As we said before, the union is when you blend two or more 3D models together to create a new one. You need to make sure your files are not damaged, otherwise, the software won’t create the union.
A Boolean Union is when all the outside facets are linked together and, at the same time, all the internal ones are deleted.
Boolean Union
It joins together different parts, creating a whole, unique mesh with the correct properties for the 3D printer.
The Boolean Union deletes everything inside the joined items, including secondary walls or errors.
Let’s see an example:
if I combine 2 spheres together, the Boolean Union deletes the intersected part.
If you’re reading this, it means you already know about the previous lesson.
When you import two or more 3D models into MeshMixer, the Object Browser will open up. If it doesn’t, click on View > Show Object Browser.
Click on the W keyboard button and you’ll see the object in its true form:
Left-click on the objects, then hold shift: Edit menu will open.
Click on Boolean Union; another tab will pop up. The object view will change as follows:
Sometimes, the Boolean Union fails
This happens when the mesh composition is not correct.
It means, the 2 objects can’t blend well together.
Even if you wanna touch up the Boolean Union parameters, this won’t do well on the union, the result will be the same.
This is why you need to know another button, the Make Solid.
It changes the 3D model into unvarying meshes. They are evener.
Let’s see the example:
click on just one of the objects; in the Edit menu, click on Make Solid.
We’ll see better this parameter later. For now, let’s just write these numbers:
Solid Accuracy: 150
Mesh Density: 150
Click on Update, then on Accept.
Now, it’s crucial to understand that with the Mke Solid, the software has re-computed the mesh.
AS you can see, the meshes are thicker and evener.
Let’s do the same with the other object.
When your two 3D objects are ready, you can create the boolean.
Select both of the models > Edit > Boolean Union.
Another window will pop up, the same one at the beginning of this article.
These parameters are useful when you need to define the boolean.
Click on Accept.
The two objects will be correctly connected.
You’ll understand the difference between Combine and Boolean Union once you click on the object.
Now we can understand why these two pictures are different:
Combine 