Strange Fillet Edge Behaviour

Rhino
,
1

Can anyone explain why applying FilletEdge Blend Edge or Chamfer edge doesn’t work on the attached ?
FiletEdge.3dm (193.8 KB)

here’s the curves

image
image1431×1104 169 KB

here’s the solid
image
image1710×1060 137 KB

here’s the result of filletedge
image
image1448×1091 97 KB

2

Also wondering why one of those top edges gives graphic issues. Other 3 top sides are fine

3

I don’t know why filletEdge fails on this. It looks simple enough.

You may want to try using this Filsrf_JoinV2.py python script which is explained in this thread

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4

Its a degenerate surface. Rhino should identify it as a Bad Object, but for reasons unknown McNeel doesn’t want to warn users about some Bad Objects.

It is bad practice to try to make this as a untrimmed surface. Its going to be trimmed eventually so it might as well start as one.

The degenerate part is just along the edge and gets cut off by adding fillets. So if you use ShrinkTrimmedSrf command after filleting the surface will no longer be degenerate.

5

The surface on top is modeled in a weird way, If you divide the surfaces along its creases you’ll see there are two parts that have tangent corners, the highlighted parts are untrimmed:

image
image1341×721 161 KB

these are untrimmed surfaces, so it means you created a tangent point for one of the corners.

6

Thanks for explaining
So what would be the best way to create the top surface from the original curves ?
I used sweep2 which I accept is a little clumsy / counterintuitive
I tried Patch to no avail

edit : edgesrf seems to give a better result

7

Exported a STEP, fillet in other CAD just ploughs right through it.

mkkkk
mkkkk972×501 28.2 KB

diamond.stp (230.0 KB)

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8

I would model that in a different way, I’ll make a short clip

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9

Thank you

10

I would do it something like this:
trimmedSrf.3dm (143.3 KB)

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12

Ah great thank you. Didn’t occur to me…
You used BooleanIntersection I take it

13

Thanks… I’m trying to model an existing keyboard key… so approaching in this way is a bit tricky… as you can’t just survey the surfaces/edges and loft (which is easier from an existing object than working out the ‘source’ shapes as you’ve done here)
But your and Jim’s approaches both very helpful in demonstrating an alternative approach. Appreciate the really quick response

14

I used the the commands Trim and Join.
Select both objects hit the Trim icon, then select the parts you want removed and then hit the Join button and your done.

1 Like
15

I should use those more… I lean heavily on Boolean. Thanks for the tip