A plasma cutter generates an arc between an electrode and the workpiece. The plasma arc melts the metal and the plasma gas removes the melted materials.
Most efficient cuts with plasma cutting
With plasma technology, all conductive materials such as mild steel, stainless steel and aluminium in the medium material thickness range can be processed. Advantages of modern plasma systems are high quality cutting results, high cutting speeds, only a small heat-affected zone and the unbeatable cost-benefit ratio compared to other cutting technologies. Plasma cutting is systematically one of the thermal cutting processes. It was originally developed for cutting metals that cannot be separated by flame cutting due to their chemical composition, such as aluminium or copper and their alloys, high-alloy steels, but also hard metals. In the industrial sector, plasma cutting systems are also indispensable when it comes to mild steel due to their numerous advantages over alternative cutting processes.
Advantages of plasma cutting
- High cutting speeds
- High-quality cutting results
- Low cutting meter costs
- Cutting of all electrically conductive materials
A plasma cutter generates an arc between an electrode and the workpiece. Plasma is also called the fourth state of aggregation. It is generated by ionising electrically conductive gas through an energy supply (high voltage). Due to the high energy density of the resulting arc, which reaches up to 30,000 degrees Kelvin, the metal melts and is blown out by a gas jet, creating the kerf.
A thermal cutting process
The cutting process is performed by a so-called pilot arc, which is ignited by feeding an ignition gas between the electrode and the nozzle with high frequency voltage (non-transferable arc). This relatively low-energy pilot arc ionizes the distance between electrode and anode (workpiece). The plasma gas is switched on as soon as the pilot arc makes contact with the workpiece. This creates the main arc while automatically increasing the current (transferring arc). The material is melted by the thermal energy of the arc and driven out of the kerf by the kinetic energy of the cutting gas.
The material must be conductive
The material to be cut must be electrically conductive for plasma cutting, as the workpiece is part of the circuit (anode). The grounding should therefore be as consistent as possible. And so that optimum cutting results can always be achieved, the type of consumables and plasma gases change depending on the material.
Electrode and nozzle influence service life of consumables
Electrode and plasma nozzle are exposed to high currents and thus high strains during plasma cutting – these are therefore components with a limited lifetime. The service life of the electrode is largely determined by the level of the cutting current, the number of ignitions and the type of plasma gas. In addition, the gas and current management at the start and end of the cut as well as the heat dissipation from the electrode play a decisive role. Essential influencing factors of the nozzle service life are:
- Nozzle diameter, mass and thermal conductivity
- Power used (current x voltage)
- Duty cycle of the arc
- Number of ignitions
- Hole punching procedure
- Optimum distance from torch to workpiece (intelligent height control)
- Purity of cutting and swirl gases: the gas air must be dry and free of oil and grease
- Intensity of cooling
- Use of certified original consumables
Manual or automated plasma cutting
A distinction is made between manual plasma cutting or automated plasma cutting with a CNC machine or robot.
Manual plasma cutter
Hand plasma cutters (also known as manual plasma cutters) are mainly used where precision, accuracy and reproducibility are less important than a quick separating cut. Manual plasma cutters are therefore not only used in the metal processing industry, but for example, the mobile version of the plasma cutter is often used for rescue work by the Federal Agency for Technical Relief (THW) or fire departments.
Plasma cutting systems (automated gantry cutting systems)
Plasma cutting machines are most frequently used in the metalworking industry. They score points in the CNC-guided 2D cutting range for thin and medium sheet thicknesses with very good cutting quality and very high cutting speeds at comparatively low cutting meter costs. Thanks to sophisticated rotating units for bevel cutting, modern CNC machines also show their strength in 3D processing: nowadays, nothing stands in the way of extremely precise weld edge preparation with bevel angles of up to 52°.
With optional additions, modern cutting systems can be used not only for processing sheet metal, but also, for example, for processing pipes, profiles and domes. Multifunctional plasma cutting machines also offer further options for processing materials: The systems can be equipped with modules to enable drilling, countersinking, tapping, marking, punching and labelling. In addition, plasma technology can be combined with oxyfuel cutting respectively flame cutting, with laser cutting or with waterjet cutting.
Robot cutting systems
Robots are still widely regarded as indispensable when it comes to preparing subsequent welding seams on already cut components. However, there is now an incomparably more efficient alternative that makes a huge difference to this supposed certainty: The new process is called ABP® – Additional Beveling Process – and enables extremely precise subsequent beveling on gantry cutting systems.
The typical cutting range in modern plasma cutting is between 1 mm and 50 mm – here, very good quality and economically extremely efficient cutting results are achieved. For higher material thicknesses, CNC cutting systems with plasma gas are usually combined with technologies for flame cutting. The following materials among others are usually processed with plasma cutting technology: mild steel (fine-grained steel, Hardox), stainless steel (V2A), chrome-nickel steel (V4A), aluminium, copper, brass, titanium, armour steel.
Where is plasma cutting used?
Cutting with plasma is applied in the most diverse industries: For example, plasma cutting systems are used in metal cutting (contract cutting or contract manufacturing), in mechanical engineering, plant and container construction, shipbuilding, ventilation construction, pipeline construction, prototype construction or vehicle construction. In other words, in all those branches of industry that deal with metal processing and cutting processes.