Vishnu Ramasamy is well versed in working with 3D printers. He’s even worked on building one that is capable of 3D printing wind turbine blades. Now, he’s taking the next step, designing and building the Arc One, an open-source low-cost, modular machine that 3D prints metal using Wire Arc Additive Manufacturing (WAAM)—a production process used to 3D print or repair metal parts.