Uneven First Layer on Prusa i3 MK3S+ After Z-Axis Calibration – Is This Normal?  

Uneven First Layer on Prusa i3 MK3S+ After Z-Axis Calibration – Is This Normal?

Hi everyone,

I’ve been using my Prusa i3 MK3S+ (kit version) since 2021, and it has been running smoothly without any major issues. However, I barely used it in 2025. Recently, I decided to bring it back into service and performed the regular maintenance as described in Prusa’s official guide.

Since I also moved the printer before restarting it, I followed the "3D Printing Handbook" recommendation and performed a Z-axis calibration. After that, I recalibrated the first layer height and printed the Prusa logo, stopping after the first layer to check the results. To my surprise, the first layer is perfect on the right side but too high on the left side (see attached photo). I tried lowering the first layer height, but the issue persists—lowering it further would risk over-compressing the right side.

What puzzles me is the significant difference over such a short distance (the logo is only ~8 cm wide). Unfortunately, I didn’t pay attention to this detail before the maintenance, so I don’t know if it was already present.

My questions:

1/ Is it “normal” to have such a difference over this distance? Before using the Bed Level Correction feature, I’d like to know if this is something expected or if it could indicate an underlying issue.

2/ I’m also a bit confused about the difference between Z-axis calibration and Mesh Bed Leveling. The documentation isn’t entirely clear to me—could someone explain the distinction ?

Any insights or advice would be greatly appreciated!

Thanks in advance for your help!

Math