That filament dryer is one of the least effective methods of drying materials I have ever seen. It continuously draws in moist air from the environment. Proper drying systems are closed loop.

Yes, it is true that with a desiccant in there the air will dry. If you have a layer of desiccant in the bottom that the air has to draw through it might be reasonably effective, and it will probably dry it enough that you will likely see decent results.

My concern with it however is that keeping filament at temperatures high enough to encourage molecular movement of the water is also high enough to oxidize the material. This is commonly called "over drying" the material (although that is not the correct term), and if you leave it in there too long you will wind up with brittle, unusable ABS.

Furthermore, when drying plastics, relative humidity is an almost useless number. 10%? At 10% RH many plastics are well above their minimum water content for processing. RH changes with temperature, and the critical number is dew point. When we dry plastics professionally, and without degradation, it is done at a fixed temperature for a set number of hours and at a dewpoint of -20 to -40F. This ensures that the air is actually dry, unlike RH, which does nothing of the sort.

With nylon of almost any grade, this type of drying cannot get it suitably dry without degrading the material and giving you brittle filament. Either you will have semi-moist filament, or you will see degradation. I know this to be true because we have a few old school dryers that are basically this exact method, except with the addition of airflow through the material, and that's the results we get with those dryers no matter what the grade. Nylon is a very finicky material to dry and process. It has a pretty narrow window between melt temp and degradation temp, and time is the most critical factor when drying or processing almost any material.


TLDR version of this post is that for many applications that type of dryer will be suitable, but at bare minimum and I promise you that better results are possible. The problem is being able to build a proper forced air dryer for a reasonable enough price for home users.

I suspect it can be done with manually changed and recycled desiccant beds, for a reasonable enough cost that the average home user can build one.

I wonder if I should just start a discussion thread on drying plastics. I have a lot of resources available to share on the subject. Mjolinor's link up there is a good start. The first method listed is what the bucket is. Just heating air from the environment and passing it through the plastic. This is less than ideal.