I created a new simulation project called 'Sandwich onderframe':
Berekening samenstelling onderbouw
More of my public projects can be found here.
@bartkeurhorst the free edges in your model seem to be the problem for the mesher. Could you try to delete all free edges in your CAD system, before exporting the STEP?
@dheiny what do you mean with free edges? i have saved my assembly als part. in this way it is a solid body in my CAD system.