I wasn't blaming the extension. I apologize if it appeared that way.

I did use metric when I designed this. But not all measurements were whole numbers.

@ogg1e said:

@tig said:

Your object is too small - SketchUp's tolerance of 1/1000" causes any very tiny edges to get omitted, because the start/end points are deemed to be coincident - then supported faces etc also fail to form.

The 'DaveR' method should circumvent the problem.
Select all of your object, and make it into a component.
Make a temporary copy of it off to one side and Scale that up, by say x100.
Edit the giant component and do the rounding etc - remembering to adjust the radii by the scaling factor - so 0.5mm => 50mm.
Now exit the edit and delete the giant temporary copy.
The original [unscaled] instance will show the desired rounding etc...

Here's a quick screenshot of it with View > hidden geometry ON [a little editing/healing was needed afterwards]...
Very tiny geometry can exist, BUT it cannot be created !

That looks like what I want!

I'm not having much luck, even with your instructions. It's still behaving the same as when it was small... No idea what I'm doing wrong.

Ok, so I spent some more time with it, and changed things like you suggested with hidden geometry and I think I have a working model now. Thanks. It was painful and time consuming to get it to a point where this extension would actually work though. The problem is if I chose to move some of the holes for the wires, I suspect I'll be back where I was before where this extension won't work.

@tig said:

Your object is too small - SketchUp's tolerance of 1/1000" causes any very tiny edges to get omitted, because the start/end points are deemed to be coincident - then supported faces etc also fail to form.

The 'DaveR' method should circumvent the problem.
Select all of your object, and make it into a component.
Make a temporary copy of it off to one side and Scale that up, by say x100.
Edit the giant component and do the rounding etc - remembering to adjust the radii by the scaling factor - so 0.5mm => 50mm.
Now exit the edit and delete the giant temporary copy.
The original [unscaled] instance will show the desired rounding etc...

Here's a quick screenshot of it with View > hidden geometry ON [a little editing/healing was needed afterwards]...
Very tiny geometry can exist, BUT it cannot be created !

That looks like what I want!

I'm not having much luck, even with your instructions. It's still behaving the same as when it was small... No idea what I'm doing wrong.

Can this be used to round the outside corners of this object? It's a headphone case, and I'd like to smooth the edges of the slots that the wires come out.

I've tried to use this plugin (and roundcorners) but I haven't had any luck so far to get it to work.

pixel-headphone-case-v2.skp