- Electron Beam Machining (EBM) is a thermal process. Here a steam of high speed electrons impinges on the work surface so that the kinetic energy of electrons is transferred to work producing intense heating.
- Depending upon the intensity of heating the work piece can melt and vaporize.
- The process of heating by electron beam is used for annealing, welding or metal removal.
- During EBM process very high velocities can be obtained by using enough voltage of 1,50,000 V can produce velocity of 228,478 km/sec and it is focused on 10 - 200 μM diameter. Power density can go up to 6500 billion W/sq.mm. Such a power density can vaporize any substance immediately. Complex contours can be easily machined by maneuvering the electron beam using magnetic deflection coils.
- To avoid a collision of the accelerating electrons with the air molecules, the process has to be conducted in vacuum.
- So EBM is not suitable for large work pieces. Process is accomplished with vacuum so no possibility of contamination. No effects on work piece because about 25-50μm away from machining spot remains at room temperature and so no effects of high temperature on work.
MRR in EBM:
Q = area of slot or hole * speed of cutting = A*V
Where power for 'Q' MRR is P = C.Q
Where,
C = Specific power consumption
Thermal velocity acquired by an electron of the work material due to EB is
Where, Kb = Boltzmann constant
M = mass of one atom of work.
T = rise in temperature
Advantages:
- Very small size holes can be produced.
- Surface finish produced is good.
- Highly reactive metals like Al and Mg can be machined very easily.
Limitations:
- Material removal rate is very low compared to other convectional machining processes.
- Maintaining perfect vacuum is very difficult.
- The machining process can't be seen by operator.
- Workpiece material should be electrically conducting.
Applications:
- Used for producing very small size holes like holes in diesel injection nozzles, Air brakes etc.
- Used only for circular holes.
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