You cannot get adequate tolerances with 3D printers. Typical 3D printing tolerances are +-0.1mm. Lego bricks are trashed at the factory if they're off by more t

You cannot get adequate tolerances with 3D printers. Typical 3D printing tolerances are +-0.1mm. Lego bricks are trashed at the factory if they're off by more than 0.02mm, and 99.9% of pieces are within 0.001mm. This is crucial for making any brick connect to any other brick. You might be able to make a handful of bricks that connect to each other in 1 configuration on a 3D printer, but you're not going to be able to make multiple batches of bricks that fit together in any configuration.