Blender: modelling and sculpting for 3D printing

What Blender is good and not so good at

Blender is run by the Blender Foundation and is free for any use. It is excellent for sculpting, characters, figurines and any freeform shapes. It works with a polygon mesh, which is why digital sculpting fits it too.

It is not suited to precise engineering parts with toleranced dimensions. CAD programs such as FreeCAD or Fusion are better for that.

Units and scale

The most common mistake from Blender is the wrong size. Blender works in metres by default, so a model with a size of 1 can be exported as one metre or one millimetre, depending on the settings. Set the units to millimetres in the scene settings and check the scale on export. After uploading, check the size, and if it is wrong you can fix it with the scale option in the calculator.

The mesh must be closed

Sculpting and boolean operations easily produce holes, overlapping faces or faces with flipped orientation. For printing the model must be manifold. In Blender the 3D Print Toolbox add-on helps, which finds errors and fixes some of them. We repair small holes automatically after upload, but for bigger errors we will write to you.

Export and your order

Sculpting and modifiers such as Subdivision or Boolean can leave faces with no thickness, flipped normals and unwelded points. The slicer then cannot tell which side is the inside. Mesh, Clean Up, Merge by Distance and a check of the normals help. Watch out for modifiers that have not been applied too: if you do not apply them before export, they may be missing from the file.

Thin parts such as the ears or fingers of a figurine hold up better when they are at least 1 mm thick. More about this limit is in the entry on smallest feature.

From Blender export STL if one colour is enough, or 3MF if you want several colours. Colours in 3MF must be assigned in a way the slicer recognises, otherwise the part prints in one. Very thin details, such as hair on a figurine, will not print with a 0.4 mm nozzle, so thicken them before export.