I am just experimenting this morning I am wondering if I am approaching this simple shape correct. I created two outside circles and linked them with a tangent circle, then trimmed the works. I then joined the three segments. I then rail swept using two small circles. It seemed like the way to go but there are unsightly joins. How should I have approached this to avoid those join blemishes. I made half and the mirror copied.

Hi Don,

Here's one method that seems to work.

Thanks Dan,

I appreciate the alternative, however, in my example the last sweep uses two different sized circles, so that is why I did only half the model and mirror copied it. Sorry my post was poorly written and that was not apparent.

Can you post the file to look at?

I don't think it is necessary to post the file at this time. I just recreated with a tangential arc as opposed to trimming a tangential circle and that seemed to have worked much better.

I just recreated that little wiggle in the surface that you show... I created the 2 circles and 3rd tangent circle then trimmed.. Then mirrored to get a closed curve.. I swept a circle along this path and all looked well.. I selected "2 profile circles" and swept those along the same path and got the wiggle in the same place you show there...

Are you changing profiles dims along the sweep? If not, just use one profile circle for the sweep.

Hey Don.
I see you were using 2 different profiles for the sweep.. Yes, when i used the tangent circle construction method, with 2 different profiles for the sweep, i get the little wiggle also.. The wiggle happened at the segment points of the curves and caused the sweep to pause and twsit on itself..

I fixed this with the original construction curves by running "rebuild" on that curve at a .001 tolerance to remove that segmented area and then the sweep followed the path well..

Sounds like you switched methods and got results already... This is FYI.

Hi Don, it's often times difficult to give very good feedback or answer questions very well just looking at screenshots instead of the actual model.

For example in your case there I would want to zoom in, look at things from several angles, turn on control points to see what those looked like, examine the control point structure of your original curves, etc... - those are all things that I can't really do just by looking at a screenshot.

So if you could please post the 3DM model file along with your question, it is a really big help.

A little lump like that in the middle of your shape could mean that there is a little wiggle or slight break in tangency in your rail curve right in that area.

Or possibly it could be a bug in MoI that should be fixed up - if I have the model file that lets me examine that possibility a lot better as well. It could be possible that it would be better for MoI to build a sweep in that situation in multiple pieces that are joined together rather than as one big long single surface piece. If that's the case then you could do the same thing currently by using Edit>Separate on your rail curve and building it in one section at a time (use the ending edge curve from the last section as the profile for the next section) to get the same kind of construction.

- Michael

Thanks all,

Michael, I will keep in mind what you said about attaching files with future questions.