Programs needed: SketchUp and MeshMixer. 

Subjects: holes closing, appropriate elements interjection, facets reversion. 

Goal: Slicing Errors Correction. 

Sometimes, MeshMixer alone is not enough to correct a corrupted file. 

A 3D printing technician would say: First, correct it, then I’ll print it for you

Now we can say: I’ll do it!

That’s why you need a software that allows you to modify the 3D.STL file, letting you add dots and lines and mesh according to your needs. 

Let’s introduce software that can partially touch up the file. 

We’ll see in the future what to do with serious 3D object errors.

SketchUp can help you correct the item for the 3D printing. With this software, you can delete unnecessary dots and lines and switch Normals. 

As we said before, a mesh has to have an insider and outsider side. Another crucial thing is that these two sides must be kept separated. It means you must be careful not to have holes in your model. 

There are few rules about how to build a good 3D printing file, you can find them in one of my previous articles. 

Filling the holes in the 3D model

First rule: the inside and outside of the model must be divided. It means, no holes allowed. 

If there’s a hole in your 3D model, it’s an error! 

You’ll recognize the hole because MeshMixer surrounds its perimeter with a blue color. 

The following pictures show how holes are viewed inside SketchUp:

Pierced Sphere
Draw a line like this one to close the hole.
Partially Closed Hole
Filled up Hole

Why couldn’t we repair the hole with MeshMixer?
Because the holes might be more than the software can handle.

Elements Intersection

The second rule is the inner space of the solid must be only one. 

This means there cannot be lines inside nor other facets. 

If you find these elements inside your 3D model, you must delete them. 

This sphere was divided to see the inside (pink part)

The following pictures show how we correct the problem inside SketchUp:

Internal Facets, inner view.
Partially deleted internal facets. Inner view.
Clean Internal Facets. Inner view.
Selection Tool: allows you to select the parts you want to delete.

Once you’ve selected all the elements you want to delete, click on CANC.

Facets Reversal

The third rule is that a solid must have ONE inner facet and ONE outer facet. There cannot be one mesh with 2 inside or outside facets.
The inner part is colored in pink, the outer part is gray/black.

Reversed Facets inside MeshMixer.

This is how SketchUp deals with the problem:

Light blue parts: inverted facets
Right-click on the facets and select Inverti Facce
Facets correctly inverted.

Sometimes, before you repair your object with SketchUp, you can have them checked by Cura. Otherwise, you import it into MeshMixer and correct the errors.

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