HOW TO DIAL IN YOUR Z-OFFSET

Z-offset is the absolute distance between the nozzle tip and the bed surface at Z0. Every other Z position in the print is relative to this baseline. If Z-offset is 0.05 mm too high, every line of the first layer is round and barely touches the bed - poor adhesion follows. If it's 0.05 mm too low, plastic has nowhere to go but sideways - elephant foot follows. Z-offset interacts with bed-levelling but isn't the same thing. Levelling makes the bed flat to the nozzle's travel plane. Z-offset sets the start height of that plane. You need both right.

Adjust when: first layer lines are gappy or smeared, after replacing the build plate, after swapping nozzles (different brands have slightly different lengths), after re-levelling, or first-layer adhesion has drifted. Don't bother when: first layer is laying down clean flattened tubes that fuse together with no gaps or smearing. If the first layer test passes, leave it alone.

1. Download a first-layer test square. Printables: search 'first layer test square' or 'first layer calibration'. Pick one that's a single layer covering a 100x100 mm area. 2. Heat the bed and nozzle to print temp for the filament you'll use most. 3. Start the print. Watch the first lines being deposited. 4. Open your printer's live Z adjustment: - Klipper: `Z_OFFSET_APPLY_PROBE` after using `SET_GCODE_OFFSET Z=<value>` while printing. Or use the LCD's baby-step menu. - Marlin: LCD baby-step menu (`Tune` - `Babystep Z`). - Bambu: during print, Settings - Z-offset or use the live Z adjust on the touchscreen. - Prusa MK4S / MK4: Live Adjust Z from the LCD. - OctoPrint: baby-step Z plugin. 5. Adjust in 0.02-0.05 mm increments while watching the lines: - Lines round, gaps between them visible: lower nozzle (negative offset / smaller Z value). Adjust -0.02 mm. - Lines smearing into a sheet, no line definition: raise nozzle (positive offset / larger Z value). Adjust +0.02 mm. - Sweet spot: flattened tubes that touch each other along their full length, with very faint individual line definition still visible. 6. Save when correct. - Klipper: `SAVE_CONFIG`. Add `Z_OFFSET_APPLY_PROBE` if using a probe. - Marlin: `M500`. - Bambu / Prusa: auto-saved by the LCD adjustment. 7. Re-test on the next print. Print another first-layer square. Should be perfect.

Adjusting before the bed has come to temperature. Cold bed = different thermal expansion = wrong reference. Adjusting in big jumps (0.1 mm or more). Z-offset is sensitive. 0.02-0.05 mm is the right step size. Forgetting to save. A live adjustment that you don't save is lost on reboot. Always save. Trying to fix bed levelling problems with Z-offset. Z-offset is one number for the whole bed. If only one corner is off, you have a levelling problem - re-level first. Squishing the first layer flat for adhesion. This causes elephant foot. Use a brim for adhesion if needed; never compensate for adhesion by over-squishing.

Z-offset and levelling go together - if Z-offset feels different in different parts of the bed, re-level first. For elephant foot caused by over-squishing, see the elephant-foot guide. For first-layer adhesion that Z-offset alone doesn't fix, see first-layer-not-sticking.