A Meshmixer quandry

[RogerInHawaii]

I have a single Component of my design, which consists of a single Body (in spite of it looking like t here's tons of separate components). I choose to "Save As STL" and have the result sent out to Meshmixer.

When I first bring it up in Meshmixer it generally looks pretty good, but there are some odd RED DOTS above and below each of several BoltsWithTruncatedWashers. I've never seen anything like that. Normally red things usually only show up after doing an Analysis/Inspector operation with Meshmixer. 

So II then actually do an Analysis/Inspector in Meshmixer and it reports a bunch of Pink Floating Surface Errors.  Interestingly those small red dots are GONE. Here's a close-up of one of those problem parts:

The pink line is pointing at what it thinks is a "Floating Surface" error. It's pointing at that very precise spot. If I move the component around within the Meshmixer view it consistently points at that very spot. So, is it pointing at that actually spot, or is it indicating a problem with that entire Bolt Head, or maybe the entire bolt and washer? But remember, this is one solid component. There really are no bolts or washers at this stage.

So, I tried clicking on JUST this individual error. Doing so attempts to CORRECT the error. 

After clicking to repair this one error:

And, lo and behold, it did indeed fix it Well, at least the error indicator went way. It's not obvious what it actually did.

BUT !! I then tried using the "Repair All" option, expecting it to repair each and every one of those identical errors on identical bolt/washer locations. And I get this:

 
The body is totally messed up. Some of the Bolt/Washers have been obliterated.

So, what's going on?

1) What is it likely actually detecting, considering that Bolts/Washers all LOOK perfectly fine to begin with and don't look any different after doing INDIVIDUAL, one-at-a-time, fixes.

2) Why does "Auto-Correct All" do such a horrible job when doing each one individually seems to work just fine?

3) What might I do in the original Fusion 360 design to avoid having these errors pop up in Meshmixer?

[laughingcreek]

Did you combine all the bodies into a single solid before exporting as a .stl?  If not  you likely have a jumble of different mesh shells combined into one mesh.  and  I'm very surprised you don't have more issues.

what does the .stl look like when you when you look at as an x-ray?  can you see the issue in the mesh body?

what happens if you "seperate" shells?  probably a cajillion bodies would be my guess.  might be able to help you narrow down where the issue is though.

even if you did create a solid first before export, you may have voids and other weirdness inside the body.  separate shells will help reveal these.

Also, fusion is perfectly happy to have solids share and edge, and to export them that way in the .stl.  This condiction gives mesh software (like mesh mixer) fits.

example of shared edge-

[RogerInHawaii]

It's a single solid body.

Where is there a "separate Shells" option? I don't see anything like that in the "Save As STL" dialog within Fusion, or in  Meshmixer.

And "look at it as an X-ray"? Where is that option?

[laughingcreek]

[RogerInHawaii]

What are the little red dots that appear when it's first brought up in Meshmixer (my first picture)? What do they mean?

The Pink "Floating Surface" errors all point at a particular point on the surface of the Bolt Head area. What is it actually telling me that's wrong with it? It's just a curved surface made from rotating a hemisphere.

[laughingcreek]

usually non-manifold edges

[Anonymous]

In Meshmixer the little red dots show non manifold issues. Either non manifold edges (more than two triangles share the same edge) or non manifold vertices (a triangle is connected to a closed surface but isn't a member of that surface). In these situations its hard to decide which triangles are the wrong ones. So MM deletes all (right and wrong) such triangles and fills the resulting hole doing a repair via Inspector.

The pink markers in Inspector point to small, isolated surfaces. This is meant to remove outliers dealing with scanning results. You may use the SmallThresh slider in Inspector to define what you consider as being small.

You may also consider to click the marker spheres one by one to repair only certain issues.