Hi Frederik,

> What is the easiest way to expand the selected yellow object equally in all directions,
> similar to the offset operation, but without creating a hollow shell?

The offset command is the way to do that, it does not create a hollow shell, that's the Shell command.

You may need to break an object up into surfaces and offset the individual surfaces - MOI is not very good at handling sharp corners where surfaces need to be extended so that they meet up.

But you can use offset on those 3 surfaces that are tangent, tangent surfaces will naturally touch each other without needing extensions.


> Is it possible to move the surfaces along their normals?

That's exactly what offset does.

It looks like you may be able to offset curves and then extrude them to make a new piece, it would help if you could post the .3dm model file.

- Michael