First Calibration

4. First calibration

What this step does

Teaches NebulaOS where your bed is. Your old calibration does not carry over: even a printer that was calibrated under its previous firmware starts fresh. One guided run, Auto Calibration, gets most printers to a good first layer; the first print then fine-tunes it.

What you need

• An empty, clean bed - nothing on it, no tools.
• About 7 minutes.
• Nothing else: no paper, no tools, no computer.

The printer moves and heats by itself during this. Keep hands and tools clear once you tap Start.

Step by step

1. On the screen, tap Tune (the fourth tab), then Calibration.

   

   The Calibration menu.

2. Tap row 4 Auto Calibration. Under it the screen says "Load cell check, nozzle clean, Z offset, bed mesh - about 7 min, no tools needed".

3. Tap Start. The screen asks first:

   The printer will home, clean the nozzle, probe and mesh the bed, then restart Klipper.

   The bed must be empty.

   Tap Start again.

4. Watch the page. It shows every step with check marks, the current one in large type with its live detail:

   Step 7 of 10                  ✓ Load cell check
   Measuring the Z offset        ✓ Homing
   touch 2 of 3                  ...
                                 > Measuring the Z offset
                                   Bed mesh
                                   Saving (Klipper restarts)
                                   Verifying
   

   The ten steps are: Load cell check, Homing, Nozzle clean (the bed heats to 65 °C and the nozzle to 150 °C first, so this is the longest wait), Heating up (checks both temperatures), Settling, Load cell check (hot), Measuring the Z offset, Bed mesh, Saving (Klipper restarts), Verifying.

5. During Saving the screen says "Klipper restarts now to save the result. The screen reconnects by itself - do not switch the printer off." Wait for it.

What you should see

• Done with the date and the new values, for example Z offset 1.669 mm (was 1.795), Bed mesh 9x9, range 0.16 mm and Your Z adjustment was reset to 0.
• Back in the Calibration menu, row 4 has a green status line with the date and the result.

If it says Failed: , the page also says Why, What to do and Nothing was saved. Fix what it names and tap Start again.

What it does not do

Auto Calibration measures the Z offset and the bed mesh, and checks the load cell. These stay separate, each with its own row in the same menu, and most new printers do not need them on day one:

• Bed Tramming - if one corner of the bed is much higher or lower than the others
• Heaters (PID) - if a temperature swings around its target
• Axis Twist - if the first layer is squished on one side and lifting on the other
• Input Shaper, E-Steps, Skew Correction, TMC Autotune - print quality later on

Which one fixes what you see: Improve your prints.

Fine-tune on the first print

The last bit of the first layer is tuned by watching it, not by measuring. That is step 6, Your first print: while the first layer goes down, Tune → Z Offset nudges the nozzle height, and every nudge is saved for the next print.

From extras/nebulaos_calibration.py:97-119 and 1736-1843 at extensions f498796, and src/nebulaos_calibration_status.cpp:34-35, 194-215 and src/guided_calibration_panel.cpp:559-561 at screen fd47cb6.

Next step

5. Set up your slicer - two lines of start and end G-code, once, before you print anything.

Need help? Troubleshooting · How this works: Calibration explained