Looking for advice on fillet best practices

[jakeseifertB52BF]

Hello,

I'm making a model that was designed around a wireframe 3D sketch, using surface patches on the wireframe, stitched together and boundary filled solid. I'm trying to put a small fillet on all the edges but even at very small radii the program throw an error saying there's a problem where edges come together.

Is there something fundamentally wrong with the way this design is modeled that the fillet command would never work? is it too angular, with too many edges coming together? Any bit of sage advice would be appreciated. Screencast is attached, as well as some screenshots for those who don't feel like watching the video.

[laughingcreek]

no screen cast.  attaching the model itself would be most helpful (export as an .f3d to hard drive and attach to a post).

have you checked the curvature quality of you edges?

what tolerance did the stitch tool have to be set to for it to stitch together?

the patch tool is a blunt instrument.  not unusual to get wonky curvature   from it if not careful.

[rushabhthakkar_910]

Attaching the Model would be great.

(https://www.autodesk.com/products/fusion-360/blog/fusion-mastery-import-export-cad-files/#:~:text=Ex....)

[jakeseifertB52BF]

Sorry, didn't realize I needed to attach the file. Should have, though. It's attached to this post.

I stitched together with .004 tolerance if memory serves. I didn't realize the patch tool was such a blunt instrument. I had a feeling it would be too convenient to be useful. There were several edges I had to extend and trim in order to get coincident edges... I'm guessing this may have contributed to the problem? I'll try to think another way to model the same sort of shape without patching.

[rushabhthakkar_910]

@jakeseifertB52BF, Have a look at this Screencast Video..!! 

(https://autode.sk/3xIyQFv) It works well for me.. 

[TrippyLighting]

@rushabhthakkar_910 That isn't a surprise if you only select half of the edges that need to be filleted 😉

[jeff_strater]

I don't know for certain that this is the case, and I will likely not have time today to look into it, but I do know that Boundary Patch can create some bad geometry on curved faces.  You can see that a little if you turn on a curvature map.  So, it it not too surprising that you have some downstream issues with Fillet.

[TrippyLighting · Accepted solution]

How familiar are you with Sub-D modeling and T-Splines ?

This is easier to design in a polygon modeler, but given that we had a model in Fusion 360 already,

I exported the design as a mesh and imported it into Blender.

There I dissolved faces and merged vertices to get a clean low poly model including triangles.

I then applied the subdivision modifier with 2 levels of simple subdivision. That eliminates the triangles.

I imported the resulting quad mesh, converted into a T-Spline, used the combine tool and filleted the sharp edge on the front.

[CADacombs · Accepted solution]

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@jakeseifertB52BF wrote:

I'll try to think another way to model the same sort of shape without patching.

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For a solid/surface-only solution:

When creating surfaces, use sketch curves instead of face edges wherever possible since they are typically of simpler geometry, mostly lines in your model.

Use Patch to make planar faces.

Use Loft to make the 4-edge twisted faces.

Any problem fillets can then be dealt with on a case-by-case basis.

[jakeseifertB52BF]

Thanks! 

I still don't quite understand (on a technical level) why the fillets would fail, or why this approach to modeling this shape is prone to failure (maybe someone on the software team could explain), but the solution you offered is helpful. I'll try replicating it myself. 

[jakeseifertB52BF]

I will also try your suggestion of using lofts for the 4 sided faces instead of patches. Thanks

[TrippyLighting]

The fillet command seems easy and because it usually just does what one expects, it is easy to assume that the fillet tool is/was easy to implement. But that could not be further from the truth! It hides a lot of intricacies from a users.

The surfaces it needs to create in cases where so many edges join in one point/vertex are quite complex. If you do this in a polygon modeler some of this will become more visible when you look at the wireframe.