Although they're still far from being common, 3D-printed metal bicycle frames do now exist. Usually they're made using a sintering process, in which a laser is utilized to selectively melt steel powder, building it up in successive layers. Now, however, a team of students at the Delft University of Technology (TU Delft) in the Netherlands has taken another approach – they've created the world's first stainless steel bike made via a welding-based 3D-printing technique.

The students worked with Amsterdam-based company MX3D, which helped bring us the Mataerial 3D printer in 2013. Unlike traditional 3D printers, which build up objects horizontally on a flat stage, the Mataerial uses a robotic arm to extrude resin onto horizontal or vertical surfaces. Those columns of resin can be curved and linked together as they're being extruded, quickly hardening into modern art-like creations.

More recently, MX3D created a version that "prints" in welded metal. It starts by laying down a blob of molten metal, then adds another blob on top of it once it's hardened, and continues that process until it's created an entire metal column. By controlling the point in space at which the welds are made, it's possible to control the orientation of the columns, even getting them to interlace with one another. No supporting materials are needed, and quite large structures can be created.

MX3D is already using the technique to build a pedestrian bridge, but it approached TU Delft about the possibility of doing something else to demonstrate the potential of the technology. The bike was the result. Its frame was built in several main sections, which were then welded to one another by hand.

A detail of the Arc Bicycle TU Delft

Called the Arc Bicycle, the finished product is claimed to weigh about as much as a traditional steel-framed bike, and is fully capable of being ridden on rough cobblestone streets.

"It was important for us to design a functional object that people use everyday," says team member Stef de Groot. "Being students in the Netherlands, a bicycle naturally came to mind. A bicycle frame is a good test for the technology because of the complex forces involved."

The Arc Bicycle can be seen in action – and being created – in the video below.

Sources: TU Delft, MX3D