Understanding the Functionality of Plasma Cutters

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Metal work has been essential to modern industry. The problem, however, is that metals are difficult to manipulate and form into specialized pieces. This is where plasma cutters come in. These tools have been around since World War II and have revolutionized the speed, accuracy, and types of cuts manufacturers can make in all types of metals. In this article, we’ll explore the science behind this system and see how one of the most fascinating tools has shaped the world around us.

Where Saws Failed


During World War II, private industry’s innovations in the field of mass production allowed U.S. factories to produce armor, ordnance, and aircraft almost five times faster than the Axis powers. One area of innovation rose out of the need to cut and join aircraft parts more efficiently. The breakthrough discovery was that charging the gas with an electric current formed a barrier around the weld, which protected it from oxidation. In the early 1960s, engineers figured out that they could boost temperatures by speeding up the flow of gas and shrinking the release hole. The new system could reach higher temperatures than any other commercial welder. In fact, at these high temperatures, the tool no longer acted as a welder. Instead, it worked like a saw, cutting through tough metals like a hot knife through butter.

States of Matter

A plasma cutter can pass through metals with little or no resistance thanks to the unique properties of plasma. So what is plasma?

There are four states of matter in the world: solids, liquids, gases, and plasma. These states are divided based on the way that molecules behave within each one. Plasma is one of the most prevalent states of matter in the visible universe. Conceptually, a plasma cutter is extremely simple. It harnesses the power of plasma to precisely cut and manipulate the metals needed to build something as large and as strong as an airplane wing.

Water can exist in three different states: solid, liquid, and gas. When water is solid, it takes the form of ice. The atoms in ice are neutrally charged and arranged in a hexagonal pattern, which allows it to hold its shape. In liquid form, water is drinkable and the molecules move slowly relative to each other, but they are still bound together. Although it has a fixed volume, it can change shape to fit any container. When water is in the form of gas, it is called steam. The molecules move independently of each other at high speeds, which means that gas has no fixed shape or volume.

The state of water is determined by the amount of heat (energy) applied to the molecules. When water is heated, the molecules become excited and break free from one another. With minimal heat, the molecules are tightly bound and water is solid. With more heat, the molecules escape the bonds and water becomes liquid. With even more heat, the molecules escape the loose bonds and water becomes gas. If gas is heated even more, it becomes plasma.

Plasma is formed when a gas is heated to extremely high temperatures. The energy breaks apart the gas molecules, and the atoms begin to split. The electrons in plasma separate from the nucleus, leaving behind positively charged ions. When the fast-moving electrons collide with other electrons and ions, they release a great deal of energy, which gives plasma its unique status and cutting power.

Plasma is not common on Earth because of its high temperatures. However, it makes up almost 99% of all matter in the universe. Plasma can be found on Earth in lightning and other places. Devices such as plasma cutters, neon signs, and plasma displays all rely on cool plasma to function. Although cool plasma cannot be used to cut metals, it has many other useful applications.

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Exploring the Inner Workings of a Plasma Cutter


The inside of a plasma cutter consists of an electrode at the center and a nozzle just below it, with a swirl ring causing the plasma to turn rapidly as it passes through. Regardless of size, all plasma cutters follow the same principle and are constructed around the same design.
Photo courtesy Torchmate CNC Cutting Systems

Plasma cutters come in various shapes and sizes, from monstrous plasma cutters that use robotic arms for precise incisions to compact handheld units found in a handyman’s shop. These cutters work by channeling a pressurized gas, such as nitrogen, argon, or oxygen, through a small channel. At the center of this channel lies a negatively charged electrode. When you power the negative electrode and touch the nozzle’s tip to the metal, a circuit forms, generating a powerful spark between the electrode and metal. As the inert gas passes through the channel, the spark heats it to the fourth state of matter, creating a stream of directed plasma moving at 20,000 feet per second (6,096 m/sec) and approximately 30,000 F (16,649 C), which turns metal to molten slag.

The plasma itself conducts electrical current, and the arc creation cycle is continuous as long as the plasma remains in contact with the metal being cut and power is supplied to the electrode. To keep this contact, protect the cut from oxidation, and regulate plasma’s unpredictable nature, a cutter nozzle has a second set of channels releasing a constant flow of shielding gas around the cutting area. The pressure of this gas flow effectively controls the plasma beam’s radius.

Click the On/Off switch to watch a plasma cutter in action.

Plasma Cutter Applications


In CNC (computer numerically controlled) cutting, you arrange your shapes on the computer screen and cut them automatically, without having to touch the material.
Photo courtesy Torchmate CNC Cutting Systems

Plasma cutters have become a vital tool in various industries, including custom auto shops, where they are used to customize and create chassis and frames, and by car manufacturers. Construction companies use plasma cutters for large-scale projects, cutting and fabricating huge beams or metal-sheet goods. Locksmiths use plasma cutters to bore into safes and vaults when customers are locked out.

Plasma Cutters for Art


Powermax 600 plasma cutter
Photo courtesy Torchmate CNC Cutting Systems

Previously, plasma cutters were expensive and used primarily for large metal-cutting jobs. However, in recent years, the cost and size of plasma cutters have reduced significantly, making them available for more personal projects. Artists and metal workers now use handheld cutters to create unique works of art that would not be possible with conventional metal-working tools. This single tool allows artists to bevel cuts, bore precise holes, and cut in any way they can conceive.

The plasma cutter is a fascinating and powerful tool developed in the 20th century. By utilizing basic principles of physics to harness the fourth state of matter, it performs with nearly magical results. As our understanding of plasma grows, one can only imagine how many more tools and applications will utilize this fantastic force of nature.

If you are interested in learning more about plasma and plasma cutters, as well as related topics, be sure to visit the links on the following page. There is a lot of additional information available.

Additional Information

Related HowStuffWorks Articles:

– How Fluorescent Lamps Work

– How Plasma Displays Work

– How Atoms Work

– What is the difference between a fluorescent light and a neon light?

More Great Links:

– Torchmate: Plasma Cutter Information

– Miller: Why Plasma?

– Plasmas.org: Perspectives on Plasmas

– Plasma Gate: Plasma on the Internet

FAQ

1. What is a plasma cutter?

A plasma cutter is a tool used to cut metal using a high-velocity jet of ionized gas, or plasma. The plasma is created by passing an electric arc through a gas, usually compressed air, and is then forced through a narrow nozzle. The result is a concentrated stream of hot plasma that melts through metal, creating a clean and precise cut.

2. What types of metal can be cut with a plasma cutter?

Plasma cutters can be used to cut a wide variety of metals, including steel, aluminum, copper, brass, and titanium. The thickness of the metal being cut will determine the power of the plasma cutter needed, as well as the size of the nozzle and the gas flow rate.

3. How does a plasma cutter differ from other cutting tools?

Compared to other cutting tools, plasma cutters offer several advantages. They can cut thicker metal than many other tools, and the cuts are cleaner and more precise. Additionally, plasma cutters can be used on a wide variety of metals, and they can cut through painted or rusted surfaces without damaging the metal.

4. What safety precautions should be taken when using a plasma cutter?

When using a plasma cutter, it is important to wear proper safety gear, including eye protection, gloves, and a welding helmet. It is also important to work in a well-ventilated area, as plasma cutting creates fumes and smoke that can be harmful to breathe. Additionally, care should be taken to avoid touching the metal being cut or the plasma stream itself, as both can be extremely hot and cause burns.

5. How do I choose the right plasma cutter for my needs?

When choosing a plasma cutter, consider the thickness and type of metal you will be cutting, as well as the power source available. Portable plasma cutters are available for smaller jobs, while larger industrial machines are available for heavy-duty cutting. Additionally, consider the cost of consumables, such as nozzles and electrodes, as well as the overall durability and reliability of the machine.

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