Surface Modeling Basics and Troubleshooting

 From:  SteveMacc (STEVEH)
4751.9 
Jops,

MoI can handle very complex models. It depends on your hardware.

The example you posted had many open edges, so it would not convert to a solid. If you seperate all the surfaces, then scale the whole lot down by a factor of 10, they will join to a solid. Then scale it back up again.

However, creating the model in the way you have, surface by surface is not the best way to approach Nurbs modelling. You should try to maintain solids as much as you can. In this case, you could create the outline in top view, extrude it , then create curves in the side view to slice off the top and bottom.

Once you have a solid model, you can refine it with booleans. You can also delete surfaces and remodel them if you need to, using blends, etc, always coming back to a solid.

It is very rare in my experience to ever have a model that is just surfaces. In the CAD world, the resulting model should always be a solid, usually by shelling if you have built from surfaces. It is impossible in the real world to have something with zero thickness.