Issue with naked edges from a loft

[Bryson_Hicks]

I am trying to 3d print a piece of ductwork. I created a loft between a rectangle and two circles. The loft seems to come out fine, but when I try to add thickness to the loft so it can be printed, 2 of the 4 edges are naked edges. What am I doing wrong?

The curves I am starting with:

The loft:

Also of note, the loft is not symmetrical. I’d like to fix that too, but it is not a big deal.

I am using the offsetsrf command to try to add thickness. 2mm, and round corners are selected. Each side has one naked corner. Here are both edges on the left side.

This corner is fine.

But the opposite corner is not.

Duct test.3dm (465.8 KB)

[theoutside (Kyle Houchens)]

might have better luck making the part solid then shelling it with the corners set to sharp. It drops one surface when you do that but its an easy fix.

how big of an offset are you looking for?

loft is pick location dependent, make sure you are picking right down the center to get them lined up. see video attached.

duct.zip (18.9 MB)

[Bryson_Hicks]

Thank you for that very helpful video. Going for a 2mm offset / wall thickness, but the 0.08" you used would be fine too. Since the cap command doesn’t add any thickness to the outside, I’ll need to increase the size of the circles by 4mm so the OD matches the planned 5.79".

When I am picking the lofts, the curves are not being selected where I click, so it still does not end up symmetrical. Can you see what I am doing wrong? Video attached.

It looks like any change to the model results in different naked edges. so mine ended up in a completely different place than yours. What command would I use to close it? New file attached.

Duct test.3dm (258.3 KB)

[theoutside (Kyle Houchens)]

they symmetry issue is the starting point you are going with-

you can adjust it by dragging those points-

make sure they are centered in the middle front-

[Bryson_Hicks]

Thanks for the help. Dragging the loft points worked perfectly.

Documenting what else I did so I can look back on it later:

I was then left with naked edges in a similar location to yours.

I then used dupedge to create curves along the bottom naked edge. I then joined the curves to create an (almost) closed circle. There was one spot where the circle didn’t fully close, but closecrv fixed that.

Like you, I used Loft to create a surface between the two naked edges.

I then used join to join the two surfaces.

I was left with one small opening.

The cap command closed it. And finally I had a closed polysurface!

[theoutside (Kyle Houchens)]

if you want to clean it up a bit, notice here-

the shell command leaves two slivers of a surface here and on the other side, that makes the inner circle incomplete.

extract them, delete them, then use mergeedge to repair the edges of that surface- then use blendsrf set to position and chain the edges.

If you are still getting that small wedge, simply delete that damaged surface, copy the good one from the other side and mirror it. once you join that in, you should have two clean edges you can then blendsrf to complete the model.

I like blendsrf set to position for stuff like this because you can chain the edges where you cannot in loft.