Sometimes there can be major errors in your 3D model, like two facets intersecting each other.
An intersection is when two elements are joined together.
Let’s see the following example.
We have this “T” shape that has some cross facets.
This item is made up of one horizontal part and another vertical one. When these two elements are perfectly combined, you’ll notice how some internal facets get deleted in favor of a good union.
The following picture shows the inner part of our joined T shape.
You’ll notice that there are some useless facets.
We’re gonna have them deleted because it’s for the best to have a unique and connected internal space.

Everything inside your 3D model is an error unless you purposely make it for a specific aesthetic effect.
That’s why it is crucial to design properly at the beginning.
MeshMixer detects the error and, if it’s not something major, the slicer will automatically correct it.

How can we correct it?
Let’s see another solution with SketchUp.
Import your model. In My case, I’ll just import my T-shaped item.
Delete one facet, just like in the picture below. This way you can see the insides.
What we notice is that there are some useless meshes in it.

This exercise is useful to understand that what you blend in together is not always correct. You always need to check the internal facets, just to make sure everything is okay.
It’s best to delete the useless facets before the actual union.

Another problem is when two items are overlapping one the other.
At first sight, you may not notice the problem, because it doesn’t show on the outside.
The overlapping creates a sort of void between the elements.


When you’re designing your object, always make sure not to leave worthless parts behind because they’ll lead to problems in the slicing phase.
See as follows:

In the picture above, two objects are overlapping, but they’re not combined together.
To blend them together, select both the items, then right-click > Facets Intersection > Selected.
Now you can check the insides and delete what is useless.
Please, notice how we go from the first pic, the “wrong” one to the second and correct one:


The third error we’re talking about can be seen from your normal point of view.
Make sure that everything in your model is linked together.
Avoid situations like this one:

It looks like a stupid error and that’s exactly what actually is: a stupid error.
Usually, it’s done by beginners because they forget to check up on everything and they discover the error in the slicing phase.
This article was about the errors of the intersection.
Leave a comment if you found it useful!