Between 0 and 60 °C — and the zero is not a typo. PLA is the one mainstream filament that will stick to a clean textured PEI plate with no bed heat at all.
Most people run 55 to 60 °C because it makes the first layer more forgiving, not because the material requires it.
What a hot bed is actually doing
Two things. It keeps the first layer soft enough to bond as the nozzle presses it down, and it stops the base of a tall part cooling and pulling away. PLA barely contracts — 0.2 to 0.5% — so the second job hardly arises.
That leaves the first-layer effect, which matters most on a plate that is not perfectly clean, or a part with a small footprint, or a printer whose Z offset is not quite right. The bed heat is compensating for something else.
What too much heat does
Above roughly 60 °C you enter PLA's own softening range, and the consequences are visible:
- Elephant's foot — the first few millimetres of the part bulge outwards under the weight of what is above them
- Dimensional drift at the base — holes and slots near the plate come out undersized
- Parts that will not release — a very hot bed can weld PLA to a smooth plate hard enough to damage the surface on removal
If your prints show a flared base, the bed temperature is the first thing to lower, before touching the Z offset.
Different surfaces want different numbers
Textured PEI grips PLA mechanically and needs the least heat. Smooth PEI relies on adhesion and wants the higher end. Glass usually needs an adhesive layer regardless, and the heat is doing more work there.
Painted or coated build sheets vary enough that the manufacturer's figure beats any general answer.
The one case for going higher
Large flat parts on a machine in a cold room. Even PLA's small contraction can lift a 200 mm footprint if the ambient temperature drops overnight. That is a room problem being solved at the bed, and a draught excluder often works better than another five degrees.
PLA's stored temperature ranges sit on the PLA page; which plate surface wants which number is worked through in the bed adhesion guide.