CAD Puzzles & Riddles

Jack K had the following advice:

First I would break down the shape into eighths (1/8), so that I could mirror to get the final shape.

For each quadrant, I would draw conic curves with the ends being perpendicular to the primary planes with tensions to whatever looked good. One conic in the top view/plane, and another conic in the front view/plane.

Then I would sweep one conic, using the other conic as the guide.

3 mirrors and all done.

A Boundary surface can make half of the model. It might actually make the entire model in a single feature, but I've not tried it yet.

With half the model made, mirror for the complete part.

The sketches use Splines to capture the desired shape.

Outside of a Low Feature Count Challenge I would have made 1/8th of the model as Jack K suggested.

Boundary Surface will do it in a single feature.

The cool thing as a single feature is no "seam" exists from mirror operations.

I've never used Inventor, so I have no idea if Boundary is a tool the two programs share.

Boundary was added to SW a while back and is sort of like a better replacement for many operations that would normally be made with Loft or Sweep.

I don't think Sweep will work on this model unless some trickery is used to leave a tiny sliver of open space.

Loft is a method that works in SW too. I have not tried a Loft yet, but I did see another model using a Loft. It looks good. In SW there is a "close loft" option. It needs to be on.

I was actually surprised when the Boundary method closed itself up at the end. I thought for sure I was going to have 75% of the model. I tried a Solid Boundary as well and it works fine. I just usually default to working with a surface for anything that looks like this.

Not sure if it will help, but here's a screenshot of the Boundary tool in action. Each of the blue groups is a half ellipse type shape. The purple group defines the outside edge of the model. I have not tried adjusting the curvature controls yet (those flags that say "None").

I have no idea why I took this approach but I did it in a very complex way. Fred has the best solution.

Outside of trying for "fewest features" I'd normally build 1/4, or even 1/8 of the model, then mirror or pattern.

Check your tangency controls though, looks like there is a little bump in the final image. Tangency control is the one downside to mirroring a symmetrical part.