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Arc Plasma Cutting & How Does It Work ?

We all know that there are hundreds of different processes available for metalwork, especially when it comes to metal cutting. You can find various options for metal cutting, especially since most metal welding processes allow metal cutting by changing a few parameters. But, not all methods can be the most efficient ones. The main reason why a lot of metal cutting processes fail to work with thicker workpieces is the lack of temperature level needed for the job.

Therefore, you will usually find an arc plasma cutting set up in almost every single professional workshop. This is one of the highly beneficial metal-cutting processes that offers wide compatibility with a variety of metals and types of jobs. And for that, it is also one of the most popular metal-cutting processes in the industry.

Today, we are going to talk about arc plasma cutting in detail. In this guide, we will discuss the working principles of the method, its benefits, limitations, and variations of the process, and also talk about step by step procedure of how arc plasma cutting is actually performed. So make sure that you go through our guide sequentially to carefully understand each concept explained here.

Let us start with the question: What is arc plasma cutting?

What Is Arc Plasma Cutting?

As we stated earlier, arc plasma cutting is a metal cutting process that allows a wide range of metals and thicknesses of workpieces to be cut without a lot of hassle. In this process, a gas is overheated up to 30000°F or about 16500°C so that it can easily go through metal. Such high-temperature levels cause the gas to change its state to the 4th state of matter, plasma. More commonly, it is called the ionic state of gas that allows the conduction of electricity.

Once the gas is ionized, it is put under pressure and passed through a nozzle over to a tungsten electrode. The arc plasma cutting machine then adds electricity that completes the circuit and allows the metal workpiece to get cut with ease. Apart from cutting, the arc plasma cutting process can also be used to simply gouge the metal. This process generates a lower amount of exhaust gasses and noise. And, it is also economical if repetitive processes are required.

Advantages and Limitations Of Arc Plasma Cutting

Just like any other metal working procedure, arc plasma cutting also features a distinct set of advantages and limitations which play an important role in its applicability for a certain job. If you are also considering installing such a machine in your workshop, you should pay close attention to the process’s benefits and, even more importantly, the demerits. If one of the disadvantages appears to be a deal breaker in your case, it would not be a good idea to invest in an expensive arc plasma cutting setup.

Advantages of Arc Plasma Cutting

  • Little to no risk of workpiece deformation.
  • Offers precise control over the cutting procedure.
  • Cuts are produced without any residue slag, given that the workpiece is made up of steel or aluminum.
  • A lot of cutting positions are available for intricate cutting jobs.
  • It is a relatively fast-cutting procedure compared to other alternatives in the industry.
  • Suitable for a wide range of ferrous and selection of non-ferrous metals.
  • You won’t need gas cylinders for arc plasma cutting.

Disadvantages of Arc Plasma Cutting

Even though the benefits of arc plasma cutting might appear pretty good to be true, there are a few limitations that have a huge impact on the compatibility and economic benefit of the process.

  • The generated bevel is about 7 degrees, if not smaller.
  • A lot of safety protocols are to be followed before applying arc plasma cutting. Failure of that could result in severe accidents.
  • You must have a compressor in your workshop to pressurize ionic gas. Otherwise, the initial setup gets very expensive.
  • The process is dependent upon a strong source of electricity, limiting its portability.
  • It is not an economical cutting alternative for thick workpieces, especially thick steel.

How Does Arc Plasma Cutting Work?PLASMA ARC CUTTING WELDING

Now that you know what the benefits and demerits of arc plasma cutting are, it should be pretty easy for you to decide whether it is economical for you or not. If you still think that this process could turn out to be profitable for your work, you should consider getting one installed in your workshop right away. But before that, let us try to understand the basic working principle of arc plasma cutting.

To understand the working principle of arc plasma cutting, you first need to understand the setup of the machine and how various components are arranged. The setup of an arc plasma cutting includes a generator, arc, electrode, torch, and nozzle. The arc is present between the electrode and the workpiece and is initiated by the pilot arc between the nozzle and the electrode. The nozzle of the machine is connected to a ground terminal via a resistor to limit the flow of current.

The generator of the machine initiates the arc since it is connected to the electrode and the nozzle. Once the arc is generated, the connected power supply maintains a low current arc. As for the gas, it is pressurized and pushed through the orifice of the nozzle. It results in the generation of the main arc that is in direct contact with the workpiece. Once the process is started, you can open the pilot arc relay to control the heat levels and avoid overheating problems.

1. Cutting Torch

The cutting torch used in arc plasma cutting also has an impact on the end result and the compatibility of the process with the given material and its thickness. Using the wrong type of torch can lead to an improper cut or failure to cut through the workpiece altogether. The cutting torch is also commonly known as a plasma cutter, plasma gun, or plasmatron based on the manufacturer and region of development.

You will also notice plasma cutting torch holders on the automatic arc plasma cutting machines. If you are looking for a cutting torch to fit with the holder, you will have to pay attention to the compatibility of the torch with the holder. Once you manage to fit the torch in the holder, make sure that you keep the torch at least ¼-inch away from the cutting plate before you start the process. It is recommended to not let the tip come in contact with the plate unless the manufacturer specifies otherwise. It is also a good practice to start the cutting process from the edge for good results.

2. High Current Arc Plasma Cutting

High-current arc plasma cutting is a process that uses, well, high-current settings for arc plasma cutting. For this method, the torch is to be mounted on an automatic carriage. With that, the machine can be programmed to move the carriage and you can obtain precise cuts on the metal. You can also perform the same using the cutting setup created for Oxyfuel cutting, given that you can tweak it to offer a suitable cutting speed.

Also, make sure that a continuous water spray is available while cutting. It is used to create a protective coverage around the plasma and reduce the resulting exhaust smoke and noise. You can also put the water spray onto the metal which is undergoing the process and get pretty much the same results.

3. Arc Plasma Cutting Positions

One of the main benefits of arc plasma cutting is that it can be used in multiple cutting angles and positions. Therefore, you can use an arc plasma cutting setup for cutting as well as gouging through the metallic surface. However, keep in mind that the cutting torch is a special type of tool which is designed only for cutting metal. So, it cannot be used for welding.

You can also use the machine in a non-flat-cutting position. But for that, make sure that you are using low-power plasma and keeping the amperage level below 100 Amps. High-power plasma arcs can be hazardous, especially if you are not performing a flat-position cutting.

4. Arc Plasma Cutting Procedure

If you are just getting started with arc plasma cutting, you must not be familiar with the procedure or wondering if there are any cautionary steps that you need to take to ensure safe and accurate results. Well, we will be explaining the arc plasma cutting process in detail right here so that you can go over the method and understand how the cutting should be performed. For better understanding, we will go through the arc plasma cutting process step by step.

  1. The very first thing that you need to do is check the pressure level and keep it around 70 PSI for good measure.
  2. Connect the ground clamp with the workpiece.
  3. Turn ON the cutting process.
  4. Before you put the cutter in contact with the workpiece, try to adjust the amperage level to match the workpiece material and thickness.
  5. Correctly position the cutting torch over the workpiece.
  6. Start the cutting arc by enabling the ignition on the machine.
  7. Now, the process gets quite simple. All you need to do is move the arc based on the cut you are making on the machine. Although, make sure that the nozzle is kept between ⅛-inch to ¼-inch from the workpiece at all times.
  8. If you are working on a thicker material, you should decrease the travel speed of the torch for effective results.
  9. Lastly, make sure that the input of the compressor is getting moisture-free input and that the filters are working properly.

As for compatible metals that can sustain arc plasma cutting, you can use the process for a wide range of ferrous as well as non-ferrous metals such as Aluminum, Brass, Cast Iron, Copper, Magnesium, Steel and Steel Alloys, Nickel Alloys, etc.

5. Controlling Factors of The Process

In an arc plasma cutting machine, there are some controllers that are to be monitored at all times for a good cutting result. On all standard machines, there are special controls provided for plasma intensity and gas flow. Apart from that, it is also important to maintain proper control of the cooling water in the process to keep the torch temperature under control. You can also make the cooling system self-contained by recirculating the water using a pump and a heat exchanger. This way, you will get an even more efficient arc plasma cutting circuit.

Different Types of Arc Plasma Cutting

There are a few different variations of arc plasma cutting that can change the efficiency of the process based on the application. These variations make the process suitable for material varying between ⅛-inch to 1½ inches in thickness. Some processes also include an additional shield of gas or water to further improve the results.

1. Dual Flow Plasma Cutting

Dual-flow plasma cutting is a process that offers an extra covering of gas blanket around the plasma arc. Usually, Nitrogen gas is used as the secondary shielding around the cutting zone. However, the secondary gas can vary based on the material that is being processed. For mild steel, carbon dioxide is preferred whereas a mixture of Argon and Hydrogen would be ideal for Aluminum.

2. Water Shield Plasma Cutting

This is a pretty similar arc plasma technique compared to the one we just saw. The key difference here is the type of element used for the additional shielding. Here, water is used instead of secondary shielding gas, thus the name water shield plasma cutting. However, there aren’t that many benefits of the process. For example, the cutting accuracy or speed does not show any significant improvement. However, you can expect a good finish on the cut part as well as an extended lifespan of the nozzle by replacing the secondary gas with water.

3. Water Injection Plasma Cutting

This is more of a modification of the standard arc plasma cutting procedure. Here, a simultaneous water jet is used alongside the nozzle orifice so that the plasma flame could be made narrower and more precise. The water jet also acts as a shielding gas and prevents contact with external contaminants and particles. There are also some changes in the construction of the tools. For example, the nozzle end used for water injection plasma cutting is made up of ceramic material to avoid the formation of double arcs.

Importance of Ventilation

There is a lot of volume of exhaust gasses and particles generated while performing the arc plasma cutting process. Therefore, one must create a proper exhaust system for the machine and ensure that it has proper ventilation. Also, it is helpful to deposit the particles directly into the water so that the hot charades of metal would get cooled down instantly. It also reduces the fumes released directly into the air.

Safety & Troubleshooting

As you may have noticed so far, the temperature levels are quite high during arc plasma cutting. Therefore, you will have to take many precautions and maintain safety standards while performing arc plasma cutting. Even a slight mistake could result in an accident. First of all, we will suggest covering the face completely to avoid coming into contact with the high-temperature particles. As for the eyes, you will need high-safety goggles that you can easily find on the market.

It is also helpful to cover ears with protective gears since the noise levels can get uncomfortably high during arc plasma cutting. Other safety precautions are pretty much standard such as gloves and protective clothing such as a workshop apron which is necessary for almost all industrial processes, let alone arc plasma cutting. You should equip yourself with a welder’s helmet since the bright arc can reduce the vision of the cutting area.

Conclusion

Arc plasma cutting is a widely used metal cutting procedure and is currently being introduced in many professional and small-scale workshops all around the country. The main reason for choosing arc plasma cutting over other options is its compatibility with a variety of materials such as Stainless Steel, Aluminum, Cast Iron, and some popular non-ferrous metals as well.

So if you also want to learn about arc plasma cutting, this is the perfect place to get a hand on the basics of the process as well as its variations and safety standards. We have covered almost all important aspects of the process here so that you can easily understand the process in detail. If you are not sure about any concept or terminology specified here, kindly drop your query in the comment section below.

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