Hi Chipp, also if you look closely at the top surface you can see that it has a bit of an undulating wave to it:



That kind of undulation is the type of artifact that often results from fitting one single curve that runs through a curvature discontinuity like you'll get at a juncture between a line and and arc. If that was the result of using the Rebuild command you could try using a tighter tolerance value like 0.001 units instead of only 0.01 units, which would reduce the undulations. But keeping it as separate arc and line pieces would give the most accuracy and keep the top to be a simple plane... It would also introduce more edges which makes for a more complex topology too though which may cause other problems later on at junctures where you've got a whole lot of edges coming out from one single vertex.

- Michael

Hi Chipp, so I think it mainly has to do with the undulations in the top surface being a bit too pronounced, here's a version where I just squished flat a wide region of the surface's control points and that also makes filleting behave better.

- Michael

Thanks Michael,

I was able to fix the problem by separating the surfaces, filleting, then combining and planar to 'seal' the solid.

That said, I didn't understand how you were able to 'flatten' the control points? Can you elaborate? It sounds like a helpful skill to have. Thanks!

Hi Chipp,

re:
> That said, I didn't understand how you were able to 'flatten' the control points? Can you
> elaborate? It sounds like a helpful skill to have. Thanks!

That was by surface control point editing. First select the top face and use Edit > Separate to break it off into an individual surface object.

Then I used Edit > Show pts to turn on control points, and selected the middle set of points about like this:



Then go to an elevation view like the Back or Right viewports, and use the edit frame to flatten the points using "flat snap". That's where you grab the corner sizing grip and drag it downwards until you see the "flat" snap point engage, like in this example here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=3378.4

If you don't get any flat snap it means the thing was already flat, that's a way to test for planarity. Also it can sometimes be of diagnostic use to do the opposite and drag the corner sizing grip outwards to stretch it and amplify the wiggles to get a better idea where they are.

Hope that helps!

- Michael