While PrusaSlicer can automatically repair many common issues with 3D models, you may encounter occasional problems that the software cannot resolve.
Parts Too Thin to Print
If a 3D model appears fine when viewed in the 3D Editor View in PrusaSlicer, but certain parts of the model are missing in the sliced Preview view, it's possible that those parts are too thin to print.. On our Prusa printers, the minimum size for vertical perimeters is about .3mm.
One solution is to scale the entire model to a larger size in PrusaSlicer until all parts are large enough to appear in the sliced Preview view.
If scaling the whole model up is not option, you may need to bring the file into a modeling program to edit the parts that need to be thicker.
Non-Manifold / Holes in Mesh
This Sculpteo page defines non-manifold objects in the following way:
"Without getting very technical, non-manifold geometry is a geometry that cannot exist in the real world. Meaning that a 3D model can be represented digitally, but there is no geometry in the real world that could physically support it. Since the mesh of the 3D model is defined by edges, faces, and vertices, it has to be manifold. If it is a non-manifold mesh, it means there are errors in the 3D model that cannot define with precision the geometry of the 3D model."
Image courtesy of Sculpteo
Non-Manifold also refers to objects, like the one below, which have holes in the mesh. Since the walls of the mesh do not have a defined thickness, the holes make it so the object cannot exist in the real world. Repairing these holes can be done automatically in PrusaSlicer, but depending on the model, it may sometimes be preferable to repair holes in a separate software.
Image courtesy of 3D Hubs
File Size Too Large
Another issue happens when trying to work with a very large file into PrusaSlicer. This can cause PrusaSlicer to run slowly, and potentially lengthen the printing time.
As explained by 3D Hub: "A mesh is 'over-refined' when the total number of triangles of the STL mesh is larger than required. This will not lead to any errors during 3D printing, but it will unnecessarily increase the size of the STL file, making it more difficult to handle. Usually, the tiny details that are represented by an over-refined mesh cannot be 3D printed, as they exceed the capabilities of most systems (in terms of accuracy and minimum feature size)."
PrusaSlicer has a built in feature, called Simplify model that can directly reduce the triangle count of any STL file. However, it may sometimes be preferable to simplify the model in a program like Blender, where you will have more options for fine tuning the model.
Image courtesy of Pinshape
Flipped / Reversed Normals
This LulzBot tutorial explains reversed normals in the following way:
"Every plane composing each shell of a 3D model has an intended inside and an outside, called a 'normal.' When a plane’s orientation is reversed in relation to those around it, it’s referred to as a 'reversed normal.' This becomes an issue when it occurs unintentionally within a model, and ranges from a tiny section of a shell, to intersecting shells of a complex multi-shell model, to an entire model with a single shell that is all reversed.
Reversed normals in the sphere on the side of the cylinder have caused inaccurate slicing that creates an unintended void."