How to Calibrate Pressure (Linear) Advance with OrcaSlicer

In this tutorial, we are gonna learn about pressure advance and how to use it to increase quality and speed of our 3D prints.

During the operation of a 3D printer, plastic material is extruded while the toolhead moves along the X and Y axis to construct the desired object. While the linear movement of the toolhead is suitable for its kinematics, the extrusion of plastic from the hotend is not linear. Ideally, in an extrusion move, a consistent volume of filament should be deposited at each stage, with no further extrusion occurring after the move is complete. However, in the absence of pressure advance (PA), there is a tendency for excess filament to ooze out of the nozzle.

Representation of how the filament moves through the hotend without any pressure compensation [1].

The Pressure or Linear Advance algorithm addresses pressure variations by simulating the hotend and extruder as a spring, acknowledging that pressure increases when filament is pushed into the extruder. It also recognizes that the pressure needed to extrude corresponds to the flow rate through the nozzle orifice. As a result, the PA system causes extra filament to be pushed into the extruder during acceleration, and this extra filament is retracted during toolhead deceleration.

The algorithm is governed by a linear coefficient ranging from 0 to 2. This linear coefficient will be individual for your printer and the specific filament type that you’re using. You’ll need different values for different filaments. If you’re interested in learning more about how pressure advance works, check the Klipper and Marlin documentation about it.

So how can we use the power of pressure advance to have better and faster prints, and why should we spend the time to test your filaments for pressure/linear advance? Here are all the advantages of correctly calibrating PA:

  • Lower values of retraction are needed
  • Higher quality at faster speeds
  • Higher quality with higher layer heights
  • Higher quality with bigger nozzle sizes
  • Better seams
  • Sharper corners
  • Better looking top surfaces
  • Better dimensional accuracy

Steps

  • Download and open OrcaSlicer.
  • Click New Project in the main window.
  • Select the appropriate profiles for your printer and the filament you want to calibrate on the left-side panel.
  • Click the drop down Calibration menu (on the top bar, next to the undo and re-do buttons).
  • Select Pressure advance.
  • Depending on your printer’s extruder setup, choose DDE (Direct Drive Extruder) or Bowden. Bowden extruders will need a higher PA value as the filament path between the extruder and the hotend is longer, and creates more play as the filament feeds. You can always reprint the test using a closer range of values.
  • Once you press OK, the text “PA Test” will show on the build plate. Don’t worry, just press Slice plate on the top right corner. Once the test has been sliced, you can check the Preview (top left corner) and see the test pattern that has been generated.
  • On preview, on the right top corner, you can click on “Line Type” and change it to “Speed” to inspect and see how the test will be changing speeds along the perimeters so you can see how each value of PA smooths out the extrusion.
  • Now send it to your printer and have it printing.

Results

With the test printed, we have to inspect it around the sections where the speed changed and check for the most consistent line. In our case it was the line with the value 0.032. Under that we can see the line thining out on the acceleration (left), and bulging out in the deceleration (right). The opposite happens above that value. If in doubt about a specific value, reprint this test around the range where it looks best for you.

In the images below you can see the difference the PA calibration makes. On the left you can see a calibration cube without PA, on the right you can see the same model printed with PA activated, using the value we found on the test. We still have some more tuning to do, but you can see how much better the part looks just by being printed with PA.

Now armed with the knowledge and practical experience gained from this calibration process, you are better equipped to optimize your 3D printing workflow. The investment of time in testing your filaments for pressure advance not only refines the performance of your printer but also ensures that you can consistently achieve high-quality prints across various filament types. As you continue your 3D printing journey, the calibration of pressure advance stands as a valuable tool in your arsenal for elevating the precision and efficiency of your prints. Happy printing!

References

[1] Klipper documentation (Pressure Advance)

[2] Marlin documentation (Linear Advance)

2 thoughts on “How to Calibrate Pressure (Linear) Advance with OrcaSlicer

  1. PA in Klipper okay, works, But doesnt work in Marlin. If I check Preassure Advance window in Orca it does nothing. What to do?

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