Electron Beam Machining
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Electron Beam Machining Akira Okada Department of Mechanical Engineering, Okayama University, Okayama, Japan
Synonyms Electron beam cutting; Electron beam drilling; Electron beam processing; Electron beam removing; Electron beam welding
Definition Electron beam machining (EBM) is a thermal machining process in which high-velocity electrons concentrated into a narrow beam are used for instantly heating, melting, or vaporizing the material. This process is used in many applications, including drilling, cutting, annealing, and welding.
Theory and Application Introduction When high-speed electrons in a densely focused beam impact with the workpiece surface, most of the kinetic energy of the electrons is converted
into heat energy. This phenomenon has been well understood since the development of electron microscopy when attempts to use the electron beam as a machining tool were made. The first EBM equipment was built in the 1950s. The beam is easily focused and deflected by electromagnetic focusing lenses and deflection lenses. The power density is also easy to control by modifying the acceleration voltage. Therefore, the electron beam enables various type of thermal machining. For this reason, it can be applied to fast and accurate drilling and high-precision welding with a deep fusion zone in the industrial field. Equipment Figure 1 shows a schematic diagram of an electron beam machining equipment. It consists of an electron beam gun for the generating electron beam, an electromagnetic coil for focusing the beam, a deflection coil for scanning the beam, an XY table for fixing the workpiece in an operating chamber, and a vacuum system. Figure 2 shows the whole view of a typical electron beam machine (Mitsubishi Electric Corporation index type). The cathode filament of the electron gun made of tungsten or tantalum is heated to 2,500–2,800 C resulting in thermal emission of electrons. The electrons are strongly accelerated with high voltage loaded to an anode. The electrons may achieve a velocity as high as 200,000 km/s. Upon leaving the anode, in order to focus the electron beam to the workpiece surface, the beam passes through the electromagnetic
# CIRP 2016 The International Academy for Production Engineering et al. (eds.), CIRP Encyclopedia of Production Engineering, DOI 10.1007/978-3-642-35950-7_6480-4
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Electron Beam Machining High voltage supply to cathode Cathode cartridge Insulator Port for pump Electron gun
Electron beam Operating chamber
Cathode filament Control electrode Anode Electromagnetic coils Deflection coils Port for pump Workpiece X-Y table
Electron Beam Machining, Fig. 1 Schematic diagram of electron beam machining equipment
coil. The spot size and the focal length are controlled by the current flowing through the coil. The size is usually from several microns to few millimeters, but an electron beam less than 1 mm in diameter can be obtained with relatively small beam currents. The power density on the workpiece surface required to melt or vaporize a metal surface is 107–1010 W/cm2. Scanning
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