Humidity is the water that permeates a body or vapor present in the atmosphere. For all living beings, water is the most necessary to survive, even more than food, but for non-living elements, humidity is usually a source of problems, since it causes the oxidation and degradation of many materials. In the case of 3D printing, more specifically in the filaments, the concentration of excessive humidity can cause a long list of problems, all with the same end, a 3D printing failed.

The effects of attracting water can lead to the following problems: increased fragility, increased diameter (possible problems with printers with Bowden type extrusion system), filament degradation, breaking filament, etc. It is also necessary to take into account the fact that the filaments that have absorbed water will have a higher temperature for the extrusion. Remember to avoid having the filaments placed in the printer if you are not going to print. They can get stuck in the extruder because when absorbing water they get fat and increase in diameter.

The following map shows the average annual relative humidity (percentage ratio between the actual amount of water vapor contained in the air and what it would need to contain to saturate at the same temperature), a value that is obtained from the average humidity registered in the twelve months of the year. The relative humidity is very different depending on which part of the European geography you are, being more pronounced in the northern part of the continent.

Image 1: Map of relative humidity in Europe. Source: NeoGAF

The main consequences of moisture in a filament are:

• Degradation of the filament: The hygroscopic filaments are prone to absorb water to a great extent, since the water molecules are attached to the polymer molecules, forming strong intermolecular bonds. These links can cause internal micro-breaks that weaken the filament structure itself.
• Extruder / HotEnd jam: The humidity of water concentrated in the filament when heated in the HotEnd evaporates, causing gaps inside the filament, turning it into a paste that clogs the barrel (Heat Break) or the nozzle. This problem is very common when using nylon filaments with high humidity percentages (> 20 %).
• Low quality 3D prints (resistance and finishing): The union of the aforementioned results in 3D prints with many problems, both mechanically and superficially. The gaps between layers (not always visible to the naked eye) caused by the evaporation of water, are critical points, where cracks are easily generated by applying low values of force. When the concentration of humidity is marked, the holes mentioned above, cause a rough and whitish surface finish.

Image 2: Problems generated by humidity. Source: PrintDry

As a reason for the evolution of the world of 3D printing, there are filaments with high resistance to moisture, such as PETG or CPE HG100, copolyesters that can be exposed to water for long periods of time without problems. Among the other filaments we found some with moderate resistance, such as PLA or ABS, and others, especially nylons and PVA, highly prone to moisture absorption, reaching high values in less than a day.

Certain users of 3D printers  use conventional methods to remove the moisture from the filament and store it, such as drying the material in a domestic oven and storing the filament in boxes with a closure that is not totally tight. These measures, apart from being dangerous in the case of the domestic furnace, are not totally effective, especially with technical and advanced materials. Here we quote a series of professional recommendations to eliminate moisture and how to store the filaments to prevent absorption:

Filament dryer

The most effective way to eliminate the moisture contained in a material is to use a filament dryer, such as the PrintDry filament dryer, a device capable of breaking the intermolecular bonds between the water and the polymer thanks to its drying temperature (35-70 ºC) and the natural air flow inside it, which drags moisture from the surface of the filament into the air that it surrounds it. The ideal value of moisture in a filament is between 10-13 %.

Storage

Both at the beginning of the use of a new coil and after drying a filament, proper storage is essential to maintain the minimum percentage of humidity. In conventional materials (PLA or ABS) and short storage intervals (<2 months) the use of your bag with a grip type closure is sufficient. In case of longer storage times or with technical and advanced materials this measure is not enough. The ideal solution is to use the PrintDry hermetic filament containers with vacuum sealing. They are high-strength plastic containers, where each user can store their filament safely without worrying about whether they pick up moisture. The potential of these containers is in the lid, since in this a vacuum valve is housed, through which and with the help of a manual pump (included with the containers), it is possible to extract the air from the interior of the container, providing storage free of dust and moisture. In this way, the correct condition of the filament can be guaranteed, although several months have passed since the coil was taken out of its original factory seal. The older, it must be taken into account that the relative humidity of the area where the material is stored affects in large quantity, this should be the least possible without harming the health of the user (A good value would be over 40 %).

Filament lifespan

The life of a filament of quality since its manufacture is 2-3 years, as long as it is in its original seal and vacuum. Once the original bag is opened, the time it takes to lose its mechanical and color properties depends on the type of material and storage. A PLA or ABS stored in the manner mentioned above can retain its properties for more than 1 year, but if it is not, it will resist a tenth of the time. In more delicate materials, such as nylons and PVA, the total loss of your life can be a few days.

It is therefore an evidence that maintaining the filaments with low humidity values (10-13 %) is a key factor to be taken into account at all times, to avoid problems before, during and after a 3D printing.

To have maximum reliability at the time of printing it is vital to have the maximum number of possible controlled variables, and humidity is one of them to ensure maximum robustness in the printing process.