3DM File
Also called .3dm, rhino file
A 3DM file is the native save format of Rhino, the CAD program most jewelry designers work in. It stores exact NURBS surfaces along with layers, object names, and units, which makes it the richest file a jeweler can hand to a render studio.
In other words, it is the working Rhino document itself, not an export, so nothing has been simplified or thrown away on the way out.
What makes 3DM different
STL and OBJ are meshes: the smooth surface has already been chopped into flat faces. A 3DM keeps the original NURBS surfaces, which are defined by maths rather than by triangles, so a curve stays perfectly curved at any zoom level.
It also keeps the structure of your work. Layer names, object names, groups, and units all travel with the file.
- Exact NURBS surfaces instead of an approximated mesh
- Layers and object names, so parts are already separated
- Units, so the ring arrives at the size you built it
- Any construction curves and reference geometry you left in
Why we prefer it
When a 3DM comes in with layers named shank, head, centre stone, and pave, half the setup is already done. We assign metals and stones to those layers rather than picking surfaces out one at a time.
Because the surfaces are exact, we also control how finely they get meshed for the render at our end, instead of being stuck with whatever resolution an STL export baked in. That is what keeps a polished band reading as glass-smooth at full resolution.
3DM is one of the four formats we accept, with STL, OBJ, and STEP. If you work in Rhino, MatrixGold, or RhinoGold, just send the 3DM.
Questions about 3DM File
Can you open a 3DM file?
Yes. 3DM is one of the four formats we accept and usually the one we prefer, because it keeps exact surfaces, layers, and units.
Should I export to STL before sending my Rhino file?
No need. Sending the 3DM directly keeps more information than an STL export, and it saves you a step.
Which Rhino version should I save in?
Any recent version is fine. If you are unsure, saving a version or two back is a safe habit for any CAD handoff.