Quick answer
A perfect first layer comes from two separate adjustments: leveling (making the whole bed evenly spaced from the nozzle) and the Z-offset (setting the exact nozzle-to-bed gap). Level the bed cold-then-warm using the paper method or your printer’s auto-leveling probe, then fine-tune the Z-offset live during a first-layer test until the extruded lines are lightly squished and fused together with no gaps.
Why leveling and Z-offset are two different things
Beginners often blur these together, but they solve different problems. Leveling (more accurately, tramming) makes the nozzle-to-bed distance the same at every point on the plate, so one corner is not high while another is dragging. The Z-offset then sets how close the nozzle sits to that leveled surface overall. You can have a perfectly leveled bed and still get a bad first layer if the Z-offset is wrong, and you can have a great Z-offset that only works in one corner because the bed is not trammed. Get both right and adhesion problems, elephant’s foot, and gaps in the first layer largely disappear.
1. Clean and heat the bed first
Wipe the plate with isopropyl alcohol to remove grease and dust, then heat the bed to your printing temperature (typically 60°C for PLA, 70-80°C for PETG). Metal expands slightly as it warms, so leveling on a cold bed and then printing hot throws your numbers off. Always level at the temperature you will print at.
2. Home the printer and disable the steppers
Run a home command (auto-home) so the printer knows where the nozzle sits. On manual-leveling machines, disable the stepper motors from the menu afterward so you can move the head freely by hand to each corner. Skipping this makes the head fight you as you position it.
3. Level the bed with the paper method (manual printers)
Slide a sheet of standard copy paper (about 0.1 mm thick) between the nozzle and the bed over the first adjustment knob. Turn the knob until you feel light, consistent friction on the paper as you slide it back and forth: it should drag slightly but not tear or lift. Clockwise lowers the bed, counterclockwise raises it. Move to each corner and repeat, then go around the bed two or three more times, because adjusting one corner shifts the others.
4. Or run auto bed leveling (probe-equipped printers)
If your printer has a BLTouch, CR-Touch, or similar probe, run the auto-leveling routine so it measures a grid of points and builds a mesh map of the surface. Make sure your slicer start G-code calls the mesh with G29 or M420 S1, otherwise the map is generated but never applied. The probe gets you within about 0.01 mm of the surface, but it still cannot set the final squish for you, which is the Z-offset’s job.
5. Level a Bambu Lab printer automatically
Bambu Lab machines (A1, P1, X1) handle leveling for you. Force sensors in the toolhead probe the plate, and the X1 series adds a micro-LiDAR scanner that can inspect the first-layer lines and compensate. You do not tram these beds by hand. Just start a print and let the automatic bed leveling run, then move on to fine-tuning the Z-offset if the first layer needs it.
6. Dial in the Z-offset with a first-layer test
Start a large single-layer test print (a big square or a dedicated first-layer patch). While it prints, open the Z-offset or “baby stepping” control in the Tune menu and nudge it in small steps, typically 0.01-0.02 mm at a time. Lowering the offset pushes the nozzle closer for more squish; raising it pulls back if the plastic is being smeared. On Bambu Lab printers use the Z-offset slider on the touchscreen or in Bambu Studio during the first layer.
7. Read the first layer to confirm it is right
A correct first layer has lines that are slightly flattened and merge into each other with no visible gaps, giving a smooth, consistent surface. Gaps or thin, round beads that do not touch mean the nozzle is too high (lower the Z-offset). A hazy, rough, translucent surface with ridges pushed up between the lines means the nozzle is too low (raise it). Change one variable at a time and re-run the patch until it looks even.
Frequently asked questions
Should I level the bed hot or cold?
Always level at printing temperature. Heat the bed (and ideally the nozzle) first, because the plate expands as it warms and cold measurements will not match how the printer behaves mid-print.
What is a normal Z-offset value?
There is no universal number. On a BLTouch or CR-Touch setup the offset often lands somewhere around -2.5 to -3.0 mm, but the correct value is whatever produces a properly squished first layer on your specific machine, so tune it visually rather than copying a figure.
Do I need to re-level before every print?
Not usually. Re-check leveling after swapping nozzles, removing a print that was stuck hard, moving the printer, or if you notice the first layer drifting. Manual beds can also loosen over time, so a periodic check helps. Probe-equipped and Bambu Lab machines re-measure automatically each print.
Why is my first layer good in the center but bad at the edges?
That is a leveling (tramming) problem, not a Z-offset problem. The Z-offset shifts the whole plate up or down evenly, so if only the edges are off you need to re-level the corners or re-run auto bed leveling to flatten the mesh.