Fillet Problems

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electrosteam
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Joined: Thu Dec 16, 2021 7:46 pm

Fillet Problems

Post by electrosteam »

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OS: Ubuntu 22.04.1 LTS (LXQt/Lubuntu)
Word size of FreeCAD: 64-bit
Version: 0.20.29177 (Git) AppImage
Build type: Release
Branch: (HEAD detached at 0.20)
Hash: 68e337670e227889217652ddac593c93b5e8dc94
Python 3.9.13, Qt 5.12.9, Coin 4.0.0, Vtk 9.1.0, OCC 7.5.3
Locale: English/Australia (en_AU)
Experimenting with simple fillets, I just don't seem able to reliably add a fillet to the curved edge.
Tried Part WB, Boolean Fusion, Copy/Shape-Refine etc, with some success but no revelation or sense of new knowledge.
Read the Manual and searched on the subject, but the mist has yet to lift.
Test Fillet 1.FCStd
(17.83 KiB) Downloaded 14 times
What do I have to do in the attached model ?
John.
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Willem
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Re: Fillet Problems

Post by Willem »

make the sketch with the arc and the 2 lines in the also in the Padbase body.
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papyblaise
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Re: Fillet Problems

Post by papyblaise »

Fillet is used to connect an angle between 2 shapes forming a single body
but a workaround exists: you make 2 sekches of the fillet section and use the edge of the sector as a path
Attachments
fillet.JPG
fillet.JPG (20.3 KiB) Viewed 828 times
Test Fillet 2.FCStd
(36.93 KiB) Downloaded 9 times
electrosteam
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Re: Fillet Problems

Post by electrosteam »

Willem,
The sector started as a sketch within the base, just padded higher.
Could you just explain again in words a novice (me) could understand.

papyblaise,
That approach is a great solution to an immediate problem.

But, this is just a test piece to try and understand what the fillet engine in the software wants as input data.

My real target is entirely different and more complex.
The image below shows a 96 diameter railway wheel with tapered oval spokes milled out of the solid.

The ambition is to have a variable radius in the fillet as it traces around the intersection of a spoke with the hub ( and then rim ).
Fillet size approximately from 2 to 5 mm radius.

I would be happy to break the fillet into sections somehow.
Starting to wonder if gaps of 0.1 mm between sections might enable management of the fillets.

I plan to export as a mesh, so something like Blender may be able to iron any blemishes in the mesh.

My preference at the moment is to concentrate on the test model as a learning exercise.

I have played with variations.
Sometimes the sector fillet will solve, provided the line fillets are solved first.
The angle between the curve and the straight edge appears to be significant, > 90 degrees works much better.
The Manual says fillets propagate across tangents, so why does the fillet sometimes propagate across the intersection of the two straight edges ?
Attachments
screenshot-e046c7b7.jpg
screenshot-e046c7b7.jpg (90.85 KiB) Viewed 740 times
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papyblaise
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Re: Fillet Problems

Post by papyblaise »

you can pass the fillet between 2 different section profiles, or use the Part wb fillet tool which allows 2 radii (a start, an end)
Attachments
fillet3.JPG
fillet3.JPG (18.41 KiB) Viewed 660 times
fillet3.FCStd
(41.02 KiB) Downloaded 8 times
electrosteam
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Joined: Thu Dec 16, 2021 7:46 pm

Re: Fillet Problems

Post by electrosteam »

Thanks for that example, it is something I will pursue.

I have done some experimenting with my simple case:

The fillet engine does not solve for an included angle between the curve (tangent) and straight line of less than about 69 degrees.
90 degrees (radial), of course, is Ok.

The fillet propagates from straight line to straight line for an included angle greater than about 172 degrees.

These explain my original problem, and provide the limit cases for future modelling.
freedman
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Re: Fillet Problems

Post by freedman »

If you need a variable then try Sweep with continuation or sweep with a loft.
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