Heavy metal

THE biggest engineering companies nowadays prefer to talk about “additive manufacturing” rather than “3D printing”. One reason is that printing is not quite the right word for some of the technologies given this label. Whereas hobbyist-scale 3D printers typically build a product by squirting out blobs of plastic, a technique called selective laser melting zaps successive layers of powder with a laser or ion beam, hardening only certain bits.

Another reason for being picky about terminology is that big companies want to stress the “manufacturing” aspect: the technology has moved beyond the development labs and is now being used on the factory floor to make complex metal parts. A pioneer in making the selective-laser melting equipment used in factories, SLM Solutions of Germany, will float on the Frankfurt stock exchange on May 9th.