STL file 3D models often peel in Prusa due to non-manifold geometry (e.g., edges shared by more than two faces) or flipped face normals—both disrupt the slicer’s ability to generate correct print paths.
Non-manifold meshes have invalid edges or "holes" the slicer can’t interpret, leading to uneven layer adhesion. Flipped normals make the model appear inside-out, causing incorrect extrusion that results in peeling.
Fix the issue by using Prusa Slicer’s built-in "Repair" feature or free tools like MeshMixer to correct the STL’s geometry before printing—this simple step usually resolves peeling.