Making an O Ring Groove

Grasshopper
1

Hi, I am still new to grasshopper and rhino so any advice is appreciated.
I am hoping to make a groove for an O ring in my part. I am unsure why but boolean components do not give me the desired output. I have tried working with Breps or meshes. I have tried every combination I can think of. Any ideas would be really appreciated! I attached a file with some of the things I tried. Just need one mesh or brep that has a groove for my O ring. Happy to learn more about why my current methodology wont work.

Thank you in advance!

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I am using Rhino 6

Edit: I have also tried using O rings that were created as untrimmed surfaces not Breps. Same result.

O Ring problem.gh (837.2 KB)

2

You are starting with a mesh, converting it to a brep using Python:

a = rg.Brep.CreateFromMesh(x, True)

That’s a big part of your trouble, IMHO. Create the “part” as a brep using GH.

1 Like
3

Unfortunately, I receive the part from a coworker as a mesh. So it needs to start as a mesh. I am happy to do it all in meshes if that’s easier but the shell part has to start as a mesh.

4

Do you want to fillet the edges?

5

there is somethin wrong with the input
it consists of 2 volumes joined in one mesh

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I think you should rebuild this mess with a clean revolved surface.

7

if it MUST remain the mesh, you could try running MeshToNURBS on the mesh and boolean difference the resulting polysurface. then mesh the polysurface. may cook your computer though, but it has worked for me in the past.

otherwise rebuild the mesh as a clean surface as Martin suggests. maybe ask your coworker for the 2D section (or circle radiuses) that generate the shape and rebuild the shape with those same parameters.

8

I don’t mean to pile on here, but there’s no problem if both components are Breps:

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It’s probably helpful for the part to be at least very slightly thicker than the diameter of the O-ring. I can imagine SDiff having a problem the the outside diameters are the same - plus that would leave 2 sharp edges at the part bottom.

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9

Okay thank you. Not sure how it got so messy but that does seem like the easiest fix!

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10

Thank you for the idea I will give it a shot!

11

Nothing to do with the modelling, but an engineering point: a normal elastomeric O-ring sits in a flat bottomed groove, not one with a semi-circular profile. (PTFE rings by contrast, being relatively inelastic, do sit in a rounded groove.)

Useful references:
Parker O-Ring Handbook ORD 5700: O-Ring Handbook
ERIKS - Technical Manual - O-Ring Gland Design Information

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12

Too bad, start with a mesh and end with a mess (mesh). No good reason to use a mesh in this case.

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13

Oh thank you so much I will give these a read!