Filaments tend to absorb moisture from humid air, with moist filament as a result. The absorption of even small amounts of moisture by filaments during storage and 3D printing degrades final part quality and causes manufacturing problems.
Moist filament can be dried, however filament drying is a technical challenge due to the combination of plastic characteristics and conditions required for drying. The commonly available filament dryers make use of some form of "warm air drying". Although this approach somewhat reduces the moisture content, it does not eliminate it. Furthermore, the high temperatures required for hot air drying can damage filaments. By using vacuum filament drying this moisture is completely removed, reducing manufacturing issues, improving part quality and keeping filaments intact and undamaged.
This page provides insight into moisture related problems for 3D printing as well as technical background for filament drying.
Moist filament and 3D Printing
Processing problems: Oozing, jams, misplaced extrusions, strings, foaming, bubbles and warping.
Final part quality: Bad layer adhesion, surface quality issues and reduced mechanical properties.
Benefits of vacuum
Lower temperatures will result in only partial removal of the moisture. Traditional techniques are not suited for the drying of plastic based filaments. The vacuum works by reducing the pressure which in turn reduces the temperature required for water to boil and evaporate. This allows filament to be printed moisture and damage free!
Warm air drying
There are two main challenges when it comes to filament drying. Firstly, filaments can’t be heated to the required temperature without degradation; and secondly, it is hard to control atmospheric humidity. The “hot air method” results in partially dried filament due to lack of evaporation, lack of migration for dissolved water and the so called “bumping” effect. Bumping occurs when small cavities hold water, preventing it from evaporating.
Vacuum Drying in the Filament Vacuum Dryer
The pictures on the right show a close up of the two hollow cubes from the pictures above. The print produced using moist PLA is on the left and the vacuum dried PLA is on the right. Here we can clearly see the deleterious impact of moist filament and the improvements which can be achieved with Vacuum Filament Drying.
The pictures below show two PLA prints from the same spool. The left one is printed with moist filament and show the effects of moisture. The right one is printed after 3 hours of drying in the Vacuum Filament Dryer. (40°C and 30 mbar absolute) The prints are not post processed in any way and show how they came out of the printer.