We all know that matter commonly exists in 3 states: solid, liquid and gas. What is not common knowledge is that matter exists in the fourth state too i.e. plasma. When energy is introduced, matter is converted from one form to another. For example, when the solid form of water (ice) is heated, liquid is formed and when the liquid is heated it changes to steam. If the level of heat keeps increasing, the gases developing into steam are ionized and become electrically conductive. This ionized gas steam is called plasma.
How Does a Plasma Cutter Work?
Energy is transmitted from a power source to a conductive material such as metal through electrically charged gas by the plasma cutter, which results in a faster and cleaner cutting process.
When air or any gas like oxygen, argon or nitrogen is passed via a small opening in a nozzle, a plasma arc is formed. The power source generates an electric arc which is introduced to the compressed gas. A jet of plasma is formed that reaches very high temperatures of around 40,000° F. This plasma jet has the capacity to cut metal. The metal turns molten and is blown away.
Components of a Plasma Cutting System
A typical plasma cutting system requires the following components:
Arc Starting Console or (ASC): A spark is produced by the ASC circuit inside the plasma torch, which in turn creates the plasma arc. The AC voltage used is usually 5,000 volts at 2 MHz.
Plasma Torch: The plasma torch helps to align and cool the consumables. The electrode, swirl ring and the nozzle are the parts that are needed to generate the plasma arc. To enhance the cut quality further, a shielding cap can be used. The inner and outer retaining caps hold all the parts of the plasma torch together.
Power Source: The power supply unit converts AC line voltage to a smooth and constant voltage of 200-400 VDC. This DC voltage supports the plasma arc and maintains it throughout the cutting process. It also helps to regulate the output of the current depending on the kind of material and thickness being cut.
Categories of Plasma Cutting Systems
Most of the plasma cutting machines can be categorised into 2 groups: conventional plasma cutting systems or precision plasma cutting systems.
Conventional Plasma Cutting Systems: These normally use air in the shop as the gas for the plasma and the plasma arc’s shape is determined by the aperture of the nozzle. This kind of plasma arc usually has an amperage of around 12-20K amps/square inch. Mostly all cutting systems that are handheld and some automated applications make use of conventional plasma systems.
Precision Plasma Cutting Systems: The highest quality and most accurate cuts can be achieved by using precision plasma cutting systems. Multiple gases like oxygen, nitrogen, pure air and a gas mixture of nitrogen, hydrogen and argon are used as the plasma gas to get the best results on varied conductive materials. The design of the consumables and torch is more complex in order to compress the plasma arc and give it more shape. A precision plasma arc is around 40-50K amps/square inch.
Essentially, all plasma cutting systems have the same working principle. However, the choice of the plasma cutter solely depends on the application it is being used for, the quality and precision of cuts required, and your individual business needs.