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20-09-2008, 10:36 PM
In electron-beam machining (EBM), electrons are accelerated ..
In electron-beam machining (EBM), electrons are accelerated to a velocity nearly three-fourths that of light.
The process is performed in a vacuum chamber to reduce the scattering of electrons by gas molecules in the atmosphere.
The stream of electrons is directed against a precisely limited area of the workpiece;
on impact, the kinetic energy of the electrons is converted into thermal energy that melts and vaporizes the material to be removed, forming holes or cuts.
EBM equipment is commonly used by the electronics industry to aid in the etching of circuits in microprocessors.
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18-07-2011, 10:43 AM
LM-40.pdf (Size: 682.28 KB / Downloads: 607)
Electron Beam Machining (EBM) and Laser Beam Machining (LBM) are thermal processes considering the mechanisms of material removal. However electrical energy is used to generate high-energy electrons in case of Electron Beam Machining (EBM) and high-energy coherent photons in case of Laser Beam Machining (LBM). Thus these two processes are often classified as electro-optical-thermal processes.
There are different jet or beam processes, namely Abrasive Jet, Water Jet etc. These two are mechanical jet processes. There are also thermal jet or beams. A few are oxyacetylene flame, welding arc, plasma flame etc. EBM as well as LBM are such thermal beam processes. Fig. 9.6.1 shows the variation in power density vs. the characteristic dimensions of different thermal beam processes. Characteristic length is the diameter over which the beam or flame is active. In case of oxyacetylene flame or welding arc, the characteristic length is in mm to tens of mm and the power density is typically low. Electron Beam may have a characteristic length of tens of microns to mm depending on degree of focusing of the beam. In case of defocused electron beam, power density would be as low as 1 Watt/mm2. But in case of focused beam the same can be increased to tens of kW/mm2. Similarly as can be seen in Fig. 9.6.1, laser beams can be focused over a spot size of 10 – 100 μm with a power density as high as 1 MW/mm2. Electrical discharge typically provides even higher power density with smaller spot size.
Joined: Apr 2012
13-06-2012, 01:30 PM
ELECTRON BEAM MACHINING
ELECTRON BEAM MACHINING.pdf (Size: 2.02 MB / Downloads: 324)
Electron beam machining (EBM) is a thermal material removal process that
utilizes a focused beam of high-velocity electrons to perform high-speed
drilling and cutting. Just as in electron beam welding (Chap. 18), material-heating action is achieved when high-velocity electrons strike the
work piece. Upon impact, the kinetic energy of the electrons is converted
into the heat necessary for the rapid melting and vaporization of any
Invented in Germany in 1952 by Dr. K. H. Steiger wald, EBM is able to
drill materials up to 10-mm (0.394-in.) thick at perforation rates that far
exceed all other manufacturing processes. Although EBM is capable of
producing almost any programmable hole shape, it is most often applied for
high-speed drilling of round holes in metals, ceramics, and plastics of any
The appearance of electron beam machining equipment is very similar to
electron beam welding equipment. Most system subassemblies such as the
vacuum system, work piece-positioning system, and vacuum chamber are
essentially identical with those used for EBW. There are however
significant differences between the two systems with respect to the electron
beam gun and power supply.
Electron Beam Gun
The function of the electron beam gun is to generate, shape, and deflect the
electron beam to drill or machine the work piece. The EBM guns resemble
those used for welding; however the similarities end there. For example.
the EBM gun is designed to be used exclusively for material removal
applications an can be operated only in the pulsed mode.
A typical triode EBM gun functions in a manner very similar to an EBW
gun (Chap. 18). An electron "cloud" is generated by a superheated
tungsten filament, which also acts as the cathode. A combination of
repewng forces from the negative cathode and the attracting forces from the
positive anode causes the free electrons to be accelerated and directed
toward the work piece.
The high-voltage power supply used for EBM systems generates voltages
of up to 150 kv to accelerate the electrons. The most powerful electron
beam machining systems are capable of delivering enough power to operate
guns at average power levels of up to 12 kw. Individual pulse energy can
reach 120 joules/pulse. To avoid the possibility of arcing and short circuits,
the high-voltage sections of the power supply are submerged in an
insulating dielectric oil.
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