Script Automates STL File Validation Before Sending to Manufacturers

Engineers often lose days to back-and-forth emails when STL files sent to manufacturers contain fixable errors such as non-watertight geometry, missing units, or flipped normals. The STL format stores only a flat list of triangles with no topology, unit declarations, or enforced normal direction, making these errors invisible inside CAD software but problematic during manufacturing. A roughly 150-line Python script using the trimesh library can automatically detect these common issues in milliseconds. The script checks for open edges indicating holes, infers unit mismatches that could shrink a 60 mm part to 0.06 mm, and validates surface normals. It exits with a non-zero status on failure, making it suitable for direct integration into a continuous integration pipeline.