Removing absorbed moisture from hygroscopic filaments to prevent steam-induced defects such as popping, stringing, and poor surface quality during printing.
Many filaments are hygroscopic: they absorb moisture from the air. When wet filament is heated in the nozzle, absorbed water flashes to steam, creating micro-bubbles that pop open during extrusion. This causes audible crackling, surface pits, inconsistent extrusion, and significantly reduced mechanical properties. Nylon and TPU are most hygroscopic; PLA absorbs moisture slowly; PETG and ABS are moderate. Even slight moisture (0.02% by weight) causes visible print quality degradation.
Dry nylon at 70-80 C for 8-12 h; PETG at 65 C for 4-6 h; PLA at 45-50 C for 4-6 h; ABS at 65 C for 4-6 h. Use a food dehydrator, filament dryer, or oven with fan (not conventional oven: temperature too uneven). Store dried filament in sealed containers or vacuum bags with desiccant (silica gel). Print directly from the dryer with a dry-box system for hygroscopic filaments.
Drying PLA above 55 C causes heat deformation: the spool softens and strands fuse. Conventional ovens without forced air have hot spots that melt spools. Silica gel desiccant must be regenerated periodically (150 C for 2 h): saturated silica gel does not dry filament. Once dry, PETG and nylon re-absorb ambient moisture in 2-6 hours: print promptly or use a dry-box.
Related terms: Stringing, Retraction, Hotend
| Field | 3D printing |
|---|---|
| Also called | filament dehumidification, drying filament |
| Source | EDi Brain: tech/fdm |
Engineer, author of The Big Book of 3D Printing and additive manufacturing expert