How the plasma cutting metal works. Areas of application

Technology and advantages of plasma cutting metal

The use of plasma cutting is widely used. It is used in mechanical engineering, the communal industry, during the construction of ships, the manufacture of metal structures. The basis of plasma cutting is the principle in which ionized air begins to conduct electric current.

Metal cutting is carried out by plasma, which is a heated ionized air, and a plasma arc. The principles of work characteristic of plasma cutting of metal will be described later.

How to Use Specialty Nozzles to Improve Plasma Cutting. Kevin Caron

What is plasma cutting

When cutting the metal with plasma, the electrically reinforced. This is possible thanks to the action of gas under pressure. The cutting element is heated to high temperature values, the result of which becomes high.quality and fast cutting of metal.

Unlike gas cutting, its plasma analogue does not contribute to overheating of the entire processed product. High temperature occurs directly at the place of metal cutting, and the remaining parts of the product are not warmed up and are not deformed.

The principle of plasma cutting of the metal is based on:

  • issuing the required voltage with a current source (standard voltage. 220 V, increased. 380 V, for cutting metal at large enterprises);
  • transmission of current to plasmotron (burner) through the cables, as a result, an electric arc lights up between the anode and the cathode;
  • feeding the compressor along the hoses of air flows to the device;
  • the action inside the plasmoron of the swirls directing flows to the electric arc;
  • passage of vortex air flows through electric shows and creating ionizing air, heated to high temperatures;
  • the closure of the working arc between the electrode and the processed surface when submitting plasmoron to it;
  • Air action under high pressure and high temperature on the processed product.

The result is a section of a small thickness with minimal influxes.

The arc is able to burn in duty if the device is not used at a specific time. With duty mode, combustion is supported automatically. When the burner is brought to the product, the arc instantly goes into operating mode and instantly cuts the metal.

After turning off the device, it is blown out to remove garbage and cool electrodes.

Electroduga is universal in its action. It is capable of not only cut, but also weld metal products. For welding, a filler wire is used, suitable for a specific type of metal. It is not air that is missed through the arc, but inert gas.

The main types of equipment and types of manual cutting devices

All equipment is divided into indirect devices intended for cutting in a contactless way, and direct action. for contact. The first type is used mainly for processing various non.metallic materials (as in the video). In them, the duty officer is formed between the nozzle and the electrode of plasmotrone.

Direct equipment is used for cutting various metals and their alloys. When working, the cut workpiece is connected to the plus output of the plasma device, becoming part of its electrical circuit. All devices for manual metal cutting are devices of the second type. direct action. In them, to create plasma, cool the nozzle and blowing the cut surface, the air is usually used, supplied from the cylinder or from the compressor. Devices are inverter and transformer.

The former, compared with the second, compact, aesthetic, consume less electricity and weigh little, which is important when working on the exit. They also have higher than 30 % efficiency and a more stable electric arc. However, inverters are less powerful and quite sensitive to voltage drops in the network. Transformers are more reliable and durable, are not afraid of nutritional jumps and they can be used to cut metals of greater thickness.

How to Use a Plasma Cutter

To choose the right device for cutting metals, you should accurately determine the circle of work for which it is supposed to be used. Namely: with what blanks it will be necessary to work, what thickness, from what metal, what is the expected intensity of loading the device.

DIY cutting. Let’s start with the basics

Before starting work, you should take care of security measures. It is necessary to make sure that the voltage of the supply network is exactly what the device is designed (380 V or 220 V), and the network conductors and its protection will withstand the load created by the device. Then you need to take care of the solid grounding of the workstation or table surrounding metal objects and sockets (do it with your own hands!).

It must be checked that power cables and an air-plasma cutting apparatus in perfect working condition and are not damaged. Connect the equipment to the network through the RCD (protective shutdown device). To protect yourself from injury and possible professional saps, you need to work in a special equipment:

  • shield or glasses of welder having glass with obscure class 4-5;
  • in gloves, jackets and pants made of dense material that close the body well;
  • in closed shoes;
  • preferably in respirator or mask.

Having connected all the elements of the device with your own hands, in accordance with the instructions for it, you should install the device in such a place and so that its body is well cool and the spray of the molten metal does not fall on it. Connecting to the equipment of a compressor or cylinder with compressed gas should be performed through oil and moisture detachment. These substances, having entered the plasmotrone chamber, can lead to its breakdown and even explosion.

It is necessary to adjust the pressure of the gas supplied to the plasmotron. it must correspond to the characteristics of the apparatus. With excessive pressure, some parts of plasmotron may become unusable, and with insufficient. the plasma flow will be unstable and often interrupted. When it is necessary to cut the containers where combustible or flammable materials were previously stored, they should be carefully cleaned. If on the surface of the workpiece that must be treated, there are oil spots, scale or rust, it is better to remove them, since when heated they can distinguish toxic vapors.

In order for the cut to go even, without influxes and scale, as shown in the video, it is necessary to choose the right speed of cutting and current strength. The following tables include the optimal values ​​of these parameters for various metals and their thicknesses.

In the absence of experience, choosing the speed of moving the cutter with your own hands will be difficult. Therefore, at first it is recommended to focus on the following: to conduct plasmotron should be so that flying sparks are visible from the opposite side of the metal, as shown in the video. The absence of sparks will indicate that the plasma has not yet cut the workpiece through. At the same time, it should be borne in mind that the excessively slow movement of the cutter has a negative impact on the quality of the cut. influxes and scale appear on the edges of the metal. In addition, plasma can unstably burn and even go out.

Types of plasma cutting

Knowledge about the functioning of the machine, you can not only collect the device, but also perform plasma cutting of metal with your own hands. over, to find detailed instructions on the Internet is not difficult. The best device for converting is a regular inverter for welding.

About metals for plasmoresis

For black metal rolling and its alloys, as the basis of plasma, active gases are used, and for color. inert. The thickness of the metal to be cut, and which can “take” the plasma.cutting tool is 220 millimeters. Thin sheet metal, can also be cut.

Regardless of the cost of plasmoresis, even the most expensive ones, do not guarantee that there will be no begging and conical cutting. Usually the cone is from 2 to 4 0.

The use of the cutting apparatus plasma makes it possible to produce the cutting of the processed metal, both in direct geometric lines and in complex curly lines, as well as perform holes. Their minimum diameter should not be less than one and a half or two thicknesses of metal blank.

Features of the apparatus

When the plasma cutting apparatus is turned on, an electric current of high voltage arrives at the plasmotor. As a result, a high.temperature electric arc is formed. The stream of compressed air, passing through the arc, increases in volume by one order and becomes conductive.

Ionized gas flow (plasma), due to passage through the nozzle, increases its thermodynamic characteristics: the speed increases to 800 m/s, and the temperature is up to 30 thousand. degrees Celsius. The electrical conductivity of the plasma is comparable by value with the electrical conductivity of the processed metal.

Metal cutting occurs due to its physical melting from the action of high temperature. Small scale, which occurs in the process of cutting, is blown away by the stream of compressed air.

The cutting speed is inversely proportional to the diameter of the nozzle of the plasma burner. To form a high-quality plasma arc, a tangential or airy-free supply of compressed air should be used.

The peculiarity of the cutting arc is that its effect is local in nature: in the process of cutting, there is no deformation or violation of the surface layer of the processed product.

Where plasma cutters are used?

Plasma cutting and welding are an indispensable method of metal processing, when it comes to working with highly alloyed steels. Since such materials are used in a huge number of industries, the use of plasma cutters is increasingly developing.

The most widespread plasma welding was in the manufacture of various metal structures. Metal plasma cutting is also widely used in heavy mechanical engineering and when laying pipelines.

Automated plasma cutter lines are spread at large machine.building plants.

Plasma cutters should be cutting absolutely any materials in its origin: both conductive and dielectric.

Plasma cutting technology makes it possible to cut steel sheet parts, especially complex configurations. The ultra.high temperature of the burner flame allows you to cut heat.resistant alloys, which includes nickel, molybdenum and titanium. The melting point of these metals exceeds 3 thousand. degrees Celsius.

Plasmoresis is an expensive professional tool, so it is practically not found in personal subsidiary plots. For single work, regardless of their complexity, masters can do with available tools for cutting metal, for example, an electric corner grinder.

Where there are tasks of cutting highly alloy alloys on an industrial scale, plasma cutting devices are indispensable assistants. High accuracy of cut, work with any material. the advantages of plasma cutters.

plasma, cutting, metal, works

Manual plasma cutting is used in industries, where it is required to make leaf parts of complex geometric contours. Examples of such industries are jewelry industry and instrumentation.

plasma, cutting, metal, works

Plasma cutters are a non.alternative tool for obtaining parts of a complex circuit, especially of thin.leaf steel. Where leaf stamping does not cope with the task of receiving products from very thin sheet rental, plasma cutting comes to the aid of technologists.

Not without plasma cutters and complex installation work on the installation of metal structures. At the same time, there is no need to use oxygen and acetylene cylinders, this increases the safety of the metal cutting process. This technological factor facilitates work on cutting metal at a height.

What metals can be cut?

With the help of plasma technology, the processing of almost any metals is ensured:

  • Cutting and cutting sheet metal made of steel, titanium, non.ferrous metals (copper, aluminum, etc. P.) and their alloys (in t.h. bronze, brass and t. D.).
  • Cutting became different thicknesses and forms of blanks. The processing of carbon and alloyed steels of almost all brands is ensured, in t.h. Highly legged stainless steels. Plazmotrons can be cut off (narrow long steel stripes) and cut the roller steel.
  • Cutting cast iron. Plasma provides its deep cut, which makes the method more effective in comparison with other technologies.
  • Cutting and processing pipes of different diameters. Special pipelines with centers are used. In addition to cutting, you can process the surface of the pipes, remove the chamfers, clean the welds, process the edges.
  • Formation and processing of holes.
  • Figure cutting of metal blanks. Special equipment allows even an artistic thread and manufacture of parts of complex shapes.

Important! For operations, different equipment is used, in t. h. CNC machines.


With plasma cutting of metals, the following technical characteristics are provided:

  • Sheet thickness and blanks. To process blanks of different thicknesses, the current strength, gas supply speed and the distance between the electrodes are regulated. This parameter significantly depends on the thermal conductivity of the metal: when it is increased, the thickness decreases and vice versa. Small portable machines are capable of cutting metals up to 10-12 mm thick, and powerful equipment up to 100 mm. It is important to consider that plasma cutting is effective when cutting steel blanks with a thickness of not more than 50–60 mm, aluminum sheets. up to 120 mm, copper products. up to 80–85 mm, and cast iron. up to 90 mm. On special combined equipment, metal cutting is provided with a thickness of up to 200 mm. Complex, curly cutting is carried out with the thickness of the blanks up to 100 mm.
  • The sizes of sheets. They depend on the dimensions of the machine desktop. The modern equipment used allows you to process sheets 2.5–3 m wide (portal machines-up to 4 m) and 4-5 m long (large-sized machines-up to 6-7 m).
  • The speed of movement of sheets. It depends on the shape of the workpiece and the thickness of the sheets. The speed of movement of sheets is usually adjustable within 50–800 mm/min. Modern CNC equipment can provide thin sheets cutting at a speed of up to 20,000 mm/min. Most often, the following modes are installed: for sheets up to 100 mm. up to 5000 mm/min, with shaped cutting. about 200–250 mm/min.
  • The angle of cut. Most often, plasma cutting is used for perpendicular cut. Without increasing the quality of the faces, the angle may have a deviation from the perpendicular by 20-50 °.
  • Roughness. In the cut zone, it is normalized by GOST and can correspond to 1.2 or 3 of the class.

The machines used provide high accuracy and high.quality cutting, regardless of thickness due to the adjustment of the parameters of the plasma flow. Does not affect the quality and presence of colorful and other protective coatings (for example, galvanizing), as well as dirt and dust.

How to choose the right plasma cutting device?

Everything is very simple here. The more powerful the plasma apparatus, the thicker the metal it can cut. If you plan to cut different thicknesses, you better choose powerful apparatus, if you cut thin metals, you do not need to buy powerful apparatus, just purchase a forty ampere apparatus. Pay attention to such a thing as the quality of the cut. Cut can be “dirty” and “clean”. Dirty cut. this is when you just need to cut off a piece of metal and it does not matter for you what cut will be, neat or not. Pure cut. This is the most evenly cut metal. As a rule, manufacturers indicate in the parameters dirty cut. To understand a pure cut, you need to take about 25% of the indicated thickness. For example, if the manufacturer indicated 12 mm, then the clean cut will be 8-9 mm. Do not think that manufacturers are deceiving you, this is a worldwide practice to indicate in the parameters a dirty cut, not a pure. This parameter shows the maximum possibility of the apparatus, and you yourself choose how to cut metal, according to “dirty” or “clean”.

In addition, before buying, it is advisable to understand how often you will include a plasma cutting device. Pay attention to the PV of the acquired apparatus. If the apparatus is 60%. So in a 10.minute cycle you can cut for 6 minutes, and 4 minutes the device will rest if PV is 100%. So you can not break away from work, the device will work constantly.

Consumable parts.

When buying a plasma cutting device, we recommend that you find out from the supplier how things are with the consumption for a plasma burner. Almost all manufacturers, together with the device, put expenditures, you can start cutting immediately, but the consumption is on, regardless of the manufacturer. And when the question arises of replacement, it turns out that where the device was bought. there is no “consuming”. We often encounter such cases when we help people choose the consumption, and it is worth admitting that it does not always work out. Consumption does not always join. So, for example, consumption for apparatus of Chinese origin is not suitable for European goods or American. In addition, there is no way to change the plasmaitron (plasma burner). different connectors. In our online store, plasma cutting devices are sold in China, all consumables for CUT burners are always available and as practice shows, Chinese consumption is suitable for almost all devices made in China.

This question is often asked by customers. There is no certain answer to it, you will understand how quickly you will need to conduct plasmatron for metal only in the learning process, it is very simple to adopt. It all depends on the thickness of the metal and the ampra capacity that you will put up. When you start the cut, you will immediately see. If you conduct plasmatron very quickly (in this case, the metal will not be cut completely) if you simply spend air and electricity very slowly (in this case). Before cutting the blanks or segments you need, we recommend that we practice unnecessary scraps to choose the optimal mode and cut speed.

Another advice, when you turn on the device. put the current to the maximum, and reduce it during the cut until you understand that this current is enough to cut your metal thickness. Start with large currents, then go to lower.

And yet, do not try to set the maximum current to cut it quickly, since the larger the current, the faster the consumption fails; Do not make too frequent ignition, because it is at the time of the ignition that intensive “weathering” with a stupefying of the insert on the cathode and its premature failure.e. Pressed on the button and cut continuously. If, under the working conditions, you need to make short cuts, for example, cut a grid. get ready for frequent replacement of consumption.

Hand plasma-fiber cutting of metals

Manual plasma cutting is carried out using portable (mobile) plasma cutting devices, consisting of:

  • The main apparatus containing a transformer and rectifier substation.
  • Power cable power.
  • Hose that walking from the apparatus to a plasma pistol. The hose package contains an air hose and power cable.
  • Plasmaetrone (plasma pistol). the formation of plasma occurs in it.

There are two main methods of manual plasma cutting:

  • Indirect cutting plasma stream. This method is used mainly for cutting non.metal materials. The electric arc forming the plasma, in this case, lights up between the electrode and the nozzle of the plasmaidron. The cut material in the formation of plasma does not interfere, and cutting is carried out by a plasma stream bursting from the cutter.
  • Direct plasma-spiritual cutting. This is just our case, since this method is used to cut metals. It is used both in manual and mechanized plasma cutting. The electric arc lights up between the electrode and the cut metal and combining with the speed of air forms the plasma. The resulting plasma stream has such a power that it literally evaporates the metal during cutting.

Manual plasma-fiber cutting has proven itself so well that it is now used in almost all enterprises that have a metalworking workshop. A large number of private traders are offered by departure services of plasma cutting, Hand devices are very mobile, they can be transferred in the hands or on the shoulder belt.

The main advantages of manual plasma devices:

  • Mobility, portables (small and medium.sized manual devices weigh from 10 to 25 kg).
  • Accessibility of use (operate from 220 V, current strength depends on the power of the device).
  • Universality (the ability to cut all types of metals).
  • Available price (manual plasma cutting devices cost from 15,000 to 70,000

Automatic plasma cutting

With the advent of manual plasma cutting, this technology began to be used together with CNC machines (numerical software control). The use of CNC machines, together with a plasma cutter, allows you to cut the sheet metal, round and profile pipes with a high accuracy (± 0.25-0.35 mm) and speed (up to 7 m/min).

The most common automatic plasma cutting of sheet metal. Medium.power plasma devices cut sheet metal up to 30 mm on breakdown. professional and powerful devices can cut sheets up to 70 mm with high quality.

The same plasma cutting apparatus can be used both for manual cutting and automatic cutting, with the exception of plasmotrons that are divided into manual and mechanized.

For cutting with CNC, more powerful plasma devices are usually used than for manual cutting. The most in demand by devices with a capacity of 65 to 125 A, the power of which comes from 380 V.

Plasma cutting on a CNC machine allows you to cut metal up to 60 mm thick with high quality.

Plasma cutting. the principle of operation of plasmotron

The plasmotron is a plasma cutting device, in the case of which a small.based arched chamber of a cylindrical shape is placed. At the exit of it there is a channel that creates a compressed arc. On the back of such a camera is a welding rod.

Between the tip of the device and the electrode light a preliminary arc. This stage is necessary, since the excitation of the arc between the cut material and the electrode is almost impossible to achieve.The specified preliminary arc emits from the nozzle of plasmotrone, comes into contact with a torch, and at this moment a working stream is already created directly.

After that, the forming channel is completely filled with a column of plasma arc, the gas forming plasma enters the plasmoron chamber, where it is heated, and then ionization and an increase in volume. The described scheme determines the high temperature of the arc (up to 30 thousand degrees Celsius) and the same powerful rate of gas output from the nozzle (up to 3 kilometers per second).

Plasma.forming gases and their impact on the possibility of cutting

The plasma.forming environment is perhaps the key parameter of the process that determines its technological potential. The possibility of:

  • settings of the heat flow indicator in the metal and current processing zone in it (due to the change in the ratio of the section of the nozzle to the current);
  • variating the volume of thermal energy within wide limits;
  • regulation of the indicator of surface voltage, chemical system and the viscosity of the material that is subjected to cutting;
  • control of the depth of the layer saturated with gas, as well as the nature of chemical and physical processes in the processing zone;
  • protection from the appearance of sailing on metal and aluminum sheets (on their lower edges);
  • the formation of optimal conditions for removal from the cutting cavity of molten metal.

In addition, many technical parameters of the equipment used for plasma cutting also depend on the composition of the environment described by us, in particular the following:

  • the design of the cooling mechanism for the nozzles of the device;
  • the option of fastening in the plasmoron of the cathode, its material and the level of intensity of the supply of coolant to it;
  • The control circuit of the unit (its cyclogram is determined precisely by the consumption and composition of the gas used for the formation of plasma);
  • dynamic and static (external) characteristics of the power source, as well as the indicator of its power.

It is not enough to know how the plasma cutting works, in addition, the gas.forming combination should be correctly selected for this, taking into account the price of the materials used and directly the cost of cutting operations.

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

Sources of manual plasma apparatus for cutting

All power supply sources work on alternating current electric networks. Most of them transform the received electricity into a direct current voltage, and the rest serve only to increase alternating current. This distribution is due to the fact that in plasmotrons operating on direct current, a higher efficiency. A variable current is used in some cases. for example, for cutting aluminum and alloys from it.

To disadvantages. power restriction (maximum current strength is usually 70–100 a). As a rule, inverter devices are used when cutting blanks of a relatively small thickness.

Transformer power sources got their name due to low-frequency transformers used in their design. They have much larger dimensions and mass, but at the same time they can have a higher power than inverter sources. Transformer devices are used for manual and mechanized cutting of metals of various thicknesses. They are more reliable, because during the jumps of tension do not fail. The duration of their inclusion is higher than that of inverter devices, and can reach values ​​in 100 %.

The duration of inclusion (PV) has a direct impact on the specifics of working with equipment. For example, if manual plasma cutting of metal, equipment for which has 40 %PV, lasted without a break for 4 minutes, then the device must be given 6 minutes of rest so that it cools down. Devices with PV 100 % are used in production where the device is operated throughout the working day. A significant drawback of transformer equipment is high energy consumption.

plasma, cutting, metal, works

The principle of operation of devices for manual plasma cutting

After the installation of manual plasma cutting is collected (all the connections and connections of its elements are made), the metal workpiece is connected to the apparatus (inverter or transformer) provided for this with the cable. The equipment is connected to the mains, plasmotron is brought to the processed material at a distance of up to 40 mm and the ignition of the on.duty (initiating ionization) electric arc is carried out. Then open gas supply.

After receiving a plasma jet, which has high electrical conductivity, at the time of its contact with the metal, a working (cutting) electric arc is formed. At the same time, the duty officer is automatically disconnected. The working arc supports the continuity of the ionization of the gas supplied, the formation of a plasma flow. If for some reason it goes out, then it is necessary to stop the gas supply, re-turn on the plasma apparatus and light the duty arc, and then put down the gas.