Repair an STL File for 3D Printing

The first thing to do is to go into the Facets tab and select Check mesh in the Clean Up Section. Then, by clicking on the mesh you want to check, you get all the errors that are detected in your mesh. Here we have:

• An object with multiple pieces

• A self intersecting mesh

• An over connected mesh

• Non manifold vertices

These two last points are linked and basically mean that there are non manifold parts in the mesh. 

We are going to solve these issues one by one.

First, we are going to separate all the pieces in this mesh by hitting Separate All in the Organize section.

The initial mesh is now separated into 6 smaller meshes. There are two different types of icon in the structure tab: meshed cube and meshed surface. A surface icon indicates that the corresponding mesh needs repairs.

So we check the first problematic mesh, which is the car, and the Check Mesh tool indicates that there are multiple pieces and non manifold parts. 

By zooming in, we can see that the 4 square wheels are linked to the body only by edges which is not possible in real-world objects.

You might think that the Auto Fix tool would solve everything for you but this is actually not very efficient. 

Here, the problem is not really solved as the car’s body is still linked to the wheels only by edges.  

So we need to solve this problem manually. To fix this issue, we can convert this mesh to a solid with merged faces. Choosing separate faces would create one solid for every single face.

By pulling the body down, we make it a manifold solid.

When we turn it back to a mesh, we have no issues anymore according to the Check Mesh Tool.

Now, we need to solve the issues linked to the other surface mesh. The Check Mesh tool indicates that there are multiple pieces, self intersecting objects and non manifold vertices.

By clicking on the Intersections tool and then on the mesh wewant to clean up, intersecting parts appear.  

When you hit the green check box, SpaceClaim solves the intersection issues.

It seems that all the meshes are clean.

But keep in mind that SpaceClaim can only spot mesh errors and not modeling errors. For instance, the bridge support does not touch the arch and is thus useless for the solidity of the structure.  

We convert the support to a solid and pull it until it is in the middle of the arch. By converting it to a mesh again and using the Merge tool in the Modify section, we avoid any self intersecting issues.

The only remaining step is to combine meshes that are in contact. At the end, we have two remaining meshes: the sphere that is inside the box and the rest of the bridge. Our STL file is ready to be printed.