OBJ to STL

From OBJ to STL for printing

OBJ is a very common format in 3D modeling, animation and video games. Many slicers open it, but STL is still the one everything accepts: printers, print shops and model sites.

The tool turns the OBJ's faces (triangles, quads or polygons) into triangles and gives you a binary STL. Textures and materials are ignored, because the printer only needs the shape.

The two things that usually go wrong: unit and axis

The unit. OBJ doesn't say whether its measurements are millimeters, centimeters or meters. Blender, for example, works in meters: a 10 cm figure can arrive as "0.1" and look tiny. That's why you see the size live and can change the unit until it matches.

The axis. In 3D printing, up is the Z axis; in Blender and video games it's usually Y. If your model comes out lying down, check "Stand it up" and it stands on the bed.

Before printing

A model made for animation or games isn't always a closed solid: it can have holes, loose faces or walls with no thickness. The tool checks the mesh and warns you if it has holes; many slicers repair them automatically, but a model made for the screen may need fixing in a modeling program.

Tips

• Blender can export STL directly, but if you already have the OBJ, you can convert it here without opening anything.
• If the size looks off, try the units in this order: millimeters, meters, centimeters.
• Game models often have zero-thickness walls (just a surface). Those can't be printed as they are, even if the STL looks fine.
• If the warning says the mesh has holes, the repair button in PrusaSlicer or Bambu Studio usually fixes it.

Frequently asked questions