topic Sweep Cut Can't Self Intersect - Why? Intended Behavior or Bug? in Fusion Support Forum

Sweep Cut Can't Self Intersect - Why? Intended Behavior or Bug?

dtroy15 — Fri, 23 Jun 2023 07:28:33 GMT

I need to use a sweep cut to create a relatively complex compound-curve surface for a hydrodynamic application. In attempting to do so, Fusion stops the operation and throws an error for a self intersecting body. I understand why a self-intersecting sweep could be problematic when creating a body. However, I don't understand why this self-intersecting sweep CUT won't work? Such a cut does not produce any impossible geometry to model or manufacture. So why can't I make this sweep cut?

I've attached an example file (separate from the part I am working on) which shows this issue.

Re: Sweep Cut Can't Self Intersect - Why? Intended Behavior or Bug?

g-andresen — Fri, 23 Jun 2023 08:57:52 GMT

Hi,

Please show a picture of a real object.

günther

Re: Sweep Cut Can't Self Intersect - Why? Intended Behavior or Bug?

TheCADWhisperer — Fri, 23 Jun 2023 10:32:27 GMT

@dtroy15

What are you attempting to model?

Experienced users tend to not use Primitives (Cylinder).

Your Hole1 appears to be at a random location?

Your Hole2 appears to be at a random location?

The circle in your Sketch4 is not dimensioned and appears to be a random size?

The circle in your Sketch4 is not perpendicular to the start of the Sweep Path?

I thought this one would be trivially simple to resolve - but after examining your file - I have found the true Design Intent to be ambiguous. I am still certain there is a simple solution but the Design Intent must be ~~better~~ understood.

You have Attached image rather than use the camera glyph to embed the image which makes it just a bit harder for anyone wanting to help...

Re: Sweep Cut Can't Self Intersect - Why? Intended Behavior or Bug?

jeff_strater — Fri, 23 Jun 2023 23:29:02 GMT

"I understand why a self-intersecting sweep could be problematic when creating a body. However, I don't understand why this self-intersecting sweep CUT won't work?"

The short answer is: Because the steps involved in a sweep cut are:

build the body produced by the sweep
subtract it from the intersecting body

Step 1 is the same as building a new body.

The geometry kernel just does not allow self-intersecting geometry to be created