PrintDry Filament Dryer

Every user of a 3D printer knows the importance of keeping the filament free of moisture, as it is a source of common problems. Detecting the problem of humidity is simple, since the finish of tbuilthe piece that is printed is soft and with many pores, in addition, during the printing you can hear mini explosions, produced by the sudden evaporation of the water inside the filament at the exit of the extruder. This water can oxidize certain elements of the extruder, such as hardened steel nozzles.

Image 1: Problems of nylons with moisture

Many users try to dry the filaments in a homemade oven, with the dangers that this entails, in addition, with the little uniformity of process because these ovens are not usually able to keep the temperature stable at such low values (35 - 85 ºC) , instability that in some cases can cause a problem more than a solution. For this reason PrintDry Pro comes to solve a problem in 3D printing, especially to users who use technical filaments, where every little detail counts in the final quality of the pieces.

Image 2: PrintDry Pro filament dryer with extra tray. Source: PrintDry

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. Certain materials, such as the Nylons, tend to gain a lot of moisture in a short time and need to be dried by applying heat on them, due to the difficulty of breaking the intermolecular bonds so strong that they form them. In this case, the use of desiccants is not sufficiently effective, since they saturate before getting enough to reduce the moisture values of the filament (less than 20%).

To solve the problem of humidity, it is recommended to use the PrintDry filament dryer, a device capable of breaking the intermolecular bonds between water and polymer thanks to the following drying parameters.

Image 3: PrintDry Pro3 features. Source: PrintDry.

Thanks to their design, the filament coils are placed in parallel in two drying chambers; allowing to dry two coils up to 200 mm in diameter.

In addition, it allows other options, which are implemented through two Kits:

• Extra tray (smaill coils): With the extra tray kit, a tray is placed on the initial drying axis, creating a new drying chamber for one spool of 1 kg (max. Ø200 mm). In this way, three small size filaments in total can be dried at the same time.
• Extra kit (large coils): By using the large coil kit, you can dry one additiona big spool between 2 and 5 Kg, with an outer diameter of up to 300 mm.

The PrintDry Pro features a digital display with 6 preset options (35 ºC, 45 ºC, 55 ºC, 65 ºC, 75 ºC, and 85 ºC) where the temperature can be easily adjusted. In addition, it has an integrated timer, so you can configure the necessary drying time for each material.

Image 4: Display PrintDry Pro. Source: PrintDry.

To understand how the PrintDry Pro works, we must talk about the following parameters:

Drying temperature

The molecules that form the filament are agitated as a function of the temperature increase to the point that the union of the intermolecular bonds between water and polymer weakens. Once the break is produced, the water molecules are released to the outside of the filament and from there to the air that is in contact with it. This air is at an elevated temperature (up to 85 °C) and with a low moisture content, thanks to the PrintDry filament dryer itself, improving and speeding up the drying process. In view of this, one should not be tempted to use the maximum temperature of the PrintDry filament dryer to dry all the filaments, since thermal degradation and / or oxidation of the filament may occur. Below is a table with the recommended temperatures and times for each material:

Table 1: Drying time and temperature according to the material

The actual temperature inside the PrintDry Pro may vary due to the ambient temperature, the location of the machine and the amount of filament or desiccant bags that are introduced inside. If the ambient temperature is high, this will affect a higher temperature inside the PrintDry Pro. In relation to the PrintDry Pro chambers, when the extra tray is used (creating an additional drying chamber) the lower chamber can have a temperature up to 8º C higher than the upper drying chamber. Also, the more material inside the PrintDry Pro, the higher the temperature.

Drying times

As it is clearly seen in the previous table, the filaments do not dry instantly. The first step is for the heat to penetrate the entire filament including the one inside the reel. Once all the material is at the optimum temperature, you should wait for some time so that the water concentrated inside the filament is positioned on the walls and then evaporated into the air. Wait for the time recommended in the table above is key to always obtain the maximum properties of the materials. In addition, to ensure that the moisture of the filament is the right one, a digital humidity meter can be used, introducing it inside the filament dryer, right next to the material that is drying. Continuing with the drying times, the use of the PrintDry filament dryer is not recommended for more than 48 consecutive hours, being necessary to disconnect until it cools. The PrintDry Pro filament dryer has an built-in timer that automatically switches off the dryer after 48 hours.

Difference in humidity concentration

This term is the concentration of moisture in the filament compared to that of the air that surrounds it. The contact of the filament with dry air (low dew point) facilitates the transfer of water to the air quickly and effectively.

Air flow 

The PrintDry Pro filament dryer obtains a natural air current by the simple effect of heating the air, it weighs less, rises, absorbs moisture, cools and descends. This process is repeated cyclically, generating a current of air that increases the drying power of the filament.

At a molecular level what happens since a filament is with a high percentage of moisture until the time after drying is summarized in four stages:

Image 5: Humidity test. Source: PrintDry

Once the percentage of humidity has been reduced to a minimum, it is advisable to store the filament in a storage box (PolyBox) or to store the material in an airtight manner. For this PrintDry Pro has a being of 5 containers of hermetic and vacuum sealing, ensuring long storage intervals without disturbing the low percentage of humidity.