FREDPublished on September 3, 2026
Print-ready STL files: the checklist before selling a 3D model
A model that looks fine on screen isn't necessarily printable — and a model that printed once isn't necessarily printable at scale. Before selling a file through 3D printing on demand, run through this checklist.
A watertight mesh
The slicer needs a closed volume: no holes, no flipped normals, no non-manifold edges. Automatic validators — FRED analyzes every file at upload — catch these defects, but it's better to fix them at the source in your CAD software or with a mesh repair tool.
Printable walls
In FDM with a 0.4 mm nozzle, aim for at least 1.2 mm wall thickness (three perimeters) on load-bearing areas, and never below 0.8 mm. Details finer than the nozzle will vanish or weaken the part.
Design for orientation and supports
A part designed to print flat, without supports, costs less (less material, less machine time) and comes out cleaner. Overhangs beyond 45° need supports: if your design can avoid them — chamfers instead of ledges, splitting into two parts to assemble — your production price drops accordingly.
Tolerances and assemblies
For parts that fit together, allow 0.2 to 0.4 mm of clearance depending on the fit. Test the assembly on a real print before selling: PLA shrinkage is small but not zero.
One last check: make sure the part fits the target build volume and that the file is at the right scale (STL carries no unit — a model in inches arrives 25.4× too big).