metal plasma. Where is plasma cutting used?

Plasma cutting metal is well suited for cutting high-alloy steels. This method is superior cutting torches minimum zone heating, which allows you to quickly make a cut, but avoid deformation of the surface from overheating. Unlike mechanical methods cut ("grinder" or machine), are capable of cutting the surface according to any pattern, obtaining unique solid shapes with minimal material waste. ? What is the cutting process technology?

Plasma cutting of metal and its principles of operation are based on the amplification of an electric arc by accelerating gas under pressure. This increases the temperature of the cutting element by several times, in contrast to the propane-oxygen flame, which allows you to quickly cut, preventing the high thermal conductivity of the material from transferring the temperature to the rest of the product and deforming the structure.

Plasma cutting of metal on video gives general idea about the ongoing process. The essence of the method is as follows:

1. Current source (powered by 220 V for small models, and 380 V for industrial installations designed for a large thickness of metal) gives the required voltage.
2. Through the cables, the current is transmitted to the plasma torch (torch in the hands of a welder-cutter). The device contains a cathode and an anode - electrodes between which an electric arc ignites.
3. The compressor forces the air flow through the hoses into the machine. The plasma torch has special swirlers that help direct and swirl the air. The flow penetrates the electric arc, ionizing it and accelerating the temperature many times over. It turns out plasma. This arc is called the standby arc, because it burns to maintain work.
4. In many cases, a ground cable is used, which is connected to the material being cut. Bringing the plasma torch to the product, the arc closes between the electrode and the surface. Such an arc is called a working arc. High temperature and air pressure permeate the required place in the product, leaving a thin cut and small sagging, easily removed by tapping. If contact with the surface is lost, the arc automatically continues to burn in standby mode. Reapplying to the workpiece allows you to immediately continue cutting.
5. After the end of work, the button on the plasma torch is released, which turns off all types of electric arc. The system is purged with air for a while to remove debris and cool the electrodes.

The cutting element - the ionized arc of the plasma torch, allows not only cutting the material into pieces, but also welding it back. To do this, use a filler wire that is appropriate in composition for a particular type of metal, and an inert gas is supplied instead of ordinary air.

Varieties of plasma cutting and operating principles

Cutting metals with an ionized high-temperature arc has several modifications according to the approach used and purpose. In some cases electrical circuit, to perform a cut, must be closed between the plasma torch and the product. It is suitable for all kinds of conductive metals. Two wires come from the device, one of which passes into the burner, and the second is attached to the surface to be treated.

The second method consists in burning an arc between the cathode and the anode, enclosed in the nozzle of the plasma torch, and the ability to cut with the same arc. This method well suited to materials incapable of conducting current. In this case, one cable comes from the device leading to the burner. The arc burns constantly in working order. All this applies to air-plasma cutting of metal.

But there are models of plasma cutters, where steam from the poured liquid is used as an ionizing substance. Such models work without a compressor. They have a small reservoir for pouring distilled water supplied to the electrodes. Evaporating, pressure is created, which intensifies the electric arc.

Advantages of plasma cutters

The principles of operation of plasma cutting using a high-temperature arc allow obtaining a number of advantages over other types of metal cutting, namely:

• Ability to process all types of steel, including metals with a high coefficient of thermal expansion.
• Cutting non-conductive materials.
• High speed of work.
• Easy learning workflow.
• A variety of cutting lines, including curly shapes.
• High cutting precision.
• Small after-treatment of the surface.
• Less environmental pollution.
• Safety for the welder due to the lack of gas cylinders.
• Mobility when transporting equipment with small dimensions and weight.

Plasma metal cutting technology

How plasma cutting works is shown in the video. After watching a few of these lessons, you can start independent tests. The process is carried out in the following sequence:

1. The product to be cut is set so that there is a gap of several centimeters under it. For this, linings are used under the edges, or the structure is installed on the edge of the table so that the part to be processed is above the floor.
2. It is better to mark the cutting line with a black marker if the work is being done on of stainless steel or aluminium. When you have to cut the "black" metal, it is better to draw a line with a thin crayon, which is more clearly visible on a dark surface.
3. It is important to make sure that the hose from the torch does not lie next to the cut. Severe overheating can ruin it. Novice welders may not see this due to excitement and damage the equipment.
4. Protective goggles are put on. If you have to work for a long time, then it is better to use a mask that will cover not only the eyes, but the entire face from ultraviolet radiation.
5. If cutting will be carried out on substrates exposed on the floor, then a sheet of metal should be placed so that splashes do not spoil the floor covering.
6. Before starting work, you must make sure that the compressor has gained sufficient pressure, and water models have heated the liquid to the desired temperature.
7. By pressing the button, the arc is ignited.
8. The plasma torch must be held perpendicular to the surface being cut. A small angle of deviation relative to this position is allowed.
9. It is better to start the cut from the edge of the product. If you need to start from the middle, then it is advisable to drill a thin hole. This will help to avoid overheating and depression in this place.
10. When conducting the arc, it is necessary to maintain a distance of 4 mm to the surface.
11. For this, emphasis under the arms is important, which is carried out with the elbows on the table or on the knees.
12. When conducting a cut, it is important to visually verify the appearance of a gap in the area covered, otherwise you will have to cut again.
13. When the cut line ends, care must be taken so that the part does not fall on your feet.
14. Releasing the button stops the arc.
15. Beats with a hammer thin layer slag along the edges of the cut. If necessary, additional cleaning of the product on an emery wheel is carried out.

Used equipment

To carry out plasma cutting, various devices and devices are used. The current source can be small and contain a transformer, several relays and an oscillator. The small models are very compact for carrying and working at heights. They are able to cut metals up to 12 mm thick, which is enough for most types of work in the workplace and at home. Large devices have a similar device layout, but have more powerful parameters due to the use of materials with a larger cross section, and increased input voltage values. Such models are transported on trolleys, and work with products is carried out by a plasma torch attached to a bracket. They can cut materials up to 100 mm thick.

Plasmatrons of both large and small devices are arranged in the same way, but differ in size. All have a handle and a start button. Each has a rod electrode (cathode) and an internal nozzle (anode), between which an arc burns. The flow swirler directs the air and accelerates the temperature. The insulator protects the external parts from overheating and premature contact of the electrodes. External nozzles are set depending on the thickness to be cut. Tips close the nozzle from splashes of molten metal. Various nozzles can be put on the end of the plasma torch, helping to keep a distance during operation and removing carbon deposits from the chamfers. The compressor supplies air through a hose, and its output is regulated by a valve.

The invention of plasma cutting made it possible to speed up work with many alloy steels, and the accuracy of the cut line and the ability to produce curved shapes help to obtain a variety of products for production processes. Understanding the functioning of the apparatus and the essence of the work performed by it will help to quickly master this useful invention.

It is used in the processing of conductive metals. The processed material receives energy from a current source by means of ionized gas. Standard system includes an ignition circuit and torch that provide the power, ionization, and control needed for high-quality, high-performance cutting on a variety of metals.

The DC output sets the thickness and speed of the material and maintains the arc.

The ignition circuit is made in the form of a high-frequency alternating voltage generator of 5-10 thousand V with a frequency of 2 MHz, which creates a high-intensity arc that ionizes the gas to a plasma state.

The cutter is a holder for consumables- nozzle and electrode - and provides cooling of these parts with gas or water. The nozzle and electrode are compressed and support the 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.

Plasma cutting is a thermal process in which a beam heats an electrically conductive metal to a temperature above its melting point and removes the molten metal through a drilled hole. An electric arc occurs between the electrode in the burner, to which a negative potential is applied, and the workpiece with a positive potential, and the material is cut by an ionized gas flow under pressure at a temperature of 770 to 1400 °C. A jet of plasma (ionized gas) is concentrated and directed through a nozzle, where it condenses and becomes capable of melting and cutting a wide variety of metals. This is the basic process for both manual and mechanized plasma cutting.

hand cutting

Manual cutting of metal with plasma is carried out using fairly small devices with a plasma torch. They are manoeuvrable, versatile and can be used to perform various tasks. Their capabilities depend on the current strength of the cutting system. Settings options manual cutting vary from 7-25 A to 30-100 A. Some devices, however, allow you to get up to 200 amperes, but they are not widely used. In manual systems, process air is usually used as the plasma and shield gas. They are designed in such a way that they can be used with various input voltages, which can vary from 120 to 600 V, and can also be used in single or three-phase networks.

Hand held metal cutting plasma is commonly used in metal fabrication workshops. thin materials, factory services Maintenance, repair shops, scrap metal collection points, in construction and installation works, in shipbuilding, car repair shops and art workshops. As a rule, it is used to trim the excess. A typical 12 amp plasma machine cuts a maximum of 5 mm of metal at a rate of about 40 mm per minute. The 100 amp device cuts a 70 mm layer at speeds up to 500 mm/min.

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

Machine processing

Mechanized metal cutting with plasma is carried out on installations, which, as a rule, are much larger than manual ones, and is used in combination with cutting tables, including those with a water bath or with a platform equipped with various drives and motors. In addition, mechanized systems are equipped with CNC and cutting head jet height control, which can include torch height preset and voltage control. Mechanized plasma cutting systems can be installed on other metalworking equipment such as stamping presses or robotic systems. The size of the mechanized configuration depends on the size of the table and the platform used. The panel saw can be smaller than 1200x2400 mm and larger than 1400x3600 mm. Such systems are not very mobile, therefore, before installation, all their components, as well as their location, should be considered.

Power requirements

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

Gas Requirements

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

Oxygen is used for mild carbon steel because it produces high quality cuts in material up to 70mm thick. Oxygen can also act as a plasma gas for stainless steel and aluminum, but the result is not entirely accurate. Nitrogen serves as the plasma and assist gas as it provides excellent cutting performance on virtually any type of metal. It is 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 low-current cutting of sheet metal up to 25 mm thick is performed, it leaves an oxidized surface. When cutting with air, nitrogen or oxygen, it is an auxiliary gas.

An argon/hydrogen mixture is typically used on stainless steel and aluminium. Provides a high quality cut and is essential for mechanized cutting of sheets over 75mm thick. Carbon dioxide can also be used as an auxiliary gas when cutting metal with nitrogen plasma, as it allows you to work with most materials and guarantees good quality.

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

What else will be required?

The choice of plasma and auxiliary gases are only two of the most important decisions to 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 storage needs to be adequate. Installing the system requires a significant amount of electrical wiring and piping for gas and coolant. In addition to the most mechanized plasma system, you need to pick up a table, a saw, CNC and THC. OEMs typically offer a variety of hardware options to suit any device configuration.

Is mechanization necessary?

Due to the complexity of choosing a mechanized plasma cutting process, a lot of time must be devoted to researching various system configurations and criteria. Consider:

• types of parts to be cut;
• the number of industrial products in the batch;
• desired cutting speed and quality;
• cost of consumables.
• the total cost of operating the configuration, including electricity, gas, and labor.

The size, shape and number of parts to be produced can determine the required industrial production equipment - the type of CNC, table and platform. For example, the production of parts small size may require a dedicated drive platform. The rack and pinion drives, servos, drive amplifiers and sensors used on the platforms determine the quality of the cut and the maximum speed of the system.

Quality and speed also depends on which CNC and gases are used. A mechanized system with adjustable current and gas flow at the beginning and end of the cut will reduce material consumption. In addition, CNC with large memory and choice possible installations(for example, flame heights at the end of the cut) and fast data processing (input/output communications) will reduce downtime and increase the speed and accuracy of work.

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

Plasma cutting of metal: equipment

Hypertherm Powermax45 is a portable machine with a large number of standard components based on an inverter, i.e. an insulated gate bipolar transistor. It is very easy to work with, whether it is cutting thin steel or 12 mm sheet metal at 500 mm/minute or 25 mm at 125 mm/minute. The device is capable of generating high power for cutting various types of conductive materials such as steel, stainless steel and aluminum.

The power supply system has an advantage over analogues. Input voltage - 200-240 V single-phase current with a power of 34/28 A at a power of 5.95 kW. Variations in mains input voltage are compensated for by Boost Conditioner technology, which provides the torch with improved performance at low voltages, fluctuating input power, and when powered by a generator. The internal components are effectively cooled with the PowerCool system, providing improved performance, runtime and reliability of the device. Another important feature of this product is the FastConnect torch connection, which facilitates mechanized use and increases versatility.

The Powermax45 torch features a dual angle design that extends nozzle life and reduces nozzle life. It is equipped with a Conical Flow feature that increases arc energy density, greatly reducing dross and producing high-quality plasma cutting. Price Powermax45 - $ 1800.

Hobart Airforce 700i

The Hobart AirForce 700i has the highest cutting capacity in the range, with a nominal cutting thickness of 16mm at 224mm/min and a maximum of 22mm. Compared with analogues, the operating current of the device is 30% less. The plasma cutter is suitable for service stations, repair shops and when building small buildings.

The device features a light but powerful inverter, an ergonomic starting fuse, efficient consumption air and inexpensive consumables torches, thanks to which safe, high-quality and inexpensive plasma cutting is carried out. The AirForce 700i is priced at $1,500.

The kit includes an ergonomic hand torch, cable, 2 replacement 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 delivers exceptional sheet metal cutting performance - faster than other manufacturers' mechanical, gas and plasma devices.

Miller Spectrum 625 Xtreme

The Miller Spectrum 625 X-treme is a small machine powerful enough to cut a variety of steel, aluminum and other conductive metals.

Powered by mains alternating current voltage 120-240 V, automatically adjusting to the applied voltage. Lightweight and compact design makes the device highly portable.

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

Reliability of Miller 625 is provided by the 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 machine. With a weight of 10.2 kg, there will be no problems with its movement. The 50 amp current generated by the digital converter and the powerful MOSFET provide efficient cutting of 16 mm mild steel and 12 mm stainless steel or aluminium.

The device automatically adjusts to the mains voltage and frequency. Hose length - 2.9 m. The pilot arc does not come into contact with metal, which allows the machine to be used for cutting rusty, raw and painted materials. The device is safe to use. Compressed air used for cutting is not harmful to humans. And the strong shock-resistant case reliably protects the device from hit of dust and debris. The price of Lotos LTP5000D is $350.

When buying a plasma cutter, you should always prioritize quality. You should beware of the temptation to buy a cheap low-quality device, as its rapid wear and tear in the long run will lead to much high costs. Of course, it’s also not worth overpaying, there are enough worthy budget options without accessories and high powers that may never be needed.

Plasma cutting is widely used in various industries such as machinery, shipbuilding, advertising, public utilities, steel structure and other industries. In addition, in a private workshop, a plasma cutter can also come in handy. After all, with the help of it you can quickly and efficiently cut any conductive material, as well as some non-conductive materials - plastic, stone and wood. cut pipes, sheet metal, make a shape cut or make a part simply, quickly and conveniently with the help of plasma cutting technology. The cut is performed with a high-temperature plasma arc, which requires only a power source, a torch and air to create. To make working with a plasma cutter easy, and the cut turned out beautiful and even, it does not interfere with learning the principle of operation of a plasma cutter, which will give basic concept how you can control the cutting process.

The device called "plasma cutter" consists of several elements: power supply, plasma cutter/plasma torch, air compressor And cable-hose package.

Power supply for plasma cutter supplies a certain current to the plasma torch. May be a transformer or inverter.

transformers they are heavier, consume more energy, but are less sensitive to voltage drops, and they can be used to cut workpieces of greater thickness.

inverters lighter, cheaper, more economical in terms of energy consumption, but at the same time they allow cutting thinner workpieces. Therefore, they are used in small industries and in private workshops. Also, the efficiency of inverter plasma cutters is 30% higher than that of transformer ones, their arc burns more stably. They also come in handy for working in hard-to-reach places.

Plasmatron or whatever it is called "plasma cutter" is the main element of the plasma cutter. In some sources, you can find a mention of a plasma torch in such a context that one might think that "plasma torch" and "plasma cutter" are identical concepts. In fact, this is not so: the plasma torch is directly a cutter with which the workpiece is cut.

The main elements of a plasma cutter / plasma torch are nozzle, electrode, cooler/insulator between them and a channel for supplying compressed air.

The scheme of the plasma cutter clearly demonstrates the location of all elements of the plasma cutter.

Inside the body of the plasma torch is electrode, which serves to initiate an electric arc. It can be made from hafnium, zirconium, beryllium or thorium. These metals are acceptable for air-plasma cutting because refractory oxides are formed on their surface during operation, which prevent the destruction of the electrode. However, not all of these metals are used because the oxides of some of them can be harmful to the health of the operator. For example, thorium oxide is toxic, and beryllium oxide is radioactive. Therefore, the most common metal for the manufacture of plasmatron electrodes is hafnium. Rarely - other metals.

Plasma torch nozzle compresses and forms a plasma jet, which breaks out of the output channel and cuts the workpiece. The size of the nozzle determines the capabilities and characteristics of the plasma cutter, as well as the technology of working with it. The dependence is as follows: the diameter of the nozzle determines how much air can pass through it per unit time, and the width of the cut, the cooling rate and the speed of the plasma torch depend on the air volume. Most often, the plasma torch nozzle has a diameter of 3 mm. nozzle length too important parameter: The longer the nozzle, the more accurate and better the cut. But you have to be more careful with this. Too long nozzle breaks down faster.

Compressor for a plasma cutter it is necessary for air supply. Plasma cutting technology involves the use of gases: plasma-forming and protective. Plasma cutting machines, designed for currents up to 200 A, use only compressed air, both for creating plasma and for cooling. Such an apparatus is sufficient for cutting workpieces 50 mm thick. industrial machine plasma cutting uses other gases - helium, argon, oxygen, hydrogen, nitrogen, as well as their mixtures.

Cable-hose package connects the power source, compressor and plasma torch. By electrical cable current is supplied from a transformer or inverter to excite an electric arc, and compressed air flows through the hose, which is necessary for the formation of plasma inside the plasma torch. In more detail what exactly happens in the plasma torch, we will describe below.

As soon as the ignition button is pressed, the power source (transformer or inverter) starts supplying currents to the plasma torch high frequency. As a result, a standby electric arc occurs inside the plasma torch, the temperature of which is 6000 - 8000 °C. The pilot arc is ignited between the electrode and the tip of the nozzle for the reason that the formation of an arc between the electrode and the workpiece immediately is difficult. The pillar of the guard arc fills the entire channel.

After the appearance of the pilot arc, compressed air begins to flow into the chamber. It breaks out of the pipe, passes through an electric arc, as a result of which it heats up and increases in volume by 50 - 100 times. In addition, the air is ionized and ceases to be a dielectric, acquiring conductive properties.

The plasmatron nozzle narrowed to the bottom compresses the air, forms a flow from it, which breaks out of the nozzle at a speed of 2 - 3 m / s. The air temperature at this moment can reach 25,000 - 30,000 °C. It is this high-temperature ionized air that is in this case plasma. Its electrical conductivity is approximately equal to the electrical conductivity of the metal being processed.

At the moment when the plasma escapes from the nozzle and comes into contact with the surface of the metal being processed, the cutting arc is ignited, and the duty arc goes out. The cutting/working arc heats up the workpiece at the cutting point - locally. The metal melts, a cut appears. Particles of freshly molten metal appear on the surface of the metal being cut, which are blown away from it by a stream of air escaping from the nozzle. This is the most simple technology plasma cutting of metal.

cathode spot the plasma arc must be located strictly in the center of the electrode / cathode. To ensure this, the so-called vortex or tangential compressed air supply is used. If the vortex feed is broken, then the cathode spot is displaced relative to the center of the electrode along with the plasma arc. This can lead to unpleasant consequences: the plasma arc will burn unstably, two arcs can form simultaneously, and in worst case- The plasma torch may fail.

If you increase the air flow, the plasma flow rate will increase, and the cutting speed will also increase. If you increase the diameter of the nozzle, then the speed will decrease and the width of the cut will increase. The plasma flow velocity is approximately equal to 800 m/s at a current of 250 A.

Cutting speed is also an important parameter. The larger it is, the thinner the cut. If the speed is low, then the width of the cut increases. If the current increases, the same thing happens - the width of the cut increases. All these subtleties relate directly to the technology of working with a plasma cutter.

Plasma cutter parameters

All plasma cutting machines can be divided into two categories: manual plasma cutters and machine cutting machines.

Manual plasma cutters used in everyday life, in small industries and in private workshops for the manufacture and processing of parts. Their main feature is that the operator holds the plasma torch in his hands, he leads the cutter along the line of the future cut, holding it in the air. As a result, the cut turns out to be even, but not perfect. Yes, and the performance of such technology is small. To make the cut more even, without sagging and scale, a special stop is used to guide the plasma torch, which is put on the nozzle. The stop is pressed against the surface of the workpiece being processed and it remains only to guide the cutter without worrying about whether the required distance between the workpiece and the nozzle is observed.

For a manual plasma cutter, the price depends on its characteristics: maximum current strength, thickness of the workpiece being processed and versatility. For example, there are models that can be used not only for cutting metals, but also for welding. They can be distinguished by their markings:

• CUT - cutting;
• TIG - argon arc welding;
• MMA - arc welding with stick electrode.

For example, the FoxWeld Plasma 43 Multi plasma cutter combines all of the above functions. Its cost is 530 - 550 USD. Characteristics regarding plasma cutting: current strength - 60 A, workpiece thickness - up to 11 mm.

By the way, the current strength and the thickness of the workpiece are the main parameters by which the plasma cutter is selected. And they are interconnected.

The greater the current, the stronger the plasma arc, which melts the metal faster. When choosing a plasma cutter for specific needs, you need to know exactly what metal will have to be processed and what thickness. The table below shows how much current is needed to cut 1 mm of metal. Please note that processing non-ferrous metals requires a large current. Keep this in mind when you look at the characteristics of a plasma cutter in a store, the thickness of the ferrous metal blank is indicated on the device. If you plan to cut copper or other non-ferrous metal, it is better to calculate the required amperage yourself.

For example, if you want to cut copper with a thickness of 2 mm, then you need to multiply 6 A by 2 mm, we get a plasma cutter with a current of 12 A. If you want to cut steel with a thickness of 2 mm, then multiply 4 A by 2 mm, we get a current of 8 A. Only take a plasma cutter with a margin, as the specified characteristics are maximum, not nominal. They can only work for a short time.

CNC Plasma Cutting Machine used on manufacturing enterprises for the manufacture of parts or processing blanks. CNC means numerical program control. The machine works according to a given program with minimal operator participation, which eliminates the human factor in production as much as possible and increases productivity by several times. Machine cut quality is perfect, no need additional processing edges. And most importantly - curly cuts and exceptional accuracy. It is enough to enter the cutting scheme into the program and the device can perform any intricate figure with perfect accuracy. The price of a plasma cutting machine is much higher than a manual plasma cutter. First, a large transformer is used. Secondly, a special table, a portal and guides. Depending on the complexity and size of the device, the price can be from 3000 USD. up to 20000 c.u.

Machine plasma cutting machines use water for cooling, so they can work the entire shift without interruption. The so-called duty cycle (duty cycle) is 100%. Although for manual devices it can be 40%, which means the following: the plasma cutter works for 4 minutes, and it needs 6 minutes to cool down.

It would be most reasonable to purchase a ready-made, factory-made plasma cutter. In such devices, everything is taken into account, adjusted and works as ideally as possible. But some craftsmen of Kulibina manage to make a plasma cutter with their own hands. The results are not very satisfactory, as the quality of the cut is lame. As an example, we give a truncated version of how you can make a plasma cutter yourself. Let us make a reservation right away that the scheme is far from ideal and only gives a general concept of the process.

So, the transformer for the plasma cutter must be with a falling current-voltage characteristic.

An example in the photo: the primary winding is from below, the secondary is from above. Voltage - 260 V. Winding cross section - 45 mm2, each busbar 6 mm2. If you set the current to 40 A, the voltage drops to 100 V. The inductor also has a cross section of 40 mm2, it was wound with the same bus, only about 250 turns.

Required for work air compressor, of course, factory-made. In this case, a unit with a capacity of 350 l / min was used.

Homemade plasma cutter - scheme of work.

It is better to purchase a plasma torch from the factory, it will cost about 150 - 200 USD. IN this example The plasma torch was made independently: a copper nozzle (5 cu) and a hafnium electrode (3 cu), the rest is "handicraft". Due to which consumables quickly failed.

The circuit works like this: there is a start button on the cutter, when it is pressed, the relay (p1) supplies voltage to the control unit, relay (p2) supplies voltage to the transformer, then it lets air in to purge the plasma torch. The air dries the plasma torch chamber from possible condensate and blows out everything superfluous, it has 2 - 3 seconds for this. It is with this delay that the relay (p3) is activated, which supplies power to the electrode to strike the arc. Then the oscillator is turned on, which ionizes the space between the electrode and the nozzle, as a result, the pilot arc lights up. Next, the plasma torch is brought to the product and the cutting / working arc lights up between the electrode and the workpiece. The reed relay switches off the nozzle and ignition. According to this scheme, if the cutting arc suddenly goes out, for example, if the nozzle hits a hole in the metal, then the reed switch relay will turn on the ignition again and after a few seconds (2 - 3) the duty arc will light up, and then the cutting one. All this provided that the "start" button is not released. Relay (p4) lets air into the nozzle with a delay, after the “start” button is released and the cutting arc goes out. All these precautions are necessary in order to prolong the life of the nozzle and electrode.

Independent production of a plasma cutter in "home" conditions makes it possible to save a lot, but there is no need to talk about the quality of the cut. Although if an engineer takes over the work, the result may be even better than the factory performance.

Not every enterprise can afford a CNC plasma cutting machine, because its cost can reach 15,000 - 20,000 USD. Quite often, such organizations order plasma cutting work at special enterprises, but this is also expensive, especially if the volume of work is large. But you really want your new plasma cutting machine, but there are not enough funds.

In addition to the well-known profile factories, there are enterprises that manufacture plasma cutting machines, purchasing only profile parts and assemblies, and making everything else on their own. As an example, we will describe how CNC plasma cutting machines are made by engineers in a production shop.

Components of a do-it-yourself plasma cutting machine:

• Table 1270x2540 mm;
• Belting;
• step details;
• Linear guides HIWIN;
• THC flame height control system;
• Control block;
• The rack-terminal, in which the CNC control unit is located, stands separately.

Machine characteristics:

• Travel speed on the table 15 m/min;
• Plasma torch position setting accuracy 0.125 mm;
• If using a Powermax 65 machine, the cutting speed will be 40 m/min for a 6 mm workpiece or 5 m/min for a 19 mm thick workpiece.

For a similar plasma cutting machine, the price will be about 13,000 USD, not including the plasma source, which will have to be purchased separately - 900 USD.

For the manufacture of such a machine, components are ordered separately, and then everything is assembled independently according to the following scheme:

• The base for welding the table is being prepared, it must be strictly horizontal, this is very important, it is better to check with a level.
• The frame of the machine is welded in the form of a table. You can use pipes square section. Vertical "legs" must be reinforced with jibs.

• The frame is coated with a primer and paint to protect against corrosion.

• Machine stands are made. Support material - duralumin, bolts 14 mm, it is better to weld nuts to the bolts.

• The water table is being welded.

• Fasteners for rails are installed and rails are placed. For rails, metal is used in the form of a 40 mm strip.
• Linear guides are installed.
• The body of the table is sewn up with sheet iron and painted.
• The portal is installed on the rails.

• An engine and end inductive sensors are installed on the portal.
• Rail guides, gear rack and Y-axis motor are installed.

• The guides and the motor are installed on the Z axis.
• A metal surface sensor is installed.

• A tap is installed to drain the water from the table, limiters for the portal so that it does not move off the table.
• Installed cable channels Y,Z and X.

• All wires are hidden in the corrugation.
• A mechanized burner is installed.

• Next, the CNC terminal is manufactured. The body is welded first.
• A monitor, a keyboard, a THC module and buttons for it are installed in the body of the CNC terminal.

Everything, the CNC plasma cutting machine is ready.

Despite the fact that the plasma cutter has a fairly simple device, it is still not worth taking on its manufacture without serious knowledge in welding and extensive experience. It is easier for a beginner to pay for ready product. But engineers who want to translate their knowledge and skills at home, which is called "on the knee", can try to create a plasma cutter with their own hands from start to finish.

Plasma cutting is very often used in industries such as shipbuilding, mechanical engineering, as well as in the manufacture of metal structures, utilities, etc. In addition, a plasma cutter is quite often used in a private workshop. With its help, any material that conducts current, and some non-conductive materials - wood, stone and plastic, are quickly and efficiently cut.

Plasma cutting technology allows you to cut sheet metal and pipes, make curved cuts or make parts. The work is carried out using high temperature plasma arc. To create it, you only need a power source, air and a cutter. In order for the work to be done quite easily, and the cut to be smooth and beautiful, you should find out how the principle of plasma cutting works.

How does a plasma cutter work?

This apparatus consists of the following elements:

• source of power;
• air compressor;
• plasma cutter or plasma torch;
• cable-hose package.

The power source for the plasma cutting machine supplies a certain current to the plasma torch. It is an inverter or transformer.

Inverters are quite light, economical in terms of energy consumption, inexpensive, however, they are able to cut workpieces of small thickness. Because of this, they are only used in private workshops and small industries. Inverter plasma cutters have 30% more efficiency than transformer ones and their arc burns better. They are often used for work in hard-to-reach places.

Transformers are much heavier, they spend a lot of energy, but at the same time they have less sensitivity to voltage drops, and with their help they cut thick workpieces.

The plasma cutter is considered the main element of the plasma cutter. Its main elements are:

• nozzle;
• cooler/insulator;
• channel required for supplying compressed air;

A compressor is required to supply air. The principle of operation of plasma cutting involves the use of protective and plasma gases. For devices that rated for current up to 200 A, only compressed air is used for both cooling and plasma generation. They are able to cut workpieces with a thickness of 50 mm.

The cable-hose package is used to connect the compressor, power source and plasma torch. The electrical cable from the inverter or transformer begins to flow current to excite the electric arc, and the hose is supplied with compressed air, which is required for the occurrence of plasma inside the plasma torch.

Principle of operation

When the ignition button is pressed, the high frequency current is supplied from the power source (inverter or transformer). As a result, a standby electric arc is formed inside the plasma torch, the temperature of which reaches 8 thousand degrees. The column of this arc begins to fill the entire channel.

After the pilot arc has arisen, compressed air begins to flow into the chamber. Breaking out of the pipe, he passes through an electric arc, heats up, while increasing in volume by 50 or 100 times. In addition, the air begins to ionize and ceases to be a dielectric, acquiring the properties of conducting current.

The plasma torch nozzle, narrowed down, compresses the air, creating a flow from it, which begins to escape from there at a speed of 2–3 m/s. At this moment, the air temperature often reaches 30 thousand degrees. It is this hot ionized air that is plasma.

At the time when the plasma begins to escape from the nozzle, it comes into contact with the surface of the metal being processed, the pilot arc goes out at this moment, and the cutting one lights up. She starts heat the workpiece at the cutting point. As a result, the metal melts and a cut appears. On the surface of the metal being cut, small particles of molten metal are formed, which are blown away from it by a stream of air. Thus, the operation of the plasma torch is carried out.

Benefits of Plasma Cutting

Metal cutting work is often carried out on a construction site, in a workshop or workshop. You can use an autogen for this, but not everyone is happy with it. If the amount of work associated with metal cutting is too large, and the requirements for cut quality are very high, then you should consider using a plasma cutter that has the following advantages:

Disadvantages of Plasma Cutting

There are also disadvantages in the operation of plasma cutting. The first of them - the maximum allowable cut thickness is quite small, and for the most powerful units it rarely exceeds 80 - 100 mm.

The next disadvantage is the rather stringent requirements for the deviation from the perpendicularity of the cut. Deflection angle should not be more than 10 - 50 degrees and it depends on the thickness of the part. If it happens to go beyond these limits, then a rather significant expansion of the cut occurs, which results in rapid wear of consumables.

Besides, working equipment quite complex, which makes it completely impossible to use two cutters at the same time, which are connected to one machine.

Conclusion

The principle of plasma cutting is quite simple. In addition, the apparatus used for this has a large number of advantages that are several times greater than the existing disadvantages. If you use it correctly, you can save a lot of time and get a quality result.

For effective processing of a number of metals, plasma cutting is often used, the principle of which is the use of a plasma arc.

1 Plasma metal cutting technology

The process of plasma arc cutting that interests us in world practice is “hidden” under the acronym PAC. Plasma is a high-temperature ionized gas that can conduct electricity. And the plasma arc is formed in a unit called a plasma torch from a conventional electric one.

The latter is compressed, and then a gas is introduced into it, which has the ability to form a plasma. A little later we will talk about how important these plasma gases are for the plasma cutting process.

Technologically, there are two cutting methods:

2 Plasma cutting - the principle of operation of the plasma torch

A plasma torch is a plasma cutting device, in the body of which a small cylindrical arc chamber is placed. At the exit from it there is a channel that creates a compressed arc. On the back side of such a chamber is a welding rod.

A preliminary arc is ignited between the tip of the device and the electrode. This stage is necessary, since it is almost impossible to achieve an arc excitation between the material being cut and the electrode. The specified preliminary arc exits the plasma torch nozzle, comes into contact with the torch, and at this moment the working flow is created directly.

After that, the forming channel is completely filled with a plasma arc column, the gas forming the plasma enters the plasma torch chamber, where it is heated, and then ionized and increased in volume. The described scheme causes high temperature arcs (up to 30 thousand degrees Celsius) and the same powerful speed of gas outflow from the nozzle (up to 3 kilometers per second).

3 Plasma gases and their effect on cutting performance

The plasma-forming medium is, perhaps, the key parameter of the process, which determines its technological potential. The possibility depends on the composition of this environment:

• indicator settings heat flow in the metal processing zone and the current density in it (by changing the ratio of the nozzle cross section to the current);
• varying the volume of thermal energy over a wide range;
• regulation of the surface stress index, chemical composition and viscosity of the material being cut;
• control of the depth of the gas-saturated layer, as well as the nature of the chemical and physical processes in the processing area;
• protection against the appearance of swims on metal and (on their lower edges);
• formation optimal conditions for removal of molten metal from the cut cavity.

In addition, many technical parameters of the equipment used for plasma cutting also depend on the composition of the medium we describe, in particular the following:

• design of the cooling mechanism for the nozzles of the device;
• mounting option in the plasma torch of the cathode, its material and the level of intensity of the supply of coolant to it;
• unit control scheme (its cyclogram is determined precisely by the flow rate and composition of the gas used to form the plasma);
• dynamic and static (external) characteristics of the power supply, as well as its power indicator.

It is not enough to know how plasma cutting works, besides this, it is necessary to choose the right combination of gases to create a plasma-forming medium, taking into account the price of the materials used and the direct cost of the cutting operation.

As a rule, for semi-automatic and manual processing corrosion-resistant alloys, as well as machine and economical manual processing of copper and aluminum, use an environment formed by nitrogen. But already low-alloy carbon steel is better cut in an oxygen mixture, which absolutely cannot be used for processing aluminum products, corrosion-resistant steel and copper.

4 Advantages and disadvantages of plasma cutting

The very principle of plasma cutting determines the advantages of this technology over gas methods processing of non-metallic and metal products. The main advantages of using plasma equipment include the following facts:

• universality of technology: almost all known materials can be cut using a plasma arc, from cast iron and copper to aluminum and steel;
• high speed of operation for metals of medium and small thickness;
• the cuts are of really high quality and high-precision, which often makes it possible not to perform additional machining of products;
• minimal air pollution;
• no need to preheat the metal to cut it, which reduces (and significantly) the burn time of the material;
• high safety of work, due to the fact that gas cylinders, which are potentially explosive, are not needed for cutting.

It should be noted that according to some indicators, gas technologies are recognized as more appropriate than plasma cutting. The disadvantages of the latter usually include:

• the complexity of the design of the plasma torch and its high cost: naturally, this increases the cost of each operation;
• relatively small cut thickness (up to 10 centimeters);
• high noise level during processing, which occurs due to the fact that gas flies out of the plasma torch at transonic speed;
• the need for high-quality and most competent maintenance of the unit;
• an increased level of emission of harmful substances when used as a plasma-forming composition of nitrogen;
• the impossibility of connecting two cutters for manual metal processing to one plasma torch.

Another disadvantage of the type of processing described in the article is that the deviation from the perpendicularity of the cut is allowed by no more than an angle of 10 to 50 degrees (the specific angle value depends on the thickness of the product). If you increase the recommended figure, there is a significant increase cutting area, and this becomes the reason for the need frequent replacement materials used.

Now you know what plasma cutting is, and you are well versed in all its features.