Electron beam micromachining

Electron Beam Micromachining

Supervisor:-Prof. Vinod YadavaMechanical DepartmentMNNIT Allahabad

Presented By:- Anurag Chaudhary

Bhaskar Singh

Content:

Micromachining Electron Beam Micromachining Mechanism Of Material Removal In EBMM Electron Beam Drilling Performance Characteristics of EBD Process Parameters Of EBMM Applications, Merits and Demerits

MicromachiningMicroMachining

Micromachining

Macro component but removal of material at micro/nano level.Micro/nano components and material removal is at micro level.Dimensions produced between greater than or equal to1μm and smaller than or equal to 999μm[1].

Micromachining processes can be classified into three sub-

categories:

1. Mechanical Micromachining -Use of Mechanical Force

2. Thermal Micromachining – Use Direct Energy

3. Chemical and Electrochemical Micromachining – Uses

Chemical Reaction

Electron Beam Micromachining It is a type of thermal micromachining processes. It uses a high-velocity stream of electrons focused on the

workpiece surface to remove material by melting and vaporization.

Fig:- Variation in Power density with spot diameter of Thermal Beam Process[3]

Mechanism Of Material Removal In EBMM[1]

An electron beam gun generates a continuous stream of electrons.

This stream of electrons is then forced through a valve that controls the beam.

After passing through valve, the beam is then focused onto the surface of the workpiece.

The kinetic energy of electrons, transferred to the work material, produces intense heating.

By this heat material is removed and vaporized.

Fig:- Schematic Of Electron Micromachining

Electron Beam Drilling CNC-EBM machine controls the main drilling parameters

and the axial movements of the workpiece and beam.

Fig:- Electron Beam Drilling Process[4]

Performance Characteristics of EBD[3]

Material Work-piece

thickness (mm)

Hole dia. (μm)

Drilling Time (sec)

Accele-rating voltage

(kV)

Beam Current

(μA)

Tungsten 0.25 25 <1 140 50

Stainless steel

2.5 125 10 140 100

Aluminium

2.5 125 10 140 100

Alumina 0.75 300 30 125 60

Quartz 3.0 25 <1 140 10

Process Parameters Of EBMM[2]

Imortance of Vacuum The need of a vacuum for the EBMM process is that air

molecules can adversely interact with the beam of electrons.

Collision between an electron and an air molecule causes the electron to veer.

Conduction Losses Conduction of heat away from the irradiated spot causes

loss of efficiency in the heating process.

Effect of Cutting Speed To minimize the thermal diffusion problem it is recommended

to pulse the beam or scan it rapidly across the surface to be machined[1].

Material Removal rate (MRR)

Where, η= Cutting efficiency P= Power (J/s) W= specific energy (J/cm3)

Where, =Specific heat =Melting Temperature =Initial Temperature =Boiling Temperature =Latent heat of fusion =Latent heat of vaporization

Application:-

Machining of titanium aircraft engine parts. Drilling fine holes (less than 50 μm) Cutting contours in sheets Cutting narrow slots (25μm) Medical and electronics industries EBMM does not apply any cutting force on the workpieces.

Merits:- Both electrically conducting as well as non con ducting

material are machined. No limitation is imposed by workpiece hardness, ductility, and

surface reflectivity. No mechanical distortion occurs to the workpiece since there

is no contact. Drilling of holes with very high aspect ratio (25:1). Single step process. Very low tool wear

Demerits:- Need of vacuum chamber that limits the work size. High initial investment and high operating cost. Limited to thin parts in the range from 0.2 to 6 mm thick[1].

Bibliography1) Introduction to Micromachining by V.K.Jain .2) Advanced Machining Process by Hassan El-Hofy.3) Manufacturing Science by Ghosh and Mallik.4) Karl-Heinz Leith, Holger

Koch, Michael Schmidt, “Numerical Simulation of Drilling With Pulsed Beam”

5) EBOPULS electron beam drilling system technical brochure, Steigerwald Strahltechnik GmbH 2006.