Laarman’s studio, you might remember, unveiled a version of this machine last year that could print resin. But metal was a significantly taller order. What’s going on here, essentially, is high-speed welding in midair. This prototype can print steel, stainless steel, aluminium, bronze or copper, each of which comes out red-hot but fuses solid within a few minutes of cooling. The team calls it “anti-gravity additive manufacturing”.