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Plasma Arc Cutting

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The torch is the holder of the consumable ... Types of Torches. Water Injected (Benedict 340) Air Plasma ... distance between torch and work piece. ... – PowerPoint PPT presentation

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Title: Plasma Arc Cutting


1
Plasma Arc Cutting
MENG 439
Dr. L. K. Gaafar
Prepared by Eng. Ahmad Hassan Sayed
2
Plasma Arc Cutting
  • PAC is a thermal material removal process that is
    primarily used for cutting thick sections of
    electrically conductive materials.
  • Plasma can be defined as a superheated,
    electrically ionized gas.

3
PAC Process
  • PAC uses a high velocity jet of plasma
    (Temperatures range from 10,000 to 14,000 oC) to
    cut through the metal by melting it.
  • The high gas flow rate facilitate the removal of
    molten metal through the kerf
  • Stream pressures can reach up to 1.4 MPa.

4
Gases Used
  • Primary Gases
  • Gases that are used to create the plasma arc.
    Examples are nitrogen, argon, hydrogen, hydrogen,
    or mixture of them
  • Secondary Gases or Water
  • Surrounds the electric arc to aid in confining
    it and removing the molten material.

5
System Components
  • Torch
  • Power Supply
  • Arc Starting Circuit

www.twi.co.uk/j32k/servlet/ getFile/jk51.html
6
System Components
A. The Torch
  • The torch is the holder of the consumable
    electrode and nozzle.
  • Responsible for forming the arc and maintain it
    in a vortex.

Groover 626
7
System Components
A. The Torch
  • Types of Torches
  • Air Plasma Torch
  • Oxygen-Injected Torch
  • Water Injected Torch
  • Dual Gas Torch

8
Types of Torches
Water Injected (Benedict 340)
Air Plasma (Benedict 337)
9
System Components
B. Power Supply
  • Constant DC current source.
  • Speed and cut thickness are determine by the
    amount of output current.

10
System Components
C. Arc Starting Circuit
  • High frequency generator circuit that produces a
    high AC Current.
  • To start the arc, the AC current ionizes the
    cutting gas, which makes it conductive to allow
    the DC current to flow through it.

11
Types of Arcs
  • Transferred Arc
  • the generated arc is between the electrode and
    the work-piece.

Benedict 336
12
Types of Arcs
  • 2. Non-Transferred Arc
  • the generated arc is between the electrode
    and the nozzle and heat is carried to the
    work- piece by the plasma gas.

Benedict 336
13
Advantages - Disadvantages
  • Cuts any metal.
  • 5 to 10 times faster than oxy-fuel.
  • 150 mm thickness ability.
  • Easy to automate.
  • Large heat affected zone.
  • Rough Surfaces
  • Difficult to produce sharp corners.
  • Smoke and noise.
  • Burr often results.

14
Applications
  • Pipe industry preparing pipe edges for welding.
  • industries for shape cutting

Cpam.engr.wesc.edu
15
Other Plasma Uses
  • Plasma Arc Welding (PAW)- plasma arc is produced
    and aimed at the weld area to weld.
  • Applications- Used for butt and lap joints
    because of higher energy concentrations and
    better arc stability.

16
Safety Precautions
  • Machine the heat affected zone (0.75-5 mm).
  • Regulate gas pressure (approx. 1-1.4 MPa).
  • Maintain constant distance between torch and work
    piece.
  • High labor safety (i.e. goggles, gloves, etc).
  • Proper training for operators.
  • Protection against glare, spatter and noise from
    the plasma.
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