Metal additive processes
GE Additive specializes in developing Powder Bed Fusion (PBF) machines for the additive manufacturing of metal parts. The two processes GE offers with in the PBF category, recognized by the American Society for Testing and Materials (ASTM), include:
• Direct Metal Laser Melting (DMLM)
• Electron Beam Melting (EBM)
Direct Metal Laser Melting process
The direct metal laser melting (DMLM) process involves the full melting of metal powder into liquid pools. As with other PBF processes, an .STL file is generated from computer-aided design (CAD) data, which guides the “printing” of sequential, micro-thin layers of fully melted metal powders. Various metals can be used, including titanium, cobalt-chrome and aluminum alloys. When printing is complete, excess powder is removed, leaving a high-resolution object with a smooth surface that usually requires little or no post-processing.
In aerospace, DMLM has been used to fabricate parts for jet engines and other airplane parts. For example, Fortune highlighted how GE is printing fuel nozzles for its CFM LEAP engines using this technology. Thanks additive’s ability to produce complex geometric structures, the design of the 3D-printed fuel nozzle reduces 20 traditionally fabricated parts down to just one.
Electron Beam Melting process
Electron beam melting (EBM) process involves metal powder melted by of a beam of electrons gathered and focused by electromagnetic coils. Given the inherent nature of the 3,000-watt electron gun, the process must be carried out in a vacuum chamber. EBM is used to print sophisticated parts and components of many kinds, including those that supply the aerospace and medical industries.
In the medical industry, EBM technology is used to fabricate one-of-a-kind orthopedic implants. The EBM process yields objects with slightly rough surfaces, so some machining is appropriate when smooth surfaces are required. However, the rough surface is actually an advantage when fabricating implants because it promotes bone-in growth.
High-quality mechanical properties are achieved, in part due to temperature consistency that strengthens fused layers. EBM machines use titanium alloys to produce parts for high-temperature, high-stress aerospace applications.
Binder Jetting process
GE Additive is developing a Binder Jet machine. This process involves a print head that moves across a bed of powder and selectively deposits a liquid binding agent in the shape of the section, bonding these areas together to form a solid part one layer at a time.
When the build is complete, the bound parts are removed from the unbound powder. Materials commonly used in binder jetting are metals, ceramics, and sand. For metal printing, a debind and sintering process is required to remove the binder and fuse the metal powder into a solid metal part.
Binder jetting is ideal for mass production applications. This technology is unlocking the power of additive design for volume production in automotive, industrial, medical and aerospace applications, among others.