The brush was created in the same manner.
Again I checked the render.
I then rotated the brush strictly by eye.
The next step was to make the meshes into reliefs as the router can’t deal with meshes. To do this I made a flat (zero height) relief.
I then selected this new flat relief and the meshes to light up the combine meshes button. Make sure you select the merge highest function. One click and it was done. In the render view the mech(red) and modified relief appear as mottled. The mesh (red in the render but green when selected without render) can now be eliminated.
The robot arm should also be merged (highest) with this new relief.