A correct average flow rate does not guarantee clean line starts and corners. Marlin explains that faster extrusion requires more filament compression before nozzle pressure becomes high enough to extrude. Pressure can therefore lag acceleration and remain high during deceleration.[1]
With an under-tuned K factor, the fast segment starts starved and the deceleration transition receives excess material. An excessive K factor reverses that pattern. Evaluate both transitions in a slow-fast-slow line instead of reacting to one corner.
Keep the variables separate: resolve basic extrusion faults, tune steady-state flow, calibrate one pressure-control system, and then recheck retraction. Marlin warns that slicer pressure advance, coast-at-end, and extra-restart features can interfere with LIN_ADVANCE.
Store K with filament, temperature, extruder configuration, nozzle size and geometry, acceleration, and test speeds. The documentation says to repeat calibration when those dependent parameters change. Firmware may also reduce print acceleration to respect extruder limits, so confirm the chosen value on the production geometry and target speed.
The staged diagnostic and record set are EyeContact's practical application of the documented mechanism; they are not a universal K value or a guarantee for other firmware.
Sources:
- https://marlinfw.org/docs/features/lin_advance.html
- https://help.prusa3d.com/article/extrusion-multiplier-calibration_2257
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