Hi Len - the Join/Union won't work because those edges are 0.007 units apart from one another and Join will only glue edge together that are up to 0.005 units apart from one another.

The root cause of the gap is that Network uses a lesser tolerance than other things to try and reduce the density and complexity of the generated surface. But in this case that reduction of complexity caused just enough sagging away from the original curves to cause a join problem.

At the moment a workaround is to select those objects, and scale them down by 1/10 in size (run Transform/Scale, type 0 [enter] to pick the 0,0,0 origin point as the scale origin and type in 0.1 [enter] to specify a 1/10 scale factor) That also shrinks the gap between them so that Join will work on those objects, then scale up after they are joined.

I'll think about what to do to help fix this up, I could try to tighten the tolerance on the network, or maybe I should create the result of Network with the original input curves as the trim curve boundaries rather than using the natural surface boundaries of the generated surface like it does now.... I'm not quite sure yet.

- Michael