If I create a simple planar object by drawing intersecting curves in a side view, and then use push/pull to give it thickness, you’d think you could just export that as an OBJ or STL and import to a slicer, to 3d Print it. However, this doesn’t work. The reason, is because the mesh uMake creates is not water-tight. Which is necessary for most 3d slicing software to slice the mesh.
The reason being: It’s creating 5 surfaces. Two are the “caps” which are planar trimmed surfaces. And the remaining 3 are 4 sided extrusions of the original curves.
These surfaces are in no way actually part of the same mesh. The vertices along common edges are not fused together. And further, the “cap” surfaces don’t even have co-incident vertices with the other three extrusions, because they’re a usually a rather low-res tesselation of a trimmed surface.
This is why I have been working so much in a 4 sided “patch” mentality in earlier threads. Because at least then, I can force resulting vertices to be co-incident, and I can fuse them (in external software).
Since u-make is absolutely NOT a solid modeler, it’s a NURBs patch modeler by process of elimination. Which is why I work that way. Which perhaps answers the OPs question about workflow for 3d printing. I have 3d printed models designed in uMake, but only by working in the way I describe.