British futurist and author of 3D Printing: The Next Industrial Revolution, Christopher Barnatt, shares his thoughts on the technologies utilized in 3D printing of high grade metals, specifically laser sintering, binder jetting, and electron beam melting (EBM).
Engineering.com: Thank you Christopher for discussing the various technologies in 3D printing of metal components with our readers.
Can you give an overview of the technologies for 3D printing of metals and their respective pros and cons?
Several technologies are now available that permit additive metal manufacturing (AMM). While different manufacturers have their own trademarked names for the processes involved, generically three of the most common are laser sintering, binder jetting, or electron beam melting (EBM).
All of these 3D printing methods lay down successive layers of a metal powder that has some of its granules fixed together to form the final object. In laser sintering (or one of its proprietary derivatives) a laser beam heats the powder granules to selectively fuse them together. Meanwhile in the binder jetting metal printing process pioneered by ExOne, a binder is selectively sprayed onto layers of a stainless steel, bronze or tungsten powder. The resultant green object is then cured, before being placed in a furnace where it is infused with additional molten metal.
Metal objects produced via laser sintering or binder jetting technologies are very strong and have many industrial and creative applications. This said, they not 100 per cent dense. Electron beam melting (EBM) solves this potential problem by using an electron beam rather than a laser to selectively fuse together layers of powdered metal.
EBM 3D printers have been pioneered by a Swedish company called Arcam, and achieve very high quality results by building fully dense metal objects layer-by-layer in a vacuum. The electron beam makes multiple passes of each object layer, (first outlining object layers and then filling in their bulk), and is moved around via electromagnetic deflection. The latter makes EBM more accurate than laser sintering, as the later relies on a mechanical process to constantly reposition mirrors that guide the laser beam. In addition to Arcam, NASA has also experimented using an electron beam for additive metal manufacturing, with its engineers terming the technology electron beam free form fabrication(EBF3).
The EBM process is restricted to high-value build materials, including several grades of titanium and cobalt-chrome. Using these metals, final parts are now being manufactured for aerospace and other specialist industrial sectors. Not least, in 2006 the Adler Ortho Group an Italian manufacturer of orthopaedic implants launched a medically certified hip implant that is manufactured using Arcam’s 3D printers. Maximum build volumes for EBM are currently 200 x 200 x 380 mm on Arcam’s A2X machine.
Engineering.com: Thank you again Christopher for your thoughts on these technologies.
Christopher Barnatt has been a professional futurist for over 20 years. He is Associate Professor of Computing & Future Studies in Nottingham University Business School, and the author of ExplainingTheFuture.com, ExplainingComputers.com and their associated YouTube channels. To date he has written nine books on future studies and computing, a well as having contributed to a wide range of other print publications, websites, radio programmes and TV shows.