HOW TO DRY 3D PRINTER FILAMENT

Most 3D printing filaments are hygroscopic - they absorb water from humid air into the plastic itself. When wet filament hits the nozzle, water flashes to steam and creates pressure spikes that produce popping sounds, blobs, stringing, and weak interlayer bonds. Drying drives the moisture back out by holding the filament above the boiling-out temperature for several hours. Different plastics need different temperatures because each plastic has a different glass-transition temperature - the temperature where it starts to soften. Dry too cold and moisture doesn't escape. Dry too hot and the spool warps or the filament fuses to itself. The right temperature is just below the softening point.

Dry when: you hear popping or crackling during printing, prints have rough or pitted surface texture, stringing won't respond to retraction tuning, layer adhesion is unexpectedly weak, or you've left a spool out of sealed storage for more than a few days (PETG, TPU, nylon especially). Don't dry when: the filament is fresh from a sealed bag with desiccant - it's already dry. Or PLA that's been in a normal room for a few weeks in a dry climate (under 30% RH) - PLA's slow absorption rate means it might not need it.

1. Choose your tool. - Dedicated filament dryer (Sunlu Filadryer S1/S2/S4, Bambu AMS dryer, PrintDry): purpose-built, accurate temperature, can print straight from the dryer. Best option. - Food dehydrator with adjustable temp (Cosori, Nesco): cheap, holds temp well. Great alternative. - Conventional oven: only as last resort - inconsistent temp, no airflow, easy to overshoot and ruin the spool. Avoid. 2. Set the temperature and time per filament: - PLA / PLA+: 45-50C / 4-6 hours - PETG: 55-65C / 4-6 hours - ABS / ASA: 60-80C / 4-6 hours - TPU: 50-60C / 4-8 hours - Nylon (PA): 70-80C / 8-12 hours - PC (Polycarbonate): 80-90C / 8-12 hours - PA-CF / PA-GF: 80C / 12 hours Critical: never exceed these temperatures. PLA above 55C melts the spool into a solid blob. 3. Load the spool. Make sure it's not pressed against the heating element. Dehydrators with mesh trays sometimes need the spool elevated. 4. Run the dry cycle. Check progress at 2 hours - many spools dry faster than the spec time if they weren't very wet. 5. Test extrusion. - Print a small test piece at normal settings. - Listen for popping. If silent, drying worked. - If popping continues, run another 2-4 hours. Some severely wet spools need 12+ hours. 6. Store dry going forward. A dried spool re-absorbs moisture in days if left in open air. Move to sealed storage immediately. See how-to-store-filament.

Drying PLA above 55C. Melts the spool. Cannot be undone. Using the conventional oven without a thermometer. Oven dials are inaccurate by 10-20C. If you must use an oven, verify with a separate oven thermometer. Drying for the spec time on a very wet spool. PETG that's been sitting out for months might need 8 hours instead of 4. Test after the spec time and extend if popping continues. Drying nylon at 60C. Too cold for nylon - moisture stays trapped. 70C minimum. Drying then storing in open air. A perfectly dried spool re-absorbs moisture overnight in humid climates. Store immediately in sealed conditions. Drying multiple spools stacked together. Reduces airflow; longer drying time, less effective. One spool at a time, or use a dryer designed for multi-spool drying.

After drying, store properly to prevent re-absorption - see how-to-store-filament. To verify a spool is wet before drying, see how-to-identify-wet-filament. For wet-filament symptoms in your prints, see fix-wet-filament.