Pressure Advance / K-factor

Pressure Advance (Klipper) and Linear Advance (Marlin) compensate for pressure buildup in the hotend to produce sharper corners, cleaner line starts, and less blobbing at direction changes.

Firmware
Pressure Advance Tuning (Klipper)

The recommended method is to print the Klipper PA tower using the built-in TUNING_TOWER macro, then visually identify the layer with the cleanest corners and least blobbing.

Usually 0 — PA tower starts here
Default 0.005 for standard PA towers
Height of the cleanest-looking layer on your test print
Recommended PA Value
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Typical Value Ranges
Setup Typical PA / K Range Notes
Direct drive (Klipper) 0.02 – 0.08 Lower values typical for direct drive
Bowden (Klipper) 0.4 – 1.5 Much higher due to tube compliance
Direct drive (Marlin K) 0.05 – 0.2 Depends heavily on extruder and hotend
Bowden (Marlin K) 0.5 – 2.0 Enable LA in Marlin config first
PLA Lower end Less viscous at print temps
PETG / ABS / Nylon Higher end More pressure buildup at higher temps
Tips

Tune per filament, not per printer. Different materials have different viscosities — you'll likely need different values for PLA vs PETG vs Nylon even on the same machine.

Pressure Advance interacts with print speed. If you change your print speed significantly, re-tune PA. Higher speeds need higher values.

Set in your printer config / start G-code. For Klipper, set pressure_advance in printer.cfg. For Marlin, add M900 K[value] to your start G-code.