Hi,
The upper and lower extremities were a bit more complicated to perform. As well as the junction of the interior void with the 4 spiral surfaces.

The principle of this ball hourglass is that the balls go down along the outside of the hourglass then go up by a screw at the top, then redo the path!

I mentioned difficulties encountered in correcting acute angle problems on spirals with the original Original_dwgTodxf_importToMoI3D.3dm file here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=10530.1

I do not know if the two subjects could be brought together?

Good, have a good Christmas holiday, see you later!

- Zooen