Sweep fails where path was extended

[dorsetdesignbuild]

I'm trying to cut a contour on the top of a guitar body.  To do so, I'm using the following procedure:

1. I project the guitar body outline into a new sketch
2. I offset the body outline inward (this will be the path of the sweep)
3. Where the offset turns in on itself, I extend the curves using splines
4. I make the splines tangent to the offset curves
5. I make a profile to be used for cutting
6. I sweep the profile along the path (the offset and extended curves), using cut

This works fine until the sweep hits the point where I've extended the offset - there it stops or throw an error.

The interesting thing is that if I draw new curves over the path, it works fine.  I'm thinking there's something different about curves that get projected.  Does anyone have a solution...

[jeff_strater · Accepted solution]

With sweep, it's all about the curvature and the size of the profile.  After modifying the path a bit, you can see where the self-intersection happens:

You can do a couple of things - reduce the size of the overbuilt profile, or reduce the curvature of the path.  The first will only get you so far.  So, I found that I need to reduce the curvature of the path.  I removed the tangent constraint, and replaced it with a Smooth constraint, and then  manipulate the fit points and tangent handles until it works.  I don't think that this is the geometry you want, but I can get the sweep to succeed:

This version is attached, FYI

[dorsetdesignbuild]

Thank you - that works great!