AUTOMOLD3D · BLOG
How to Repair a Non-Manifold STL for 3D Printing
Non-manifold edges can make a slicer or mold workflow ambiguous, so inspect the mesh before attempting a repair.
Start by locating open boundaries, intersecting shells, and zero-thickness areas. A mesh can look correct in a viewer while still containing topology that has no unambiguous inside and outside.
Use an automated repair pass only for small gaps or simple welding problems. If a repair removes fine features or changes a scanned surface, compare the result with the original before exporting it.
Validate the repaired mesh in the preview and open the exported STL in your slicer. A watertight result is useful, but it is not a substitute for checking scale, orientation, and printable wall thickness.