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Demystifying Self-intersecting Sweep

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Message 1 of 3
glenn-chun
8549 Views, 2 Replies

Demystifying Self-intersecting Sweep

I've read some misunderstandings about self-intersecting sweep in this forum.  I would like to clarify what's allowed and what's not.

 

There are three types of self-intersections in the Sweep and Coil features in Inventor:

 

Type 1. Single-face self-intersection

 

A face is not allowed to intersect itself.

type1_single_face_self_intr.png

 

Also, cross-sectional profiles are not allowed to intersect each other.

type1_sweep_along_high_curvature_path.png

 

The above type is regarded as "illegal geometry" in Autodesk ShapeManager, the geometric modeling kernel for Inventor, AutoCAD products, and Fusion 360.  We do not have any plan to allow this type in the future.

 

Type 2. Self-intersections around circular path segments

 

Not allowed in Inventor 2013 and earlier.  Allowed in Inventor 2014 (a patent-pending technology).  Make sure the profile plane is perpendicular to the path.

 

Sweep Cut example:

type2_sweep_cut.png

 

Sweep Join example:

type2_sweep_join.png

 

Type 3. Face-face intersections

 

a. General case: Intersections between two different faces of the result body are not generally allowed in Inventor 2012 and earlier. Allowed in Inventor 2013 and later.

 

type3a_ff_intr.png

 

b. Coil case (sweep along helix):  Not allowed in Inventor 2013 and earlier.  Allowed in Inventor 2014. 

 

type3b_helix_sweep.png

 

The first example above has only one lateral face which intersects itself, so it belongs to Type 1. The second example has two lateral faces created from the two circular arcs of the profile.  The polygonal profile doesn't need any special treatment because it creates multiple lateral faces.

 

The What's New documentation for Inventor 2014 shows Types 2 and 3b:

http://wikihelp.autodesk.com/Inventor/enu/2014/Help/0000-What_s_N0/0001-What_s_N1/0003-Part3

 

All of the above examples can be found in the attached zip file.  You can open the parts in Inventor 2012 or later.

 

Hope this helps,

 

Glenn

Autodesk ShapeManager Development



Glenn Chun
Sr. Principal Engineer
2 REPLIES 2
Message 2 of 3
bverboort
in reply to: glenn-chun

Nice work Glenn,

 

Thank you!

 

Have you guys given any thought to the way these self-intersections should get handled in drawings?

 

Currently it appears the have the potential to block progress when applying annotations.

 

Best,

Brian

Message 3 of 3
johnsonshiue
in reply to: bverboort

Hi Brian,

 

Do you mind posting an example showing the issue? Or, you can send it to me directly (johnson.shiue@autodesk.com).

Many thanks!

 



Johnson Shiue (johnson.shiue@autodesk.com)
Software Test Engineer

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