Plasma Cutter (plasma arc cutting) is a modern machine that performs the process of welding and cutting most accurately. A plasma cutter is a tool that cuts through electrically conductive materials like steel and other welding materials, which are of different thicknesses using accelerated hot plasma.
Plasma cutting traces its origin back to the 1960s. It was a sophisticated version of plasma welding technology in the 1980s. The combination of CNC technology made plasma cutting more effective, accurate, and fast. By the 1990s, it was possible to create and cut customized designs with it. However, CNC plasma cutting was limited to flat surfaces only using only two-axis (x and y).
It was better than the existing metal-cutting methods because it did not create metal chips while processing. Moreover, the finishing edge is also clean with accurate cuts. It had a huge demand for mass productions and repetitive cutting in the factories.
What Is Plasma?
Plasma is a gas, and it is an electrically conductive medium in which it has an equal number of positive and negative charges. When the atoms in the gas become ionized, these charged particles are produced. The plasma gases are formed using argon, hydrogen, or nitrogen. These gases are used in the conventional system, tungsten as an electrode. In the case of copper with hafnium as an electrode, oxidizing gases such as air or oxygen can be used.
Plasma is considered the most abundant state of matter in the universe. It is produced when the gas is heated, as when the liquid is boiled, it changes into a gas. Plasma is sometimes considered the fourth state of matter, different from solid, liquid, and gas.
Components Of Plasma Cutter
The plasma cutter setup consists of a plasma table, motors, cables, plasma torch, cables, gantry, encoders, and drive amplifiers. The plasma cutters always use a copper nozzle to compress the gas stream with the arc flowing through it. The weldor needs a welding gun, welding torch, and plasma torch to generate plasma from the nozzle.
Plasma tables are a crucial part of the entire process because the process involves a lot of spark and heat. Nozzle generates electric currents for creating plasma to cut metal sheets on the plasma table. You need to add other tools to your plasma tables like a computer, plasma torch, gantry, and ventilation fans for better performance. Here are two types of plasma tables that you can consider-
This budget table is less expensive and is better for cooling and ventilation purposes while working. You do not need a separate dust collector for cleaning debris. It keeps the heat of the plasma torch in check by quickly submerging and resurfacing it in water. Other benefits include heat distortions, fewer arc flashes, and noise.
This table is more expensive and has an in-built ventilation mechanism. It is capable of clearing debris and fumes of the processed metals to clear through the perforated surface. For better functioning, you can add a turbine-style fan in the center of the table too.
Importance Of Plasma Torch
The plasma cutter machine is considered an electrically heated gas stream. Inside this plasma stream, electricity was flowing through the gas and compressed through a small opening that is dense and moves very fast. The resulting stream can melt and blow through most of the metal, called a plasma torch.
As mentioned above, the plasma cutting torch usually uses a copper nozzle to compress the gas stream with the arc flowing through it. Tungsten is a great electrode material, and a small plasma torch uses a ‘pencil’ style electrode that is entirely made of tungsten with sharp edges.
But in the presence of oxygen or compressed air as a cutting gas for the metal, tungsten burns up. Initially, the plasma torch is moved while the sheet of metal to be cut remains stationary. So, these torches are fitted to the cutting table. Another method is also used to cut the metal by touching the torch tip to create a spark and using the high-frequency circuit as a spark plug.
The plasma cutter torches are different from that of the oxy-fuel process. It uses a pilot arc to melt the metal. In the oxy-fuel process, the air or oxygen will oxidize the metal. And finally, the heat from the exothermic reaction will cut the metal.
Materials That You Can Cut With Plasma Cutter
The plasma cutters using pilot arc are used to cut the metals that form stainless steel, aluminum, and cast iron. Compared to the oxy-fuel process, plasma cutter torch using the pilot arc method is more competitive. And this can cut carbon, stainless steel, aluminum, nickel alloys, titanium which are electrically conductive.
Which one is better- Mechanized or Handheld Plasma Machine
Either you can go for a manual or handheld plasma cutter or a CNC plasma cutter as per your requirement. Manual plasma cutter is easy to use, rotate, and carve on the surface area of metal sheets and plates, pipes, and straps up to 38 mm. They are quick and good for welding, metal fabrication, and cutting small shapes. But you cannot get accuracy and even cutting because of handheld posture. So, here you have to compromise the cutting quality if you are not excellent in cutting.
On the other hand, by using a mechanized plasma cutter you can achieve high-quality cutting, smooth finishing, and faster production simultaneously. You need to feed the instructions to your computer software and can cut up to 150 mm. It will direct the whole cutting process without any manual interference. However, it uses linear motion cutting, and you need to be sure of all the coordinates for the cutting process. If any technical error occurs, it will ruin the entire process.
Advantages Of Plasma Cutter
Here are some of the advantages of using a plasma cutter-
Electrical-Conductive and High Alloy Metals
Plasma cutters are capable of cutting electrically conductive metals appropriately. The other cutting methods used for these metals are not as effective. For electrically conductive metals, it is a quicker and cheaper method to rely on.
It can cut high alloy aluminum and steel materials easily and accurately. You can cut very thick metals with precision.
Plasma cutters are an advanced form of cutting metals because they can cut precise and complicated designs with sophistication. The cutting edge will be clean and smooth. You can use it for welding complicated tools as well.
You can attach a computer and command the plasma cutter for cutting the desired shape through software. CNC plasma cutting allows creating complex cutting effortlessly.
Ease To Use
Plasma cutters are easy to use. You do not need to perform any complex calculations or need elaborate machinery. There is no need to pre-heat the plasma torch. It comes fully computerized.
Plasma cutters are capable of fast cutting of metals than the rest of available technology like oxy-fuel. Handheld plasma cutters are quick to cut metal sheets, and you can easily rotate them as you want.
CNC plasma cutters are fully automated, and updated versions do not require manual efforts. It has replaced manual labor in hazardous places. Moreover, automation provides faster and accurate cutting.
They are safe to use if you take preventive measures like proper gear, mask, and ventilation space. The plasma tables contain an in-built exhaust system to reduce fumes and debris. The underwater plasma cutting process generates low heat and noise.
How To Use A Plasma Cutter
The basic principle of the plasma cutting machine is that the arc is formed between the electrode, the cathode, and the workpiece creating a high velocity. Generally, inert gases are passed through the copper nozzle, blown out when the gas begins to flow and cut the molten metal.
Here are the steps of the CNC plasma cutting mechanism-
- Install the setup and check proper internet connection, voltage, and cable wires.
- Place the metal on the table and check the height of the plasma torch.
- You need to send “M-codes” and “G-codes” to the plasma torch through the computer software and start running the CAD files.
- Monitor the cutting process and keep the nozzle and torch cool by using ventilators.
- After completing the process, take the metal for post-processing manually.
The plasma arc cutting machine is an alternative method to the oxy-fuel process. The plasma cutter has a hot melting point sufficient to cut the metal and uses a pilot arc type to initiate the arc. The plasma cutting machine also uses several methods to initiate an arc. All these power plasma cutter uses inverter type of Infineon IGBT-Insulated Gate Bipolar Transistors.
Plasma cutters are heavily used for manufacturing different components for industrial, agricultural, and local market usage. They are used to carve and create complex designs, symmetrical prints, complex cutting of metals.
They are a good source for welding and metal fabrication. It is easier to repair and cut complex automotive parts with a plasma cutter.
Plasma cutters are faster and can cut accurately and effectively. That is why they are best suited for industrial production belts and mass production.
Scrapping And Dismantling
They are perfect for dismantling and scrapping unused and outdated materials. They can easily cut them as per the instructions.
They are also used for restoration, welding, and cutting in the construction sites for buildings and bridges.
Shipbuilding is another important platform where we use plasma cutters for making and dismantling ships.
Limitations Of Plasma Cutter
Here are some of the shortcomings of a plasma cutter that you should know-
The processing area for cutting metals is limited to 160-180 mm if you do it on the table. If you are doing underwater cutting, it is limited to 120mm only.
Hardening Of Edges
Though you will get a smooth cutting edge by plasma cutting, the edges might get hardened. Excess heat production during cutting affects the metal edges.
Only For Regular Business
If you are looking for occasional cutting and not commercial purposes, a plasma cutter will be expensive. This is best suited for specialization projects only. Moreover, you can go for cheap alternatives for cutting purposes like hacksaw blades or grinders.
It requires separate motors for all axis rotations and a lot of cable setup. Thus it consumes more power and increases your electricity bill.
You will also need to do post-processing the edges and surface of the resolidified metals. The dross formation requires manual post-processing.
Configurations For Plasma Cutting
Initially, plasma cutting was restricted to the plane surface only by using only two-axis, but now you can cut in more dimensions. Here are three configurations that you can use for plasma cutting-
It is the basic configuration of every plasma cutter. Using it, you can plasma cut up to 150 mm thick metal on plane surfaces at a 90-degree angle. It has an “x” and “y” axis for cutting motion.
By adding the third axis “z,” the 3-axis configuration can also cut metal into other angles. You can produce three-dimensional designs using this configuration because it allows you to tilt the cutter and carve on the surface. The cutting remains the same throughout the metal thickness. It is a good option for welding, making holes, and chamfer edges.
The third configuration is based on a fixed plasma torch and moving workpiece in the longitudinal axis on the plasma table. It also uses a three-dimensional axis to cut long sections like tubes or pipes. This process is used for welding pipework.
How To Cool Plasma Cutter
Plasma cutting generates a lot of heat and spark. Thus it is necessary to cool down the machine components for longer use. Water is the best coolant for it. The plasma torch is the most heated part because it produces nitrogen-based plasma gas. So, you can inject water into it. Due to high constriction, the temperature will rise to 30,000 degrees celsius.
Another method to cool the plasma cutter is to use high-powered exhaust fans and a proper ventilation setup. This will significantly cool down the temperature and lessen the risk of double curvature, nozzle-break, and cutting speed during cutting and welding. It will clear the fumes and debris and slow the heating process.
Things To Consider While Plasma Cutting
Here are a few tips to follow if you want a hassle-free process-
Proper Assembly Of The Components
It is the most important thing before starting the cutting or welding process. Make sure the nozzle is properly attached to the plasma torch. And the plasma gun is at the correct height. The computer and encoder cables are well connected, and you have a good internet connection.
Selecting The Appropriate Gas And Its Pressure
You need to select appropriate gas for plasma because it is crucial for effective cutting. The purer gas will provide more sophistication in the cutting and welding process. If you are using nitrogen gas or oxygen gas, it should be at least 99.5% pure.
You need to regulate gas pressure as well because it will directly impact the plasma arc. The plasma arc will be larger in diameter during the low gas pressure.
Cutting Area And Cutting Speed
The plasma torch will cut the metal as per the given command. It has its working area limitations. So, you need to check the cutting dimensions as well as plasma torch height and speed. The cut value should be in positive numbers.
Always remember that the plasma cutter will cut inner contours in the opposite direction. If you are carving the outer part, the nozzle will cut clockwise, and it will cut anticlockwise for inside carving. Cutting speed is important to check the cutting kerf of the heated portions and surface area quality.
Precautions During Plasma Cutting
Since plasma cutting involves a lot of spark and heat, you need to be extremely conscious while doing it. Do not forget to wear proper gear like eye-wear, face shield, leather gloves, jacket, and an apron. Always maintain a minimum distance while cutting objects because the sparks can injure you.
Ensure that you are not working near flammable objects because plasma can easily burn them and cause hazards. The working area should have enough space for proper ventilation and have a first-aid kit for an emergency. It is better to have a fire-extinguisher to avoid any long harm.