I included a Vector Display component in that GH definition that shows the direction of the face normals (or face plane Z-axes) and on the example I included they all seem to point outwards but if you plug your polyhedron into the Brep component at the start you might find that some of your face normals point inwards and some outwards. You are right to spot that this will need fixing somehow. If they all point the wrong way you can use a Flip component I believe - FlipPolysurface if you are working with a Brep and FlipMesh for a mesh!
If the normals are inconsistent you can use UnifyMeshNormals if you are working with a mesh but if you have a Brep with mixed up face normals I would try and fix that manually in Rhino first.
FaceNormals often refer to those of a mesh not a Brep and meshes are typically made up of faces with 3 or 4 edges although if you are working with meshes with faces that have more than 4 edges check out the NGon plugin.
There are excellent Mesh Topology components that give you the Face-Face, Face-Edge and Edge-Face topology of a mesh but I’m not sure if this exists for nGon meshes.
Top tip… if you right click your Brep component and select “Internalise Data” it includes the geometry in the GH definition so we can see what you are working with.
I can see you have converted your Brep to a mesh. Use the MeshEdges component to understand what that has done… it will have converted it to a mesh made up of faces with 3 edges and this is probably not helpful…
Red is a Brep, purple is a mesh. You can see that the polyhedrons faces in the purple mesh have been split into mesh faces that have 3 and 4 edges. I imagine, for fabrication, you will want to keep the faces of the polyhedron intact, not split into more faces?
