Linear advance is a technology which predicts the pressure build-up in the extruder when printing at higher speeds. The firmware of the printer uses that prediction to decrease the amount of filament extruded just before stopping and decelerating, which prevents blobs or artifacts at the sharp corners.
To see the speed increase, you must test on larger models! PrusaSlicer limits the minimum time per layer to 15 seconds and in case the limit is crossed, print speed is lowered. This prevents insufficient cooling and ugly prints. Printing one Marvin will not be any faster than before.
Linear Advance for advanced users
If you are using other slicer than out PrusaSlicer, or if you just want to tweak and play around with different values, you can manually change the settings in gcode script.
The K values (the parameter affecting how much Linear Advance affects the print) we measured and tested are as follows:
- PLA: M900 K30
- ABS: M900 K30
- PET: M900 K45
- For Multi-Material upgrade version 1 (NOT the latest one): M900 K200 for all materials
These values are preset in our PrusaSlicer. The K value is set in the custom gcode section in the Filament Settings tab, NOT under the printer specific custom gcode.
Simplify3D, Cura, ... users just need to add “M900 K??” into the starting gcode script. Keep in mind you need to manually change that for different filament materials. Only PrusaSlicer has custom gcode for each filament preset and therefore the K value is changed automatically. Set the desired speed and print something (large enough for speed to show up). If sharp corners have blobs, increase K value. If you see missing filament, decrease the K value.