Can you 3D print a STEP file? (No, you don’t need to convert it to STL)

Yes. If you have a STEP file — a .step or .stp straight out of Fusion 360, FreeCAD, SolidWorks or Onshape — it can absolutely be 3D printed, and you don't need to convert it to STL yourself first. Plenty of guides still tell you to export an STL before sending a part anywhere. That advice is out of date, at least here: you can drop a STEP file straight into the quote tool at /printing.html and get a price on the spot, exactly as if it were an STL.

Here is what the two formats actually are, why STEP is often the better one to send, and what to do if a file refuses to quote.

STEP vs STL: exact maths vs triangles

A STEP file is a CAD solid. It records the part as real geometry — a 10 mm hole is stored as a true 10 mm circle, a curved face as the actual curve, with proper units attached. It is the format CAD packages use to pass exact models between each other.

An STL is a mesh: the surface of the part approximated by flat triangles, and nothing else. No units, no true curves, no idea the part is solid. When you export an STL from CAD, the software chops every curve into facets at whatever tolerance you picked. Too coarse and circles come out visibly polygonal; too fine and the file balloons. Either way, the exact geometry is gone for good.

A printer does ultimately need a mesh — slicers work on triangles. The real question is who does that conversion, and how carefully.

Why this matters for replacement and functional parts

For a decorative model it barely matters. For a bracket that bolts to something, a bush that presses onto a shaft, or a lid that has to clip back onto the original enclosure, it matters a lot. A sloppy STL export can shave a faceted tenth of a millimetre off a hole and turn a sliding fit into a hammer fit.

Since most parts worth printing from CAD are exactly these — replacement parts and functional pieces drawn to measured dimensions — sending the STEP keeps those dimensions exact right up to the moment of printing. We do the mesh conversion in-house at a tolerance suited to the printer, not whatever a CAD export dialog defaulted to. STEP also carries real units, so the classic STL mishap of a part arriving at inch scale instead of millimetres simply can't happen.

What we accept

The upload form at /printing.html takes .step and .stp up to 50 MB, alongside STL and sliced 3MF as before. Exports from Fusion 360, FreeCAD, SolidWorks and Onshape are all fine — anything that writes standard STEP is. Parts up to 255 mm in each direction quote instantly, in any of our materials, at the same price as the equivalent STL. There is no surcharge for the conversion and no waiting for a manual review.

One tip: export just the part you want printed, not the whole assembly. A STEP containing one solid body converts cleanly and quotes in seconds; a fifty-part assembly leaves us guessing which piece you actually want.

If your STEP file won't quote

Occasionally a STEP file won't convert — usually a very complex assembly, a surface model rather than a true solid, or an export from an older CAD package. If that happens you'll see a clear message rather than a wrong price. Two ways forward: re-export just the solid body you need (in Fusion 360, right-click the body rather than the whole design; in FreeCAD, select the single Part object before exporting), or send the file over via /contact.html and we'll convert and quote it by hand.

And if you're not sure the part is printable at all, send it anyway. The quote costs nothing, and if something about the design won't survive printing we'd rather tell you before any plastic moves.