Electron Beam Melting
Electron Beam Melting is an additive manufacture technology specifically aimed at printing metal objects. It is essentially the same as selective laser melting in that layers of powder are successively melted to form a 3D object. However, instead of using a laser device to direct energy down onto the powder bed, a high energy electron beam is used.
To discuss Electron Beam Melting, please share your thoughts here: EBM Forum
Electron Beam Melting works by generating an 'electron beam' using an electron gun, and then directing the beam using electromagnetic coils, very much like a Cathode Ray Tube (CRT) Television or Oscilloscope. An essential part of the electron gun is a vacuum atmosphere which allows the free electrons to move without hindrance.
Electron guns are scalable, therefore very high energy beams can be generated for relatively little material cost. Further, electron beams can be directed using electromagnetic coils instead of a mirror apparatus (as is the case with laser based printers).
A very pure vacuum is required for the electron gun to operate efficiently, therefore the design and fabrication of a suitable vacuum chamber can be unfortunately expensive and technically demanding.
The MetalicaRap Project comes underneath the RepRap project, whose general goal is to make a self replicating device. The MetalicaRap can theoretically print some of the parts needed to make an electron gun. The project is headed by Rapatan and is at the forefront of open source electron beam technology!
A quote from the MetalicaRap Wiki...
"MetalicaRap is an open 3D metal & home solar cell printer, based on the principles of electron beam welding and vapor deposition. MetalicaRap is currently in the design stage. The goal is to have affordable home-manufacturing of solar cells, key electrical parts and milled-quality metal parts."
More information can be found here
Arcam is currently the world leader in electron beam melting technology.