Plasma cutting metal is well suited for cutting high-alloy steels. This method is superior to gas cutters due to its minimal heating zone, which allows you to quickly make a cut, but avoid surface deformation from overheating. Unlike mechanical methods cutting machines (“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 operating principles are based on amplification of the electric arc by acceleration with gas under pressure. This increases the temperature of the cutting element several times, in contrast to the propane-oxygen flame, which allows for a quick cut without allowing the high thermal conductivity of the material to transfer the temperature to the rest of the product and deform the structure.

Plasma cutting of metal in the video gives a general idea of ​​the process. The essence of the method is as follows:

1. Current source (powered from 220 V for small models, and 380 V for industrial installations designed for large metal thicknesses) produces the required voltage.
2. The current is transmitted through the cables to the plasma torch (the torch in the hands of the welder-cutter). The device contains a cathode and anode - electrodes between which lights up electric arc.
3. The compressor forces a stream of air that is transmitted through hoses into the apparatus. 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. The result is plasma. This arc is called a pilot arc because it burns to maintain operation.
4. In many cases, a work cable is used that is connected to the material being cut. By bringing the plasma torch close 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 penetrate 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. Repeated application to the product allows you to continue cutting immediately.
5. After finishing the work, the button on the plasmatron is released, which turns off all types of electric arc. The system is purged with air for some time to remove debris and cool the electrodes.

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

Types 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, the electrical circuit must be closed between the plasma torch and the product to perform the cut. It is suitable for all kinds of conductive metals. Two wires come from the device, one of which goes into the burner, and the second is attached to the surface being treated.

The second method consists in burning an arc between the cathode and anode, enclosed in a plasma torch nozzle, and the ability to make a cut with the same arc. This method is well suited to materials that are unable to conduct current. In this case, one cable comes from the device leading to the burner. The arc is constantly burning in working condition. All this applies to air plasma cutting of metal.

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

Advantages of plasma cutters

The operating principles of plasma cutting using a high-temperature arc allow you to obtain a number of advantages over other types of metal cutting, namely:

• Ability to process any type of steel, including metals with a high coefficient of thermal expansion.
• Cutting materials that do not conduct electrical current.
• High speed ongoing work.
• Easy to learn the work process.
• Various cutting lines, including curly shapes.
• High cutting precision.
• Minor subsequent surface treatment.
• Less environmental pollution.
• Safety for the welder due to the absence of gas cylinders.
• Mobility when transporting equipment that is small in size and weight.

Metal plasma cutting technology

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

1. The product to be cut is positioned so that there is a gap of several centimeters underneath it. To do this, pads are used under the edges, or the structure is installed on the edge of the table so that the part being processed is above the floor.
2. It is better to mark the cutting line with a black marker if the work is carried out on of stainless steel or aluminum. When you have to cut “black” metal, it is better to draw a line with thin chalk, which is more clearly visible on a dark surface.
3. It is important to make sure that the torch hose is not lying near the cut site. Severe overheating can ruin it. Novice welders may not see this due to excitement and damage the equipment.
4. Safety glasses are worn. If you have to work for a long time, it is better to use a mask that will cover not only your eyes, but also your 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 need to 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 deviation angle relative to this position is allowed.
9. It is better to start cutting from the edge of the product. If you need to start from the middle, it is advisable to drill a thin hole. This will help avoid overheating and depression in this place.
10. When conducting an arc, it is necessary to maintain a distance of 4 mm to the surface.
11. For this, it is important to support your arms, which is done with your elbows on the table or on your knees.
12. When making a cut, it is important to visually verify the appearance of a gap in the traversed area, otherwise you will have to cut again.
13. When the cut line ends, care must be taken to prevent the part from falling onto your feet.
14. Releasing the button stops the arc.
15. A thin layer of slag is knocked off with a hammer along the edges of the cut. If necessary, additional cleaning of the product is carried out using an emery wheel.

Equipment used

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

Plasmatrons of both large and small devices are designed the same, 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 installed depending on the thickness being cut. The tips cover the nozzle from splashes of molten metal. Various attachments can be attached to the end of the plasma torch to help maintain distance during operation and remove carbon deposits from the chamfers. The compressor supplies air through a hose, and its output is controlled by a valve.

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

One of the popular types of metal processing is its cutting. There are many ways to obtain the required shape from a single sheet, but in this material we will look at the principle of operation of plasma cutting.

Plasma cutting. In fact, there is a golden mean. The advantages of cutting metal with plasma combine all of the above technologies. The main advantage is that there are no restrictions on the type of material processed. Just in terms of thickness.

• aluminum alloys 120 mm
• copper alloys 80 mm
• steel 50 mm
• cast iron 90 mm

The equipment varies from industrial to household, so the technology is accessible to everyone. Let's take a closer look at it.

Plasma cutting of metal - operating principle

A two-component medium acts as a cutter:

• An electric arc operating according to the classical scheme - a discharge between the cathode and anode. Moreover, the material itself can act as an anode if it is a conductor.
• Gas arc. Heating under the influence of an electric arc (temperature reaches 25000º C), the gas is ionized and turns into a conductor of electric current.

The principle of operation of plasma cutting is shown in detail in this video.

As a result, plasma is formed, which is fed under high pressure into the cutting area. This hot gas stream literally evaporates the metal, and only in work area. Despite the fact that the temperature of plasma cutting is measured in tens of thousands of degrees, there is practically no impact on the boundary zone.

Important! Correctly selected speed allows you to get a very narrow cut without damaging the edge of the material.

The source of plasma cutting is a plasma torch.


Its task is to light the arc, maintain the operating temperature, and blow molten metal out of the cutting area. Since plasma cutters are designed for processing any solid materials, including dielectrics, the formation of an electric arc is carried out in two ways:


Figure a) shows a direct action cutter. Cathode assembly (8) along with the assigned cathode (6) are one of the electrodes. The second electrode (anode) is workpiece (4)– a metal with good electrical conductivity.

The power cable of the plasma torch is connected to it. Plasma cutting tip (5) in this scheme it acts as a housing. From separated from the cathode insulator (7). Gas is supplied inside fitting (1) and forms a plasma jet consisting of electric (2) and gas (3) arc.

What is the device

Device structure

The plasma cutter is a rather complex apparatus, consisting of several main components:

Plasma torch

This element is a plasma cutter, in fact, the main element of the device that produces plasma. The plasma torch is connected to other elements of the device using a cable and hose through which air and electric current are supplied.

It must be said that there are two types of cutters:

• Direct action. An arc occurs between the metal workpiece and the cutter. These are the plasma torches that are used to work with metal;

• Indirect. The arc discharge occurs inside the plasma torch itself. This allows the machine to be used for cutting non-metallic materials.
  The plasma torch contains two main elements:
• Nozzle. This part forms a plasma jet. The metal cutting speed, cut size and cooling intensity depend on its diameter and length.
  As a rule, the nozzle diameter does not exceed 3 millimeters, and the length is 9-12 millimeters. The longer the length, the better the quality of the cut, but the less durability of the nozzle itself. That's why best option when the length of the nozzle is one and a half times greater than its width;

• Electrode. A metal rod, usually made of hafnium. The electrode provides excitation of the electric arc for air plasma cutting.

Power supply

The job of the power source is to supply current to the plasmatron. There are two types of power supplies:

• Transformer. They are weighty and consume a lot of energy, but they are less sensitive to temperature changes. In addition, the thickness of the workpiece that the machine is capable of cutting can reach 40-50 mm;

• Inverters. Lighter, more compact and energy efficient. In addition, inverters provide a more stable arc.
  The disadvantages are that they can be used for cutting sheets no more than 30 millimeters thick.

Compressor

To operate a plasma cutter, gas is required, which ensures the formation of plasma and is responsible for cooling the plasma torch. Therefore, a compressor is used to supply gas to the nozzle.

In devices with a current not exceeding 200 A, air is used as a gas. Such a machine can cut workpieces up to 50 millimeters thick.

An industrial machine works with other gases such as argon, helium, nitrogen, hydrogen, etc.

Cable-hose package

As I said above, this element combines the individual components of the device into a plasma cutter, i.e. The hose supplies gas to the nozzle, and the cable supplies current to the electrode.

Operating principle

What is plasma

We’ve figured out the devices of the device, now let’s look at how a plasma cutting machine works, and what the word “plasma” actually means. So, plasma is air or other gas heated to a high temperature and in an ionized state. The heating temperature can reach 30,000 degrees.

The operating principle of the device is as follows:

1. When the ignition button is pressed, high frequency currents are supplied to the electrode;
2. A pilot arc is formed between the nozzle and the electrode, the temperature of which reaches 8000 degrees;
3. Then compressed air is supplied to the nozzle;
4. The air breaks through the arc, as a result of which it heats up and increases in volume a hundred times. In this case, it is ionized, and the air acquires conductive properties;
5. When the plasma comes into contact with the workpiece, a cutting arc is formed, and the pilot arc goes out. As a result, the metal is easily cut, and the air is blown away from the cutting line.

You can make a plasma cutting machine yourself. An inverter is usually used for this welding machine, however, you can make the device “from scratch”, using the diagrams available on the Internet.

Nuances of choice

When choosing a plasma cutter, you need to pay attention to the following points:

• Versatility. There are devices that can be used not only for cutting metal, but also for stick electrode welding, as well as for argon arc welding.
  However, it should be remembered that versatility usually has a bad effect on the quality of operations performed and productivity. As a rule, a universal plasma cutter cannot cut workpieces thicker than 11 mm;
• Current strength. The higher the current, the hotter the arc heats up; accordingly, the faster plasma cutting is performed, and the maximum thickness of the part that can be cut using this method increases.
  Therefore, you first need to decide for what purposes you need a plasma cutter, i.e. what parts you will have to work with. If you are cutting steel up to 20 mm thick, a device with a current of 20 A will be sufficient.
  If the thickness of the metal is greater, then a more powerful plasma cutter will be needed - with a current of 40-60 A. For industrial devices, the current can reach 200 A or more;

• Electrical network type. Household plasma cutting machines can operate on a 220 V network, but their current strength, as a rule, does not exceed 40 A. Industrial machines operate on a 380 V network;
• Duration of activation. Each plasma cutter has such a characteristic as PV, which is calculated as a percentage. This indicator indicates the time that the device can operate.
  The basis is a working cycle of 10 minutes. If the PV is, for example, 70%, then the plasma cutter can work for 7 minutes, after which it must cool down for 3 minutes. If the indicator is 40%, then the device can operate for no more than 4 minutes, after which it must cool down for 6 minutes.
  There are devices with 100% duty cycle that can be used continuously. They usually have water cooling;
• Compressor. The plasma cutter can have a built-in or separate connected compressor. For domestic purposes, devices with a built-in compressor are more convenient, but they are low-power.
  If a plasma cutter is needed for professional work, a separate compressor is required. The main requirement for the compressor is to provide the plasmatron with constant air pressure, i.e. without pulsations, and the air must be dry. In addition, the air pressure created by the compressor must necessarily meet the requirements of the device;

• Convenience. The plasma cutter must have a sufficient length of cable and hose package. If the device is needed for domestic purposes, it is desirable that it be compact and easy to transport.

A plasma cutting machine must be purchased with a small power reserve - this will increase its durability.

Brief overview of models

Finally, we will briefly consider several devices that have received positive reviews from users. These include:

• FoxWeld Plasma 33 Multi;
• TelWin Plasma 60 HF;
• Svarog;
• Resanta IPR-25;
• Gorynych.

FoxWeld Plasma 33 Multi

This model is a multifunctional household device for plasma cutting, operating on a 220 V network. Its main feature is the ability to be used as a welding machine for manual arc welding.

The maximum cutting current of this model is 30 A. This allows it to cut 8 mm thick steel.

The price of this device is 33,000 rubles (the price is current for spring 2017).

TelWin Plasma 60 HF

This model can be classified as industrial, since it has a relatively high power - the current is 60 A, and it is also designed to operate from a 380 V network.

The device can cut steel up to 20 mm thick. In addition, the manufacturer draws attention to the following advantages of the model:

• The presence of a microprocessor that controls many parameters of the device;
• Possibility of adjusting current strength;
• The built-in pressure gauge allows you to monitor air pressure.

This plasma cutter costs 110,142 rubles.

Svarog CUT-40

This model is a powerful household plasma cutter, the current of which reaches 40 A. This allows it to cut steel up to 12 mm thick. PV at maximum current is 60%; for household devices this figure is quite high.

It should be noted that despite the Slavic name “Svarog”, this device is produced in China. But, despite this, users have no complaints about its quality and reliability.

The cost of Svarog CUT-40 is 33,000 rubles.

Resanta IPR-25

Resanta is another household plasma cutter made in China with a current of 25 A. The manufacturer claims that this “baby” is capable of cutting metal up to 12 mm thick.

Another advantage of this device is its relatively low cost - the price is 28,900 rubles.

Gorynych

Gorynych is a multifunctional device from a domestic manufacturer. In addition to plasma cutting, electric welding is also available to him.

Gorynych’s current strength is not large, 3–10 A, which allows him to cut metal up to 8 mm thick. Its main feature, in addition to its versatility, is water cooling. This allows the device to work continuously for 25 minutes.

In addition, it is very compact - the weight of the device does not exceed 0.7 kg. The price is within 43,000 rubles.

Conclusion

Now you know how a plasma cutter works and what to look for first when choosing one. Additionally, I recommend watching the video in this article. If any nuances are not clear to you, write comments, and I will be happy to answer you.

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

1 Metal plasma cutting technology

The plasma arc cutting process that interests us in world practice is “hidden” under the abbreviation PAC. Plasma is a high-temperature ionized gas that can conduct electric current. A plasma arc is formed in a unit called a plasmatron from a conventional electric one.

The latter is compressed, and then a gas is introduced into it, which has the ability to form plasma. Below we will talk about the importance of such plasma-forming gases 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 there 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 between the material being cut and the electrode. This preliminary arc comes out of the plasma torch nozzle, comes into contact with the torch, and at this moment the working flow is directly created.

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

3 Plasma-forming gases and their effect on cutting capabilities

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

• indicator settings heat flow in the metal processing zone and the current density in it (due to a change in the ratio of the nozzle cross-section to the current);
• varying the volume of thermal energy over a wide range;
• regulation of surface tension, chemical composition and viscosity of the material being cut;
• control of the depth of the gas-saturated layer, as well as the nature of chemical and physical processes in the treatment zone;
• protection against the appearance of underwater marks on metal and (on their lower edges);
• formation optimal conditions for removing molten metal from the cutting 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 device nozzles;
• option for mounting the cathode in the plasmatron, its material and the level of intensity of coolant supply to it;
• control circuit of the unit (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 source, as well as an indicator of its power.

It is not enough to know how plasma cutting works; in addition, you should select the right combination of gases to create a plasma-forming environment, taking into account the price of the materials used and the direct cost of the cutting operation.

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

4 Advantages and disadvantages of plasma cutting

The very principle of operation of plasma cutting determines the advantages of this technology over gas methods for processing 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 truly high quality and high-precision, which often makes it possible not to carry out additional mechanical processing of products;
• minimal air pollution;
• there is no need to preheat the metal to cut it, which makes it possible to reduce (and significantly) the burning time of the material;
• high safety of work due to the fact that cutting does not require gas cylinders, which are potentially explosive.

It is worth noting that according to some indicators, gas technologies are considered more appropriate than plasma cutting. The disadvantages of the latter usually include:

• the complexity of the plasmatron design and its high cost: naturally, this increases the cost of each operation;
• relatively small cutting thickness (up to 10 centimeters);
• high noise level during processing, which occurs due to the fact that gas flies out of the plasmatron at transonic speed;
• the need for high-quality and most competent maintenance of the unit;
• increased level of release of harmful substances when nitrogen is used as a plasma-forming composition;
• 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 deviation from the perpendicularity of the cut is allowed no more than an angle from 10 to 50 degrees (the specific angle depends on the thickness of the product). If you increase the recommended value, there is a significant expansion of the cutting area, and this becomes the reason for the need for frequent replacement of the materials used.

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

Metal cutting is necessary in many technological processes. Almost always, machining begins with cutting and cutting the material. One of the most convenient and economical methods is plasma metal cutting. It allows you to obtain workpieces of any shape, which require almost no further processing.

Principle of operation

For plasma cutting of metal, a plasma jet is applied to the workpiece. Plasma is a stream of ionized gas heated to a temperature of thousands of degrees, which is electrically conductive and moves at high speed. The formation of a plasma arc from an electric one is carried out using a plasma cutter. The operating principle of the plasma cutter and the stages of the cutting process:

• A pilot electric arc is formed, which is ignited between the electrode of the plasma cutter and its nozzle or the metal being processed.
• After the pilot arc is formed, compressed gas is supplied to the chamber. It expands in volume and heats up to a temperature of 20,000 °C.
• The electric arc ionizes the gas, it becomes a conductor of electricity and turns into a plasma jet. This jet heats the metal in the processing zone, melts it and produces cutting.

For metals and non-metallic materials are used different principles gas plasma cutting. There are two ways to process materials:

• The arc burns between the plasma torch and the product. This is how a direct action cutter works. The product must be conductive. If it is necessary to cut non-metallic products, the indirect method is used.
• The arc is ignited in the plasmatron itself between the electrode and the nozzle. The electrode is the cathode, and a positive potential is applied to the nozzle.

In the second case, any materials can be processed: plastics, stone, concrete. No potential is applied to the part and no electrical conductivity is required.

Plasma cutting equipment

For metal cutting with plasma, industrial and household use. All plasma cutting units include:

• power supply;
• plasmatron;
• compressor for pumping compressed gas;
• cables and hoses used to connect equipment elements.

The power source may be an inverter or a transformer. Inverter units are lightweight, economical, and have a high efficiency. They are often used in small industries. They have a current limitation of 70 A and are capable of cutting only small material up to 30 mm thick.

Transformer devices are more powerful, have greater weight and size. They are more resistant to voltage surges, capable of long continuous operation and are often used in CNC machines. Equipment with a water cooling system is capable of cutting metal up to 100 mm thick. Power supplies for cutting using oxygen have a current strength in the range of 100-400 A. When using nitrogen as a plasma gas, this range increases to 600 A.

The plasma torch is the main unit of all installations. It includes:

• internal electrode;
• working nozzle;
• insulating housing with cooling;
• plasma-forming substance supply device.

Depending on the processing conditions, different gases are used for plasma cutting. Oxygen and air are used for steels and alloys. Air plasma cutting is used for processing low alloy steels. When processing non-ferrous metals, plasma-forming gases can be argon, nitrogen, and hydrogen. This is due to the fact that in an oxygen environment, non-ferrous metals begin to oxidize. A mixture of argon and hydrogen is most often used for cutting stainless steel and aluminum.

The temperature of the gas flow is in the range of 5000-30000 °C. At lower temperatures, non-ferrous metals are processed, at higher temperatures, refractory steels are processed.

The flow speed is in the range of 500-1500 m/s. The setting is made depending on the thickness, characteristics of the material being processed and the duration of work.

Manual processing

Before starting work, the inverter or transformer is connected to the AC mains. The workpiece is connected to a power source. The next stage is bringing the nozzle and the workpiece closer together. There should be 40 mm between them. After this, you can light the pilot arc. When the arc ignites, an air flow is supplied to the nozzle, which is ionized and forms a plasma jet.

When working with a plasma cutter, you must follow safety rules. A special suit and protective face shield must be used. Temperatures during plasma cutting reach thousands of degrees, and this can be dangerous for humans. Therefore, we must strive to automate the process.

Advantages and disadvantages of plasma processing

The operation of plasma cutting units is often implemented in various technological processes related to cutting and cutting of metallic and non-metallic materials. This is due to the following advantages of plasma arc cutting technology:

But the plasma cutting method also has disadvantages. These include:

Despite these shortcomings, plasmatrons find everything greater application both in large enterprises and in small home workshops. The use of plasma cutting speeds up the processing of alloy steels, and the accuracy of the cut line and the ability to cut curved shapes make plasma cutters indispensable in many production processes.