Steel ball in sphere 3D print model

Use a steel (or glass or wooden) ball with 8 mm diameter and wait until half of the sphere is printed, then put the ball carefully in the half sphere (while the 3D printer is running). You can also put a ring. The sphere that you will obtain will have a support material inside. This has to be cleaned at the end (quite difficult) :-( The Sphere has 30 mm diameter, printed in a homemade printer in 1 hour with 1.75 mm Pla filament, 20% infill, 0.5 mm layer height, 30 mm/s speed.