Basics of Plasma Cutting - A Guide
Dec 15, 2023
If you're new to plasma cutting, you may find the process a bit daunting. However, with the right guidance, you can quickly master the basics of this simple and efficient cutting technique.
Plasma cutters are relatively straightforward machines and the plasma arc is much easier to handle than welding arc. Additionally, the entire setup is much less complex than the Oxy-acetylene cutting process. In this article, we will guide you through the basics of plasma cutting and show you how to set up your equipment for optimal results. By the end of this article, you'll be well on your way to making precise and efficient cuts with your plasma cutter.
What is Plasma and How Does the Plasma Cutting Process Work?
When working with plasma cutters, plasma is defined as an electrically heated gas that becomes ionized gas or electrically conductive. Plasma is the fourth state of matter and is created by heating the air to extreme temperatures. This ionized air/gas under pressure becomes a plasma cutting arc that is used to slice metal.
The plasma cutting process begins inside the plasma torch, where an electrode receives electricity from the machine, and compressed gas or air is supplied through the torch. Once the electrode initiates the arc with the conductive metal (work-piece), the plasma gas arc is born. At this point, the compressed gas conducts the electricity and becomes plasma that bursts under high pressure through the small opening at the end of the nozzle.
This electrically conductive air is a plasma arc that cuts the metal thanks to the incredibly high temperature that is concentrated in that small dot where the plasma touches the metal piece. The plasma arc formation begins when a gas such as oxygen, nitrogen, argon, or even shop air is forced through a small nozzle orifice inside the torch. The gas flow is then ionized by a spark from the electrode, creating a pilot arc. Once the pilot arc touches the metal, it ionizes the metal and creates a path for the plasma arc to follow.
Plasma cutting technology uses plasma to transfer energy from a power supply to any conductive material, resulting in a cleaner, faster cutting process than with flame cutting. The plasma arc heats the metal to its melting point and then blows away the molten material with a high-velocity jet of ionized gas. The shielding gas, such as argon, carbon dioxide, or nitrogen, is used to protect the cut from oxidation. The plasma cutting process can cut through any conductive metal, including mild carbon steel, stainless steel, aluminum, and copper.
What Can You Cut With a Plasma Cutting Process?
Plasma cutting is a thermal cutting process that can cut any electrically conductive metal. This includes mild carbon steel, stainless steel, aluminum, copper, or any other non-ferrous metals. As long as the metal conducts electricity, it can be cut with a plasma cutter. It is a clean process that makes smooth cuts as long as your plasma cutter has enough power for the thickness you are working with.
Plasma cutting has a wide range of applications and can be used in your home garage, outside (when it is not raining), in a welding shop, on site, or wherever you need to cut conductive material. It is a much easier process to learn than oxy-fuel cutting and does not require oxy-acetylene gas tanks, which are a fire hazard and require a special storage area.
How Does It Fare Against Oxy-fuel Cutting?
Oxy-fuel cutting can only cut steel and ferrous metals that support the oxidizing process. That's because it cuts by burning or oxidation. This means that you can't oxy cut aluminum and stainless steel, for example.
When cutting metal with a plasma arc, you don't need to preheat it unlike with Oxy cutting. Oxy cutting is only a better choice if you are cutting very thick metals or if you are working in a place where electricity is not available or desired. But for regular hobbyist use, plasma cutters are a much better choice.
Plasma cutting requires air pressure, so you will need an air compressor. But unlike gas fuel bottles, you don't have to "refill" the air supplies. Air is literally everywhere and it's free. Although a compressor isn't free, neither are the gas tanks and they are much more difficult to move around.
Storing a plasma cutter is simple. Unplug it and place it in a relatively safe area, and there should be no problems while owning an Oxy-Fuel system requires much more caution.
In summary, plasma cutting can cut any electrically conductive metal, while oxy-fuel cutting is limited to steel and ferrous metals. Plasma cutting requires an air compressor, but it is easier to store and move around than gas fuel bottles. It is also a cleaner process and does not require preheating the metal.
What to Look for When You Are Evaluating a Plasma Cutter for You
When it comes to purchasing a plasma cutter, there are several important factors to consider. In this section, we will discuss the most important features and specifications that will have a big impact on the machine's abilities and cost.
The Maximum Cut Thickness and Amperage
The maximum cut thickness and amperage of a plasma cutter are important factors to consider. Every plasma arc cutting machine is rated for a certain clean cut thickness and maximum cut/severance thickness, and this is more or less in accordance with its amperage power output. The maximum clean cut represents the thickness that you can cut without any difficulties, and the maximum severance cut is the thickness that the machine will cut, but it may struggle, be slow, and the cut's edge will not be as pretty. The amperage will dictate most of the plasma arc cutting thicknesses, but so will the type of metal being cut. Some metals are more difficult to cut than others. For example, a 55 amperage output may be enough to do a clean cut on a 1/2" mild steel plate, but your cutting speed will be slower if you were to do the same thickness and amperage with stainless steel. It is important to choose a plasma cutter that can handle the thickness of the metal you will be cutting.
The Plasma Cutter Duty Cycle
The duty cycle of a plasma cutter represents the time period when your machine can work in contrast to the time period when it needs to rest. It is presented in percentage value and for the time intervals of 10 minutes. When it comes to plasma arc cutting thick materials that sit in the range of the maximum thickness the plasma cutter can handle, you will be pushing the machine to its maximum duty cycle, so you should pay attention. Just keep it somewhere in your head that as you approach the maximum time use that the machine should rest. The resting periods let the machine cool down so that there is no damage to the internal circuitry.
A High-Frequency Start or a Blowback Plasma Cutter?
A High-Frequency start plasma cutter is a good choice if you don't use any electrical devices in the workplace area. The High Frequency plasma arc start can interfere with the surrounding electronics like cellphones, laptops, CNC machines, other tools and machines and etc. The blowback technology pilot arc plasma start is a different method that is safe to surrounding electronics. These plasma cutters have a special system inside the plasma torch that initiates the pilot arc by an electrode movement which opens the circuit and causes the electric spark. Blowback start plasma cutters are more expensive, but they are a better choice if you use sensitive equipment in the work area.
The Power Input and Portability
The power input and portability of a plasma cutter are important factors to consider. Some plasma arc cutters work only when plugged in a 220V power supply while many offer dual voltage capabilities 110V / 220V. However, you should pay close attention to the amperage output when the unit is in the 110V mode. It will not be able to produce the maximum amperage that it can produce with the 220V input. The portability of the plasma cutter is also something to consider. If you are a welder and your work site is constantly changing depending on the job, it is very helpful if your machine is light and you can actually work with the voltage that's available on site.
Plasma Cutter Consumables
Your plasma cutter will need what is commonly known as consumables. These parts are replaced often and are generally not very expensive. However, some brands don't offer a good price to quality ratio of their consumables, and you will be replacing them very often. These consumables include but are not limited to nozzle tip, shield cup, gas ring, electrode, and etc. This will depend on the brand.
In summary, when you are evaluating a plasma cutter for you, it is important to consider the maximum cut thickness and amperage, the plasma cutter duty cycle, whether to choose a High-Frequency start or a blowback plasma cutter, the power input and portability, and the cost and quality of the consumables. By considering these factors, you can choose the right plasma cutter for your needs and budget.
How to Plasma Cut
If you are new to plasma cutting, it is important to know some basics before you begin. This section will cover plasma cutting safety and cutting technique.
Plasma Cutting Safety
Although plasma cutting is not as dangerous as welding, it still poses some risks. The plasma cutter can output extremely high voltage, up to 10 times what welding machines output. Therefore, it is important to take safety precautions.
- Wear proper welding attire to protect yourself from sparks and molten metal. This includes ArcCaptain leather gloves, a leather apron, proper welding pants, and welding boots.
- Be mindful of your surroundings. Do not stand in water, and do not use a plasma cutter if your hands and body are wet/sweaty. Wear nonconductive footwear and gloves.
- Protect your eyes with a welding helmet or safety glasses that have a proper DIN shade rating for plasma cutting.
These are just some of the basics of plasma cutting safety. Always follow the instructions that come with the machine manual and the work safety codes and standards in your area.
When it comes to cutting technique, there are a few things to keep in mind.
- A good technique for beginners is to use a drag shield extension for your plasma torch. This will allow you to rest the torch on the workpiece, making it easier to be precise when plasma arc cutting.
- Place your plasma cutting torch at an angle of about 60 degrees from the horizontal plane and about 30 degrees from the vertical plane while initiating the pilot arc. Then proceed to rotate the torch to the vertical position.
- Find an adequate cutting speed in accordance with the metal thickness. You can do this by observing the angle at which the molten metal is being pushed down the cutting line and by examining the cut quality.
- If you move too slowly, the molten metal dross will leave a residue at the bottom of the cut. If you move too fast, there will not be a clean penetration from the top. The angle at which the molten metal should fall from the cutting line when observed from below is about 20 degrees.
It is best to test some cuts on scrap metals. Start with thin pieces of metal until you get the hang of it. With some training, you will develop your technique and this will come easy to you.
Remember to always wear appropriate safety equipment, such as gloves and a helmet, and ensure proper ventilation to avoid inhaling slag and fumes. By following these basic steps, you can achieve quality cuts with precision and efficiency.
In conclusion, plasma cutting is a relatively easy process that requires proper preparation and a quality machine. Safety protocols should always be followed to avoid accidents. If you are new to plasma cutting, it is recommended to start with scrap metal and practice gradually. Don't expect perfect cuts from the beginning, but with practice, it becomes straightforward. Compared to oxy cutting, plasma arc cutting is easier and less time-consuming. If you encounter any issues during a project, troubleshooting is usually straightforward and can be done with the help of online resources or a professional. Proper repair and maintenance of your plasma cutter will ensure its longevity and optimal performance.
Frequently Asked Questions
What safety precautions should be taken when using a plasma cutter?
Plasma cutters can be dangerous tools if not handled properly. Here are some safety precautions you should take when operating a plasma cutter:
- Always wear protective gear such as gloves, eye protection, and a welding helmet.
- Make sure the work area is well-ventilated to prevent the buildup of toxic fumes.
- Keep the plasma cutter away from flammable materials.
- Never touch the electrode or workpiece with your bare hands while the plasma cutter is on.
- Make sure the workpiece is properly grounded to prevent electrical shock.
How does plasma cutting differ from laser cutting in terms of application?
Plasma cutting and laser cutting are both thermal cutting processes, but they differ in terms of application. Plasma cutting is better suited for cutting thicker materials, while laser cutting is better suited for cutting thinner materials. Plasma cutting is also faster and less expensive than laser cutting.
What are the key advantages of using plasma cutting over other cutting methods?
Plasma cutting offers several advantages over other cutting methods, including:
- Ability to cut through thick materials quickly and cleanly.
- Low operating cost and minimal maintenance requirements.
- Ability to cut a wide range of conductive materials.
- Ability to make intricate cuts with high precision.
Which materials are unsuitable for cutting with a plasma cutter?
Plasma cutters are designed to cut through conductive materials such as steel, stainless steel, and aluminum. However, they are not suitable for cutting through non-conductive materials such as wood or plastic.
Can you describe the basic steps involved in operating a plasma cutter?
Here are the basic steps involved in operating a plasma cutter:
- Set up the plasma cutter and connect it to a power source.
- Choose the appropriate cutting tip and install it on the torch.
- Turn on the plasma cutter and adjust the amperage and air pressure settings.
- Hold the torch perpendicular to the workpiece and trigger the plasma arc.
- Move the torch along the cutting path, maintaining a consistent distance from the workpiece.
What are the fundamental principles that govern the operation of a plasma cutter?
Plasma cutters work by passing a gas, such as air or a mixture of gases, through a high-frequency arc. This causes the gas to ionize into plasma, which is a highly energetic state of matter. The plasma is then directed through a small orifice in the cutting tip, where it comes into contact with the workpiece and melts the metal. The molten metal is blown away by the force of the plasma, resulting in a clean cut.