AU

Tyr with `clean=False` in the last line: ```python part = part.faces('>Z').workplane().polarArray((stator.diameter/2- 2*stator.slot_diameter - stator.wall_distance), 0, 360, 16).circle(stator.slot_diameter/2).extrude(stator.port_thick, clean=False) ```

Yes.

@lorenzncode what do you think? Do you want to finish your PR first?

AFAICT the issue occurs only with intersecting circles. Do you confirm?

I don't think cadquery will help you with that, you'll need to make yourself familiar with the underlying cad kernel (OCCT). There are chances, that what you need is already...

@jniclas note that `each` requires callables with the following signature: ```python Callable[[Union[cadquery.occ_impl.geom.Vector, cadquery.occ_impl.geom.Location, cadquery.occ_impl.shapes.Shape, cadquery.sketch.Sketch]], cadquery.occ_impl.shapes.Shape] ``` Yours was returning a `Workplane` and not a `Shape`.

The point was that you need to return a `Shape` and not a `Workplane`. So if you insist on using `cq.Workplane`, it *could* be: ```python def perFace(face: cq.Face): return cq.Workplane(origin=face.Center()).box(1,1,1).val()...

With master I get the following (AFAICT correct) result. 

Confirmed. AFAICT this is not related to tagging (same results when directly exporting the resulting compound), but rather smth wrong with the orientation of faces.

Multiple objects can be exported in one STL, but AFAIK STL does not convey topology information. Maybe try 3MF? And what is your question actually?