[FR] (feature summary) Smallest linear component of UBL mesh should generally be normal to the xy plane.

[apulver]

Is your feature request related to a problem? Please describe.

No response

Are you looking for hardware support?

No response

Describe the feature you want

Tramming will tend to make the physical bed align with the printer's xy plane. If I understand correctly, G29Jx computes and applies a rotation to the mesh so that its smallest linear component is normal to the bed. It approximates the bed by probing three or more points and using least squares.

My question is, would it be better if there were also the option to rotate the mesh so that its smallest linear component is normal to XY and save that transformed mesh? Then, optionally, the user could still perform a 3x3 or 4x4 G29Jx before a print to compensate for errors in tramming, but the saved mesh itself would not be overwritten.

The advantage here is that physically tramming the bed will tend to align it with the stored mesh, which seems relatively foolproof.

Additional context

No response

[apulver]

Also, I don't mind implementing the feature myself if there are no objections to merging it.

[apulver]

It would probably not be a bad idea to also have this as an option for bilinear leveling, if the code doesn't do this already (it doesn't seem to but I haven't looked that close). That is, an option to have "level bed" automatically remove the planar component of the set of probed points right after the bed is probed, so that the set of points is aligned with the xy axis. Any difference between the bed's planar component and the printer's XY axis can always be corrected by tramming. I think most people would understand roughly the distinction between tramming, i.e. physically aligning the bed's planar component with the xy axis and leveling, i.e. using software to correct for (non-planar) imperfections in the bed/print-surface. The documentation could use some work in this regard.

It would also be a good idea to follow up on bugs such as the one cited above, to make sure that the code for calculating and performing rotations, least squares, etc. is in good working order.