How to Prepare an STL File for Printing

A little preparation makes your STL cheaper and quicker to quote and avoids surprises. Here is a practical checklist.

1. Make sure it is watertight

The mesh should be a closed, solid surface with no holes or gaps — what is called manifold. Non-manifold meshes confuse slicers. Most CAD tools have a check-and-repair option; run it before exporting.

2. Get the scale and units right

STL does not reliably store units, so a model can arrive ten times too big or too small. Note the intended real-world size when you send it, and if your software lets you set export units, use millimetres.

3. Consider wall thickness

Very thin walls may not print well or may be fragile. As a rough guide, keep functional walls at least around 1–1.5 mm. If in doubt, send it anyway and we will flag anything too thin.

4. Think about orientation and overhangs

You do not have to orient the model yourself — we do that to balance strength, finish and supports — but be aware that steep overhangs need support material, which adds cost.

5. Export at sensible resolution

Export with enough triangles to keep curves smooth, but you do not need an enormous file. Somewhere in the low-to-mid megabytes is usually plenty.

Not sure about any of this? Send the file as-is. We check every file for printability and tell you what, if anything, needs attention.

Upload your STL.