What Is Plasma?
One of the four fundamental states of matter is plasma. It comprises a gas of free electrons and ions, atoms, or molecules with one or more orbital electrons removed (or, in rare cases, an additional electron attached).
Plasma is the most prevalent type of ordinary matter in the cosmos, excluding dark matter and the even more elusive dark energy. Plasma is mainly connected to stars, such as our Sun, and it can also be found in the rarefied intracultural medium and perhaps even in intergalactic space.
By heating a neutral gas or exposing it to a strong electromagnetic field, plasma can be created artificially. Plasma is electrically conductive due to the presence of free-charged particles. Collective electromagnetic fields control the dynamics of individual particles and macroscopic plasma motion, and both are extremely sensitive to externally imposed fields.
Numerous contemporary technological innovations, such as plasma televisions and plasma etching, rely on the plasma’s reactivity to electromagnetic fields.
What is Plasma Arc Machining?
It is possible to remove material from the workpiece using plasma arc machining. In this procedure, the workpiece’s material is melted and removed using a high-velocity jet of hot gas. A plasma jet is another name for this heated gas moving at high speed.
A gas or air will begin to ionize into positive, negative, and neutral ions when heated to a temperature of more than 5000 °C. The temperature of an ionized gas, such as air, ranges from 11,000 to 28,000 degrees Celsius and is referred to as plasma.
Arc heating of the gas or air produces plasma, which is then used to remove material from the workpiece. Therefore, the entire procedure is known as plasma arc machining.
In this procedure, material from the workpiece is removed by melting it with a high velocity of hot air.
The metal used as the workpiece determines the gas used in plasma arc machining.
Plasma arc machining is employed for cutting alloy steels, stainless steel, aluminum, nickel, copper, and cast iron.
The Process of Plasma Arc Machining
The fundamental idea is that a copper nozzle with a fine bore restricts the arc that forms between the electrode and the workpiece. This raises the plasma’s temperature and speed as it leaves the nozzle.
The plasma is more than 20,000 degrees Celsius hot, and its velocity is almost as fast as sound. The plasma gas flow is raised when cutting is done so that the deeply penetrating plasma jet can cut through the material and remove the molten material in the efflux plasma.
A plasma gun is used in plasma arc machining. The chamber of a plasma gun contains a tungsten electrode. This tungsten electrode is attached to the DC power supply’s negative end in this instance. As a result, tungsten serves as a cathode.
While the nozzle is linked to the positive terminal of the DC power supply, as a result, the plasma gun’s nozzle serves as an anode.
When we apply power to the system, an electric arc forms between a cathodic tungsten electrode and an anodic nozzle. We obtain an ionized gas due to the collision between the gas atoms and the electrons of an electric arc that occurs as the gas makes contact with the plasma.
Thus, the plasma condition we desired for plasma arc machining is achieved. Now that this plasma is being directed at the workpiece at high speed, the machining operation begins. One thing to remember is that a significant potential difference is used to achieve the plasma state.
High temperatures are needed for the entire process. Overheating is a possibility since the nozzle releases hot gases. A water jacket is used to avoid this overheating.
The Components of Plasma Arc Machining
- Plasma Gun
Plasma is produced using several gases, such as nitrogen, hydrogen, argon, or a combination of these gases. The chamber of this plasma weapon contains a tungsten electrode. The nozzle of the plasma cannon is connected to the positive terminal of the DC power source, and this tungsten electrode is connected to the negative terminal. The gun receives the necessary gas mixture. A powerful arc is created between the anode and the cathode.
The electron from the arc then collides with the gas molecules, causing the gas molecules to become ionized and heat to be produced as a result.
- Power Supply
A DC power supply is used to develop two terminals in the plasma gun. A significant potential difference is introduced between the cathode and anode to create a powerful arc that can ionize the gas mixture and turn it into plasma.
- Cooling Mechanism
The plasma gun has a cooling system since the hot gases from the nozzle cause it to heat up. A water jacket cools the nozzle. A water jet surrounds the nozzle.
This plasma arc machining can deal with various materials. Using this method, several metals like aluminum, magnesium, carbon, stainless steel, and alloy steel can be worked.
The Applications of Plasma Arc Machining
- It can be used to cut alloy steel, stainless steel, cast iron, titanium, aluminum, and alloys of copper and nickel, among other materials.
- It is employed for cutting profiles.
- It works well for turning and milling difficult-to-work-with materials.
- It can be used for underwater cutting, stack cutting, contour cutting, and piercing.
- Plasma arcs can also be used to apply thin films of refractory compounds to metals, polymers, and ceramics in an even manner.
The Advantages of Plasma Arc Machining
- It can cut through any metal.
- The rate of cutting is high.
- It can cut plain carbon steel four times faster than a typical flame-cutting procedure.
- It is employed for the rough turning of extremely challenging materials.
- The deformation of sheet metal is decreased due to the high cutting speed, lowest cut width, and superior surface finish.
The Disadvantages Of Plasma Arc Machining
- It creates a surface that is tapered.
- Noise protection is essential.
- The equipment is expensive.
- Both the operator and anybody working nearby must wear eye protection.
- Scale formation and oxidation occur. Thus, it needs to be protected.
- There may be metallurgical modifications to the work surface.
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