45 °C for 4 to 6 hours. The ceiling here is low and it is not negotiable.
PLA's heat deflection band runs from 52 to 60 °C. A dryer set to 60 °C — a perfectly reasonable figure for most other filaments — is inside the range where PLA softens, and a softened coil under its own winding tension fuses to itself.
A spool that has welded together cannot be unwound. It is scrap, and it was destroyed by the process meant to save it.
PLA is the material that least needs this
The data layer marks drying as not required for PLA, and that is right. PLA tolerates humidity better than any other filament on this site, and a spool that has sat open for a few weeks will usually print fine.
What does happen, over months, is a gradual coarsening: a slightly rougher surface, occasional light popping, a little more stringing than the same spool gave when new. It is subtle enough that people often blame the printer.
When it is worth doing
- A spool that has been open for several months, particularly in a humid climate
- Any PLA that audibly crackles at the nozzle
- Filled and blended grades — wood-filled PLA is marked as needing drying, because the wood particles absorb water independently of the polymer
Plain PLA that has been in a sealed bag with desiccant since it arrived does not need drying, and running it through a dryer achieves nothing except risk.
Doing it without a dryer
An oven is the usual improvisation and the usual disaster. Domestic ovens cycle well above their set point, and the lowest setting on many is already past 52 °C. If you have no alternative, use an oven thermometer rather than the dial, and accept that you are gambling a spool.
A food dehydrator with an adjustable thermostat is the cheap tool that actually works, because its whole design brief is gentle heat and moving air.
Storage beats drying
A sealed box with fresh desiccant keeps a spool at its arrival condition indefinitely, costs nothing to run, and cannot weld anything. Drying is the repair; storage is the fix.
A six-hour cycle in a 50 W dryer costs about 5 cents, which you can confirm for your own unit in the print cost calculator. PLA's stored schedule and its softening band are on the PLA page; equipment and storage are the subject of the drying guide.