Download Non Traditional Machining Processes MIME - 6980

Non Traditional Machining Processes
MIME - 6980
Presented by,
Electron Beam Machining
 Abhijit Thanedar
 Naga Jyothi Sanku
 Pritam Deshpande
 Vijayalayan Krishnan
 Vishwajeet Randhir
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.
ELECTRONS
HIGH
VOLTAGE
VAPORIZATION
EDM
RADIATION
THERMOELECTRIC
ION STREAM
HOT GASES
ELECTRON
BEAM
AMPLIFIED
LIGHT
LASER
IONIZED
MATERIAL
ION BEAM
PLASMA ARC
NON TRADITIONAL MACHINING
PROCESSES - THERMOELECTRIC
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 UB
• the kinetic energy absorbed by the electrons during their
trajectory through the accelerating field is
E = (me0/2) ve2 (1 + 3 ve2/4c2 + 5 ve4/8 c4 +…)= e UB
Where me0 is the electron rest mass, v e is the electron velocity, c is the
velocity of light and e is the electron charge.
Relation between velocity and acceleration voltage
VELOCITY OF LIGHT
3
8
10
Ve (m/s)
6
10
1
6
Ub
10
ELECTRON BEAM
e=EU
HEAT RADIATION
E=hv 
X-RAYS
E=hv eU
BACKSCATTERED ELECTRONS
SECONDARY ELECTRONS
E50eV
THERMIONIC ELECTRONS
E<1eV
SURFACE TEMPERATURE (T)
RANGE OF ENERGY
CONVERSION
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 gun
• Telefocus 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
ELECTRON
GUN
WORK
BEAM
GUIDANCE CHAMBER
SYSTEM
SOURCE
FOCUSING DEFLECTION
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
TUNGSTEN
IRON
TITANIUM
POWER
ALUMINUM
METAL REMOVAL RATE
Parameter Zones
Thermal processing of solids.
Thermal processing of thin films
Non – thermal processing
Parameters and their influence
Power density
Drilling of all materials
FILAMENT
BIAS CUP
ANODE
FLOW OF ELECTRONS
FOCUS COIL
DEFLECTION COIL
METAL VAPOR
MOLTEN METAL
HOLE
Parameters for drilling various materials
Thickness
Hole
Drilling speed
Acclerating
Avg beam
Pulse
Pulse
(in)
diameter (in)
(Sec)
voltage(kv)
current
width
Frequency
(microamp)
(micro
(cps)
sec)
0.010
0.0005
<1
130
60
4
3000
0.030
0.012
30
125
60
80
50
0.010
0.001
<1
140
50
20
50
0.040
0.005
<1
140
100
80
50
0.40
0.005
<1
140
100
80
50
0.100
0.005
10
140
100
80
50
0.016
0.003
<1
130
100
80
50
0.125
0.001
<1
140
10
12
50
Examples of EBM Drilling
Examples of EBM Drilling
Examples of EBM Drilling
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
dB, and perforation rate ns
2
1
db
.1
0.01
S