Drying filament properly

Damp filament is the single most misdiagnosed problem in 3D printing. People rebuild their whole profile over a week, when the actual fault is that the spool has been sat on a shelf since spring.

How to tell

• Popping, hissing or crackling at the nozzle as it prints
• A rough, slightly foamy surface where it should be smooth
• Stringing that appears out of nowhere on a profile that used to be fine
• Filament that snaps when you bend a short length by hand

Temperatures and times

• PLA and Silk PLA — 45 to 50°C for 6 hours
• PLA-CF — 55°C for 8 hours
• PETG — 65°C for 6 hours
• ABS and ASA — 65°C for 4 hours
• TPU — 50°C for 6 hours

Go hotter than this and you risk the spool softening and the filament fusing to itself, which turns a damp spool into a dead one.

What to dry it in

A purpose-made filament dryer is easiest and holds temperature properly. A food dehydrator works well. An oven can work on its very lowest setting with the door propped open, but domestic ovens overshoot badly and many will not go low enough to be safe for PLA.

Then keep it dry

Drying is undone in days if you put it straight back on the shelf. Seal it in a bag with fresh silica the moment the print finishes. PETG, nylon and TPU pick moisture up fastest; PLA is more forgiving but not immune.

How long have you got?

On an open shelf in a normal UK house, PETG is noticeably worse within a fortnight and PLA within a couple of months. In a garage or a workshop, halve both.