Here is a cool 12 meter steel pedestrian bridge that was 3D printed by robots. It is also fitted with smart sensors. Dutch designer Joris Laarman worked with MX3D to build this bridge which will eventually span a canal in Amsterdam. For this project, 6-axis robots were used to build the structure in the air from molten steel.
It took 6 months to complete this using 4 robots. The above video shows what it took to complete this.