Fillet Edge Inner Corner Problem


I am having an issue with an inner corner I do not know how to address. This model is a rudimentary divider. My slicer, Simplify3D does not like the inner corner to the right of the “1” tab and splits my model in two. I looked closely and the inner corner fillet seems to be the problem.

How do I make the fillet round this inner corner correctly?

LanyardTemplate.3dm (2.6 MB)


The problem is the top and bottom flat surfaces are not one surface. That causes filletedge to fail.

Its pretty easy to fix. First extract the top and bottom surfaces and delete them. Then extract the 4 fillets and untriim the ends that are not complete. Then trim the ends to a 45 degree line and join and cap (see file)
fixFillets.3dm (354.8 KB)


Wow, I am very very new at Rhino and 3D modeling. I was tempted to respond with “can you hold my hand through these steps!”. Ultimately it was easy, but took me lots of trial and error time with each command.

This problem taught me how to ExtractSrf, Untrim, Trim, Join, and Cap. I exported to STL and Simplify3D slices the model correctly now.

With this solved, I decided to Extract the number, and recap the top. I am printing 12 of these dividers, with the tab shifting for each one. Looks like I need to create each model, with each requiring the steps you outlined above to fix this inner corner(s) issue. Guess I could have left the number. I just realized there isn’t a good way to just move the tab and save each iteration.

Jim, thank you very much for taking the time to steer me in the right direction!



All of those are important tools to know if you want to become proficient with Rhino.

No you don’t need to do that. The issue is that your top and bottom surface were not one surface. If they had been one surface then FilletEdge would have been able to do the fillet all the way around. It is not hard to make this shape so that the top and bottom are one surface.

The most efficient way to do what you are trying to do is to draw all the profiles that you need in 2d. In other words, the tabs are included in the 2d outline (not as a separate piece). Then you can extrude all the shapes in one operation and fillet all the edges in the next operation. Then add the numbers where needed.


My decision to join objects rather than draw them out caused the problem. I drew the 2D outline including the tab and the fillet worked just like you said it would.

My last question is, if you were doing this small project, would you draw 12 separate dividers, hand shifting the tab to the right, or is there a better way to “move” the tab over, split the polyline, fit the tab in, then save the file?

Thank you very much!


You can use Array command and do something like this
Lanyard_12.3dm (242.3 KB)

It looks like you can select all 12 squares and tabs and run Trim them all in in one go by clicking 12 times and then run join while everything is still selected . You can also use curve boolean but I think that will be more mouse clicks.