Bed leveling and Z-offset

These are the two calibrations that have the biggest impact on print quality. Both control the relationship between the nozzle and the build plate.

The difference

• Bed leveling (also called "mesh leveling" or "auto-bed-leveling/ABL"): makes the nozzle stay the same distance from the bed across all X-Y positions, even if the bed itself isn't perfectly flat. Done with a probe (Bambu, Prusa, Klipper) or by manually paper-dragging at corners (older Ender, Mini+).
• Z-offset (also called "live Z" or "first layer height"): sets that distance. After leveling, the nozzle is parallel to the bed; Z-offset is how high above the bed it sits.

You need BOTH. Levelling without setting Z-offset will give you a uniformly bad first layer. Setting Z-offset without levelling will give you a print that's perfect in the middle and terrible at the edges.

When to re-level

• After any nozzle change
• After any belt or pulley adjustment
• After moving the printer
• After ~50 hours of printing
• If you swapped in a different build plate
• If first layer suddenly looks bad in just one corner

Auto-leveling workflow (Bambu / Prusa / Klipper / most modern)

1. Heat the bed to its print temperature for your material (PLA prints level differently than PETG-temp bed)
2. Heat the nozzle to ~150 C (hot enough to soften any residue, cool enough not to flow filament)
3. Wipe the nozzle tip with a brass brush or pinched-off bit of cardboard
4. Run the auto-level routine
5. After, the printer stores a mesh in memory

Some printers (Bambu, K1) re-level at the start of every print. Others (Prusa MK4) only when you tell them to. Check your printer's behavior.

Manual leveling workflow (older Ender, Mini+, etc.)

1. Heat bed + nozzle to print temps
2. Wipe nozzle as above
3. With the printer at home (Z=0), slide a sheet of standard 80gsm paper between the nozzle and bed
4. At each corner: turn the bed-screw until you feel slight drag on the paper. Not stuck -- slight drag.
5. Re-check all four corners twice. Adjusting one moves the others slightly.

Setting Z-offset

After leveling, start a real print (or the slicer's Z-offset calibration). Watch the first layer being laid down.

Look for:

• Too high: lines are round/ridged and don't merge into each other. Gaps between lines. Lower Z-offset by 0.05mm.
• Too low: lines look stretched/translucent or you can see the nozzle dragging into the previous line. Raise Z-offset by 0.05mm.
• Just right: lines are slightly squished, sitting flat against each other with no gaps. No drag marks. This is what you want.

Most slicers (Bambu Studio, OrcaSlicer, PrusaSlicer) let you adjust Z-offset live during the first layer.

How much does a small Z-offset error matter?

A lot. 0.05mm is a big change. 0.1mm is the difference between a stuck print and a falling-off one. Use the in-slicer live adjustment until you see good extrusion, then save the value.

Per-material Z-offset

PETG benefits from being printed slightly higher than PLA (less squish). TPU needs to be even higher (it's flexible and can snag). Many printers let you store a separate Z-offset per material profile -- use that.

Symptoms that look like Z-offset but aren't

• Elephant foot (bulging first 3-4 layers): usually bed temp too high, not Z-offset
• Corner lifting (warp): bed not hot enough, not Z-offset
• Uniform "bumpy" first layer everywhere: cleanliness, not Z-offset
• One corner sticks, opposite doesn't: leveling, not Z-offset