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The sweep results in self-intersecting surface

I'm getting this error for some of the objects but not all.
See attached
I'm using this command to extrude the 1" circle along the pline PATH.
V 18.2.20 x64

Entities in set: 1
Specify height of extrusion or [Direction/Path/Taper angle]:P
Select extrusion path or [Taper angle]:
Modeling operation error:
The sweep results in self-intersecting surface
Error occurred during extruding.

BC Extrude.JPG
1027 x 629 - 64K
Grate 113018.dwg


  • edited December 2018

    I have never understood this limitation of the _Sweep command. Nor do I understand why only certain paths in the example result in self-intersecting surfaces. But in your shoes I would not use splines for the paths. Using 'normal' filleted polylines is the more logical choice I think. It will fix the issue you are having. And polylines are easier to dimension.
    Another reason for redoing the paths: there are some disturbing inaccuracies in the drawing.

    Also consider using the _DmThicken command instead of the _Sweep command. _DmThicken does not create self-intersecting surfaces either, but is the more efficient command here.

  • Self-intersecting geometry can occur if a path radius is too small for a large profile.
    doesn't seem to be the case here, at least as it looks for expected geometry.
    So I think it is a problem inside of the path object, where arc and line components
    meet, like small overlaps or multiple vertices at one point.

  • Roy,
    Thanks for taking a look & the advice.
    I was able to draw a continuous pline for the new path & yes I found the "disturbing inaccuracies"
    The plJoin would not work as I drew the original lines in varying UCS, but this attempt worked.
    I think I'll start from scratch to fix some errors in accuracy.
    This is only my third 3D project this year so obviously, I need more practice with this.
    The DmThicken did not seem to have a path option, so I'm at a loss as to how it would work.

    BC Extrude 2.JPG
    1211 x 611 - 107K
  • Thanks for the insight, Michael.

    My first attempt I drew lines in two different UCS & then the PLjoin would not work but the JOIN did but created splines.
    When I drew pline tracing the existing I got a pline I could use for the path.
    I think created my own problems when I created the paths incorrectly.

  • When using _DmThicken you do not select profile entities and then paths. You just select paths and then specify a distance.

  • So in my case, the 1" round object has 3 segments. I would need to radius them together with a 4 or 6' radius.

    The extrude with path works when the pline is constructed properly (my mistake).

  • Does the "2D" Tool to champfer or fillet edges of 2D Polylines work also
    for "3D" Polylines - so in different directions or planes in 3D space - like
    in the given example ?

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