How to use Plasma  Cutter

How to use Plasma Cutter

There is an existing but concealed notion that technicians who have ever experienced the use of plasma arc cutting machines rarely want to return to oxyacetylene cutting or mechanical cutting processes such as saws, cutoff wheels, shears, and snips. This notion poses to be correct for some reasons being that the latter can induce fatigue and stress, increase work time and make work overwhelming; but on the other hand Plasma cutting can improve productivity and lower cutting costs. It does not require a preheat cycle, cuts any metal that conducts electricity, permits portability around job sites, minimizes the heat-affected zone (HAZ). Plasma units also can gouge, pierce, bevel, cut holes, and trace shapes.

Here are few hacks on how to use plasma cutter, of which anyone who seek knowledge can possibly use but this resource is specifically for welding technicians, material/metallurgical engineers, fabricators, maintenance personnel, artisans, students, apprentices and probably ‘Do-it-yourself’ fanatics and advocates.

PLASMA

Plasma is the fourth fundamental state of matter (the others includes: solid, liquid and gas), It consists of a gas of ions – atoms which have some of their orbital electrons taken off– and free electrons. Plasma can be artificially generated by heating a neutral gas or subjecting it to a strong electromagnetic field to the point where an ionized gaseous substance becomes increasingly electrically conductive. The resulting charged ions and electrons become influenced by long-range electromagnetic fields, making the plasma dynamics more sensitive to these fields than a neutral gas.

Plasma and ionized gases have properties and display attributes unlike those of the other states, and the transition between them is mostly a matter of nomenclature and subject to interpretation. Based on the temperature and density of the environment that contains a plasma, partially ionized or fully ionized forms of plasma may be produced. Neon signs and lightning on streets and supermarkets are examples of partially ionized plasmas.

What Is Plasma Cutting?

Plasma cutting is a quick and easy means to cut any metal that conducts electricity. Operating a hand-held plasma cutter is actually very simple. The cutting is achieved by sending an electric arc through a gas that is passing through a narrow or constricted opening which then increases the temperature of the gas to the point that it enters a 4th state of matter. We all are familiar with the first three: i.e., solid, liquid, and gas. Scientists call this additional state plasma.

Note that the cutting tip of the narrow opening would have a length normally in the range between 0.9 mm – 1.5 mm and a temperature range between 25,000 – 30,000 OF (13871.1 – 16648.89 oC) for plasma state to be attained.

Metals that plasma cutter can cut

Plasma cutters can cut through ferrous and non-ferrous metals. It will cut virtually any metal that conducts electricity such as: stainless steel, mild steel, carbon/alloy steels, Aluminium and its alloys, cast iron and steel, bronze and Brass, Hard faced materials/clad sheet, copper, Titanium alloy, Bimonic alloy, Pewter, Lead, Tin alloys, etc .

Steps To Set Up A Plasma Cutter:

1. Connect a suitable air compressor to the plasma cutter.

2. Connect your plasma cutter to a 240V or 415V supply (depending on the machine’s capacity).

3. Connect the earth lead to your work-piece.

4. Connect your plasma torch to the plasma cutting machine.

5. Select your cutting amperage (the higher the amps, the thicker the materials).

6.Switch on your torch handle and move the torch across the work as the plasma arc cuts the metal.

Once you can set up, you are well on your way in getting any metal cutting job done. You can start from the edge of work or pierce a hole in the middle of the metal. Cut perfect circles with a circle cutting kit and make unique shapes using a template. Know that there are other ways to use a plasma cutter provided you follow the safety rules for it, but this will get you started.

Few steps on how to use a plasma cutter

1.Find a safe workspace and put on your complete PPE

It is best practiced to use your plasma cutter in a well-ventilated area to curb any form of explosion. Also ensure you wear suitable personal protective equipment for your safety.

Cover flammable material with flame-proof covers and keep it at least a distance of about 35 feet (11 m) from the plasma cutter.

2.Rest the drag shield on the bottom edge of the metal

Place your drag shield at the bottom edge of your metal. The drag shield is the copper piece that covers the plasma torch. Be certain to hold the drag shield straight down so that it makes a perpendicular angle with the metal.

Use a drag shield to increase the ease and accuracy of your cuts by allowing you to rest the torch on your metal while following the cut traces.

If your plasma cutter doesn't have a drag shield, hold it 1⁄8 inch (0.32 cm) from the metal and maintain a perpendicular angle (900) between the torch body and the metal.

3.Remove the trigger lock and press the plasma cutter trigger

Maintain a perpendicular angle to the metal from the drag shield or torch body and raise the trigger lock. Now, press and hold the trigger—an arc of plasma should spray downward from the tip of the plasma torch.

Make sure sparks spray from the bottom of the metal after pressing the trigger. If not, your plasma cutter is not powerful enough for the thickness of metal you are trying to cut.

4.Move the torch along the metal slowly and evenly

As you move the plasma arc across the metal, it should penetrate it through to the bottom. If no sparks are spraying outward from the bottom of the metal, this means the arc is not effectively penetrating it. Either you are moving the torch too fast, the stream is not being directed straight down, or the plasma cutter has insufficient amperes.

Adjust the speed of your cut as you drag the blade so that you always see sparks at the bottom of the metal. For example, if you are moving too fast and don't see any sparks, slow down your speed until you do.

If you see an excessive stream of sparks, increase your speed.

5.Angle the plasma torch toward the end of the metal and release the trigger

Once you reach the end of the metal, angle your plasma torch slightly toward the edge of the metal. Once you do, pause for a moment and then release the trigger. This will ensure that you sever the metal completely.

Difference between a clean and severance cut

Clean cut

A Clean Cut is where the machine will cut all the way through the material and the cut parts will fall away from each other leaving only minimal dross on the bottom edge which can easily be pulled off using pliers etc.The cutting marks will start off straight and then give a slope of a small angle towards the bottom of the cut. The metal should require no extra working before being welded together etc.

Severance cut

A Severance Cut is where the user is using the machine close to its maximum cutting thickness capability. The cutting speed will be much slower compared to a clean cut and the metal will require some cleaning up towards the bottom edge. Plasma Cutting Speed, Amperage and Cutting Tip Size.

Your cutting speed when plasma cutting is dictated by the amperage used and the size of the material to be cut.

If you are cutting 4mm with a 30A machine, you could either set the amperage to 20A and have a medium travel speed, or you could set the machine to maximum 30A (which will cut 8mm clean) and enjoy a faster travel speed, however you may experience slightly more dross at the bottom of the cut this way.

Caution

  1. Wear heat-resistant gloves and work boots (safety shoes).
  2. Always wear a welding helmet and safety goggles to protect your head, eyes and face.
  3. Always wear ear plugs or ear muffs.
  4. In terms of clothing, wear a non-flammable and heat-resistant apron over work pants and a welding jacket.
  5. Wear a respirator mask to protect your lungs.

Contact us for all your personal protective equipment and more information about plasma cutter.

13th May 2020 Egbujua Michael C.

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