How to Prepare an STL File for 3D Printing

You’ve modelled your part and exported an STL. Before you send it to print, a few quick checks save you a reprint — and most print problems start in the file, not the machine. Here’s the short checklist we wish every file passed.

1. Get the units right

The single most common mistake: exporting in the wrong scale. An STL has no built-in units, so a part modelled in millimetres can arrive looking like it’s in inches — 25× too big. Always confirm your model is in millimetres and note the intended size when you send it.

2. Make the mesh watertight

A printable mesh must be “manifold” — a fully closed, solid surface with no holes, flipped faces or gaps. Most slicers choke on a mesh with holes. Most CAD tools have a mesh check / repair option; run it before exporting.

3. Respect minimum wall thickness

Walls thinner than ~0.8–1.2 mm may not print reliably (or at all). If your design has fine details or thin shells, thicken them or tell us the finest feature so we can advise. Text and engravings should be at least ~1 mm deep/wide to show up cleanly.

4. Design in tolerances for fitting parts

If two printed parts need to fit together — or a print needs to slot onto something — leave a small gap (typically 0.2–0.4 mm of clearance). A model that’s dimensionally perfect in CAD will often be too tight once printed, because of normal material expansion.

5. Think about orientation and supports — or let us

How a part is oriented on the bed affects its strength, surface finish and how much support material it needs. This is the fiddly part — and it’s exactly what we handle for you. You don’t need to orient, add supports or slice anything. Send the raw STL and we’ll prep it properly.

What file formats can I send?

STL is the standard, but we also accept STEP and OBJ. No file yet? Send a clear reference image or a link and we’ll help from there.

Send it over

Run those five checks, then send your file — we’ll quote from the real geometry and flag anything that needs a tweak before we print.

Send your file for a quote →