All over these forums, when people get low print quality, the first comment is, almost without fail, “Your filament must be moist! You need to dry it out!”
Based on that advice, I built a big old honkin’ dry box to hold all my filament, and I keep it at 125°F (~50°C) and suck as much humidity as possible out of it using a closed-loop dehumidifier. OK, great! Except that now I have a new problem: Brittle filament (Basic PLA). Specifically, brittle filament that breaks into pieces all throughout the feed-train from the AMS to the print head. I spent a good 3 or 4 hours disassembling everything in the feed-train, pushing out little bits of broken filament (with some brand new, presumably moist, filament), and then re-assembling it all. Perhaps needless to say, it’s not an experience I’m eager to repeat.
What am I doing wrong? When I don’t keep the filament dry, I get crummy prints, and get admonished to dry my filament. When I do religiously keep my filament dry, I seem to end up with this brittle filament that takes the machine out of commission if some poltergeist happens to breathe on it wrong. Clearly people are able to use these systems reliably, so I must be doing something wrong.
I would be grateful for any advice anyone could share. Thanks!
When I dry my filament with a dryer, it’s between 6-24 hours…maybe a little more if I’m printing from a dryer.
Your drying your filament 24/7, I think this might be your problem.
I can’t say if lowering the temp would help or not…maybe just turning it off when you don’t need to dry.
Gonna have to wait until one of the smarter physics users chimes in
@lion7718 is right. You don’t want to “dry” filament with heat continuously. Plastics have lots of things like plasticizers mixed in that keeps them flexible. Baking the filament dries those out too just like it does with water.
You don’t have to keep filament hot to keep it dry. Some build cabinets, some use sealable bags, some use impervious polyethylene sealing food storage containers. You really want to only dry filament once, or no more than as needed.
How much you need to dry is another issue. You only need to dry as much as you need to get good prints. More than that wastes energy and can remove the additives that keep filament flexible.
Do some searches and look for filament storage. I tried to find a specific link to a particularly good thread but am not finding it right now. But lots of good information is here and available.
Last, dehumidifiers don’t typically pull humidity that low. They are generally intended to reduce humidity to human comfort levels which can still be too high for some filament types. You might want to get some humidity meters to be able to put numbers to your drying and storage too.
The temp in the box is as stated. The RH wavers between 10% and 15%. The temp seems to be doing most of the work, as I pretty much never have to empty the dehumidifier. I have meters.
There is a trick to “humidity” levels. It’s generally relative humidity which has a temperature dependence. Take a plastic bag full of humid air at some RH value and heat it up and the RH drops. Relative humidity is how much water is in the air compared to how much water it can hold. As you heat air it can hold more water. So hot air at low humidity can still have a fair amount of water in it.
So while 10-15% RH is pretty good for filament storage for many people, that’s at room temperature. If your storage was at room temperature the humidity would be a fair bit higher. This is the part about dehumidifiers not really drying the air “a lot”. They dry some but aren’t expected or desired to really wring air out to dry as death valley.
You don’t say what kind of filaments you are working with (maybe I missed it) but PLA is pretty forgiving and can print well with higher moisture content than stuff like TPU or PETG. That’s just side information but something to keep in mind if you use them. The bigger issue seems to be long term heat and what it does to your filament.
Like @lion7718 said, you can dry your filament for a day or so but take it out of the hot box and put it in an impervious container for storage. And Ziplock bags are semi-permeable. It’s slow but over long time they approach no container at all.
