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Vertex on revolve axis

vidyut_vivekkumar
vidyut_vivekkumar Member Posts: 2 ✭
in Community Support

Hi Onshape community,

My project has a sketch with a point on the axis I'm trying to revolve around, but the revolve feature says it's self intersecting. I don't see anything self intersecting when I check the sketch.

https://cad.onshape.com/documents/a398f96ab77e7c2712b2088c/w/96b1384b7b0609deda5c3695/e/a8d9d3102e601e013ad41a0b

The model in question ^^^

Answers

  • jelte_steur_info
    jelte_steur_info Member Posts: 676 PRO

    did you make it public? I couldn't get in

  • bernard_bieg
    bernard_bieg Member Posts: 3 ✭

    Hi,

    Also beginner here. I am experiencing the same problem and it seems to be a bug. When point is on revolving axis full revolve cannot be created. I move point outside revolving axis just tiny bit and is OK.

    image.png image.png image.png
  • robert_scott_jr_
    robert_scott_jr_ Member Posts: 904 ✭✭✭

    Seems like this should work. I retraced the sketch image. Fully defined sketch with upper right vertex coincident with revolve axis. Full revolve fails. Revolve of 359.9 degrees is successful. - Scotty

  • Oliver_Couch
    Oliver_Couch Member Posts: 230 ✭✭✭

    This shouldn't need to work. Why are you trying to create infinitely thin geometry? What's your overall goal?

    Something infinitely thin is not possible to manufacture.

  • robert_scott_jr_
    robert_scott_jr_ Member Posts: 904 ✭✭✭

    What resulted in the revolve is a solid with a very small wedge gap in it. Thus, I don't understand the reference to 'create infinitely thin geometry'. - Scotty

    Screenshot 2024-12-12 100141.png

    Document (part studio 2)

  • _anton
    _anton Member, Onshape Employees Posts: 550 image
    https://forum.onshape.com/discussion/comment/110866#Comment_110866

    If the vertex is right on the revolve line, the revolve would be infinitely thin at that point. This is called "nonmanifold geometry", and our geometry kernel disallows that.

  • Oliver_Couch
    Oliver_Couch Member Posts: 230 ✭✭✭
    https://forum.onshape.com/discussion/comment/110866#Comment_110866

    A full revolve would create two faces which touch in their centres, where there is no edge.

    In real life if you tried to do this you would break through the material.

    By doing an incomplete revolve you are creating edges at that point, which necessarily has to be allowed. The two cases are topologically very different

  • robert_scott_jr_
    robert_scott_jr_ Member Posts: 904 ✭✭✭

    Thanks for responding. So, intersecting a point with the axis results in no thickness i.e. no geometry at that point?

    Screenshot 2024-12-12 121702.png

    . - Scotty

  • S1mon
    S1mon Member Posts: 4,507 PRO

    Bingo. That point results in non-manifold geometry, which the Parasolid kernel can't handle. There's a vertex which is both inside and outside at the same time, which isn't allowed.

    Simon Gatrall | Product Development, Engineering, Design, Onshape | Ex- IDEO, PCH, Unagi, Carbon | LinkedIn

  • MDesign
    MDesign Member Posts: 1,461 PRO
    https://forum.onshape.com/discussion/25648/vertex-on-revolve-axis

    Although technically not self intersecting. It's kind like asking a computer or calculator to divide by zero. Error

  • robert_scott_jr_
    robert_scott_jr_ Member Posts: 904 ✭✭✭

    Good analogy. Thanks All. - Scotty

  • mahir
    mahir Member, Developers Posts: 1,324 ✭✭✭✭✭

    Also called a knife-edge. Something most CAD doesn't handle well.

  • bernard_bieg
    bernard_bieg Member Posts: 3 ✭

    Got it. Thanks for all answers.

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