Filament Drying Guide: Temperatures, Times, and Why It Matters
Dry all engineering filaments before every print session — including freshly opened factory-sealed spools. PLA and PETG benefit from drying if stored open for more than a week. Use a dedicated filament dryer or food dehydrator.
Moisture is the most common cause of failed prints that get blamed on settings. Hygroscopic filaments — materials that absorb water from the air — print with stringing, surface bubbling, popping sounds from the nozzle, poor layer adhesion, and reduced mechanical properties. In most cases, drying the filament before printing completely resolves these issues.
Why Moisture Causes Problems
When a filament strand passes through a hot nozzle, any absorbed water instantly vaporises. This creates micro-bubbles in the melt, which appear as surface texture defects, cause stringing, weaken layer bonds, and in severe cases produce audible popping from the hotend. The effect is particularly severe with Nylon materials, which can absorb enough moisture in a few hours of open-air exposure to significantly affect print quality.
Drying Equipment
Dedicated filament dryers (PrintDry, eSun eBOX, Sunlu S2) are the most practical option. They maintain consistent temperature and allow printing directly from the dryer, keeping the filament dry throughout the job.
Food dehydrators work well and are inexpensive. Check that your model can maintain the required temperature accurately — some cheaper units run significantly hot or cold.
Conventional ovens work but require care. Most domestic ovens are not accurate below 70°C and may spike well above the set temperature. Use an oven thermometer to verify actual temperature before putting filament in. Never leave the oven unattended with PLA, which can soften and deform at temperatures your oven might spike to.
Never microwave filament spools. The spool itself may contain metal components, and uneven heating can damage the filament.
Drying Temperature and Time Reference
| Material | Temperature | Time | Notes |
|---|---|---|---|
| PLA | 50°C | 6 hours | Low priority if recently opened |
| PLA+ / PLA-CF | 55°C | 6 hours | Slightly higher than standard PLA |
| PETG | 65°C | 6 hours | Benefits noticeably from drying |
| ABS | 80°C | 6 hours | Important for large prints |
| ASA | 65°C | 6 hours | Moderate sensitivity |
| TPU | 65°C | 6 hours | Dry if stringing is excessive |
| PET-CF | 65°C | 6 hours | Less sensitive than Nylon-based CF |
| PA12 (Nylon 12) | 80°C | 8 hours | High priority — absorbs moisture fast |
| PC | 80°C | 8 hours | Very hygroscopic — dry every session. Paper spool users can go to 100°C |
| PA6 / PA6-CF | 80°C | 12 hours | Critical — even brief exposure degrades quality |
| PA12-CF | 80°C | 12 hours | Critical — dry before every session |
| PPA-CF | 100°C | 12 hours | Critical — paper spool required (plastic warps at this temp) |
What About Factory-Sealed Spools?
Dry them anyway. Vacuum sealing does not guarantee zero moisture content — the filament absorbs some moisture during the manufacturing and extrusion process itself, and sealing simply stops further absorption rather than removing what is already present. Storage conditions during shipping and warehousing vary. For standard materials a freshly opened spool is usually fine, but for engineering filaments — particularly Nylon, PC, and PPA-CF — treat every spool as requiring drying before first use.
Do Matte Filaments Need Extra Drying?
No. Matte filaments use silica or chalk additives to create the matte surface finish, but these additives do not meaningfully change moisture absorption. The base polymer determines drying requirements — matte PETG dries the same as standard PETG.
Signs Your Filament Needs Drying
- Popping or crackling sounds from the nozzle during printing
- Unusual stringing between features
- Rough, textured, or bubbled surface finish
- Weak layer adhesion or parts that delaminate easily
- Thin wisps of material at the start of extrusion
How Long Does Dried Filament Stay Dry?
This depends entirely on the material and humidity. In a typical Sydney workshop:
- PLA: stays usable for weeks on an open spool
- PETG: benefits from reseal after each session
- PA12/PA6: absorbs meaningful moisture within 2–4 hours of open-air exposure
- PC and PPA-CF: treat as dry for a single print session only
Best practice: dry engineering materials before every print session. Keep them on the dryer or in a sealed container with fresh desiccant between sessions.
Spool Compatibility at High Temperatures
Standard plastic spools (polypropylene or similar) are generally stable up to around 80°C. At higher drying temperatures — required for PPA-CF — plastic spools can soften and warp, jamming the filament. Use paper spools or transfer filament to a heat-safe cardboard spool before drying at 100°C+.
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