Hi @StevenVickers Thanks for your solution!
Sorry for two trivial questions on your practice:
1. Why do you prefer Studio Surface where people generally use Thru Curve Mesh?
2. Why do you bother to extract 4 short curves simply to get G0 continuity?
In example 1, you're trying to assign curvature to surfaces that are pretty much circles. You can assign curvature from side to side because your Bridge Curves are G2, however top to bottom you're using arcs to define that direction and expecting arcs to be curvature continuous to the planes which sit on the top and bottom tangencies to the tubes.
If you look at Steve's example (which I have not), I will bet the upper and lower surfaces between the rings have non-planar surfaces, which there isn't anything WRONG with that, but the result and which method you use is going to depend upon the requirements you have to meet.
The other option might be to change the cross sections of the tubes such that they're more appropriate for G2 and all at the same height from top to bottom.
See my attached NX11 file and note the 2 red splines - I'm hoping those are the cross sections needed on the tubes for a common top to bottom height, or close to it, with G2 in the top to bottom direction.
NX 184.108.40.206 MP11 Rev. A
GM TcE v220.127.116.11
GM GPDL v11-A.3.7
Just use Studio Surface as it is easy to switch from Through Curve to Through Curve Mesh construction and I quick way to show the main point of not going to a sharp corner.
The continuity of the Fill was just an oversights on my part. Need to edit the feature.
If I really wanted high quality surfaces I would however use a different method to using Fill. If I find time I will create another version.
I thought Fill Surface was designed as a simple patching tool.
Before Fill Surface, N-sided or Through mesh curves were my main tool for that. I'm not sure when Patch Openings came about but by the time I noticed it Fill surface was introduced.
For the work I do, mainly soft tooling and fixtures for sheet metal stampings. Fill Surface is my go-to command for patching holes from bad offsets or poor quality imported geometry. For almost 20 years I've only had an Advanced Designer license, Now I have an automotive Supplier engineering license. I'm still discovering "new to me" tools.
Elmhirst Industries, Specializing in Prototype sheet metal stampings and assemblies
Production: NX 12.0.2 / Autoform r8 /WorkNC 2020.0
PC: Rave Cadbeast: Intel(R) i7-4790K CPU @ 4.GHz /32gb ram /NVIDIA Quadro P2000 on Win10 Pro