Thanks Michael
That is very easy after the explanation.
I had tried as I have wrote to use sweep than boolean diff.
I did not think of trim instead of boolean diff

Thank you very much for the help as always
Regards
Olga

Hi Olga - I see I didn't read your message carefully enough and that you did already try sweep and boolean, now that explains why that was all set up nicely to do the sweep! :)

The boolean operations tend to expect interactions more between solids and planar curves. This is because planar curves are more natural to define a volume, and the booleans are more generally focused on volume type operations.

In this case you have a non-solid surface and a non-planar curve, you'll need to use Edit/Trim in this case to cut the surface instead of using a boolean.

- Michael

Basically you can pretty much consider that the booleans are kind of a shortcut wrapper that combine Trimming, then automatic detection of which pieces to discard based on where the pieces are within different volumes, then combined by Joining together the resulting pieces.

When you're working with solids, this combination action of the booleans tends to be very convenient and saves several manual type editing type steps.

But if you are working with open surfaces instead of solids, it tends to be more likely that you will use the "low level" Trim and Join type tools instead.

You can actually use surfaces in booleans in different cases as well, but when there are no volumes involved the "automatic detection of which pieces to discard" part doesn't really apply. That's when Trim becomes better because you specify exactly which pieces you want to keep and discard in that case.

- Michael