With the upgrade from the Prusa Mk3 to the Mk3.5, bed leveling support in Octoprint is unfortunately no longer available.

Some people have problems with the new expansion joints on which the print bed is mounted. Therefore, the silicone or Nylock mod is still a good and important tool for generating a very level print bed.

Update:

There is now a newer and easier plugin-based version of this guide for OctoPrint users.

The manual MBL method in this article still works, but the new guide uses the Prusa Leveling Guide plugin to display the mesh result directly in OctoPrint. I recommend using the newer guide.

Read the newer guide here:
Prusa MK3.5 / MK3.5S Nylock or Silicone Mod Guide with OctoPrint

Here I’ll show you how to do it without the Octoprint plugins.

If you primarily use PLA, preheat the extruder and heatbed to 170°C/60°C. Wait 1–2 minutes to avoid temperature fluctuations. (This should be done after each adjustment to obtain accurate measurement results.)

Use Terminal of Octoprint or Pronterface:

Send “G28” (Homing)

Send “G29 P1” (Meshbed leveling 7×7)

Send “G29 T” (Get the meshbed results)

Now we have a list of data. Copy it into a text editor. It should look like this:

Now we take the 3×3 measurement points marked in red from the list. (See image)

Add the 9 values ​​to this list:

         0       1       2

2 | -0.045  -0.044  -0.028

  |

1 | -0.033  -0.048 -0.028

  |

0 | -0.033  -0.040  -0.048

        0       1       2

Now simply paste the short list onto this website: https://bbbenji.github.io/PMSBLM/

There you can see how to adjust the Nylock mod screws.

Repeat this process until you reach a maximum difference of approximately 0.035mm or better.

The first layer then needs to be recalibrated.

I recommend printing this for checking: https://www.printables.com/model/36706-bed-level-test

PS: If anyone can program MK3.5 support for the Prusa Leveling Guide https://github.com/scottrini/OctoPrint-PrusaLevelingGuide, that would be super great 😀

I have had this configuration running smoothly for over a year now without having to recalibrate.