Hi sven, even though it's hard to see it unless you zoom in closely, there is just barely enough of a gap between those pieces so that it won't join.

Did you build those piece with the Network command?

There is currently a problem that you can run into with Network - it fits the network surface to a looser tolerance to avoid generating excessively heavy surfaces when making a network through a lot of curves at once.

But sometimes that looser tolerance can result in the shapes being just barely away from the joining tolerance (which is 0.005 units) as well, that seems to be what you have run into here.

That is something that needs to be fixed up in Network, so that the curves on the outermost boundary of the network will get fit to the regular tight tolerance so that they will join more reliably.

Right now one way you can work around that problem is to scale the objects down by 1/10 in size, then do the join, then scale back up again - that's how I made the attached version which has that part joined now. That works because scaling down also scales down the size of the gaps and puts it within the 0.005 unit join tolerance.

Right now the idea with Network is more for building a larger sculptured surface and not so much for making smaller patches like you are doing here.

- Michael