How to fix heat blobs on small details in Bambu Studio
Small features blob because each layer finishes before the one below it has cooled. In Bambu Studio, set the filament's minimum layer time to at least 8 seconds (Filament → Cooling) and slow small perimeters to 25 mm/s (Process → Speed). Big layers are unaffected; only the tiny, fast ones slow down.
Why it happens
A layer of a small detail, like an eye, a claw, a pin or the top of a letter, can print in a second or two. The nozzle comes straight back and lays hot plastic on plastic that is still soft, so the detail sags and rounds into a blob.
Tall, thin parts and the tips of models suffer most, because every layer near the top is small. It often shows up only on part of a model, which makes it look like a random defect.
The settings in Bambu Studio
- Slow printing down for better layer cooling → Layer time
slow_down_layer_timeFilament settings → Cooling8 s for PLA and PETG, 6 s for ABS/ASA (they need warmth to bond), 10 s on Quality when the fastest layer is under 3 s. - Small perimeters
small_perimeter_speedProcess → Speed25 mm/s for small loops (eyes, claws, joints, letter tops).
Names are from Bambu Studio 2.x. The settings search box finds either the name or the key.
Good to know
- Printing a second object on the same plate also helps: each layer then has more time to cool before the nozzle returns.
- TPU keeps its own slow profile; Plateright skips layer-time changes for it.
- The layer time is a filament setting, so it applies to the whole project, not one object.
What Plateright checks
The report measures how long the fastest layer on every plate takes and how many layers are tiny islands (under 12 mm²), then sets the layer time and small perimeter speed only when the project needs it.
Questions
Will a longer minimum layer time slow down the whole print?
No. Only layers that would finish faster than the minimum slow down. Normal-sized layers print at full speed, so the extra time is usually a few minutes on small parts.
Why do only the small parts of my model blob?
Because only they finish fast enough to stay hot. A large layer takes long enough that the plastic below has cooled by the time the nozzle returns.
Should I turn the part cooling fan up instead?
For PLA the fan is usually already at 100% on small layers. Time is what fixes it: the layer has to wait, and more air cannot replace that. For PETG, raising the fan past its profile limit hurts layer bonding.
Related fixes
Updated September 28, 2026.