electron beam micromachining
TRANSCRIPT
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.