Why use this? If someone sees the QR code on your thing in real life, they can find the design and make their own copies with just a photo of it. Theoretically, you could even assign this job to a machine, looking around the web (or your tool box) for things that can be duplicated.

pip install --upgrade https://github.com/l0b0/qr2scad/tarball/master

To install a specific version X.Y.Z (only 0.6.2 onward):

pip install https://github.com/l0b0/qr2scad/tarball/vX.Y.Z

1. Create an OpenSCAD file with your QR code:

    qr2scad < qr_code.png > qr_code.scad
   

2. include qr_code.scad in your OpenSCAD file.

3. difference the qr_code module from a flat surface.

4. Create the thing.

5. Use a marker, paint or other substance to fill the holes with a contrasting color.

6. Clean off excess color to get a crisp, scannable QR code.