Bed Level Correction

Updated 1 month ago ​by Martin Lexa

Together with the Mesh Bed Leveling, the Bed Level Correction is one of many features designed to allow users to compensate for even the slightest imperfections in the first layer. It allows to virtually raise or lower the heatbed on the Left, Right, Front and Back sides, essentially enabling you to have a different Live-Z value on each of the four sides of the heatbed. This feature is most beneficial if you frequently need to use the entire area of the heatbed.

This calibration is not mandatory and is not done on the printers purchased as assembled.

How to use Bed Level Correction

Starting from firmware 3.5.2, the adjustment limit is +/- 100 microns (μm) instead of +/- 50 microns (μm) in the previous versions. Even 20 microns can make a huge difference, so when using this function, make small incremental changes. Just like in the Live-Z adjust, negative values lower the nozzle closer to the heatbed.

Before we begin, clean the entire surface of your heatbed with 90% (or more) isopropyl alcohol.
  1. Run a First layer calibration to get a good baseline calibration.
  2. Slice this STL model for your printer version using the Prusa Slicers default PLA settings, 20 mm layer height.
  3. Print the gcode prepared in the previous step with a PLA filament (ideally light and opaque color). The print is just one layer high and takes up most of the printable surface. You do not have to print the entire file, stop the print as soon as the differences in layer height across the plate are obvious.
  4. Evaluate where the layer is too squished and full of scars and where there are gaps in between the lines.
  5. Go to the LCD Menu -> Calibration -> Bed level correction. There, you can adjust Left/Right/Front/Rear values (understood from your point of view, as you are looking at the printers LCD).
  6. Edit the values, we suggest going in steps of +/- 10. These values will be added to the baseline Live Z value set in step 1. Remember, a negative value will decrease the distance between the nozzle making the layer more squished. A positive value will increase the nozzle-bed distance, curing the scars on your first layer.
  7. Repeat steps 3 to 6 until you are satisfied with the result.

For example, let's say your Live Z value is -1.000 and that the layer is too squished in the front and that you see gaps between the lines on the left side.

  • Front: you need to enter a positive value (at the end it will be 25 for example) to make the layer less squished
  • Left: you need to enter a negative value (at the end it will be -10 for example) to make the layer more squished
The Bed Level Correction values are reset to 0 every time you start the Calibration Wizard or the XYZ calibration. Once you find your ideal values, write them down as a backup.


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