Naked edges


I’ve had a read of a few topics on here regarding naked edges. I’ve managed to repair the majority of them however there are still 9 that I can’t repair. Most of them do not have a matching edge, so it’s not a case of tolerance. Two of the edges should join - I get a pop up window with the tolerance, but when I click join they do not join.

Another problem which only started today is that when I join all the surfaces into one polysurface it becomes a bad object. Before I join them I analyse and it find no bad objects. This was not happening last week when I had the exact same file open.

I require the whole object to be one closed polysurface so I can create a solid file for 3D printing. I’ll try and upload the file on here so folk can have a look.

Any help and advice much appreciated!


MACLEOD V1 good copy 3.3dm (2.3 MB)

Hi Seumas - what command have you been using to Join the surfaces? If you are using JoinEdge, please see Help about this command - in general, avoid it; surfaces should join with the Join command if they are within tolerance and should be fixed if they are not. I ask because most of these surfaces have large edge tolerance, which suggests that they have been forced to join when in fact the edges are out of tolerance. If your goal is a 3d print, JoinEdge can be useful, but it will tend to leave your objects in an bad state if you want to do anything that requires accuracy down the road.

I notice you also have some pieces that are joined or look like you want them joined, when in fact they are part of the same underlying surface, as in the main surfaces on the blade - these are split in two unnecessarily as far as I can see, which is a further complication…


Hi Pascal,

thanks for the reply.
Yes you are right, I have mostly been using the joinedge command. I want the model to be as accurate as possible, as I hope to have a model cast in either brass or stainless at some point.


Can I ask how you joined the two pieces of blade like that?

Hi Seamus - the two surfaces are trimmed from identical underlying surfaces, so:

Delete one of the two.
Trim with the border curve from above.

(note the border curve is not all that clean in the area where the two surfaces were joined - I did not deal with that)


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Perfect thanks very much, certainly looks smarter now.
Any advice with regards to generally tidying the model up? naked edges and so on?

It might be a bit of work - I’d RebuildEdges on all of the surfaces, then Join and see where the nakeds are. There will be more of them… then, depending on the situation, Untrim and Intersect and then Trim with the resulting curve, or, MatchSrf to suck untrimmed edges over to a nearby one…


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OK thanks very much, I’ve done RebuildEdges and Joined, now have 53 naked edges. But still as before - before joining there are no bad objects but once joined the entire polysurface is bad?

Ah - ExtractbadSrf to find the bad guy(s). Usually, DupBorder, Untrim, then Trim will fix these.


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Thanks again, this doesn’t seem to be working for me? I’ve tried this process then ran the check again and instead of 1 bad surface I now have 6

Hmm - worked out OK here.

  1. ExtractBadSrf
  2. Invert Hide
  3. Select all, DupBorder

One by one

If the surface changes - that is if it was really trimmed and not ‘trivially trimmed’, retrim with the border curve, otherwise leave it alone.

There is one small triangular surface which pinches down to a point at one end - this surface is planar, so I deleted it and replaced it with a PlanarSrf from the border curve.

Here, it all joins together as a valid object, though not closed…

BTW, you can do the same trick as before on the two internal cylinder parts - these are one cylinder, so Join, DupBorder, Explode, delete one, and Untrim/Trim the other with that border curve.

There are a lot of edges that need help once they are rebuilt… there’s a bit of work here.


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Thanks very much for your help, this is all useful information.
I’ve joined the cylinder sections like you say, and that seems to have cured the bad object problem.

So now just 41 naked edges to look forward to repairing!


Hi Pascal,

just wanted to say thanks very much - managed to get them all sotred without using the joinedge command.
Now have one closed polysurface


Good you have a closed poly now. I also have loads of naked edges and all kinds of mistakes in my .stl files which worried me a lot. I found out that a lot of times there is no problem at all as long as your model is closed. Naked adges do not allway mean that your model is not closed. I run my stl through simplify3d and can check in the preview if something is wrong with my model.

Regards, René