STL, 3MF, STEP or OBJ: which format to send and why
What each format stores, which one loses information, which avoids the classic scale mistake, and which to send if you want the part fixable.
There are two families of format, and confusing them causes half of all problems. Mesh formats — STL, OBJ, 3MF — describe the object’s skin with triangles. Solid formats — STEP, IGES, your CAD’s native file — describe the mathematical surfaces and the operations that made them. A triangle cannot be turned back into a cylinder: which is why the loss only runs one way.
| Format | What it is | Stores units | When to use it |
|---|---|---|---|
| STL | Triangle mesh | No | The standard; fine if you export properly |
| 3MF | Mesh with metadata | Yes | The best mesh option |
| OBJ | Mesh, colour optional | No | Coming from Blender or a scan |
| STEP | Exact solid | Yes | If you want it to be fixable |
The short recommendation
If you work in parametric CAD — Fusion, SolidWorks, Onshape, FreeCAD, Inventor — send the STEP. It preserves the most information of the universal formats, does not depend on your software version and, above all, it lets the part be corrected: thickening a thin wall, filleting an edge or opening out a hole takes seconds on a solid and is a nightmare on a mesh. Send the STL as well and it is better still: one to show exactly what you expect, one in case something needs touching.
If you work in organic modelling — Blender, ZBrush — or you are coming from a scan, a mesh is what exists and that is fine: send 3MF if you can, and binary STL if not. There what matters is not the format but that the mesh is watertight with no inverted faces.
Do you accept STEP and native CAD files?
The configurator on the site works with STL, OBJ and 3MF, which is what it can preview and measure to price instantly. If what you have is STEP, IGES or a native file, send it through the contact form and we convert it at no charge: it beats a rushed export.
Is quality lost going from STEP to STL?
Always, because curves get approximated with flat triangles. What decides how much is the export tolerance: at 0.01 mm the loss is far below anything a machine can print, so it is irrelevant. At many programs’ default tolerance, a cylinder can arrive visibly faceted.
Can I send a SketchUp file or a PDF?
A SketchUp model can be exported to STL, though it is worth checking because the mesh often comes out open. A PDF, a DXF or a 2D drawing is not a 3D model: they describe outlines, not volume. A dimensioned drawing is enough to model the part from, but that is design work and is quoted separately.