Plasma Arc Plasma Arc CuttingCutting

Dr. L. K. GaafarMENG 439

Plasma Arc CuttingPlasma 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.”

PAC ProcessPAC 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.

Gases UsedGases 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.

System ComponentsSystem Components

Torch Power Supply Arc Starting Circuit

www.twi.co.uk/j32k/servlet/ getFile/jk51.html

System ComponentsSystem Components

The torch is the holder of the consumable electrode and nozzle.

Responsible for forming the arc and maintain it in a vortex.

A. The Torch:

Groover 626

System ComponentsSystem Components

Types of Torches: Air Plasma Torch Oxygen-Injected

Torch Water Injected

Torch Dual Gas Torch

A. The Torch:

Types of TorchesTypes of Torches

Water Injected (Benedict 340)Air Plasma (Benedict 337)

System ComponentsSystem Components

Constant DC current source.

B. Power Supply:

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.

System Components

C. Arc Starting Circuit:

Types of ArcsTypes of Arcs

1. Transferred Arc:the generated arc is between the electrode and the work-piece.

Benedict 336

Types of ArcsTypes 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

Advantages - Advantages - DisadvantagesDisadvantages 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.

ApplicationsApplications

Pipe industry – preparing pipe edges for welding.

industries for shape cutting Cpam.engr.wesc.edu

Other Plasma Uses 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.

Safety PrecautionsSafety Precautions

Machine the heat affected zone

Regulate gas pressure 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.

THANK YOU STUDENTSTHANK YOU STUDENTS