Pressure Advance tuning

Pressure Advance (PA) is a Klipper feature that compensates for the pressure lag in the melt zone — the delay between when the motor commands more flow and when molten material actually reaches the nozzle. In FGF (pellet) printing, the melt volume is much larger than in filament printing, so PA behavior is different.

Default starting values (G1)

Nozzle size	pressure_advance	smooth_time
3 mm	0.3	0.5
5 mm	0.3–0.4	0.5
8 mm	0.2–0.3	0.5

When PA helps

Blobs or over-extrusion at corners and direction changes
Oozing during travel moves
Inconsistent line width at the start and end of each pass

When PA does NOT help (or causes problems)

Under-extrusion overall → adjust Rotation Volume first, not PA
Layer shifting → belt/mechanical issue, not PA
High PA values (> 0.75) can crash Klipper — the firmware cannot handle the acceleration compensation at high values combined with rapid speed transitions. Confirmed: PA 0.75 in vase mode with PETG CF causes an error immediately after the purge line. If this happens, lower PA to 0.4 or below.

Tuning procedure

Method 1 — Klipper PA calibration print

In the Mainsail Console, set a PA test value and print:

SET_PRESSURE_ADVANCE ADVANCE=0.3 SMOOTH_TIME=0.5

Print a calibration pattern (corner test or tower)
Examine corners: look for the value where corners are sharpest without under-extrusion
Adjust and repeat

Method 2 — Live adjustment from display

During a test print, adjust PA from the KlipperScreen display:

Navigate to the Pressure Advance setting in the tune menu
Increase in steps of 0.05 and observe corner quality

Saving the value

Once you find a good value, save it to printer.cfg:

[extruder]
pressure_advance: 0.3
pressure_advance_smooth_time: 0.5

Or use SAVE_CONFIG after setting via console.

Material-specific notes

Material	Typical PA range	Notes
PETG virgin	0.3–0.4	Standard starting point
PETG GF (glass fiber)	0.3–0.4	Lower end if speed errors occur
PETG CF (carbon fiber)	0.3–0.4	At 0.75 causes errors at purge
PLA	0.2–0.3	Less ooze than PETG
rPLA	0.2–0.3	Similar to PLA

Vase mode (spiralize)

Vase mode (spiralize outer contour): set Pressure Advance to 0 when using vase mode. Any PA value creates visible artifacts on the continuous spiral wall — the compensation pulses appear as a repeating texture on the outer surface. PA = 0 produces the smoothest result for vase mode prints.

Notes

PA tuning is nozzle-size dependent — retune when changing nozzle diameter
At very high MVS values (> 300 mm³/s), PA becomes less effective; prioritize Rotation Volume calibration first