STL
The most common format. It describes the surface as a triangular mesh without units or colour. This is entirely sufficient for a single-colour part. Export at a fine enough resolution to keep curves smooth, and use millimetres.
OBJ
Similar to STL, with optional colour and texture information. We use its geometry for FDM printing. Upload associated files together if your OBJ refers to a material file.
3MF
A modern format that stores geometry, units, colours and several parts in one file. If your software exports 3MF, it is often the cleanest choice, especially for multi-colour models.
STEP and STP
The exchange format used by CAD applications. It describes exact surfaces and edges instead of a triangular mesh, so there is no resolution loss. You do not need to convert STEP to STL; upload it directly. It is ideal for technical parts with exact dimensions.
Recommendation
- From a CAD application: STEP
- Multi-colour model: 3MF
- Single-colour model from a download source: STL
- Where possible, upload one closed solid per required part