A broken file in, a closed solid out.
Every defect /tools/model-check reports — holes, inverted faces, edges shared by three faces — is fixed as soon as you drop the file. Then you set it up for the print: which face goes down, how big it is, where to cut it to fit the printer, and whether it needs pins to go back together.
How it works
Fixes in the right order, then manifold checks.
Corners within 10 nm are welded, then collapsed and duplicate triangles go. Each shell is then walked across its shared edges so every triangle faces the same way, and turned over whole if its volume comes out negative. Edges used by three or more faces (two bodies touching along a line) are unzipped and re-paired by angle round the edge. Remaining holes are capped with the triangulation of least total area (Liepa's method), never folded back over the face next to them. Finally, overlapping shells are merged with manifold-3d's union.
An inside-out shell sitting wholly inside a bigger one is left as it is: that is a hollow on purpose, like a resin print's drained interior, not a mistake. Everything after that — scale, mirror, turn, simplify, cut, pin holes, split — is a manifold-3d operation on the repaired solid, so the result is always closed.
Checked on 500 deliberately broken files — holes punched, up to a fifth of the triangles flipped, faces doubled, collapsed triangles added, two bodies set edge to edge, whole files turned inside out — made from simple solids, gears, trays, Gridfinity bins and ZORVA's own models. 499 came out as clean closed solids; the last was closed and accepted by manifold too, but the checker found one edge shared by four faces. The operations were checked on 500 more combinations: every part closed, on the bed and apart from the others, and no volume lost to a cut beyond the pin holes.
Which defects can it fix?
Holes in the surface, flipped triangles, whole shells turned inside out, duplicate or collapsed faces, bodies touching along an edge, and shells pushed into each other. It does not guess at missing geometry: a big hole in a curved surface is capped with the tightest surface across its rim, not the original curve.
Which face should go down?
Usually the biggest flat face: it grips the bed and needs the least support. But layers are weakest along Z, so a part that bends under load — a hook, a bracket — should be laid so the load runs along the layers, even if that costs supports.
How much pin clearance?
0.15 mm per side for a hand-press fit on most FDM printers; 0.1 mm for a tight fit to glue later; 0.2–0.25 mm if your printer prints small holes undersize. Pins print upright, 0.6 mm shorter than the two holes together so the halves close flush.