The plasma state is the fourth state of matter, which is transformed from the gaseous state of matter after sufficient energy. The plasma state is a conductive gas with conductive properties. Plasma cutting is the use of optimized design nozzle holes to produce a variety of physical benefits to compress high temperatures and ionized gas to fuse metals with conductive properties. CNC plasma cutting has been recognized by users at home and abroad due to its fast cutting speed, high energy density, and good cutting quality. It is currently widely used in many industries such as shipbuilding, boilers, and construction machinery. In the past ten years, increasing the cutting speed, improving the cutting accuracy and quality, and extending the life of consumable parts have always been the hot spots of plasma cutting technology. With the continuous advent of new technologies such as oxygen long-life cutting and high-precision plasma cutting, CNC plasma cutting is becoming more and more competitive in the manufacturing industry. To ensure good cutting quality, the equipment needs to constantly replace consumable parts during operation. If used and operated improperly, high-efficiency and high-precision cutting may be buried by expensive operating costs, which will cause trouble to the enterprise.
In the CNC plasma cutter, the consumable parts commonly considered include electrodes, nozzles, swirl rings, and protective caps. They each play an important role in plasma cutting.
The primary function of the electrode is to provide energy to the plasma arc, and the electrode is connected to the negative pole of the plasma power supply. Secondly, during the start-up process, the electrodes simultaneously transmit high voltage, that is, a high frequency so that the cutting gas is ionized and starts the arc normally. Since the electrode is the main contact part of the cutting arc, it becomes very hot. In the electrode in the oxygen cutting process, its front-end emitter is composed of a lead core. The electrode for cutting stainless steel and aluminum alloy is composed of a tungsten core, which can withstand the temperature. Generally, the plasma power supply with a higher cutting current uses coolant for cooling, and the plasma power supply with a lower cutting current uses air for cooling.
The lead core at the tip of the electrode is a very important part. Because the core is a poor conductor of heat, the manufacturer adopts a special processing technology to make the lead core and the surrounding copper tightly bonded, thereby ensuring the best electrical and thermal conductivity. Different cutting currents use lead cores with different diameters to ensure the best heat transfer and exchange effect.
The inside of the electrode is made by very precise machining, with positioning grooves. The internal design of the electrode must ensure that the floating water pipe and the electrode can ensure precise coaxiality to ensure the cooling effect. The outside of the electrode has a special design of thread and installation positioning shoulder, which can ensure the concentricity with the nozzle and swirl ring during installation.
The main function of the nozzle is to further compress the high-temperature plasma gas, increase its energy density and speed to provide excellent cutting quality. The nozzle is also the main component of the ionized gas (formation of the plasma cutting arc) circuit. The design of the nozzle is very complicated. Physically it must be able to withstand high-temperature airflow to ensure that the airflow can pass through the nozzle hole without melting the nozzle (copper). The structural design should also consider the electrode, Accurate coaxiality between the swirl rings to improve the stability of cutting quality. In the oxygen long-life fine plasma cutting designed by Hypertherm, the nozzle used uses vortex-like airflow technology to form a non-ionized cooling layer between the nozzle hole and the ionized gas, thereby extending the service life of the nozzle. The double-layer compression technology can further increase the energy density (approximately 4 times the energy density of conventional plasma). The application of floating positioning technology ensures the precise coaxiality between the nozzle, swirl ring, and electrode.
3. Vortex ring
The main function of the vortex ring is to make the plasma gas form a vortex-like pair of gas around the electrode and then enter the nozzle. It controls the arc concentration to the center of the electrode and improves the flow path through the nozzle hole. The cutting angle enhances the centrifugal effect so that the unionized gas forms a cooling layer between the nozzle and the cutting arc, which plays a cooling role and improves the service life of the nozzle. Secondly, the swirl ring must ensure the coaxiality between the nozzle hole and the electrode and also insulate the negative electrode and the nozzle. Its main feature is the precise vortex hole and size, and the inner and outer seal ring.
The vortex ring is made of volcanic rock. The volcanic rock has the characteristics of excellent insulation and high-temperature resistance. It has been verified that the vortex ring formed by a natural volcanic rock through precise mechanical processing and final baking is durable.
4. Protective cap
The primary function of the protective cap is to prevent the nozzle from being damaged by the double arc during perforation and to prevent the nozzle from contacting during stable cutting. The protective cap helps to cool the nozzle and it also controls the cutting angle of the cut material.
The main hole of the protective cap must be completely concentric with the nozzle hole. The vent hole is very important for controlling the cutting angle, and its size and tolerance requirements are particularly strict.
If you want to know more about how to improve the service life of the consumable parts of the CNC plasma cutter, how to increase the service life and reduce the operating cost of the machine, please read the article "How to improve the service life of the consumable parts of the CNC plasma cutter".