3D print a QR code sign that actually scans
A 3D printed QR code needs enough contrast and large enough modules to survive the printing process. A visually attractive code can still fail if the individual features are too small or merge together. Always test scanning before committing to the final print.
Contrast
Use strong light/dark contrast.
Module size
QR modules are small square features. If they become too small for the nozzle and slicer, the code can lose readability.
Quiet zone
Keep sufficient clear space around the code.
Test before final print
Use the generator's fit/size warning and test the actual scan.