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) is a process where high-velocity electrons concentrated into a narrow beam are directed toward the work piece, creating heat and vaporizing the material. EBM can be used for very accurate cutting or boring of a wide variety of metals. Surface finish is better and kerf width is narrower than those for other thermal cutting processes.
To achieve the fast evaporation of the material, the power planar density in the beam cross-section must be as high as possible: - values up to 10^7 W/mm^2 can be achieved at the spot of impact. As the electrons transfer their kinetic energy into heat in a very small volume, the material impacted by the beam is evaporated in very short time.
EBM equipment in construction is similar to electron beam welding machines (see electron beam welding
Electron beam welding is a fusion welding process in which a beam of high-velocity electrons is applied to the materials being joined. The workpieces melt as the kinetic energy of the electrons is transformed into heat upon impact, and the filler metal, if used, also melts to form part of the weld...
EBM machines usually utilize voltages in the range of 150 to 200 kV to accelerate electrons to about 200,000 km/s. Magnetic lenses are used to focus the electron beam to the surface of the work-piece. By means of electromagnetic deflection system the beam is positioned as needed, usually by means of a computer.
Vacuums must be used to reduce contamination, and minimize electron collisions with air molecules. Because work must be done in a vacuum, EBM is best suited for small parts. The interaction of the electron beam with the work piece produces hazardous x-rays, and only highly trained personnel should use EBM equipment.