Pressure advance (also called Linear Advance on Marlin or Input Shaper compensation on some firmware) is a firmware feature that compensates for the delay between the extruder pushing filament and that pressure actually reaching the nozzle tip. It’s one of the reasons Bambu Lab printers print accurately at 500mm/s when older machines produce bulging corners and inconsistent lines at 150mm/s.
Why Pressure in the Hot End Is a Problem
When the extruder pushes filament, the plastic in the melt zone compresses slightly before pressure builds enough to flow out the nozzle. When the extruder stops, residual pressure continues pushing material out momentarily. At slow speeds, this barely matters. At high speeds, it creates bulging at corners (over-extrusion when the print head slows) and thin lines mid-segment (under-pressure during acceleration).
Pressure advance pre-compensates: it adds extra extruder pressure before a speed increase and reduces pressure before deceleration. The result is consistent line width regardless of print head speed variation.
How It Affects Your Printing
On Bambu Lab printers, pressure advance is configured automatically per filament profile and runs transparently. You don’t need to tune it manually unless you’re creating custom profiles for unusual materials. In Orca Slicer, the calibration tools include a pressure advance test that generates a visual pattern you use to find the right K value for your specific filament.
For most hobby printing on Bambu hardware with standard profiles, pressure advance is handled correctly out of the box. If you see corner bulging or inconsistent line widths on a custom profile, pressure advance calibration is the first thing to check.
Frequently Asked Questions: Pressure Advance
What does pressure advance do in 3D printing?
It compensates for the lag between extruder motor movement and filament flow at the nozzle tip. This prevents over-extrusion at corners, improves line width consistency at varying speeds, and is one of the key factors enabling high-quality printing at modern speeds.
Do I need to calibrate pressure advance?
On Bambu Lab printers with standard filament profiles, no. The profiles include calibrated pressure advance values. For custom filament profiles or third-party materials not in the preset list, using Orca Slicer’s pressure advance calibration test produces better results than the generic default.
Is pressure advance the same as Linear Advance?
They’re the same concept under different names. Linear Advance is the Marlin firmware term. Pressure Advance is the Klipper/Bambu firmware term. Both address the same pressure lag compensation problem with slightly different implementation approaches.
