Hi Paolo,

>>I used the same curves in rhino40 with networksurf with a better result(third picture)

Hmmm.. but what was the tolerance settings? When you set the tolerance for Rhino's NetworkSrf command to:

edge curves: 0.001
interior curves: 0.1

you get the same 'bad' result for your input curves.

The structure of those curves is somewhat inappropriate for the network command...

I think when you changed a units and allow object to re-scale on unit system change in MoI, then you were actually creating a geometry using tolerance 1mm (1 meter multiplied by 0.001).

Petr