Hi Steve,

> Some of the other things that start to happen, I might try
> to union 2 solids and , in stead of 1 single solid, it ends
> up removing 1 solid.

Just in general that kind of thing can happen if one of the objects is not actually a solid anymore and has ended up with an opening in it, or if the solid has become ill formed and does not have a uniform inside and outside region to it anymore - that can happen if pieces of your solid are made up of surfaces that intersect themselves, like they bunch up in some awkward way and push through some other portion of themselves. Or the equivalent thing can happen if the trimming boundary of a surface intersects itself, that kind of messed up trimming boundary will usually have some weird shaded display in that area as well.

So anyway I don't know if that helps but that's the type of stuff to look for when you run into that.

You can tell if your object has become an open surface by looking at the type indicator in the upper-right corner of the screen, if it says "Joined srf" or "surface" instead of solid then it means it has an opening in it somewhere.

- Michael