We often need to export 2D engineering type drawings, drawn in Rhino, to .dwg for sending to clients. There have been a number of bugs in Rhino 6, that I have been hoping will be sorted out in Rhino 7. I test them now in Rhino 7 WIP 7.0.20042.9575, 2020/02/11, and some have been fixed but there are now others. I will list these issues under seperate topics to keep responses clear.
We very often need to create a 2D drawing in model space, and not use layouts (or paper space as it is called in AutoCAD). So to create a detailed view, we make copy of the 2D curves (in model space), and scale those curves up by the factor of the detailed view we want to show. Then to dimension that detailed view, we set the length factor of that dimension style to 1 / the zoom factor of the detailed view.
When opening a 2D drawing exported from Rhino 6, or from Rhino 7 WIP, in a .dwg program like Draftsight, NanoCad, or AutoCAD, that Length factor of the dimension style is not exported to the .dwg file:
The result is the dimension are all incorrect in the exported .dwg file:
Exporting from Rhino 5, did not have this issue. The first time a part was fabricated off a drawing exported from Rhino 6, we had major problems to sort out. The only work around for us is to export drawings from Rhino 5! It would be great if this issue can be sorted out in both Rhino 6, and Rhino 7.
I know it is intended that 2D drawing detail views be done in Layouts in Rhino, and doing it that way, that Length factor export to .dwg is not an issue, but many of our clients, and our suppliers work with detailed views scaled up in model space, and we need to be able to sometimes stick to this format.