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O-ring groove


paulmcz

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I have a cylinder inside a custom valve (see the drawing) This rotates inside cylindrical hole of the valve body. I want the hole in the cylinder sealed with an O-ring (green groove). My question is - how to draw this on the AutoCAD so the cross section of the O-ring groove is as close to a square as possible along entire perimeter of the groove. Is it even possible on the AutoCAD? Obviously, what I drew is wrong.

 

Thanks.

O-sq-groove.dwg

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Jochen, thanks for your response. Yes, this is what I had in mind. I thought that some newer version of Autocad would have it as a native command. Does it?

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I think the proper solution is to create a profile on the surface of the cylinder and then sweep an object around that profile to cut the groove, just as a CNC router would cut the groove in the physical part, but I couldn't work out how to combine the lines, arc and splines into a continuous sweep path.

 

So here's my flawed attempt where I created surfaces representing the top and bottom of the groove, then LOFTed them together into a solid to represent the void.

O-sq-groove2.dwg

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Thanks nestly. Interesting approach! Maybe, the CNC milling or routing function will be in one of the next version of Autocad. The old pen plotters worked similar way too. Not exactly a new technology.

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Thanks nestly. Interesting approach! Maybe, the CNC milling or routing function will be in one of the next version of Autocad. The old pen plotters worked similar way too. Not exactly a new technology.

 

Autodesk already has software solutions for this.

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Late to the party again (a party that has already successfully concluded), but here is another option.

 

this option uses the uvVectorMap routine, as mentioned by GP_, to help locate and map a flat curve to the cylinder face. The cylinder in this case had the face offset inwards 0.06, to generate a centerline for a sweep operation.

Test.dwg

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You're welcome, Paul.

 

I do have to admit that this exercise highlighted a couple of shortcomings to the Vector Map plugin. I had intended to post the new beta soon - might have to retool a bit first.

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Not to take anything away from the solution, (which I believe works perfectly in theory) but AutoCAD seems to struggle with the straight vertical segment (which should be the simplest geometry in the whole sweep since it doesn't curve or twist). I noticed it because of the lag when moving/copying as well as trying to OSNAP to the solid sweep. AutoCAD2011 displays it differently than newer versions and demonstrates what AutoCAD seems to have trouble with.

 

Oring groove.gif

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. . . . AutoCAD2011 displays it differently than newer versions and demonstrates what AutoCAD seems to have trouble with.

 

That does look pretty ugly. Unfortunately I don't have 2011 to test against. For the sake of curiosity, what happens if you switch to one of the wireframe displays?

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Seems odd that only the copies display that way. Properties seem to be identical, and I have trouble Osnaping to both.

 

oring groove2.gif

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That is pretty odd. Don't even have a good guess at the problem.

 

I do know why there is difficulty snapping to the solid - the base sweep path is periodic so is treated as one continuous spline with only one endpoint, one midpoint. Conceivably, NEA osnap should work, limited PER. Definitely no CEN. AutoCAD does have a way to go with how it deals with Spline/Nurbs geometry.

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