over a gram of water weight.
I just got in some more 20g. packs of Wisedry silica gel desiccant packs. On the back of the bag, it says “20 grams for up to 1.4 cubic feet (=40L)”. Also be aware that humid air rises, dry air sinks so put the desiccant at an elevated level in your container(s).
On a side note; I noticed when drying filament in the Creality Space Pi drier, cracking the lid a little every five or so minutes causes the humidity reading to fall instantly by a percent or two.
You can do the math, follow recommendations or use ready to go silica packs that come with a chart showing how much (fridge/freezer) volume can be taken by one bad and when to change them…
In reality though it just means you have a lot of work and only ever use the minimum amount of beads.
I don’t like this and find way too much hassle…
I have just over half a kilo of silica gel in my AMS…
Last a very long time and keeps the indicator at 1 …
For the storage I have printed containers that fit inside the spool and food vacuum sealer bags it properly tortured with a needle roller before filling.
The later can be refreshed in the microwave if won’t get the beads too hot and melt the bag.
For the former I have 1 litre pickle jar that I empty the spoiled beads into until full.
Then it goes on the scale followed by the microwave and I slowly tip them into a pre-heated jar to let the moisture escape.
Once the scale no longer goes down and the beads are blue I close the lid and have them ready for the printed containers.
What about reach and volume issues ?
The bags have plenty of space, so moving the beads around is no issue.
And if you leave a bit of head room in the containers you can do the same without even opening them.
Once I see more spoiled than blue beads I change them, no drama…