How to fillet mirrored part

[MobiusStrip]

Hi all. This is in

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OS: macOS 10.16
Word size of FreeCAD: 64-bit
Version: 0.20.2.29603 (Git)
Build type: Release
Branch: (HEAD detached at 0.20.2)
Hash: 930dd9a76203a3260b1e6256c70c1c3cad8c5cb8
Python 3.10.8, Qt 5.15.4, Coin 4.0.0, Vtk 9.1.0, OCC 7.6.3
Locale: C/Default (C)
Installed mods: 
  * Manipulator 1.5.0
  * lattice2 1.0.0
  * Help 1.0.3

I have a body that contains a ShapeBinder to a sketch in another body. I can extrude and mirror it (which is the state in the attached screen shot), but attempting to fillet it fails; no doubt because of the mirror. I've seen advice to mirror the body itself in the Part workbench, so I tried that (file attached). But this creates an unexpected hierarchy of the original part being a child of the mirrored half in the model treeview. Selecting the parent only selects the generated mirrored half, and filleting only applies to half. What's the solution? Thanks!

[Shalmeneser]

Sketch(000) lacks some tangency, so the fillet will not propagate itself all around.

You can do the fillet inside or outside the mirror feature.

[chrisb]

Selecting the parent only selects the generated mirrored half, and filleting only applies to half.

In case of using Part workbench, you have to union the mirror and its source before filleting. It remains of course the tangency issue mentioned by Shalmeneser.

[MobiusStrip]

Thanks for the help! Where was (and what was the nature of) the tangency issue? This sketch was used to create the larger extruded part without any apparent problem.

Also, is there some other way to accomplish this without going from Part Design to Part workbench?

[drmacro]

Thanks for the help! Where was (and what was the nature of) the tangency issue? This sketch was used to create the larger extruded part without any apparent problem.

Also, is there some other way to accomplish this without going from Part Design to Part workbench?

The fillet attempts follow the edge, if a curve meets a line or other curve and is not tangent or only nearly tangent, the filleting process terminates.

There is nothing wrong with using Part and Part Design, assuming you understand the ramifications of doing so.

To do it in Part Design, you would probably fillet the feature and then select both the feature (pad) and the fillet, then use the Mirror feature tool in Part Design.

[chrisb]

Also, is there some other way to accomplish this without going from Part Design to Part workbench?

Shalmeneser has shown two ways of doing this without Part workbench.

[MobiusStrip]

Thanks! But I have been unable to find where the tangency problem is in my shape. I was asking where (what edge, what shape) suffered from the problem. Is it in the sketch that the ShapeBinder is referring to, or somewhere else?

[Shalmeneser]

Sketcher_ConstrainTangent
4 points along the line but only one tangency.

[MobiusStrip]

Thanks for that! But I don't think both sides can be tangent; it doesn't appear to be geometrically possible. In fact, on a couple of occasions if I applied tangency, it broke the vertices apart to satisfy it (deleting the coincident constraint). Also, why would tangency be required at every vertex? The sharp corners aren't tangent. I understand that the vertices must be coincident (the shape must be closed). Is there a way to verify that the shape is closed?

And is there a way to see why recomputation has failed? The message in the report window to check the report window is obviously useless.

[drmacro]

Thanks for that! But I don't think both sides can be tangent; it doesn't appear to be geometrically possible. In fact, on a couple of occasions if I applied tangency, it broke the vertices apart to satisfy it (deleting the coincident constraint). Also, why would tangency be required at every vertex? The sharp corners aren't tangent. I understand that the vertices must be coincident (the shape must be closed). Is there a way to verify that the shape is closed?

And is there a way to see why recomputation has failed? The message in the report window to check the report window is obviously useless.

"Is there a way to verify that the shape is closed?"

• Open the sketch
• Select a few dimensional constraints and deactivate
• Attempt to drag edges around
• If any verts separate it is not closed

Or, use Sketch>Validate sketch

If those can't be tangent then I'm guessing some dimensions and/or constraints need to be reconsidered.