how does a plasma cutter work

How Does a Plasma Cutter Work

Today I will explain to you how does a plasma cutter work, the tools involved, and the different types of plasma cutting systems.

A plasma cutter uses electrically conductive gas as the power to cut through metals. The different types of gases used include nitrogen, oxygen, compressed air, and argon, which are forced through the small nozzle orifice in the torch.

The external power supply generates an electric arc, which is introduced to the high-pressure gas flow as a plasma jet. The plasma jet can attain a high temperature of 40,000 degrees Fahrenheit, quickly cutting through the workpiece and blowing away the resulting molten material. 

How Does a PlasmaCutting System form Plasma?

Plasma is the fourth state of matter. Most people know the states of matter as solid, liquid, and gas. You get plasma when you heat the gaseous state further, which means plasma is simply ionized gas

Plasma has open electrons and positive ions, meaning it has no electrical charge. Plasma arc is generated when the gas is forced through the small nozzle at high pressure. Gases like argon, oxygen, nitrogen, and compressed air are mostly used in this process. 

The plasma cutter has a power supply that induces electrical current into your gas, making the plasma cutter ready to cut. The cutter can reach super-high temperatures enabling it to easily cut through various materials including metals. 

Components of a Plasma Cutter

Plasma cutters have parts that work together enabling the cuter to function. Understand these parts and their functions to comprehend the working mechanism of the plasma cutter. Below are the most important components you need to know and understand. 

Plasma Torch

This is the part that aligns the consumables and cools them. Consumables come with everything necessary to generate plasma arc.

For instance, it has a nozzle through which the compressed air is released. Also, it has an electrode and swirl ring. The plasma torch has both the inner and outer shield caps that hold the parts together. 

Power Supply

The plasma cutter uses a power supply that can convert AC into constant DC power to run the device. The DC power enables the cuter to cut properly. Have a power supply that can easily change the voltage depending on the type of material you are cutting. 

Arc-starting Console

This is a vital part of the plasma cutter and it starts the whole cutting operation. The unit generates a spark that ignites the plasma and starts up the cutting. Without a spark, your unit can’t ignite, which means you can’t achieve the high temperature necessary for cutting the materials. 

How Does a Plasma Cutter Work?

The plasma cutter works by creating an accelerated jet of extremely hot plasma through the workpiece or material to make the cut. The hot plasma jet comes from the compressed gas or air passing through a high-speed small nozzle of the torch pointed to the material. 

The electrical arc comes from the external power supply which immediately ionizes the gas creating a plasma jet. The accelerated plasma jet supplies extremely high heat to melt down the material as the combined high-speed plasma compressed gas blows away melted metal pieces during cutting. 

Working Mechanism

Once you turn on the plasma cutter, it forces compressed air through the small nozzle.

However, the compressed air lacks the heat needed for the plasma to work. The heat is produced by the contact method when the nozzle and metal touch physically to create a circuit that allows the discharge of electric current from the electrode, creating a spark that starts the cutting process. 

Some plasma cutters use high-frequency methods to create a pilot arc without actual physical contact between the material and machine. The high-frequency cut quality torch comes close to the metal and upon getting in contact sparks and transforms it into the arc. 

Once the plasma arc reaches the steel, it passes the generated heat into the machine. The fast plasma speed and extreme temperature ensure the heat transfer is not fast enough. This means the plasma cutter is in the proximity of the oncoming plasma to melt into a liquid slag. As the cutter moves to new areas, it produces a plasma cut which solidifies the liquid slag giving a clean cut like a saw. 

Categories of Plasma Cutting Systems

Plasma cutters are grouped into two categories; conventional and precision plasma systems. But what are they? 

Conventional Plasma Systems

These systems use shop air as the primary plasma gas. The face of the plasma arc is defined by the nozzle orifice. The system uses plasma arc amperage of approximately 12-20 K amps per sq. inch. All handheld plasma cutters use conventional plasma. This is mainly because of the forgiving part of tolerances. 

Precision Plasma Systems

These systems are also known as high current density. They are engineered and designed to produce the sharpest and highest quality cuts this is only achieved with plasma.

The consumables and torch designs are complex and include additional pieces to constrict further and shape the plasma arc. The precision plasma arc uses 30-50K amp per sq. inch.

This plasma system can use gas varieties like oxygen, nitrogen, high purity air, and argon/hydrogen/nitrogen mixture for optimum results of different conductive materials. 

What is the Plasma Cutting Operation?

Plasma cutting systems use either handheld or precision plasma operations. 

Handheld Plasma Operation

This is where the electrode, air plasma, and consumable parts are in contact inside the torch when the cutter is off. The moment you squeeze the trigger, the power supply produces a DC current which flows through the connection initialing plasma gas flow.

Once the plasma gas builds up enough pressure, the nozzle and electrode are forced apart causing an electrical spark converting the air into the plasma jet.

Besides, the DC current flow switches from the electrode to the nozzle. The airflow and current continue until the trigger is released. 

Precision Plasma Operation

Here the electrode, plasma torch, and nozzle don’t touch and are separated by a swirl ring with small vent holes transforming the plasma gas into a swirling vortex. When the power supply gets a start button, it generates a maximum of 400V DC and initiates plasma gas flow through the hose leading to the plasma torch.

The nozzle is connected to the power supply’s positive potential via the pilot arc circuit with the electrode at a negative.  

The Arc starting console generates a high-frequency spark causing the plasma gas to ionize and be electrically conductive creating a plasma arc.

Once the pilot arc has contact with the workpiece, the current path chances and starts flowing from the electrode and not the nozzle which explains the shape of the plasma jet. 

To cut the selected amperage, the power supply ramps up your DC current and gets a new plasma gas for the workpiece. A shielding gas flows from the shield cap to reshape and impact the plasma arc to give you a quick and super-precise cut. 

FAQs

Can a MIG welder be used as a Plasma Cutter?

Yes. But you need a carbon electrode and air compressor along with other small items. You also need to keep the amperage between 25-50 and increase your wire feed speed. Change your air from carbon dioxide to nitrogen or air. Alternatively, you can just buy a MIG welder plasma cutter combo machine. 

How thick can a Plasma Cutter Cut?

If you are using a handheld plasma cutter, the maximum cutting thickness capacity is 38mm. However, a precision plasma cutter can cut steel of 6-inches thickness. Plasma cutters can handle any electrically conductive metal of thickness 1-2 inches comfortably. Metal thickness beyond 2-inches requires expert and careful cutting. 

Do you Need a Welding Mask for Plasma Cutting?

No, you don’t. But if you are doing a long continuous operation, it’s best you wear a welding mask. Also wear a welding mask if you are operating an 800amp plasma torch at a distance similar to a welding torch. This protects your eyes and ensures you can continue cutting the exact location with clean cuts. 

Can a Plasma Cutter Cut Wood?

A plasma cutter can cut through any electrically conductive material. Wood is not electrically conductive. The materials should conduct electricity like steel, aluminum, copper, brass, etc. This means plasma cutters are not conducive for cutting non-conductive materials like glass and wood. 

How long Do Plasma Cutter Consumables last?

The lifespan of the consumables depends on the extent of usage. Consumables wear out with time and should be replaced to get better performance. The electrode and nozzle wear out quicker than other consumables because they are directly involved in the cutting arc. 

Replace the nozzle when the hole becomes too large visible through visual inspection. Replace the electrode when the pit grows beyond 1-1.6mm. 

Final Word

Understanding how does a plasma cutter work is very essential before you start working with it. 

A plasma cutter is a powerful machine that can cut through different conductive materials. The cutter can make complicated, angled, and curved cuts and work on thick materials. 

This is the perfect cutter. If there is a malfunction, use your knowledge of the cutter components to locate the problem, replace and continue cutting. 

Understand the cutting process to avoid injuries from improper handling of the machine. The melting and solidifying process is super fast and gives you a precise cut. 

Feel free to make inquiries if you have a question. 

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