OBJ file: what it is and how to print it

What is inside an OBJ file

The OBJ format was developed in the 1980s by Wavefront Technologies for its animation software. It is a readable text file of the points and faces that make up the surface of a model, in other words a polygon mesh.

An OBJ often comes with an .mtl file of materials and images with textures. These are used to show colour in graphics and games. Like STL, OBJ does not store units. The Library of Congress also has a description of the format.

When to send OBJ

OBJ is fine when the model was made in Blender or ZBrush, or comes from a 3D scan. You upload it just like an STL, pick a material and strength, and see the price straight away.

We do not use the textures and colours from the .mtl file for printing, we print the shape. If you want a part in several colours, save it as a 3MF and assign colours to the individual parts of the model.

What to watch out for with OBJ

• Units. Blender works in metres, so your model may arrive a thousand times too small. You can fix it with the scale in the calculator.
• A closed shape. Models from graphics software are often just surfaces with no thickness, such as thin leaves or hair. The printer needs a closed solid with a wall of at least about 1 mm. We repair small holes in the mesh automatically.
• Large scans. We accept a scan with millions of faces up to 50 MB. If it is bigger, simplify the mesh. With a 0.4 mm nozzle you will not see the difference in the print.