Plasma arc cutting: technology and operating principle

Plasma arc cutting is performed by a constricted arc, which can easily cut metal by melting it along the cut line. The gas passing through the arc discharge is highly ionizing, creating a plasma jet that removes molten metal from the cut.

Plasma arc cutting of metal is accomplished by striking an arc between the metal workpiece and a non-consumable tungsten electrode located inside the cutting head. Gas-discharge arc plasma has a very high temperature, ranging from 5,000 to 200,000°C. The gases used generate the plasma and provide the necessary protection for the tungsten electrode from oxidation. Nitrogen, argon, mixtures of argon and nitrogen, air, and hydrogen are successfully used for this purpose. The electrode is lanthanated tungsten grade VL-15, which is located within the plasma torch nozzle. The resulting plasma jet has a high flow rate, an elongated cone shape, and its exit corresponds to the nozzle cross-section.

Plasma arc cutting is performed using a DC power source, with the negative terminal connected to the tungsten electrode and the positive terminal connected to the water-cooled nozzle. The arc itself burns between the electrode and the nozzle. Then, when a gas mixture is supplied from the internal cavity of the nozzle, a plasma jet is formed that cuts the metal.

Plasma arc cutting is used for thin metal, and its speed depends on the metal's mechanical and chemical properties, as well as the cutting parameters. This type of cutting can be performed not only mechanically but also manually. Plasma arc cutting is suitable when other cutting methods are difficult or even impossible. This applies to cutting corrosion-resistant alloy steels, magnesium, aluminum, copper, titanium, and cast iron. During the cutting process, the metal is not included in the arc's electrical circuit; the arc burns independently. A special feature of cutting aluminum and its alloys with a thickness of 5 to 20 mm is that this process occurs in nitrogen, and for thicknesses of 20 to 150 mm, in nitrogen-hydrogen mixtures. Using an argon-hydrogen mixture containing 35-50% hydrogen improves the quality of the cut surface. When cutting stainless steel up to 20 mm thick, pure nitrogen is used, and for thicknesses between 20 and 50 mm, a mixture of nitrogen and hydrogen (50% of each) is used. To cut mild steel up to 50 mm thick, compressed air is used as the working gas.

Plasma arc cutting equipment enables precise and high-quality metal cutting. The KHARKOV-P machine can cut sheets up to 1550 mm long and 3000 mm wide, with thicknesses ranging from 3 to 32 mm, depending on the metal type and its properties. The torch travel speed ranges from 100 to 20,000 mm/min, and the plasma generator power consumption is 16 kW. The NiPrintRJ-180E machine features automatic cutting, air plasma cutting, and can cut various thicknesses.

CNC plasma arc cutting equipment, equipped with Haypertherm, is capable of quickly and very high-quality production of highly complex products, while ensuring maximum repeatability of the product. The device is easy to learn to operate, and basic computer skills are sufficient.