STL, STEP or OBJ: which CAD file do you actually need?
The three formats every jewellery project ends up asking for — what each one is good at, and when to request which.
Every finished commission is delivered as a set of files — but not all files do the same job. Choosing the right format up front saves a revision round and makes sure your caster or printer gets exactly what they expect.
STL — the workhorse for printing and casting
STL describes a model as a mesh of triangles. It is the universal language of 3D printers and most casting bureaus. If your goal is to grow a wax or resin pattern and cast a piece, STL is almost always what you hand over.
The trade-off is that a mesh has no notion of a clean curve or an editable feature — it is a fixed surface. Ask for an appropriate resolution: too coarse and you see facets on a polished band; too fine and the file balloons for no benefit.
STEP — the choice when the model must stay editable
STEP is a precise, solid CAD format. It keeps true curves and parametric-quality geometry, which matters when a manufacturer needs to tweak a prong, adjust a shank, or verify tolerances. If your workflow passes through professional CAD/CAM, request STEP alongside your STL.
OBJ — when colour and presentation matter
OBJ carries mesh geometry like STL but can also reference materials and texture, which makes it handy for renders and client-facing previews. It is a presentation and interchange format more than a production one.
A simple rule of thumb
- Casting or 3D printing a physical piece → STL.
- Handing to a manufacturer who will edit the geometry → STEP.
- Rendering, marketing images, or design review → OBJ.
Not sure? Tell us how the file will be used when you submit your brief and we will recommend — and deliver — the right set.
