A1 and A1 mini: first layer too low, wavy or scraping the plate (hotend shifting)
Guide based on the manufacturer's official documentation; usi3d has not yet verified it on a machine.
Technology: FDM · Brand: Bambu Lab · Symptoms: Uneven first layer (thin and thick areas), Does not stick to the bed · Updated on 9 October 2026
Symptom
On the A1 or A1 mini the first layer comes out too squashed, wavy, with raised edges or peeling off, or the nozzle almost rubs the plate and hardly any plastic comes out.
Likely causes, from most to least likely
- Bed levelling has not been run, especially after changing or replacing the plate.
- The hotend shifts downwards under extrusion pressure: loose heater assembly screws or a buckle that is not latched or is damaged.
- The lower part of the hotend has play.
Checks to tell which one it is
- With the nozzle below 50 °C, try to move the hotend by hand: it should have no play.
- Check that the heater assembly buckle is properly latched.
- Check whether bed levelling was enabled when you sent the print.
Before you start
Before taking anything apart, cleaning or adjusting it, switch the printer off and unplug it, unless a step says otherwise, and do not touch the nozzle, the heater block or the bed until they have cooled down. If in any doubt about electricity, heat or moving parts, stop and ask a professional.
Step-by-step fix
Level before printing
Enable bed levelling in the slicer before sending the print, especially if you have just changed the PEI plate.
Check: The first layer comes out even.
If that does not fix it: Check the hotend (next step).
Retighten the heater assembly
Wait until the hotend is below 50 °C and switch the printer off. Remove the front cover and take the hotend out as shown on its sticker. Remove the three M3×10 heater assembly screws with the H2.0 key, turn it over and retighten the four small M2×6 screws with the H1.5 key, taking care not to strip them.
Check: The heater assembly is firm.
If that does not fix it: Check the buckle (next step).
Latch the buckle and recalibrate
Refit the hotend making sure the heater assembly buckle is fully closed: if it is not, or it is damaged, the hotend can drop while printing. Refit the cover, power on and run auto bed levelling from the Calibration menu.
Check: The hotend does not move when pushed and the first layer prints well.
If that does not fix it: If the buckle is broken, replace the heater assembly or contact Bambu Lab support.
Temporary tweak in the start G-code
Only as a stopgap while you fix the cause: in the printer start G-code in the slicer, the line G29.1 Z{-0.02} sets the offset for the textured plate. If the layer is too low, raise it slightly (for example to -0.01 or 0); if it is too high, lower it. Rough range: -0.02 to 0 mm on the textured plate and -0.01 to 0.01 mm on smooth plates, which need their own line as described in the Bambu Lab guide.
Check: The first layer comes out right.
If that does not fix it: Go back to the default value and focus on levelling and hotend retention: the tweak can create defects elsewhere.
Prevention
- Always level after changing or replacing the plate.
- When fitting the hotend, check that the buckle is latched and there is no play.
Still not fixed?
Tell usi3d's AI about your case: choose your printer, describe what you see and add photos if you like. It proposes checks step by step, with their sources.
Printers it applies to
The Bambu Lab A1 family: A1 and A1 mini.
Official sources
This guide summarises the official documentation linked here:
This guide is general information: usi3d has summarised it from the official documentation linked here, and it may not match your model, its version or its firmware. If in doubt, follow the manual and the support of your printer's manufacturer. You decide what you do with your machine, and working on it may affect its warranty.