Fillet edge issue

I got issue with fillet edge of solid not trimming and joining.
10 radius, RollingBall

Fillet Edges.3dm (403.4 KB)

Hi, there is an easy solution for this. Simply decrease the Absolute tolerance to 0.01 units, then run the “Fillet edge” command, and it will make the operation properly. Then you can revert back to your original tolerance of 0.001 units.



@nxrhino You can also explode the object > extend the side sloped surfaces as well as the back surface so they fully intersect even after running FilletEdge > join side surfaces and FilletEdge them > CreateSolid to make it all back into a solid. See the attached file.
Fillet Edges_VS.3dm (1.2 MB)

Hi @Rhino_Bulgaria and @nxrhino

My 2 cents: Lowering tolerances to get things to join up is a bad piece of advice! It’s bound to get you in trouble later on - especially if the data are going downstream to CAM, 3D print or similar.


To add to @Vanessa’s idea: explode the whole thing, untrimall, extendsrf all sides of all surfaces, so that they have some “overshoot”. Use createsolid to well… create a solid. Now use filletedge and it works.

HTH, Jakob

Fillet Edges JANO.3dm (260.2 KB)

I further examined this particular 3d model and it seems like the top and bottom surfaces were made using “Sweep 2 rails” or “Loft” via projected curves laying on the larger back surface. Something with the tolerances is a bit off. Their edges at the middle point basically don’t touch the large back surface. If “Sweep 2 rails” was used, the “Refit rails” sometimes make them way too far from the actual rails. The same happens with “Preserve first cross section” and “Preserve second cross section”. A good way to preliminary check whether everything is intersection before joining the surfaces into a solid is to use the “Object intersection” tool.

Extending the top, bottom and back surfaces, like Vanessa proposed, resolves the issue. The side surfaces seem OK, but if it’s not important to keep their original topology they could be also extended and re-trimmed to avoid further issues.

By the way, projected curves are often inaccurate, even if you use 0.000001 mm as a default Absolute tolerance. I always temporarily increase the Absolute tolerance by 10x when I make projected lines, object intersection, split or trim, and it works much better. Then I revert to the default one for the next operations.