Electron Beam Machining (EBM)

• 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 workpiece 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 25-50 μm 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 electron beam is

Where, K_B = 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 unconventional 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.