2Plasma Arc CuttingPAC 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.”
3PAC ProcessPAC 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 kerfStream pressures can reach up to 1.4 MPa.
4Gases Used Primary Gases: Gases that are used to create the plasma arc. Examples are nitrogen, argon, hydrogen, hydrogen, or mixture of themSecondary Gases or Water:Surrounds the electric arc to aid in confining it and removing the molten material.
5www.twi.co.uk/j32k/servlet/ getFile/jk51.html System ComponentsTorchPower SupplyArc Starting CircuitgetFile/jk51.html
6System 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
7System Components A. The Torch: Types of Torches: Air Plasma Torch Oxygen-Injected TorchWater Injected TorchDual Gas Torch
8Types of Torches Air Plasma (Benedict 337) Water Injected (Benedict 340)
9System ComponentsB. Power Supply:Constant DC current source.
10System 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.
11Types of Arcs Transferred Arc: the generated arc is between the electrode and the work-piece.Benedict 336
12Types 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
13Advantages - Disadvantages Cuts any metal.5 to 10 times faster than oxy-fuel.150 mm thickness ability.Easy to automate.Large heat affected zone.Rough SurfacesDifficult to produce sharp corners.Smoke and noise.Burr often results.
14Applications Pipe industry – preparing pipe edges for welding. industries for shape cuttingCpam.engr.wesc.edu
15Other Plasma UsesPlasma 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.
16Safety Precautions Machine the heat affected zone Regulate gas pressureMaintain 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.