Additive manufacturing may have started with polymers, but production of metallic components is now the fastest-growing sector of the 3-D printing industry, according to a report by industry analysts Wohler Associates.

Sales of metal-based additive manufacturing (AM) machines rose to 348 in 2013 from 198 in 2012, an increase of more than 75%, says the Wohlers Report 2014, the latest edition of the company’s annual review of the 3-D printing industry.

"In some ways, metal AM has come further in 10 years than polymer AM has in 25 years," says the report, authored by industry consultants Terry Wohlers and Jim Caffrey. Production of aerospace components and orthopedic implants is driving demand.

More than 90,000 hip implants have been produced using metal AM, and beginning in 2015 GE Aviation will produce more than 30,000 fuel nozzles annually for the Leap-1 engine, the report notes.

"Additional opportunities for production metal applications will emerge, so this subset of the industry could possibly grow at a pace that this industry has never seen," Wohlers says.

Globally, the market for additive-manufacturing products and services grew 34.9% in 2013, to an estimated $3.07 billion, the report says. This compares with growth of 32.7% in 2012, 29.4% in 2011 and 24.1% in 2010.

"The past four years are up significantly from previous years, and the market has nearly tripled over this period of time," Wohlers says, forecasting continued strong growth.

The 2014 report projects worldwide AM sales will exceed $7 billion by 2016 and more than quadruple to about $12.5 billion by 2018.

A limitation on adoption by the aerospace industry has been the size of components that can be produced additively, but machines with larger working volumes are becoming available.

Aerojet Rocketdyne has purchased three large selective laser melting machines under a new U.S. Air Force contract to design and demonstrate large-scale AM parts for liquid rocket engines.

The company has purchased two Concept Laser X Line machines with a 600 x 400 x 500-mm (roughly 25 x 16 x 20-in.) build envelope and one EOS M400 with a 400 x 400 x 400-mm working volume.

Sciaky, meanwhile, has received the first order for its electron-beam additive manufacturing system, from an unidentified major aerospace parts maker. The system has a 110 x 110 x 110-in. build envelope.