How a Plasma Cutter Works

Many of you won’t be familiar with the word plasma; however, it is one of the emerging technologies in the modern world. In addition to the three states of matter that we study in elementary physics, plasma is the fourth one. This state is of immense importance and scientists have used it in many a technology so far. Plasma is the highly ionized gas molecules that have so much energy that they become electric conductors.

Exploiting this principle of plasma conductivity of gas, a plasma cutter efficiently aids in the cutting process by facilitating any conductive material with energy from a power supply.

This guide will tell you how a best plasma cutter works.

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THE FILLER GAS IN THE

The gas filled inside it can be air at atmospheric pressure, nitrogen, oxygen, argon and the like. The cutter hits the gas with an electric arc. As the gas moves through a constricted nozzle orifice, its temperature rises so high that its molecules gain enough energy to enter into the plasma region or state. In physics, the mass flow has its own law. It says that the product of area and velocity is a constant. So as the gas in plasma state passes the small opening of the gas, it attains a high velocity or speed and gushes through molten metal, cutting it out. The term used for this stream of gas is “plasma jet” and it attains temperature as high as 40,000° F quickly; thus, blowing away the molten metal. Not only it cuts the metal but also it shields the cut when redirected round the perimeter.

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COMPONENTS

Power supply

As the plasma arc requires an unvarying energy source for its continuity, the cutter can’t run on AC supply and it works only on a DC supply. Thus, a power supply is used. It is there for the conversion of AC line voltage (single-phase or three-phase) into a DC output. The range of this smooth and constant D is 200-400 V. The current output is also in regulated form and it directly depends on the type of the material in process and its thickness.

Arc Starting Console

As its name suggests, the ASC circuit is responsible for arc formation and it is a very important component. The spark is in form of an AC voltage, having a value of about 5,000 V at 2 MHz inside the plasma torch.

Plasma torch

Some of the other parts include

  • Swirl ring
  • Nozzle
  • Electrode
  • Inner and outer retaining caps
  • Shielding cap

Plasma torch ensures their cooling and alignment. These consumable parts are necessary for arc generation and the retaining caps hold them together.

TYPES OF PLASMA CUTTER

There are two categories:

  • Conventional system

The working gas is air in this type and the arc shape depends on the nozzle orifice. The Ampere current it supplies per unit area in inches is approximately 12-20k A per square inch. Handheld tools mostly use this type.

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  • Precision system

With the use of precision plasma cutter (high current density), it is possible to achieve the sharpest and highest quality cuts. Although the torch and the consumable circuitry has a bit more complex design, the amperage for precision cutter is 40-50K amps per square inch. In order to optimize the results, multiple gases work in precision tool to increase efficiency.

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HOW A PLASMA CUTTER WORKS

Many different types of plasma cutters are available in the market. They differ in the technique used for arc production.

In some, a spark plug is in use. Some have isolated electrode and nozzle, yet others have them linked.

Whatsoever is the method of arc generation, first the gas is taken to the plasma state and then arc is generated to make it cut through the metal.

In the precision cutter, the plasma torch houses the electrode and nozzle. There is a swirl ring to isolate both of them so that they don’t touch. Now, this swirl ring coverts the straight-line plasma flow into a swirling vortex by the use of small vent holes.

STEP 1

When the power supply receives a start command, it gets in action and generates a DC voltage. The magnitude of the DC is 400V. Now, the power supply directs the gas to pass through hose going into the torch. The electrode is at a negative potential with respect to the nozzle, which has a positive potential due to its contact with the positive terminal of the power supply. The pilot arc provides this contact.

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STEP 2

The arc is basically a spark, a high energy and high frequency flash that splits the gas molecules into ions. Now, the Arc Starting Console generates a high frequency spark resulting in the formation of the highly conductive plasma gas. The current has now a path between electrode and the nozzle, plasma is in pilot arc form.

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STEP 3:

After the target metal (earthed through the supports of the cutting table) and pilot arc are in contact, the current chooses a new path to flow. Instead of passing through the electrode, now it has a path through the target metal or any other work piece.

This turns off the high frequency of the arc and it dies out.

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STEP 4:

Now, the power supply meets the current requirement set by the operator. It raises the DC current until the desired cutting amperage is available. Now the pre-flow gas gets replaced by the plasma gas, which is responsible for carrying out the cutting process. One more gas is in use, which provides protection through a shield cap, commonly known as secondary shielding gas. Its path is just outside the nozzle.

 

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STEP 5:

A sharper and cleaner cut is made possible by the shape of the shield cap; the shield gas further presses the plasma arc resulting in best possible results. This is how a best plasma cutter works.

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CONCLUSION

After read this guide, you must have become familiar with working of a plasma cutter. The best plasma cutter works to maximize the output and productivity. If you found it informative, share it ahead and don’t forget to leave your comments.

Image Source: Torchmate.com

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