Hi Frenchy, it looks like there are some problems with the surface of the interior wall - there are two spots where the surface forms some loops on itself. I've highlighted them here. The upper one is a pretty small loop.



These kinds of "inside-out" loops can cause problems, especially in things involving intersections such as the booleans.

It looks like that inner surface must have been the result of an offset of the outside surface - the offset needs to be cleaned up in this case before using it. Probably in this case you'd want to offset the outside edge curve instead of the surface - curve offsetting has more automatic cleaning up and trimming built into it than surface offsetting. Then revolve the offset curve to make the inner surface.


> Ps a volume in MoI (like exo.3dm) is a "surfacic" object or a "volumic" object?
> (surfacic against solid)

Well, it's kind of both. But in common CAD terms this would be a volume, "solid" object.

All objects are made out of surfaces. Surfaces can be joined to each other and share a common edge. If every edge of every surface is joined to another edge, then a complete connected skin is formed, which then can differentiate between the "inside" of the object and the "outside" of the object - this is a volume.

This is the usual method of defining a solid for CAD programs, it's called a "Boundary Representation", or "B-Rep".

Sometimes this is confusing to people since you can separate such an object and work on the individual surfaces of its skin and then join them together later. It is common for people to feel that being able to work on the surfaces means that an object isn't "really a solid". But this is not the case - if there is a way to determine the "inside" and "outside" of an object, then it functions as a volume.

- Michael