Level bed test first layer

Check your first layer thickness over the entire bed and check your printing limits.

A parameterized and very simple bed level test print. A circle in the middle followed by square rounds to the very edge. From OpenSCAD, set values for very limits of your bed, make stl, slice in your fav. slicer and print.

For Cura, you'll have to likely enable the 'print thin walls' feature and check that to get all lines to print.

For my 235mm x 235mm bed, I'm managing to get 232 x 232 mm. Maybe I could eek out another mm or two, but that is good enough for me.