Short answer: send a STEP file if you can. Use 3MF for full-colour parts. A high-resolution STL is fine too, and we can convert most native CAD formats. All of these can be uploaded to our instant quote.
| Format | Use it for | Notes |
|---|---|---|
| STEP (.step / .stp) | Preferred for MJF and FDM parts | Exact geometry. We control the print resolution, and fine features such as threads and small holes come through accurately. |
| 3MF | Recommended for full-colour parts | Carries colour, units and geometry in one file. |
| STL | Fine for single-colour parts | Only as good as its export settings. Use high resolution (see below). |
| OBJ | Colour parts, if 3MF is not available | Include the texture and material files with it. |
| Native CAD | SolidWorks, Inventor, Fusion 360, Catia and others | We can usually convert these. Ask if unsure. |
Why we prefer STEP
A STEP file describes the true shape of your part, with real curves and surfaces. An STL is a mesh of triangles, a faceted approximation fixed at the moment it was exported. With STEP we choose the right mesh resolution for printing, so curves stay smooth, holes stay round and threads keep their form. It also makes it easy for us to check dimensions and spot design issues before printing.
When to use 3MF
For full-colour parts on our HP Jet Fusion 580, 3MF is the best format. It holds the colour or texture information alongside the geometry and units, in a single file. A plain STEP or STL has no colour data, so it will print white or in a single colour.
If you send an STL: export settings
Low-resolution STLs are the most common cause of faceted curves and poor small features. HP recommends these export settings:
- Chord height (deviation): 0.05 mm or finer
- Angle tolerance: 1°
- Units: millimetres
If your CAD system offers a "fine" or "high" quality setting, use it.
Common file problems that delay orders
- Wrong units: a part exported in inches but read as millimetres comes out 25 times too small.
- Coarse STLs: visible facets on curves and holes.
- Thread call-outs instead of modelled threads: cosmetic threads in CAD do not print. See TN-001 and TN-002.
- Several parts in one file: send one part per file, or tell us the quantity of each.
- Open or broken meshes: we can usually repair these, but a STEP file avoids the problem.
Tell us what the file can't
A file shows shape, not intent. Alongside it, tell us your cosmetic (A) surfaces, critical dimensions, finish and quantity. Our TN-006 guide to design and specification explains why this makes a better part.