What Is Plasma Cutting?
Plasma cutting melts materials through a jet containing ionized gas at high temperatures. The jet is at temperatures not below 20,000°C and functions to melt and blow away material from the melted part.
Plasma Cutting History
Plasma cutting was designed from plasma welding during the 1960s and has become very productive. Plasma cutting became a productive method for cutting sheet metal or plates in the 1980s. This method became popular because it had various advantages over traditional metal and oxyfuel cutting methods.
Some of the advantages presented include accurate cuts and cleaner cut edges. The initial plasma cutting equipment was large, and some were very expensive, so plasma cutting was mainly used for large productions. By the 1980 and early 1990s, plasma cutting technology had computer numerical technology.
Plasma Arc Cutting Safety Considerations
Fire hazards; It would help if you used approved safety glasses with a side shield and a helmet for eye safety. Protect the body by wearing undamaged and dry clothes and gloves.
Well-grounded; It would help if you fixed the cable connections properly. Besides, replacing the broken cables should ensure no bare spots to avoid shocks.
Dim lights; Protect the eyes from the bright UV and infrared lights by wearing a face shield or glasses with the right lenses.
Clear air; Avoid breathing the fumes and gases produced during plasma cutting by working in ventilated areas or wearing an air-supplied respirator.
Inverter Plasma Cutter
Use Inverter plasma cutter to rectify the mains supply, which is a heavy mains-frequency transformer, to DC. You can feed to a higher frequency transistor inverter, which allows the smaller transformer to reduce weight and size.
The initial transistors were MOSFETS, but others like IGBTs perform the same function. Parallel MOSFETs could fail due to one transistor activating prematurely—a reason for using IGBTs. Inverter plasma cutters are light and very powerful, for instance, the ones without power factor correction.
However, you cannot use some with generators.
Technological Advancements In Plasma Cutting
Plasma torches advancement; With technological advances, experts have devised torches with a smaller nozzle with thinner arcs.
CNC with torches; These plasma torches, engineered in the same cutting machine with a CNC control system, produce aesthetic finishes.
MOSFETs and IGBTs; The initial transistors were MOSFETS transistors, but others like IGBTs are now common. Parallel MOSFETs fail due to one transistor activating prematurely, which is why IGBTs were invented.
X-definition plasma; It is the most recent advancement in plasma cutting technology. You can produce quality cuts on various materials.
Plasma Cutting Vs. Laser Cutting
Plasma cutting; Plasma cutting is the process of melting materials through the use of a jet containing ionized gas at high temperatures. The jet is at temperatures not below 20,000°C, melting and blowing away material from the cut. You can use this method with all types of metal having a medium thickness.
Laser cutting; Laser cutting involves using a high-power laser beam directed via optics and a CNC to cut the material as required. The laser beam heats, melt, vaporize, or blow away the melted part of the material. This method can cut various materials, including metal and non-metals.
Plasma Cutting Process
Pilot Arc Initiation
In the beginning, the start command prompts the power source, which generates a voltage of up to 400VDC. It causes the compressed plasma gas to flow into the torch assembly. Usually, it consists of a plasma nozzle and an electrode.
Turning on the power source also creates a negative voltage on the electrode to initiate a cathode for the pilot arc. A positive voltage is created at the nozzle to serve as an anode for the pilot arc.
A complete circuit arc circuit generates a high frequency and high voltage potential, producing a high-frequency spark. The spark is responsible for making the plasma gas ionized and becomes electrically conductive. Here, electrically conductive and low resistance current produces the current path. It is through this path that energy discharges and flows.
Main Arc Generation
The pilot arc created in the above step flows out with the plasma gas via the opening of the nozzle. Typically, these two combined flow towards the electrically conductive and grounded material.
The material ionizes the surrounding area partially along the low-resistance current path. Here, the main arc finally comes into contact with the material and is transferred to the workpiece.
It happens as the gas flow causes the pilot arc to move. The protruded pilot arc produces the main arc. Typically, this arc is responsible for the literal cutting operation. Additionally, it portrays the material as being part of the created primary arc circuit.
Heating And Melting
The plasma cutting nozzle aids in constricting the ionized gas together with the main arc. Usually, it happens when the two move via the opening of the nozzle. This constriction increases the energy and density of the plasma.
These cutters produce a hot plasma up to temperatures of 20,000°C that moves to the material at a very high speed. A combination of kinetic and thermal energy is vital in the cutting operation.
Plasma cutting works through a melt-and-blow method where the metal is heated, melted, and vaporized, leaving a cut. As the ionized gas hits the material surface, the thermal energy is absorbed, generating heat that melts the metal.
You should remove the melted or weakened part in the workpiece. You can remove it by blowing by the compressed air and the kinetic energy. The cut length or size is determined by the nozzle and the current
Which is again predetermined by the operator and set through the CNC interface. Too high or low plasma flow may lead to cuts with less accuracy and application failure. It is therefore vital to monitor the process.
It initiates the heating, melting, and eventually blowing away the material on the workpiece. After which, you can move the plasma arc. The movement can be done manually or automatically across the working surface to create accurate and precise cuts.
If you opt for the manual option – move the plasma torch across the line you are cutting. However, if you opt for automated operations, the plasma torch head moves across the surface, creating the necessary cuts.
Disadvantages Of Plasma Arc Cutting
Plasma arc cutting is not suitable for cutting thicker metals, and if you need to cut thicker materials, you can consider other methods. It is because of their fleeting nature, which limits them to a thickness of approximately one inch.
If you don’t carry out this cutting procedure in water, it produces excess noise that may harm the ears. The noise reduces when working in water. That is why manufacturers prefer working in water or using other methods.
Cutting using the plasma arc cutting method produces a lot of fumes that are not safe for operators and can be harmful. Avoid breathing the fumes and gases produced during the plasma cutting by working in ventilated areas or wearing an air-supplied respirator.
The plasma arc cutting method also produces bright flashes, which can harm the eye if not correctly protected.You can achieve eye protection by putting on the approved safety glasses with a side shield and a helmet.
Configurations In CNC Plasma Laser Cutting
This form is the commonly used CNC plasma cutting configuration and is popular for producing flat parts. Usually, the cutting edge is at an angle of 900 to the workpiece surface. This configuration applies to high-powered CNC plasma cutting beds for cutting profiles in metals that are 150 mm thick.
It is the same as 2-axis plasma cutting but has an added rotation function. With this feature, you can tilt the CNC plasma cutting head – as it moves in a 2-dimensional path. This configuration can cut at angles other than 90 degrees. Of course, they are are consistent throughout the cut.
They create cuts on tubes, pipes, or other structures with a long sections. The head of a plasma cutter is always intact. At the same time, the material moves along the cutter. Of course, the system rotates along the axis. Thes best part – this technique creates cuts into the thick sections.
Advantages Of Plasma Arc Cutting
Plasma Arc cutting can produce odd shapes and curves using a precise beam. You can achieve this by manually guiding plasma torches into the material as a line manually using a pencil.
Plasma arc cutting creates cuts on materials at high speed and efficiency since quick cuts avoid abrasion on materials. Plasma is faster and more efficient than other cutting methods with minor damage.
You can cut all heat conductive metals through the plasma arc cutting technique. Therefore, it is suitable for almost all cutting processes, and various industries prefer it over other cutting methods.
The equipment used in plasma cutting is easy to clean, and the torches do not require frequent replacements. Cleaning is also simplified, and the machine does not need frequent repairs if appropriately maintained.
Since plasma cutting uses inert gases, it is much safer for operators when compared to other cutting methods that rely on oxygen. It is because oxy-fuel poses a risk of exploding or self-igniting when stored.
Several factors influence the cost of plasma cutting techniques, including low maintenance and setup fees. Other factors include low operational cost and the fact that it doesn’t require much training for operators.
The machine can be used in water when cutting materials, resulting in smaller HAZ. It also ensures that the machine produces less noise compared to other cutting methods with much noise.
Plasma cutting works much faster and can handle materials of approximately 50 mm thickness.
The process produces cuts of excellent quality with much ease and no or minor damage.
People Also Ask:
Plasma cutting is suitable for all manufacturing processes with all heat conductive metals. Therefore, it is suitable for almost all cutting processes and can be used where precision and accuracy are essential.
Both plasma cutting and laser cutting methods come with benefits and limitations. However, the choice will depend on the material you want to cut. It would help if you considered the thickness of the material, the quality needed, and the precision of the application. For instance, plasma cutting can only handle metals, while laser cutting can do even non-metals.
A plasma cutter can use four gases: nitrogen, oxygen, argon-hydrogen, and compressed air. Each gas comes with benefits and limitations; therefore, the choice will depend on the needs of a procedure.
Plasma cutters are suitable for cutting through carbon steel, stainless steel, aluminum, and brass. The cutter cannot handle any other material apart from metals.
The jet is at temperatures not below 20,000°C and functions to melt and blow away material from the melted part.
We use plasma cutting in a range of industrial applications such as:
- Automotive industry
- Fabrication industries
- Construction industry
- Aerospace and defense
- Electrical equipment
- Medical devices