What is a messy mesh?

A messy mesh means that there are errors in your 3D design (specifically what we call "non-manifold" mesh errors) which mean your part can’t be 3D printed. There can turn up in several different forms (you can see the whole list here) but typically it means there are holes, internal faces or extra edges in your mesh which shouldn’t be there.

How can I find out where the errors are?

Sometimes these errors can be super tricky to find - they might be very small features, or completely hidden from view (like internal walls). Depending on the software you’re using, there are a few neat tricks you can use to help you locate the issue.

For all STL files, we recommend Netfabb - just follow our tutorial here.

There’s also a few software-specific tools which can help:

Sketchup - Solid Inspector plugin. Note: If you want to export your DAE to STL for checking with netfabb, make sure you scale up your design in mm.
Blender - Ctrl-Alt-Shift-M (selects all non-manifold vertices) You can then use “.” on the numpad to view the selected vertices.
3DS Max - STL check modifier.
Rhino -  CheckMesh & associated tools

How can I fix it?

The best way to fix your STL files depends on the software you’re using. For programs like Blender and SketchUp, it’s often easier to just delete the areas with errors in them and re-build the geometry by hand.

In all cases, your best defense against a messy mesh is to keep it in mind from the beginning, and make sure your mesh is clean and manifold throughout the modelling process.

For most STL files, we recommend using Netfabb to repair messy meshes - just follow our tutorial here.

Some software packages such as Solidworks and Alibre are what we call “solid modelers”. These, by definition, create meshes which are free of messy mesh errors. On the rare occasions that they do occur, we recommend using Netfabb to find and repair.

If you’ve got any useful hints or tips for finding and repairing non-manifold meshes, feel free to share!