System information

dcc80de on Arch Linux

Expected behavior

A manifold mesh representing the helical extrusion, for example

Actual behavior

If I increase the angle just a bit I get a self-intersecting mesh:

and increasing the angle just slightly more gives naked edges instead:

Additional information

Note that the issues are present even with "force NURBS surfaces to triangle mesh".

This example (unit square at unit distance from axis): helix.zip
Non-trivial example (8x rotated 2 beziers approximating involute that is almost a triangle): gear90.zip
This also occurs when applying helix to a circle.

#472 seems relevant.