Looks like the nozzle is too close (z-offset is wrong) or too much filament is extruded (flow rate is too high).
this post was submitted on 21 May 2026
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I would guess the z-offset should be fine because for any other filament it works correctly.
I will try to print a test for determining the flow rate for this specific filament after my print is done. I am using the default Bambu settings at the moment, and didn't have any issue on other filaments so far, but I guess it's worth checking out.
Then it might be flow or inconsistent extrusion. Try doing calibration available in Orca (probably same thing in Bambu slicer).
I've been out of using 3d printers for about 2 years due to building a house, so I've forgotten all the terminologies used. Anyways when I had this issue on my ender 3 it was because I was using too much filament and the edges of each line was merging in to the next then pushing upwards slightly.
I had to really tinker with my first layer. What I had to do was make the initial layer a bit taller but also use slightly less filament. Sorry I can't go more in-depth with the terminologies.
It worked though, I even got great first layers when using petg and wood based filament.
Any chance the filament is unevenly extruded from the manufacturer? Try measure the spool in few places with some calipers to verify that the filament thickness is exactly 1.75mm, and that it doesn't vary.
Also, might be worth it to check your flow rate/extrusion multiplier setting to ensure that the amount of plastic extruded matches what it is trying to do.
I have read that the Bambu filaments do not guarantee with same thickness very well compared to other manufacturers (0.03mm instead of 0.02mm tolerance) and this could play a factor with small nozzles. I had in mind to try other manufacturers, but they are not so easily available for similar price in my area, so I have postponed it until I finish my current project, but I am keeping it in mind.
I should probably buy some calipers and actually measure it.
It looks to me like the nozzle is too close to the bed. This seems to be a common issue with a couple of possible causes. Have you checked if the four screws that hold the hotend to the linear rail are screwed in correctly?