A typical extrusion-type 3D printer is comprised of the extruder itself, a build platform where material is deposited, and some sort of movement system that covers each of the three axes. On a Cartesian layout, that movement is linear on rails, and motors pull belts to slide the extruder or build platform left to right, front to back, and up and down. Robot arms can be used in place of a rigid linear system like that, but are confined by their reach. Now, roboticists from Singapore’s Nanyang Technological University have built ambulatory robots that can cooperate to 3D print large structures.
The problem with a traditional Cartesian 3D printer is that it can only make parts that are smaller than itself, because those linear rails have to cover the entire build envelope. Printing an large structure like a building requires an even larger gantry setup, or an enormous robot arm. That’s expensive, and moving the printer or finished building afterwards is very difficult. These robots solve that problem by working together and moving around as necessary to print a structure.
Each robot is a large arm mounted to a mobile base. In place of a conventional end effector, the arms have a nozzle for extruding concrete. The work of printing a complete structure can be divided up between multiple robots, which will then move from one location to another extruding concrete. It’s essentially the robotic version of a team of masons building a wall. While the robots are constrained by how high they can reach, that can be solved with the use of scaffolding like what is common in traditional construction.