An STL (Stereolithography) file is a standard 3D file format that represents the surface geometry of a 3D object using triangular facets. It's one of the most widely used formats in 3D printing and computer-aided manufacturing due to its simplicity and universal compatibility across different software and hardware platforms.
The STL format works by approximating the surface of a 3D object with a mesh of triangular faces. Each triangle is defined by three vertices and a normal vector that indicates which side of the triangle is the "outside" of the object. The more triangles used, the smoother and more accurate the representation becomes, but the file size also increases.
STL files can be either ASCII or binary format. ASCII STL files are human-readable text files that list all the triangle coordinates, making them easy to inspect and debug. Binary STL files are more compact and load faster, making them the preferred choice for most applications.
When preparing a 3D model for printing, the STL file serves as the input for slicing software. The slicer reads the triangular mesh and converts it into the layers and toolpaths that the 3D printer will follow. The quality of the STL file directly affects the quality of the final print.
Common issues with STL files include non-manifold geometry (holes or gaps in the mesh), inverted normals (triangles facing the wrong direction), and overly complex meshes that can cause slicing problems. Most 3D modeling software includes tools to check and repair STL files before printing.
While STL files are excellent for 3D printing, they have limitations. They only contain geometric information and don't preserve other data like colors, textures, or material properties. For applications requiring this additional information, other formats like OBJ or 3MF may be more appropriate.
