Why do filaments absorb moisture?

Most printing materials are highly hygroscopic, which means that they easily absorb ambient moisture. Even tight factory packaged filament is not always suitable for use when removed out of the box. We should bear in mind that the purchase of the material itself is not the last step before printing.

For the 3D printing process to run properly, it is essential to prepare the filament properly. Heating the material at the appropriate temperature or using a specialised drying cabinet eliminates moisture that the filament could have absorbed.

Adverse effect of moisture on filaments

Hygroscopicity, or filament susceptibility to absorb moisture, is an undesirable phenomenon in this case, but it occurs very often, especially among engineering materials. How does it look in practice? Water settles on the outer material layers and penetrates inwards having a direct impact on the 3D printing process and models.

The hygroscopicity of filaments causes significant problems during the printing process itself, not always visible at first glance. Even a small amount of moisture in the material can have an adverse effect on:

 

1. mechanical parameters of the print– when printing with the use of engineering materials that have certain properties, we cannot afford to lose their mechanical parameters
2. model quality – air bubbles may appear on printout walls
3. layer lamination – capability of successive print layers to join
4. high porosity – the structure of material that has absorbed moisture after printing may be “foamed”. This manifests as a large number of pores that form when filament is extruded from the nozzle. Water molecules in contact with a hot nozzle evaporate forming bubbles. This translates directly into the density of the print structure (as evidenced by a lighter colour) and lower dimensional accuracy.

 

The key to obtaining the desired properties of a printed part is proper drying of the material before printing. What does this process consist of?

To remove excess moisture from material, it is necessary to place a filament spool in a suitable device to dry it. One method for drying is by heating.The time and temperature at which the heating operation should be carried out depends on the material used.

At what temperatures should materials be heated?

Most engineering materials should be heated before printing to get rid of the moisture absorbed by filament from the environment. In appropriate annealing conditions, we will observe the evaporation of moisture from material. Be careful if the temperature is too high. The filament can deform. It is recommended to follow manufacturer’s guidelines.

How do we know at what temperature to dry the material before using it?

Before implementing each new material, the 3DGence R&D team checks the conditions under which a given material performs best. Based on its own experience, the team develops recommendations that can be used by every user of 3DGence machines.

Check the recommendations for some engineering materials for heating them after removing them out of the box.

 

1. PA6 [3DGence]:

material that needs to be heated at 85°C for at least 24 hours.

2. Nylon 680 [Taulman3D]:

material that needs to be heated at 70 – 80°C for approx. 8 hours.

3. ULTEM AM9085F-1010 [Sabic]:

material that needs to be heated at 120°C for at least 24 hours

4. PolyMide CoPa [Polymaker]:

material that needs to be heated at 60 – 80°C for approx. 12 hours

5. PEKK-A [Kimya]:

material that needs to be heated at 60°C for at least 12 hours

6. PEEK [3DGence]:

material that needs to be heated at 75°C for at least 24 hours

 

Proper preparation of materials is necessary for the proper printing process. There are several ways to dry filaments.

Use a dedicated dryer

There are many devices on the market that are dedicated to drying materials.

At 3DGence, we use a professional Drying Oven SLW 53 laboratory dryer to heat materials before use.

Drying filaments in a cooking oven. Is it a good idea?

The filament drying operation, as an indispensable part of the industrial 3D printing process, should be carried out under fully controlled and predictable conditions. Drying filaments in a cooking oven does not allow full control and may even damage the material and disrupt the entire printing process.

Yes, even if we heat up the filament before printing, during the process itself, which often lasts long, the filament can absorb ambient moisture again, if it is not properly protected. That is why, to print from engineering materials with high hygroscopic properties, we should use industrial 3D printers equipped with a heated filament chamber. A heated filament chamber maintains a high temperature and restricts access of printer’s ambient air, thus preventing material from absorbing moisture again.

What effect moisture can have on the printout - example

According to the recommendations, ULTEM filament should be heated for 24 hours at the temperature of 120⁰C. For of this test we checked what happens to the print if we do not dry this material before the printing process. We placed unheated ULTEM in the heated filament chamber of the 3DGence INDUSTRY F420 printer and started printing.

We can see that over time, the heated chamber in the 3DGence INDUSTRY F420 printer helped to evaporate moisture from the outer coils of the material. This had a significant impact on the quality of the model, which improved with the gradual removal of water from the filament. The porosity of the printed sample also decreased over time.

Tight factory packaging does not guarantee that our material has not absorbed moisture and that it will be suitable for printing without prior preparation. Although there are no visible visual differences, only the weight measurement and the appearance of the print itself can indicate that the material has absorbed some water.

1. 3D printing

If our filament is not prepared well, during extrusion from the nozzle, we can:

1. observe the formation of bubbles on the printout,
2. observe visible evaporation of moisture,
3. hear a hissing or cracking noise when printing.

The consequence is a loss of extruded material used to make the layer and pores embedded in the printout structure, which weakens the printed item.

2. Material weight measurement

The filament weight in the package may be close to the weight of the material left in a humid environment, indicating that the filament manufacturer does not always provide appropriate conditions during packaging.

Let's see the example

After unpacking, the weight of the Nylon 680 [Taulman] filament was 466.5 g (after subtracting the weight of the spool). The material was left for 24 hours under average temperature conditions of 23°C and air humidity of 48%. Has the material absorbed ambient moisture? Yes, after weighing the material, it turned out that its weight increased by 0.6 g to 467.1 g. Preprocessing before printing proved necessary. The material was heated in accordance with the recommendations and placed for 8 hours in a heated printing chamber at a temperature of 70°C in the 3DGence INDUSTRY F340 machine. Heating the material reduced its mass to 464.2 g. This means that the heating process removed moisture from the filament weighing 2.9 g, which is 0.62% of the filament, as before heating.

1. It is important that we are aware how to use 3D printing materials.
2. Preprocessing is crucial and proper material preparation for printing will have a significant impact on our final print.
3. It is worth using the recommendations of material manufacturers or knowledge bases
4. Remember that despite the lack of visible differences after unpacking the material, it does not mean that the filament has not absorbed moisture. We can check it only by measuring the filament and the weight and assessing the appearance of the print. For the safety of the process and printing, we always assume that new material, even tightly packaged, requires drying in accordance with the manufacturer’s recommendations.
5. We should also pay attention to the proper protection of filament against moisture during the printing process. Heated chambers in industrial 3D printers guarantee that the right temperature is maintained for our material.
6. It is also important to safely store filament after printing (closed tight with desiccant in a shaded place).