Coincident constraint is not able to create a closed profile with an offset - Fusion

[acpigeon]

This is very strange. I have two ellipses, one drawn directly and the other an offset. I am trying to use lines to cut a slice out so I can build a clamp. If I constrain the lines to the outer ellipse it will not create closed profiles. If I extend the lines beyond the outer ellipse without constraints, it creates the expected closed profile. Screen recording of the behavior, and file attached.

This post has been edited due to: @heather_tracy added the product to the title to help more community members find this topic. 

[TrippyLighting]

My recommendation would be not to constrain any other sketch element to any offset geometry. Offset sketch geometry often creates problems in sketches,  particularly when combined with an ellipse or spline. @rohit.bapat 

If you create the outer ellipse first, and then offset to the inside, and then constrain the line endpoints to the original outer ellipse, things work as expected.

[HughesTooling · Accepted solution]

You should either intersect this surface to create the projection or use the original ellipse in the sketch for the other component (rather than project complex edges) so you get an ellipse rather than a spline in your sketch.

Using the projected ellipse still creates a spline for the offset but you no longer see the problem with the profiles not being closed. See attached file.

[dsouzasujay]

Hi @acpigeon 

Agree with @HughesTooling 
As a workaround, you can 'Break' the sketch, shared in below video.

[acpigeon]

Thanks, yes this works also.

[acpigeon]

Thanks, I didn't realize offsets were problematic.

[acpigeon]

Thanks, I didn't think of using the sketch geometry instead of the surface.