Pressure advance is a firmware-level correction that compensates for the delay between the extruder pushing filament and that filament actually appearing at the nozzle tip. At low speeds it’s irrelevant. At the speeds modern printers run, it’s the difference between sharp corners and rounded blobs, between clean wall starts and ooze artifacts. Bambu Lab calls this feature Pressure Advance. Klipper calls it Pressure Advance. PrusaSlicer calls it Linear Advance. Same concept, different names.
The Problem Pressure Advance Solves
Filament is a compressible column under the pressure of the extruder. When the extruder pushes faster, pressure builds in the melt zone before the increased flow rate actually exits the nozzle. This delay is small but measurable at high speeds.
The practical result: at the start of a printed line, the nozzle moves before full pressure builds, producing under-extrusion at line starts. At the end of a line, the extruder stops but residual pressure in the melt zone continues pushing filament out, producing over-extrusion, blobs, and ooze at corners and line ends.
Pressure advance (PA) pre-compensates for this by pushing extra filament just before a speed increase and retracting slightly just before a deceleration. The result is consistent extrusion through speed changes, producing sharper corners and cleaner wall starts.
Does Bambu Lab Handle This Automatically?
Yes, to a large degree. Bambu Lab printers run a pressure advance calibration as part of their full calibration sequence. The calibration prints a test pattern and uses the camera or sensor to measure the results, then stores a per-filament PA value that applies automatically during printing.
When Bambu’s automatic calibration is sufficient: For standard filaments (PLA, PETG, ABS) using Bambu Lab brand or major third-party brands with similar rheology, the automatic calibration produces good results. Most users running standard materials never need to touch PA manually.
When manual PA tuning is worth doing: Unusual filament types (very soft TPU, high-temperature engineering materials, specialty composites), third-party filaments that print very differently from standard formulations, or situations where corner artifacts persist after normal calibration. Also relevant for makers who print a specific filament in very high volume and want to squeeze out maximum quality.
How to Run Pressure Advance Calibration on Bambu Lab
Automatic (recommended):
- Load the filament you want to calibrate</r
- On the printer touchscreen: Calibration > Flow Dynamics Calibration (this is Bambu’s term for pressure advance calibration)
- Confirm the filament type and plate
- Run the calibration. It prints a test pattern and measures results automatically.
- The resulting PA value is saved and applied automatically when that filament profile is selected in future prints
Manual tuning via calibration test print:
If you want to manually verify or override the automatic value, print the Orca Slicer Pressure Advance calibration pattern (built into Orca Slicer’s calibration menu). The test prints a series of lines at different PA values. Examine the test pattern: find the PA value that produces the cleanest corner geometry with no blobs or gaps. Enter that value in your filament profile.
In Bambu Studio: PA value is stored per filament profile under Filament > Advanced > Pressure Advance. Access it by editing the filament settings for your specific material.
Signs Your Pressure Advance Needs Tuning
| What You See | Likely Cause | Direction to Adjust |
|---|---|---|
| Blobs or bulges at corners | PA too low. Residual pressure over-extrudes at corner deceleration. | Increase PA value |
| Gaps or under-extrusion at line starts | PA too high. Over-compensating by pulling too much back before line starts. | Decrease PA value |
| Rounded corners on outer walls | PA too low, printer not compensating enough for ooze at corners. | Increase PA value |
| No visible improvement after PA adjustment | The issue may not be PA-related. Check temperature, retraction, or partial clog. | Investigate other settings |
