Plasma cutting of metal. Metalworking equipment

Plasma cutting is used when processing conductive metals. The processed material receives energy from a current source through ionized gas. The standard system includes a current source, an ignition circuit and a cutter that provide the power supply, ionization and control required for high-quality, high-performance cutting of various metals.

The output of the DC source specifies the thickness and speed of the material processing and maintains the arc.

The ignition circuit is implemented in the form of a high-frequency alternator of 5-10 thousand V frequency of 2 MHz, which creates a high-intensity arc, ionizing gas to the state of the plasma.

The cutter is the holder for consumables - the nozzle and the electrode - and provides cooling of these parts with gas or water. The nozzle and the electrode are compressed and maintain an ionized jet.

Manual and mechanized systems serve different purposes and require different equipment. Only the user can determine which one is best suited to his needs.

Metal cutting by plasma is a thermal process in which a bundle of ionized gas heats an electrically conductive metal to a temperature higher than its melting point and removes the molten metal through the hole made. An electric arc arises between the electrode in the burner to which the negative potential is applied and a billet with a positive potential and the material is cut by an ionized gas stream under pressure at a temperature of 770 to 1400 ° C. The jet of plasma (ionized gas) is concentrated and directed through the nozzle, where it is condensed and becomes capable of melting and cutting a wide variety of metals. This is the main process for both manual and mechanized plasma cutting.

Manual cutting

Manual cutting of metal by plasma is done with the help of sufficiently small devices with a plasma torch. They are maneuverable, versatile and can be used for various tasks. Their capabilities depend on the current strength of the cutting system. The parameters of the manual cutting settings range from 7-25 A to 30-100 A. Some devices, however, can produce up to 200 amperes, but they are not widely used. In manual systems, technical air is usually used as the plasma-forming and shielding gas. They are designed in such a way that they can be used with a different input voltage, which can vary from 120 to 600 V, and can also be used in single- or three-phase networks.

Manual plasma for metal cutting is commonly used in workshops that handle fine materials, factory maintenance services, repair shops, scrap metal reception points, for construction and assembly jobs, shipbuilding, auto repair shops and art workshops. As a rule, it is used for cutting excess. A typical 12-amp plasma machine cuts a maximum of a 5-mm layer of metal at a speed of about 40 mm per minute. A 100-ampere device cuts a 70 mm layer at a speed of up to 500 mm / min.

Typically, the manual system is selected depending on the thickness of the material and the desired processing speed. A device that provides high current strength, works faster. However, when cutting with a high current strength, it becomes more difficult to control the quality of work.

Machine Processing

The mechanized cutting of metal by plasma is performed on installations that are generally much larger than manual ones and is used in combination with cutting tables, including a water bath or a platform equipped with various drives and motors. In addition, the mechanized systems are equipped with a CNC and jet-head height control, which can include preset torch height and voltage control. Mechanized plasma cutting systems can be installed on other metalworking equipment, such as stamping presses, laser cutters or robotic systems. The size of the mechanized configuration depends on the size of the table and the platform used. Sawing machine may be smaller than 1200x2400 mm and more than 1400x3600 mm. Such systems are not very mobile, so before installation, all of their components should be provided, as well as their location.

Power Requirements

Standard power supplies have a maximum current range from 100 to 400 A for oxygen cutting and from 100 to 600 A for nitrogen. Many systems operate in a lower range, for example, from 15 to 50 A. There are systems with nitrogen cutting with a current of 1000 A and higher, but they are rare. The input voltage for mechanized plasma systems is 200-600 V in a three-phase network.

Gas requirements

For cutting soft and stainless steel, aluminum, as well as various exotic materials, compressed air, oxygen, nitrogen and a mixture of argon and hydrogen are usually used. Their combinations serve as a plasma-forming and auxiliary gas. For example, when cutting mild steel, the starting gas is often nitrogen, plasma-forming - oxygen, and compressed air is used as an auxiliary.

Oxygen is used for soft carbon steel because it produces high quality cuts in material up to 70 mm thick. Oxygen can also act as a plasma-forming gas for stainless steel and aluminum, but the result is not very accurate. Nitrogen serves as a plasma and auxiliary gas, because it provides excellent cutting of almost any type of metal. Used at high currents and allows processing sheet metal up to 75 mm thick and as an auxiliary gas for nitrogen and argon-hydrogen plasma.

Compressed air is the most common gas, both plasma and auxiliary. When a low-current cutting of sheet metal with a thickness of up to 25 mm is made, it leaves an oxidized surface. When cutting with air, nitrogen or oxygen is an auxiliary gas.

A mixture of argon with hydrogen is generally used for processing stainless steel and aluminum. Provides a high-quality cut, and is necessary for mechanized cutting sheets with a thickness of more than 75 mm. Carbon dioxide can also be used as an auxiliary gas when cutting metal with nitrogen plasma, as this allows to work with most materials and guarantees good quality.

A mixture of nitrogen with hydrogen and methane are also sometimes used in the plasma cutting process.

What else is needed?

The choice of plasma and auxiliary gases is only two of the most important decisions that must be taken into account when installing or using a mechanized plasma system. Gas tanks can be purchased or rented, they are available in various sizes, and appropriate conditions must be created to store them. The installation of the system requires a considerable amount of electrical wiring and pipes for gas and coolant. In addition to the most mechanized plasma system, it is required to choose a table, a cutting machine, a CNC and a THC. OEMs usually offer a variety of hardware options that are suitable for any device configuration.

Do you need mechanization?

Due to the complexity of the choice of the mechanized process of plasma cutting, it is necessary to spend a lot of time researching various configurations and criteria of the system. Please note:

• Types of parts that will be cut;
• The number of industrial products in the batch;
• Desired speed and quality of cutting;
• Cost of consumables.
• The total cost of operation of the configuration, including electricity, gas and labor.

The size, shape and number of parts produced can determine the necessary industrial industrial equipment - the type of CNC, table and platform. For example, the production of small parts may require a platform with a specialized drive. Rack drives, servo drives, drive amplifiers and sensors used on platforms determine the cutting quality and the maximum system speed.

Quality and speed also depends on what kind of metalworking equipment, CNC and gases are used. A mechanized system with adjustable current and gas flow at the beginning and at the end of cutting will reduce the consumption of materials. In addition, with a CNC with a large memory capacity and a choice of possible settings (for example, a flare height at the end of the cut) and fast data processing (input / output communication) will reduce downtime and increase the speed and accuracy of operation.

Ultimately, the decision to purchase or upgrade a mechanized plasma cutting system or use a manual one must be justified.

Plasma cutting of metal: equipment

Hypertherm Powermax45 is a portable device with a large number of standard components based on an inverter, i.e. an insulated gate bipolar transistor. Working with it is very easy, regardless of whether the thin steel or sheet metal is cut 12 mm thick at a speed of 500 mm / minute or 25 mm at a speed of 125 mm / min. The device is able to generate more power for cutting various types of conductive materials, such as steel, stainless steel and aluminum.

The power system has an advantage over analogues. The input voltage is 200-240 V single phase with a power of 34/28 A at a power of 5.95 kW. Changes in the input voltage of the network are compensated by the Boost Conditioner technology, thanks to which the cutter demonstrates increased performance at low voltages, with variations in input power, and also with generator power. Internal components are effectively cooled using the PowerCool system, which provides increased productivity, operating time and reliability of the device. Another important feature of this product is the FastConnect burner connection, which facilitates mechanized use and improves versatility.

The Powermax45 torch has a double-angle design that extends nozzle life and reduces operating costs. It is equipped with the function of Conical Flow, which increases the energy density of the arc, which significantly reduces the dross and produces high-quality plasma cutting. Price Powermax45 - 1800 $.

Hobart AirForce 700i

Hobart AirForce 700i has the greatest cutting ability of this line: the nominal thickness of cutting is 16 mm with the speed of 224 mm / min, and the maximum - 22 mm. In comparison with analogues, the operating current of the device is 30% less. A plasma cutter is suitable for service stations, repair shops and for the construction of small buildings.

The device is distinguished by a light but powerful inverter, an ergonomic start-up fuse, efficient air consumption and inexpensive consumables of the burner, which ensures safe, high-quality and inexpensive plasma cutting. The price of AirForce 700i is 1500 $.

The kit includes an ergonomic manual burner, cable, 2 interchangeable tips and 2 electrodes. The gas consumption is 136 l / min at a pressure of 621-827 kPa. The weight of the device is 14.2 kg.

The 40 amp output provides exceptional sheet metal cutting performance - faster than mechanical, gas and plasma devices from other manufacturers.

Miller Spectrum 625 X-treme

Miller Spectrum 625 X-treme - a small device, powerful enough for cutting various types of steel, aluminum and other conductive metals.

It is powered by an alternating current network of 120-240 V voltage, automatically adjusting to the applied voltage. Lightweight and compact design makes the device very portable.

Thanks to the Auto-Refire technology, the arc is controlled automatically, eliminating the need to constantly press the button. The nominal cutting thickness at a current of 40 A is 16 mm at a speed of 330 mm / min, and the maximum thickness is 22.2 mm at 130 mm / min. Power consumption is 6.3 kW. The weight of the device in manual execution is 10.5 kg, and with a machine cutter - 10.7 kg. As the plasma gas, air or nitrogen is used.

The reliability of the Miller 625 is provided by Wind Tunnel technology. Thanks to the built-in high-speed fan, dust and debris do not get inside the device. LED indicators inform about pressure, temperature and power. The price of the device is 1800 $.

Lotos LTP5000D

Lotos LTP5000D is a portable and compact plasma device. At a weight of 10.2 kg problems with its movement will not arise. The 50-ampere current produced by the digital converter, as well as the powerful MOSFET transistor, provide an effective cutting of soft steel with a thickness of 16 mm and 12 mm of stainless steel or aluminum.

The device automatically adjusts to the voltage and frequency of the network. The length of the hose is 2.9 m. The auxiliary arc with the metal does not contact, which makes it possible to use the apparatus for cutting rusty, unworked and painted materials. The device is safe to use. The compressed air used for cutting is not harmful to humans. A sturdy impact-resistant housing reliably protects the device from dust and debris. Price Lotos LTP5000D - 350 $.

When buying a plasma cutter, you should always give preference to quality. One should beware of the temptation to purchase a cheap low-quality device, since its rapid wear in the long term will lead to much greater costs. Of course, it is also not worth overpaying, there are enough decent budget options without accessories and high capacities that may never be needed.