Plasma Cutting: Process, Types, Advantages and Disadvantages
Most raw material processes incorporate some form of metal fabrication processes. There are metal parts or tools in virtually every manufacturing environment. The specific requirements of metal cutting in different industries have given rise to a variety of metal cutting methods.
The list of metal-cutting methods is long: Electrochemical machining, laser cutting, grinding, water jet cutting, and shearing. Others are punching, abrasive cutting, thermal cutting, and plasma cutting process, among many others.
As one of the precise and exciting metal cutting technologies, plasma cutting is popular in many industries and applications. Once you have touched this method, you may never look back. In this article, we delve into the details of this technology for cutting metal.
What Is Plasma Cutting?
From the science classes, there were generally three states of matter namely liquid, solid, and gas. But there is a fourth state of matter: Plasma. In basic terms, a state of matter occurs when the preceding state receives more energy and heat. Therefore, plasma is a result of a gas getting a lot of energy.
Following that background, plasma cutting is about using the energy of plasma to cut a conductive material. Plasma is a mixture of energized ionized particles, molecules, and atoms. When this mixture meets a material, it imparts on it by cutting.
Plasma cutting is applicable in different areas including shops, construction sites, and auto garages. It is a cost-effective process that uses affordable consumables. Although this process produces fumes and struggles to cut thick materials, it is relatively versatile and safe.
How Does a Plasma Cutter Work?
The process of creating a plasma cut follows these steps:
CAD design of the part
Choosing the appropriate metal
Inspecting the plasma gas cutting machine
Performing the plasma gas-cutting
Post-cutting activities
Computer-Aided Design of the Part
The machinist begins the plasma cut process by using CAD software to design the desired product. When the 2D design is ready, the operator will store it .dxf file style. The next step in the design phase is to import this file to CAM software, and eventually, to G code for the CNC machine.
Metal Selection for Plasma Cutters
Like for every fabrication project, a careful selection of materials is essential. You want to note that plasma gas cutting has its limits. Depending on the specific machine, there could be thickness limits. If unsure, consider consulting to ascertain the metal sheet or plate size that is suitable for an air plasma machine.
Plasma arc Machine Preparation
Before using the plasma cutting machine, it is critical to inspect it carefully. You want to be sure that there are no hazards as you cut the metal plate or sheet. It is also a way of ensuring that the cutting quality will be optimal.
The Plasma Cutting Stage
When it comes to the cutting step, the most important thing is supervision or monitoring. Yes, the CNC machine is already set, but it’s worthwhile to ensure that the plasma cut parameters are as designed. In case of anomalies, it will be easy to address them promptly.
The machine torch releases intense heat, which cuts the material. The air plasma is so hot that it cuts even the toughest materials, including carbon steel.
Post-Plasma Cutting
When the cutting step is complete, it is time to remove the fabricated part and analyze the results. The presence of slag along the plasma cut edge is common. A grinding wheel or sledgehammer is enough to remove these imperfections.
In busy fabrication environments, they typically have a person dedicated to ensuring that the plasma cut edge is of the highest quality. The goal is to get a flawless surface finish, allowing the demonstration of the quality cut edge of plasma cutters.
Main Components of a Plasma Cutter
Considering all the science that is behind plasma cutting, it is understandable to think that the components are complex. The reality is this machine comprises straightforward components. The plasma cutter contains the following main components:
Plasma Torch:
If you have seen a welding torch, then you will have no problem identifying the torch used in plasma cutting. The role of the plasma torch is to generate the arc that cuts the metal. A critical part of the plasma torch is the electrode, which is the source of the electric arc.
The plasma contains parts that are either permanent or of consumable life. Examples of parts that wear out over time are the retaining cap and electrode.
CNC Controller:
The interaction between the plasma cutting action and the CNC machine is through programming. The machinist must first prepare a 2D design and convert it into G code. For the CNC machine to follow the G code instructions, it needs a special component – the CNC controller. The controller sends the instructions to the motors.
Power Supply:
The formation of the plasma jet requires electricity input. The constant-voltage DC should be at least 200V. Since the electricity in the socket is direct current, the plasma cutting machine must convert it to direct current. It also generates the appropriate current and voltage for the generation of the plasma stream.
Table:
To cut the sheet metal or plate using this method, you need to place it on a stable surface. Most of these machines come with a table for that purpose. There are instances where the raw material can even stay underwater during the cutting process.
Drive System:
This system executes the path of the plasma. It helps move the plasma jet according to the design. Central to this system are the motors and linear drives. The motors create rotary motion while the linear drives convert it to linear motion.
Gas Supply:
The plasma-cutting process needs an air/gas supply. Some plasma cutters will use an air compressor, while others draw the gas from canisters. To control the gas supply, the system incorporates a gas console. This part of the gas supply system takes care of plasma jet pressure and flow rate.
Types of Plasma Cutting
The plasma cutting technique is perpetually undergoing improvements. Designers of these newer versions seek to minimize environmental pollution, enhance cut quality, and add power to the machine. These efforts have given rise to different versions of the cutting method including the following:
Plasma arc cutting utilizing a secondary medium – A gas or water medium combines with the plasma torch components to control the plasma arc even further. The parameters that this type helps control include the cut speed and cut quality.
Water injection plasma arc cutting – As the name suggests, this cutting method incorporates water in the cutting process. The design aims to constrict the plasma arc. Most of this water remains in the cutting area to provide cooling to the workpiece and the plasma torch.
Plasma arc cutting with increased constriction – By enhancing the constriction capability, this type of plasma cutting can attain specific capabilities. For instance, it can manipulate the nozzle or rotate the plasma gases.
Underwater plasma arc cutting – This type of plasma cutting is ideal for depth ranges of 60 mm – 100 mm. It is energy-consuming, but air pollution.
Plasma gouging – This type of plasma arc cutting is focused on forming bevels or grooves on the surface. For its versatility, the technique is common in welding and general fabrication projects.
Plasma marking – This is a different kind of plasma cutting because it does not fully cut the material. Instead, it creates marks on the surface. Users use this technique to generate text and lines on the surface. The method is popular in decorations and identification.
Advantages and Disadvantages of Plasma Cutting
Advantages
Affordability
Compared to alternatives such as waterjet and laser cutting, plasma cutting is very affordable. Gone are the days when you could only get an ineffective cutting machine with a low budget. At a lower price, plasma cutters produce cut quality that can rival more expensive solutions.
Scalability
If there is a highly scalable industrial material cutting technology, it is plasma cutting. Many aspects of the process support scalable needs in the industry. The fact that the plasma cutting systems feature different power levels means that the user can always get a suitable setup.
Other aspects that support scalability are:
A wide range of thicknesses
Different sizes of cutting tables
Can support varying production volumes
Capability to integrate with CNC and other processes
Rapid Turnaround
The cutting speed for plasma cutting is unmatched. As you do not need to preheat the material, the speed of the cut is high. As a result, the turnaround is fast. You can cut many parts within a short time, which is good for business.
Warping Management
Cutting methods that produce heat are likely to cause metal warping. This can degrade the quality of the final product. The faster speed of cutting in plasma cutting minimizes this challenge. Plasma control technology is also effective in minimizing the problem.
Disadvantages
Material Limitations
While plasma cutting can work metals with highly reflective surfaces, the process can be problematic. Copper and aluminum are in that category of metals. They can produce inconsistent plasma cuts unless the machinist employs special techniques.
Noise and Fumes
The plasma-cutting method produces a lot of fumes and noise. Therefore, you must use the method in a ventilated or open area.
Power Supply Demands
Using this technique requires a lot of electric current to create the electric arc. The amperage demand can be as much as 300A. It means that the wiring in the shop wiring must be high quality. One should also provide surge protection.
What Are the Materials Plasma Cutting Can Cut?
There is a long list of materials that plasma-cutting technology can cut. One of these materials is steel. Manufacturers often use plasma cutters to machine or cut various types of steel, including carbon steel and mild steel. Whether thin or thick steel, the plasma gas method is capable of producing a clean cut.
You can also use this technique to cut copper, a popular material in electrical projects. However, getting a clean-cut quality on this material can be challenging due to its high conductivity.
Also on the list of materials that plasma cutting can work on is aluminum. Those in the automotive and aerospace spaces are aware of the relevance of this machining method. Due to the high conductivity of aluminum, getting a clean cut requires good skills and a selection of cutting parameters.
Plasma cutting is also good at cutting brass. You will mostly find this application in the decorations industry. Like the other highly conductive materials, brass cutting can be a little challenging.
Titanium may be reactive, but its application in medical and aerospace fields means that some cutting solution is inevitable. That solution comes in the form of plasma jet cutting.
Users of cast iron, particularly in the construction industry, are familiar with plasma cutting. They use the solution extensively in fabrication.
Plasma Cutting General Tolerances
The general tolerances for plasma cutting are not as impressive as those of waterjet cutting or laser cutting. The method has a tolerance range of between +/- 0.005″ and 0.020″. The exact tolerance depends on the specific material thickness.
If you are looking for tighter tolerances, you may want to try alternative cutting processes. Note that plasma cutting presents a kerf taper on the material. The heat around the cut also affects the level of tolerance that you can achieve with the method.
Conclusion
To conclude, plasma cutting is not as complicated as it sounds. As long as you use a quality plasma cutter and follow the cutting guidelines, this method gives a quality cut. Of course, you want to adhere to safety precautions, for instance, wearing PPEs.
If you are new to this technique, start with scrap or inexpensive materials. Given the drawbacks of the process with tolerances, don’t expect perfect cuts immediately. However, you will produce better cuts with the process with time.
With our many cutting methods, we are experts at using plasma cutting in different projects. Your manufacturing needs are in good hands at Aria Manufacturing. Do not hesitate to contact us with your prototype and manufacturing requirements.
Author
Gavin Leo is a technical writer at Aria with 8 years of experience in Engineering, He proficient in machining characteristics and surface finish process of various materials. and participated in the development of more than 100complex injection molding and CNC machining projects. He is passionate about sharing his knowledge and experience.