What is plasma?
Before going into the details of how a plasma cutter works, it is essential to understand the concept of plasma. Most people know that there are three states of matter: liquid, solid, and gas. But there is also a fourth state of matter. And that’s plasma. Every state of matter undergoes a change if you heat it. For example, water changes from its solid state (ice) to liquid when you provide heat. If you heat water further, it changes to gas. Now, if you increase the heat intensity, the gases that form the steam will become electrically conductive and ionised, resulting in plasma. Plasma cutters use this type of electrically conductive gas from a power supply to transfer energy to a conductive material. It provides cleaner and faster cuts compared to oxyfuel.
When you heat gas, it produces a plasma arc. When you pass gases like nitrogen, argon, or oxygen through a tiny nozzle, it generates an electric arc inside the torch. You need to force the gas through the nozzle orifice inside a torch to generate the electric arc followed by using external power supply to the high-pressured gas flow. This entire process results in plasma jet. A plasma jet can reach almost 40,000° F. It can pierce through a work piece and also blow away molten material within a few seconds.
Plasma System Components
Power supply – The plasma power supply provides constant DC voltage with a range between 200 and 400 VDC. The power supply is responsible for converting any single or even three phase AC line voltage to DC power. The DC power helps to maintain the plasma arc on DXF files for plasma cutting while cutting. It is also responsible for regulating the current output depending on the type of material and thickness that you want to process.
Arc Starting Console – This circuit works slightly differently from the power supply. It uses AC voltage of 5,000 VAC at 2 MHz to produce sparks inside your plasma torch. Plasma arc is created in the process.
Plasma torch – A plasma torch cools the consumables and provides them with proper alignment. Some of the most common consumable parts required in a plasma arc are swirl ring, nozzle, and electrode. You may use an additional shielding cap to improve the overall cut quality. The torch also comes with retaining caps both on the inner and outer portions so the parts remain in place.
There are two categories of plasma cutting systems: conventional and precision cutting.
In conventional plasma systems, you use shop air as your primary plasma gas. The orifice of the nozzle decides the shape of the plasma arc. The amperage of this arc usually ranges between 12 and 20K amps PSI. You will notice that all handheld systems use conventional plasma. In fact, many mechanised applications also use this system because of its part tolerances.
Precision plasma systems, on the other hand, provide the sharpest and highest quality cuts that plasma arcs can achieve. The designs of the consumables and torches are more complicated. Plus, there are additional pieces in the unit that define the shape of the arc. The designs are highly accurate. Most of these arcs range between 40 and 50K amps per square inch. You may use various gases, such as high purity air, argon/hydrogen/nitrogen mixture, nitrogen, and oxygen as your primary plasma gas to get optimum results on different types of conductive materials.
Tomahawk® Air Plasma is one of the most common handheld plasma systems you will come across. In this system, the nozzle consumable parts and electrode touch each other inside the torch. This happens when the system is off. As soon as you press the trigger, the power supply sends DC current through the system. It flows inside this connection, thus initiating the gas flow inside the torch. It takes a few seconds for the gas to build sufficient pressure. Once it reaches the required pressure level, the nozzle and electrode detach, causing an electric spark. This spark converts the gas into a plasma jet. The DC current immediately converts from electrode to nozzle and travels through the system into your workpiece. It will again go back to its initial position until you release the trigger again.