FreeCAD

I'm using principles of 'close enough. I almost exclusively use the Part Design WB.

Technically I should probably model this in Blender. I know Blender has a way to wrap and unwrap like I hinted. This post was really a fishing attempt to see if anyone here knew of a way to do the same thing in freecad.

To model this, the first trick is to pick the best origin point. I'm using the screw pivots where the arms fold to hold my X-axis. The inside face of the lens is 146.6mm in diameter and is my primary reference surface for the lens. The shape of the lens is all done by creating sets of 2 sketches that are only used for references. These references are only used to attach a datum plane. The datum planes hold the sketches that pad and pocket the solid shape.

If I really wanted to make this better I could do so by making more complex sweeps while only building the part with reference to the outside face of the lens, because it is not a perfectly circular dimension. After the surface features are complete for this face, I could use the defeaturing add-on workbench to extract just the outside face from the PD body. With this face by itself, I could create a filled offset in the Part workbench. Then I would be able to cut the circular inside diameter from the X/Y axis to rebuild the 146.6 mm inner face.

In my experience that tree would have around a 50/50 chance of failing if I tried it. The task would cone down to how well the offset in the Part workbench is calculated. Even with this entire setup, I would not be able to control things like a varied edge finish on different parts of the lens so that I could model the mechanical properties better. I'm not super worried about the surface in freecad because I will need to sand and polish the print anyways.

Thanks though. Hopefully you can follow the explanation. When I started with freecad years ago, I might have tried something like the draft WB but almost everything belongs in a Part Design workflow. It is simply a matter of knowing how to pick good references, setting your origin well, avoiding referencing off of π as much as possible, and NEVER importing edges or points from 3d geometry.

Yeah, I just have to waste a day making a doughnut every time because the memorized workflow is not compatible with my use case. Blender is made for people that use it every day. I'll use it to fix a mesh once in awhile when that will save me substantial time, but that is about all I can do with it efficiently.