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Filament dryer – Wet filament

Today we talk about how the filament can deteriorate in contact with the humidity of the air and how to recover it with a dryer per filament. Every plastic polymer, during all the phases of working, if it comes into contact with the humidity has the tendency to retain it, until it reaches a saturation value that depends on various factors. Fundamental factors include the amount of moisture surrounding the polymer, temperature, and even composition.

In the previous sentence I said an inaccuracy and I point it out! I shouldn’t have said “every plastic polymer” but “all the plastic polymers used in 3D printing”. Where does this distinction come from?


Hygroscopy is, in other words, the tendency of a material to be hygroscopic is the physical property of the material to absorb moisture (hence water) from the surrounding environment. Not all plastics are hygroscopic, for example polyethylene, polypropylene and PVC (to name a few) are not hygroscopic. So the moisture fails to penetrate deep and stops on the surface, making them suitable for all the hydraulic applications in which they are usually used.

As previously said, however, the materials for 3D printing are all hygroscopic. Here, too, there is a difference though.

The peculiar value of hygroscopy, however, differs, and not by little in base rendering some better than others for being used, when the printing is finished, in a humid environment. In fact, PETG is poorly hygroscopic, followed closely by ABS and ASA and again by PLA.
Hygroscopy then forms a bond between the molecules that form the polymer and the water molecules. The water inlet itself carries modifications that degrade the material’s own mechanical strength and the possible formation of surface bubbles, irregular withdrawals as a result of heating, structural stresses, and a series of deformations and ruptures.

Filament dryer

The Nylon, special case

In general, the arrangement of a material to combine with water goes hand in hand with biodegradability. In fact, the reaction with water molecules is the first step of a material to be degraded by the environment (the second as we know is temperature). This is why PLA is more hygroscopic than ABS or PETG.
As usual, every rule has its exception. In this case it is the Nylon, with a very high hygroscopicity (perhaps the most hygroscopic of all plastic materials) that does not affect its strength and durability.
In this regard, the article dedicated to this material with exceptional qualities also contains a procedure that, taking advantage of its typical hygroscopicity, proposes a method to obtain very lively prints.

How to recognize a filament that has taken moisture

Does humidity affect so much with the quality of 3D prints? Although you won’t like the answer but is a big YES. But how do you notice that the material has taken moisture and then the bad press is attributable to hygroscopy?
An easy method to recognize a wet filament is to try to bend it. From slightly flexible in an optimal situation it begins to break with extreme ease at every minimum stress.
Other warning signs that must make us think that our filament has taken moisture is:

  1. The overall print quality drops dramatically and is no longer comparable to that of some time before.
  2. The shell is irregular.
  3. The filament is extruded with difficulty and with a certain frequency there are gaps of entire layers or real holes.
  4. The heated material emits real crackles when it passes to be heated. The way moisture, transformed into vapour, flows out of the plastic into fusion.
  5. Reduction of the mechanical strength of the material, often with delaminations with minimal application of force.

Ascertained that the filament has taken moisture what we do? We throw it all away? Absolutely not, here’s how to recover a damp filament.

Dryer for filament

There are special filament dryers. These are sold at unreasonably high prices and have the same functions as food dryers! So I can only recommend the latter!
Using a food dryer to dehydrate our wet rolls is really simple. There are only a few changes to be made and the precautions to use the latter. I summarize:
  1. Try to choose Circular Filament Dryer that fits the typical shape of the coils.
  2. The dryer should be modular with lid. This is because it will be easy to adapt with minimum effort.
  3. Opt for a digital dryer that respects the set grades with little tolerance.
  4. As always opt for a quality product.

Which filament dryer to choose

Making a pre-selection I would like to report to you a dryer with all the features in order, here it is:

Or here are some possibilities for all pockets:

The round shape will welcome your reel, you can simply remove the shelf and in their place insert some cardboard (both the temperatures are 55/60 degrees). Just roll in the right size and bother everything to form a perimeter on which to rest the lid. Once placed inside the coil, it will take from 3 to 6 hours at 55/60 degrees to recover any coil of wet filament.

It will take a little longer to recover the wet nylon if you are following the guide to change the color. In that case it will take almost a day!

Filament dryer

A significant positive side effect is also the finding of a food dryer, which works and can be used with food! So be able to dry chilli, fruit and even meat if you are lovers!

Modifications to the filament dryer

Don’t forget you have a 3D printer! So you can build an ad hoc barrier for each dryer you choose, even if you’re going to save money. You can do this simply by extruding an empty cylinder of the right size. In one solution or in pieces and then assemble it only later.

Some caution: the thickness of the project perimeters must be multiple of the diameter of your nozzle. Use a temperature-resistant material such as PETG, ASA, etc… The PLA begins to soften after 60/70 degrees and you risk finding a shapeless mass after a few hours.

You can also find something pre designed on thingiverse, here are some examples:

You can find many more through the Thingiverse search engine by simply typing Dryer. It goes without saying that if the shape is correct and only the size is different remember that you have the tool to scale (enlarge and shrink) a model directly from slicer. On Cura for example in the left part between the editing buttons of the model.

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