Non Traditional Machining Processes MIME Presented by, µAbhijit Thanedar µNaga Jyothi Sanku µPritam Deshpande µVijayalayan Krishnan µVishwajeet Randhir Electron Beam Machining

Introduction - A Brief History Development of EB technology is closely related with advances in vacuum engineering and electron optics In 1905, Marcello von Pirani successfully melted Tantalum In 1938, magnetic lens were introduced to focus EB It was only in 1965, all techniques were put together and secured a place in production processes list.

Classification of NTM processes Classification based on the energy source Mechanical Electro-chemical Chemical Thermo-electric EBM uses Thermo-electric Energy.

GENERATION OF ELECTRON BEAM: The electron beam is formed inside an electron gun, which is basically a triode and consists of: A cathode which is a hot tungsten filament emitting high negative potential electron A grid cup, negatively biased with respect to filament, and An anode at ground potential though which the accelerated electrons pass

Energy Conversion at the point of action electrons are accelerated in the electrostatic field of the beam source to attain a kinetic energy, E = e U B the kinetic energy absorbed by the electrons during their trajectory through the accelerating field is E = (m e0 /2) v e 2 (1 + 3 v e 2 /4c v e 4 /8 c 4 +…)= e U B

Relation between velocity and acceleration voltage

BEAM ACTION ON IMPINGEMENT ON MATTER

Machine Tools The three major subsystems that make up an electron beam machining system are –power supply, –electron beam gun, and –the vacuum system.

Modern EBM Drilling Machine

POWER SUPPLY Pulsed DC Voltage range up to 150 kv to accelerate electrons Systems capability can go as high as 12 kw high-voltage sections of the power supply are submerged in insulating dielectric oil

ELECTRON GUN gun is designed to be used exclusively for material removal applications and can be operated only in the pulse mode It has a cathode, bias electrode, anode, magnetic coil/lens (to converge the beam), variable aperture, 3 final magnetic coils (used as magnetic lens, deflection coil, and stigmator) and rotating disc.

Gun Types 2 electrode gun

3 Electrode Guns

Modified 3 Electrode Guns Rogowski gunTelefocus gun

Four Electrode Array gun

High-perveance guns Pierce gun

Guns with Curved Electron Trajectories

Guns with Concave Emmiting Surface and center bore in cathode

Beam Guidance

MATHEMATICAL MODEL: Energy of Electrons: The kinetic energy of the electrons can be written as: K.E.=Ee=1/2 mV2. Where, m= mass of electron. e= charge on electron.(joules) E= voltage. V= velocity of electron.(cm/sec)

Number of electrons per second (N): N= I n. Where, I= beam current. n= electron per second per amp current.

Total Power : P= E I Energy Required to vaporize Workpiece: Material removal rate : G = nP/W.(cm3/sec) Where: P = Power.(watts) n= cutting efficiency. W= Specific energy required to vaporize metal. (joules/cm3) W=[C(Tm-20)+C(Tb-Tm)+Hf+Vv] Where: C= Specific Heat, Tm = Melting temperature Tb = Boiling temperature, Hf = Heat of fusion, Hv = Heat of vaporization

MRR Vs POWER

Parameter Zones

Parameters and their influence Power density

Drilling of all materials

Parameters for drilling various materials

Examples of EBM Drilling

Hole Diameter Vs Pulse Charge

Depth & Diameter Vs Beam Current

Depth of Cut, Milling Width Vs Input Energy

Relation between material thickness s, hole diameter d B, and perforation rate n s