When I exported the PCB design as a 3D file, the thickness of the PCB was incorrect.
I had to set the board thickness to 0.89mm so that the PCB thickness of the 3D model would be 0.8mm.
It seems that the solder mask, top and bottom copper layer thicknesses are not included.
It’s pretty difficult for anyone to answer you, things work differently on V5, V6, V7, V8, V9 let alone all the revisions in between. (and don’t forget the nightlies)
I had to set the board thickness to 0.89mm so that the PCB thickness of the 3D model would be 0.8mm. It seems that the solder mask, top and bottom copper layer thicknesses are not included.
This statement is correct for kicad v9. The bare pcb does not include the outer copper and not the silkscreen. Copper and silkscreen can be added as additional items on the pcb (depending on your step export settings).
As the previous poster mentioned this was changed between kicad v8–>v9 and this change tries to more precisely reflect the physical structure of the board.
Coincidence or not, just 3 days ago someone reported this changed behaviour on gitlab (PCB: File -> export -> step exports the wrong thickness (#20896) · Issues · KiCad / KiCad Source Code / kicad · GitLab), but as said in my view this is not a bug, but merely a more precise board representation.
