Hi Pilou,

> I try to extract and offset the curvated curves but that is not always success!

For which step do you not have success? The copying, the flattening, the offsetting?

I just tried doing it on your model over here and did not see any problems...

If you have a problem with an offset for example, could you post a model file with the particular curve that you are trying to offset?

Also I would still recommend to delete everything instead of one surface and work from there, then extrude the final result to get the solid.

- Michael