topic Re: Looking for help with a Fillet in Fusion Design, Validate & Document Forum

Looking for help with a Fillet

SauberC9 — Thu, 10 Sep 2026 13:04:31 GMT

Hello everyone - I'm dealing with a small issue that I'm sure will take the pros about 10 seconds to solve. I am making a printable model of a sunglasses frame, and have been making some small adjustments to the size of the frame. In my old version (red circle), I was able to fillet between the main frame and the earstem. And in the new version (blue circle), where I'm changing around the thickness of the main frame, I'm no longer able to make that same fillet. The error message I'm getting is

"Cannot fillet edges that have more than two adjacent faces"

However, it appears to me that there are two adjacent faces, as this new version is nearly identical to the old one.

I know there are workarounds to smooth out this angle, but I'm looking to understand why the fillet worked the first time, but not the second time. Any insight would be hugely helpful!

Re: Looking for help with a Fillet

dsouzasujay — Thu, 10 Sep 2026 14:52:49 GMT

Hi @SauberC9 ,

My suspicion is that when the thickness of the main frame was changed. There may now be an additional very small or split face around that joint, or the geometry may be meeting exactly along an edge or vertex. Either situation can result in an edge effectively being associated with more than two faces, which prevents the fillet from being calculated.

This would also explain why the previous version fillets successfully even though the two versions look nearly identical.

A couple of things worth checking:

Roll the timeline back to just before the thickness change, then move forward feature by feature to see exactly when the additional edge or face appears.
Inspect the circled portion closely for very small or overlapping faces/edges. Turning on hidden edges can sometimes make these easier to spot.

If you are able to attach the Fusion .f3d file, that would be the best way for us to identify exactly which face or edge is causing the non manifold condition and explain what changed between the two versions.

Re: Looking for help with a Fillet

SauberC9 — Thu, 10 Sep 2026 16:03:04 GMT

I went back in time, redid all the steps a few times to draw the earstems and join the earstems to the main frame, and still kept running into the error.

I used Claude to make a script that would show me any joints in the model where there were edges with more than 2 adjacent faces, and the script identified the very joint that I was trying to fillet (very interesting use case for Claude), showing me that there were 4 faces.

I then zoomed in as much as I possibly could to see if there were overlapping edges in the drawing, and viewed the part in Shaded and Wireframe with hidden edges to make sure I wasn't missing any, and still could not see them. Bizarre.

Here's the file attached - it could just be a corrupted file that's just not going to work, but wanted to see if there's some obvious mistake I'm making here that I can avoid later on.

Thanks!

Re: Looking for help with a Fillet

TrippyLighting — Thu, 10 Sep 2026 18:04:38 GMT

@SauberC9 Before you do anything else, please fully constrain and dimension your sketches. Otherwise your design likely is going to run into trouble!

The earpiece you'll have to build not using a single loft. The curvature on the edges you are trying to fillet is somewhat irregular.:

Re: Looking for help with a Fillet

TheCADWhisperer — Thu, 10 Sep 2026 19:23:31 GMT

@SauberC9 wrote:
...but wanted to see if there's some obvious mistake I'm making here that I can avoid later on.

(view in My Videos)

Re: Looking for help with a Fillet

bhavani_sankuratri — Wed, 16 Sep 2026 06:30:06 GMT

Hi @pareskymichael,

Hope you are doing good! I wanted to follow up and see if you had a chance to look into the TheCADWhisperer's post. Please let us know if you still need any help on this.

Re: Looking for help with a Fillet

SauberC9 — Wed, 16 Sep 2026 13:30:41 GMT

Hello all -

Thank you very much for the feedback. Taking into account the feedback on this thread (and spending a lot of time refining and simplifying the model, basically redoing the entire thing), I no longer have the problem.

Ultimately I believe the solution was to not have a sketch at the initial plane upon path and having that drawing loft all the way to the end of the earstem. Instead, I had one sketch along the path - at the end. And then I lofted the initial face from where the plane begins - to the sketch at the end of the earstem. Using that initial face instead of a sketch immediately beginning along the path ultimately eliminated the "Cannot fillet edges that have more than two adjacent faces" error I was running into.

I've screencapped the before and after for more context. Thanks for all the help!