Of course you can revolve two halves 180° but why don’t you revolve one half 360°?
Because a 360 degree rotation of 1/2 produces an Untrimmed surface, not a closed Brep
What is the expected benefit of having a closed brep versus an untrimmed surface when the object is converted to a mesh and exported as STL?
Because of the way Rhino works, any time you export anything other than closed Breps as an STL file there are likely to be mesh errors in the STL. I think the reason for this is that there are mis-matched vertices with any thing other than closed Breps. In most cases the problems with these can be resolved by running the resulting STL file through Netfabb, but for large STL files this does not always work. And it is annoyingly (for me anyway) time consuming.
I never convert my final geometry into a mesh before exporting as an STL. For reasons I don’t understand the STL files Rhino creates from it’s native internal formats are better than those it creates from meshes. “Better” means they print with smoother curves and surfaces.
Did you convert one teardrop surface / brep to a mesh and then create all the copies and export?
No. I combine (Brep Join) the teardrop with other Breps and then export that as an STL file. I don’t understand how meshes work and can never seem to get them to do what I want. Plus they react to changing variable inputs in ways that are surprising and unexpected (at least to me,)
How many of those teardrops?
It varies. For what I’m currently working on the number is basically determined by total print time. This one took a bit less than 15 1/2 hours:
But this one, which is maybe 30% larger, would take around 34 hours:
3D printing is a hobby for me, so I have never had any formal training, and never had to meet anyone else’s specifications for anything. I do know a fair amount about how software that creates 3D geometry works (I used to write it), so I try to use methods that produce good results as easily as possible.