Fillet/blend edge problem

When there are singularities in Rhino, problems always arise, as in this case.
The fillet / blend edge (3.0 unity, for example) on the red top edge cannot be performed. This is a case where Rhino should try to make it work.
(I tried some time ago with Siemens Nx and it works perfectly).

P.S. not even the shell works on this volume!
Fillet edge and shell problem.3dm (340.2 KB)

Fillet or blend is possible but you’d have to create a loft with the corners of the rectangular part already filleted.

Yes, singularities are a problem, but even though this may work in NX, doesn’t mean it will create good geometry. In this case I would simply avoid having singularities to begin with. Check out the file included with this post, it has my approach to something like this.

-First, I brought everything back to theoretical sharps.
-Next, I split the tapered faces with isocurves matching up to the edges of rounds in the rectangle portion.
-Used BlendSrf to make the blends (yellow surfaces)
-Created a couple BlendCrv and used Sweep2 to create the orange surfaces.
-Finally I used XNurbs to fill in the small green corners.

p.s. You can also use NetworkSrf, or Sweep2 and MatchSrf to do this, but I have XNurbs and it’s just faster.

The shell does fail, but this is not a surprise because the rounds will collapse to zero or less than zero when you offset this. I didn’t want to spend the time, but I would use OffsetSrf to offset the main shape with theoretical sharp edges and blend it with the same steps as outlined above.


Fillet edge and shell problem_Mark.3dm (445.2 KB)



For problems like this. I up the degree of the cylinder surface to 3 or 5 depending on the continuity of the blends. It’s so much easier to match surfaces with the same degrees.