Linear advance

Updated 1 month ago ​by Tomáš Chvalina

Linear advance is a new 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. 

For users who do not want to play with all of the settings. Just flash the FW 3.1.0 into your printer and update the Drivers to 1.9.2! PrusaControl automatically downloads new settings and Linear Advance is enabled too.

To see the speed increase, you must test on larger models! Slic3r 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 advance users

If you are using different slicers (aside from Slic3r PE or PrusaControl), or you just want to tweak and play around with different values, you can manually change the settings in gcode script. 

However, if you do not understand the concept of gcodes yet, or never played with editing it, stop reading and leave it for later :)

The K values (the parameter affecting how much Linear Advance affects the print) we measured and tested are as follows: 

  1. PLA: M900 K30
  2. ABS: M900 K30
  3. PET: M900 K45
  4. Multi material printer: M900 K200 for all materials 

These values are preset in our Slic3r PE. The K value is set in custom gcode section in the Filament Settings tab, NOT under the printer specific custom gcode. PrusaControl uses the same K values but will not allow users to edit.

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 Slic3r PE 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.

Please note that different brands and colors of the same material may require a slightly different K value when printing at extreme speeds, however our presets should be fine with all of them. 

If you would need any help you can contact us at info@prusa3d.com. Yet with linear advance, the best procedure is just to test different K values on your own. However, we are still available and ready to help you at any time. :)


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