Plasma arc machining (PAM) is a process that uses ionized gas called plasma to remove material from a workpiece. A gas like nitrogen or hydrogen is heated to over 5000°C to become ionized plasma through an electric arc between an electrode and nozzle. This high-velocity plasma jet, which reaches temperatures over 11,000°C, is directed at the workpiece to melt and blow away the material. PAM can machine hard and brittle metals with good accuracy and is used to repair jet engine blades and cut profiles for applications like nuclear submarines and rocket motors.

1. Plasma Arc Machining
J. Hemwani, GPC Betul (MP) 460001

2. PAM --- Process
 When a gas or air is heated at a temperature of more
than 5000 °C, then it will start getting ionized.
When the temperature of the ionized gas reaches above
11000 °C it is called plasma.
This plasma is produced by heating the gas with the help
of an electric arc and this plasma produced is used to
remove the material from the work piece. so the whole
process is called Plasma-Arc Machining.
J. Hemwani, GPC Betul (MP) 460001

3. PAM --- Process
 Nitrogen, hydrogen, argon or mixture of these gases are
used to create plasma, in a plasma gun.
 Plasma gun has a chamber which has a tungsten
electrode. This tungsten electrode is connected to the
negative terminal of the DC power supply.
 At the bottom of the chamber there is copper nozzle of the
plasma gun, which is connected to the positive terminal of
the DC power supply.
 The required mixture of gas is supplied to the gun. A
strong arc is produced between the anode and the cathode.
J. Hemwani, GPC Betul (MP) 460001

4. PAM --- Process
There is a collision between the electron of the arc and the
molecules of the gas and due to this collision, gas molecules
get ionized.
 Heavy potential difference of D.C. is applied across cathode
and anode so that arc produced is strong and is able to ionize
the gas mixture and convert it into high velocity plasma.
This plasma jet is directed towards the work piece, the
plasma melts the work piece and the high velocity gas blows
away the molten metal.
In this way PAM is used for removing material from the work
piece.
J. Hemwani, GPC Betul (MP) 460001

5. PAM --- Process
 Due to the high temperature generated from the arc,
electrons from some atoms will be displaced and atoms are
ionized ( electrically charged ) and the gas turns into plasma.
As the gas is ionized, a large amount of thermal energy is
liberated.
A water jacket is used to cool the Chamber hence the
cathode and anode remain cool despite of hot gases
continuously passing through it.
J. Hemwani, GPC Betul (MP) 460001

6. J. Hemwani, GPC Betul (MP) 460001

7. PAM --- Advantages
1 Hard as well as brittle metals can be easily machined
with this process.
2 Plasma Arc Machining gives a faster production rate.
3 Small cavities can be machined using this process with
good dimensional accuracy.
4 It can be used for rough turning of very hard materials.
5 It is also used in machines that are used to repair jet
engine blades.
J. Hemwani, GPC Betul (MP) 460001

8. PAM --- Disadvantages
1 The equipment used in PAM are very costly.
2 Metallurgical changes take place on the surface of the
work piece.
3 The consumption of inert gas is high.
4 As oxidation and scale formation takes place, shielding is
required.
J. Hemwani, GPC Betul (MP) 460001

9. PAM --- Applications
1 The PAM used in the nuclear submarine pipe system.
2 PAM is used for welding rocket motor case.
3 PAM is used for profile cutting.
J. Hemwani, GPC Betul (MP) 460001

10. PAM --- Operating Parameters
 Nozzle size : 0.30 to 6.30 mm diameter
 Current Supply : 50 to 1000 ampere
 Temprature : 11000°C to 28000°C
Gas : 10% Hydrogen and 90% Nitrogen
Gas Floe Rate : Primary – 0.4 to 5.6 cu meter/ hr
Secondary -- 11.3 cu meter/ hr
J. Hemwani, GPC Betul (MP) 460001

11. THANK YOU
J. Hemwani, GPC Betul (MP) 460001