Essay on ELECTRON BEAM MACHINING

2654 Words Feb 11th, 2014 11 Pages
Electron Beam Machining (EBM)

19.1

Process Principles

19.2

Equipment

19.2.1 Electron Beam Gun
19.2.2 Power Supply
19.2.3 The Electron Beam Machining Systems
19.3

Process Parameters

19.4

Process Capabilities

19.5

Application Examples

19.6

Process Summary

19.7

References

19.1 PROCESS PRINCIPLES
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
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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. Before passing through the anode, the beam travels through a bias electrode, which controls the flow of electrons and acts as a switch for generating pulses.
After passing through the anode, the electron beam is diverging rapidly and traveling at approximately one-half the speed of light. A magnetic coil, which functions as a magnetic lens, repels and shapes the electron beam into a converging beam. The beam is then passed through a variable aperture which results in the removal of stray electrons from the beam's fringe areas, thus reducing the fmal focused spot diameter and producing a more favorable beam energy distribution for machining applications.
Beneath the aperture are three final magnetic coils that are used as the final magnetic lens, deflection coil, and stigmator. Pinpoint focusing is accomplished with the lens, and a small amount of controllable beam

deflection is achieved with the deflection coil. The stigmator corrects minor beam aberrations and ensures a round beam at the work piece.
To protect the electron beam gun from metal spatter and vapor, a series of rotating slotted disks are often mounted
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