offset() within Locations context

[nanosonde]

Hi!
I am new to build123d and the CAD world.

I am currently trying to do the following:

with BuildPart() as mypart:
    Box(width, height, thickness)

    with Locations(mypart.faces().sort_by(Axis.Z).last):
        with Locations((0, 10, (depth/2))):
            Box(width, window_height+thickness, depth)
            offset(amount=-thickness, openings=mypart.faces().sort_by(Axis.Z)[-1])

The first box is supposed to be some base plate where I would like to place a shell on top.

When I try to compile this, I get the following error:

    offset(amount=-thickness, openings=mypart.faces().sort_by(Axis.Z)[-1])
  File "C:\Users\User\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.11_qbz5n2kfra8p0\LocalCache\local-packages\Python311\site-packages\build123d\operations_generic.py", line 633, in offset
    solid.offset_3d(openings_in_this_solid, amount, kind=kind).fix()
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\User\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.11_qbz5n2kfra8p0\LocalCache\local-packages\Python311\site-packages\build123d\topology.py", line 1284, in offset_3d   
    offset_occt_solid = offset_builder.Shape()
                       ^^^^^^^^^^^^^^^^^^^^^^
OCP.StdFail.StdFail_NotDone: BRep_API: command not done

When I removed the Locations context, I do not get an error. However, the position is of course not as intended.

So the questions is: is the offset()operation supported under a Locations context?

[gumyr]

offset is supported as used here. The problem here is likely that the offset can't be computed correctly given the geometry of your part. It would help if you provided values for: width, height, thickness, depth and window_height so I could replicate exactly what you're trying to create.

[nanosonde]

Ok, thanks for replying back.

height = 120.0
width = 135.0
depth= 40.0
thickness = 5.0
window_width=125
window_height=95

[gumyr]

Ok, now I can see the problem:

By specifying the offset amount as -thickness when the tab on the main box is thickness high the offset if impossible to create as the part's minimum dimension must be at least 2*thickness. If the offset amount is set to -1, it works as follows:

Notice how the offset is creating a hollow section in the small tab as well.

Good luck with your project.