Revolving a Chamfer: "self-intersecting part"

Tru7h

Hi Onshape community,

I'm building a cube part which needs a chamfer or fillet around a radius at one end. 

Here's the model in question:
https://cad.onshape.com/documents/b85abe8bdcf5d2c7143f049a/w/51f6d0201850ae8454cf22cc/e/2a79e73cd5fb80646ca7ce76

I'm attempting a revolve in remove mode to cut a chamfer on the part around a radius. I can't find another way to do that with the Chamfer or Fillet tool. It just wants to cut the corners along the square. This part will be lathed.

The error I'm getting when trying to rotate elements of Sketch 2 around the axis is: "Resolve1 did not generate properly. Resolve would create self-replicating part. <- Sketch 2"

FWIW I've also tried this with a triangle shape, rather than a radius, as searches popped up other people having this problem trying to create domes and spheres. Same issue. Also, changing the Revolve Type has no effect.

What on earth is going on?

mahir

You're probably creating degenerate geometry (knife edges). Change your sketch to look like this, and it will work.



But I don't think that's the look you're trying to accomplish. If you change the sketch plane, you can make the "fillet" start right on the corner. You end up with this more polished look.

https://cad.onshape.com/documents/ff35a763860bd9a6eb7448a0/w/8ea63a4b6f8f2356ea3a6cea/e/07fa1fd5ff7d6f318410c363

mahir

You're probably creating degenerate geometry (knife edges). Change your sketch to look like this, and it will work.



But I don't think that's the look you're trying to accomplish. If you change the sketch plane, you can make the "fillet" start right on the corner. You end up with this more polished look.

https://cad.onshape.com/documents/ff35a763860bd9a6eb7448a0/w/8ea63a4b6f8f2356ea3a6cea/e/07fa1fd5ff7d6f318410c363

Tru7h

Thanks, that's definitely the problem! For the life of me, I can't figure out how you placed that sketch where you did though.


AAAAND all a guy has to do is open his big mouth for the solution to become obvious. Custom plane. Got it.

mahir

I created a plane using the 3-point method (which is similar to line-pt in other CAD systems).

brian_jordan

Further to @mahir's comment, a plane can be created between the Front and Right planes using the Mid Plane method; as with so much in Onshape there are many ways of doing this. As to which is best?

mahir

Fancy. I knew you could midplane parallel planes, but I didn't know it could be used to bisect planes at an angle.

owen_sparks

Mid plane is a great example of pre-selection logic on an OS feature.  If we click, front plane, right plane, plane feature, accept, then it's clever enough to know that as we've selected 2 planes we can only want a mid plane.  So done in 4 clicks. 

We need more pre-selection cleverness in OS

Owen S,

brian_jordan

Well, you live and learn! @owen_sparks thanks for this tip and +1 for pre-selection cleverness.