Hi Ced, could you post a 3DM model file with the curves in it that you're doing Network with?

Join can glue 2 surfaces together into a new combined object, but the object is still composed of the original 2 surfaces whose edges now have information about both surfaces so they are clustered together. If you want a single larger surface for use with Flow, you would usually need to make the curve inputs into Flow to be made up of single curve segments, and form them out of a single Network command. Depending on what you have the Rebuild command can be useful for that: http://moi3d.com/3.0/docs/moi_command_reference10.htm#rebuild . It can be bad though to try and force a single Network to go through too many shape changes in one single go though, that tends to make things hard to control.

If you are trying to make a complex semi blobby shape all in one single go with Network, it could be possible that a polygon modeling program would be better suited for what you're doing rather than a structured CAD program like MoI. But I'd be able to give better advice if I could see the geometry looking at your 3DM file.

- Michael