Electron beam melting
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|Electron Beam Melting Hardware|
Electron beam melting (EBM) is a type of additive manufacturing (AM) for metal parts that was originally patented and developed by Arcam AB in Sweden. ASTM classifies EBM as a powder bed fusion technique, which also includes selective laser melting (SLM). The main difference is that EBM uses an electron beam as its power source, as opposed to a laser. EBM technology manufactures parts by melting metal powder layer by layer with an electron beam in a high vacuum. In contrast to sintering techniques, both EBM and SLM achieve full melting of the metal powder. The term selective laser sintering (SLS) is mostly historical and is sometimes used to describe full melting or plastic processes.
This solid freeform fabrication method produces fully dense metal parts directly from metal powder with characteristics of the target material. The EBM machine reads data from a 3D CAD model and lays down successive layers of powdered material. These layers are melted together utilizing a computer controlled electron beam. In this way it builds up the parts. The process takes place under vacuum, which makes it suited to manufacture parts in reactive materials with a high affinity for oxygen, e.g. titanium. The process is known to operate at higher temperatures (up to 1000 °C), which can lead to differences in phase formation though solidification and solid state phase transformation.
The powder feedstock is typically pre-alloyed, as opposed to a mixture. That aspect allows classification of EBM with selective laser melting (SLM) where competing technologies like SLS and DMLS require thermal treatment after fabrication. Compared to SLM and DMLS, EBM has a generally superior build rate because of its higher energy density and scanning method.
Recent work has been published by ORNL, demonstrating the use of EBM technology to control local crystallographic grain orientations in Inconel. Other notable developments have focused on the development of process parameters to produced parts out of alloys such as copper, niobium, Al 2024, bulk metallic glass, stainless steel, and titanium aluminide. Currently commercial materials for EBM include commercially pure Titanium, Ti-6Al-4V, CoCr, Inconel 718, and Inconel 625.
Titanium alloys are widely used with this technology which makes it a suitable choice for the medical implant market.
The U.S. implant manufacturer Exactech has also received FDA clearance for an acetabular cup manufactured with the EBM technology.
Aerospace and other highly demanding mechanical applications are also targeted.
The EBM process has been developed for manufacturing parts in gamma titanium aluminide, and is currently being developed by Avio S.p.A. and General Electric Aviation for the production of turbine blades in γ-TiAl for gas-turbine engines.
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