Why is this a "surface border"?

I’m down to just one complaint in Solid Inspector. But, I can’t figure out why it is a “surface border”.

I can’t find any holes to fix, even when I zoom way in.

How do I figure out what’s wrong and how to fix?getting close.skp (158.2 KB)

A “surface border” occurs when an edge is used by only one face, so it creates a hole between the inside and outside of a candidate solid. In your model, the flaw is very subtle: there are actually two edges along the indicated line, one used by the top face and one used by the side face. You can prove this by carefully selecting the edge from the side and then deleting it. Only the side face will be lost, which means there is another edge being used by the top face

!double edge

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Just a note: If you change the style so Profiles are set to 1, those sorts of double edge things will be much easier to see.

In this particular case they are so close together that even that doesn’t reveal the issue! I found it after noticing a peculiar z-fighting on that edge as you orbit. If you view from the side, it appears green (color by axis). If you view from above, it turns black (a different edge that doesn’t have color by axis). As you orbit it takes on a strange partially green, partially black due to the z-fighting.

With Edge Color set to All the same and Profiles set to 1, that “edge” looks suspicious to me on my display. Slightly thicker than a single edge.


What’s the best way to fix this? Drawing a triangle to close such a small gap will probably lead to a complaint about a short edge on one side.

I’m trying out Vertex Tools,but so far they haven’t helped me with this sort of thing. Probably, I just have learned to use it correctly yet.

So, if I delete the edge that makes the top surface go away, they draw a line across where that surface was, the surface comes back.

But, that same edge is still flagged as a surface border when I run Solid Inspector again.

Here’s a fairly easy fix:

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I’d try that, but what is the red x in @shep? Do I need another extension

Also, is the face that you closed last (with the diagnal line) flat? I’ll need to extrude that surface.

It’s just Delete.

So, I followed those steps and have a solid. But when I delete the horizontal line on the last completed face the entire face disappears. I think that means the face is not flat So, I can’t extrude that entire face.

That iss pretty close to where I started. I had a solid, but that side was not flat. Apparently, when I did edits to get it flat, I introduced that surface border.

Sorry I didn’t mention that in original post–needs to be a solid AND that surface needs to be flat.

Meant to say …

But when I delete the DIAGONAL line on the last completed face the entire face disappears.

Unfortunately your model has a lot of issues with out of plane edges. The ones on the right side are just the tip of the iceberg. It’s too bad you can’t just start from scratch and model it correctly. I redid the model but the dimensions of your model are strange and not having any better information to work with, I’m skeptical that things are exactly right. It is solid, however.

I did use some additional sides for some of the curves to make smoother rounded surfaces. That accounts for the bulk of the file size difference. No diagonals to get faces to form.

getting closer.skp (295.3 KB)


Wow, I appreciate you doing that!

but the dimensions of your model are strange

Yes, they are scaled up by 1000x. Is that what you meant?

How long did that take you? (So, I know how unskilled I am and how things might be much easier once I’ve done several of these).

No. I meant a lot of the dimensions are like the ones shown here. There’s no reason to intentionally create dimensions like that and there’s really no reason for imprecision like that when modeling.

Maybe 45 minutes or an hour. It would have taken less time if I’d had a battery to measure off of instead. I spent a lot of time fixing out of plane geometry because I was trying to get decent references for the new model.

A bit of a note here.
If you are planning to 3d print this, be aware that prints shrink, different amounts depending on the material, the size and the printer. So designing anything that has to be fractions of a millimeter accurate is very much a question of trial and error.