Equipment for separation plasma cutting of metals. The principle and technology of plasma cutting of metal. Disadvantages of plasma cutting

Several different methods are used for cutting metals, which differ from each other in efficiency and cost. Some methods only apply for solutions industrial tasks , some can also be used at home. The latter includes plasma cutting. The cutting efficiency of this method is limited only the right choice installations and experience of the master. What is plasma metal cutting? What is the principle of work based on? In what areas is this metal cutting method used?

Plasma Cutting Basics

In order to understand the basics of cutting metal using the plasma method, you must first understand what plasma is? The final quality of cutting will depend on understanding how the plasmatron is designed and the principle of working with this device.

Plasma heat treatment of metals depends on certain parameters a working jet of liquid or gas that is directed under pressure onto the surface of the treated area. To achieve the required effect, the jet must be brought to the following levels:

1. Temperature - for plasma to appear, the air must be heated almost instantly to 5-30 thousand degrees. Fever achieved by creating electric arc. When the required temperature is reached, the air flow is ionized and changes its properties, becoming electrically conductive. Plasma metal processing technology involves the use of dehumidifiers that remove moisture, as well as air injection systems.
2. Speed ​​- the jet is directed onto the surface of the material under high pressure. We can say that plasma cutting of metal is based on heating the material to the melting point and instantly blowing it out. In this case, the operating speed of the jet is approximately 2−5 km/sec.
3. Availability electrical circuit. You can learn everything about cutting metal with plasma only in practice. But certain features need to be taken into account before purchasing the installation. Thus, there are direct and indirect plasma torches. And if for the former it is necessary that the material being processed be connected to a common electrical network (acting as an electrode) and pass electricity, then for the latter there is no this need. In this case, plasma for cutting metal is obtained using an electrode that is built inside the holder. This option is used for metals and other materials that do not conduct electricity.

Another quite a few important point, which must be taken into account, is that plasma cutting of thick material is practically not carried out, since it is ineffective and leads to high financial costs.

Principle of operation

The main operating principle of plasma metal cutting can be described as follows:

1. The compressor supplies air under pressure to the plasma torch burner.
2. The air flow instantly heats up due to the action of electric current on it. Taking into account the heating, the air mass begins to pass electricity through itself, as a result of which plasma is formed. In certain plasma torch models, inert gases are used instead of air flow.
3. Plasma cutting of metal, if we consider it in more detail, is carried out by a method of narrowly targeted rapid heating of the surface to the required temperature with further blowing out of the molten material.
4. During the work, some waste inevitably appears, which includes cuttings or residues sheet material after cutting out the required parts, as well as the remains of molten metal and scale.

Since the process is associated with instant heating of the processed material to liquid state, then its thickness when cutting should be:

• copper - 8 cm;
• aluminum - up to 12 cm;
• cast iron - up to 9 cm;
• alloy and carbon steel - up to 5 cm.

There are two main methods of processing materials on which the characteristics of plasma cutting will depend. Namely:

1. Plasma jet - in in this case the arc appears directly in the plasmatron. The plasma jet processing method is universal, as it makes it possible to process non-metallic materials. The only drawback is the need to regularly replace the electrodes.
2. Plasma-arc - this option is suitable for any type of metal that can conduct through itself electricity. As a rule, plasma arc cutting is used for industrial equipment. The meaning of this method is that plasma appears due to an arc that occurs directly between the plasma torch and the surface of the material being processed.

Plasma cutting works on the principle of conventional arc cutting, but without the use of conventional electrodes. Moreover, the effectiveness of this processing method depends directly on the thickness of the material being processed.

Cutting accuracy and speed

As with any other method heat treatment, during plasma cutting, some melting of the metal occurs, which affects the quality of the cut. There are other features that are characteristic of this method. Namely:

1. Melting of edges - regardless of what modes of material processing are used, and the professionalism of the craftsman who performs the work, it is impossible to avoid a slight melting of the surface during the very beginning of the work.
2. Taper - taking into account the performance of the installation and the professionalism of the technician, the taper can vary between 4-12 degrees.
3. Speed ​​of work - conventional cutting of metal using a plasmatron is carried out quickly and with low power consumption. According to GOST and technical specifications manual equipment, plasma cutting speed is no more than 6500 mm/min.
4. Cutting characteristics - the speed and quality of the cut will depend on what specific operations need to be performed. Therefore, the low quality parting cut is the fastest to make, with mostly manual machines being able to cut metal up to 65mm. For shaped processing of parts, material thicknesses up to 45 mm are possible.

The quality of work will significantly depend on the level of professionalism of the master. An accurate and clean cut with minimal deviation from the required dimensions can only be made by a worker with specialized education. Without necessary preparation It is unlikely that it will be possible to make a curly cut.

Processing of non-ferrous alloys

When processing non-ferrous metals, they are used various ways cutting taking into account the density of the material, its type and other technical indicators. To cut non-ferrous metals, the following recommendations must be followed:

1. Aluminum cutting- for material up to 7 cm thick, compressed air can be used. Its use is impractical when the material density is low. High-quality cutting of aluminum sheets up to 2 cm is achieved using pure nitrogen, and with a thickness of 7-10 cm using hydrogen and nitrogen. Plasma cutting of aluminum with a thickness of more than 10 cm is carried out using a mixture of hydrogen and argon. The same composition is recommended to be used for thick-walled high-alloy steel and copper.
2. Cutting stainless steels- the use of compressed air is not recommended for the work; taking into account the thickness of the material, pure nitrogen or mixtures with argon can be used. It must be taken into account that stainless steel is quite sensitive to the action of alternating current, which can lead to changes in its structure and faster decommissioning. Stainless steel cutting is carried out using an installation that uses the principle of indirect action.

Scope of use of plasma cutting

The use of plasmatrons is so popular for a reason. With relatively simple operation, as well as the not very high cost of manual equipment (unlike other cutting devices), high performance can be achieved regarding the quality of the resulting cut.

The use of plasma metal cutting has become widespread in the following production areas:

1. Construction of metal structures.
2. Processing of rolled metal - using plasma you can cut almost any type of metal, including ferrous, refractory and non-ferrous.
3. Various areas industry, aircraft manufacturing, capital construction buildings, mechanical engineering, etc. - in all these areas it is impossible to do without the use of plasma cutters.
4. Parts processing and artistic forging. Using a plasma cutter you can make a part of almost any complexity.

Using Plasma Cutting Machines manual settings didn't replace it. Thus, artistic plasma cutting makes it possible to produce unique parts that exactly correspond to the artist’s intention for use as decorative ornaments stairs, railings, fences, railings, etc.

Advantages and disadvantages

Almost none industrial production, which is somehow connected with rolled metal, cannot do without metal cutting. Cutting precise holes, figured decorative cutting, quick cutting into blanks sheet metal- all this can be done quite quickly using a plasma torch. The advantages of this method are as follows:

1. Economical- the plasma method has a significant advantage over standard methods of processing materials. There is only one limitation, which is related to the thickness of the material. It is economically unprofitable and impractical to cut steel with a thickness of more than 50 mm using a plasma torch.
2. Mobility of plasma hand-held units.
3. High speed parts processing and productivity. Unlike the conventional electrode method, the speed of work increases by 5–12 times.
4. Cut all types of metals (copper, aluminum, steel, stainless steel, titanium, etc.).
5. Safety.
6. Accuracy- deformations due to thermal load are almost imperceptible and subsequently will not require additional processing. In this case, the accuracy of plasma cutting is 0.24−0.34 mm.

All these advantages of plasma cutting explain why this method is so popular not only for production purposes, but also for domestic needs.

But, speaking about the advantages, it is necessary to note certain negative points:

1. Clear requirements regarding the processing of parts. The master must strictly observe the angle of inclination of the cutter in the region of 10-50 degrees. Failure to comply with this rule will accelerate the wear of component parts and will also affect the quality of the cut.
2. Limitations related to the thickness of the cut. Even with powerful equipment, the highest density of the processed material cannot be more than 10 cm.
3. Besides, work equipment very complex, which makes it absolutely impossible to use two cutters at the same time that are connected to one unit.

Comparison of laser and plasma cutting

The difference between plasma and laser cutting metal consists in the methods of action on the surface of the material. Laser equipment provides greater processing speed and productivity, and after completion of work there is a lower percentage of melting. The disadvantage of laser devices is their high price, and also that the thickness of the material being processed must be no more than 2 cm.

A plasma torch, unlike a laser, is much cheaper and also has wider functionality and scope of application.

Recently, the use of plasma flow for cutting materials has become increasingly popular. The scope of use of this technology is further expanded by the appearance on the market of hand-held devices that are used to perform plasma cutting of metal.

The essence of plasma cutting

Plasma cutting involves local heating of the metal in the separation zone and its further melting. Such significant heating is achieved through the use of a plasma jet, which is formed using special equipment. The technology for producing a high-temperature plasma jet is as follows.

• Initially, an electric arc is formed, which is ignited between the electrode of the device and its nozzle or between the electrode and the metal being cut. The temperature of such an arc is 5000 degrees.
• After this, gas is supplied to the equipment nozzle, which increases the arc temperature to 20,000 degrees.
• When interacting with an electric arc, the gas is ionized, which leads to its transformation into a plasma jet, the temperature of which is already 30,000 degrees.

The resulting plasma jet is characterized by a bright glow, high electrical conductivity and exit speed from the equipment nozzle (500–1500 m/s). Such a jet locally heats and melts the metal in the processing zone, then it is cut, which is clearly visible even in a video of such a process.

In special installations, various gases can be used to produce a plasma jet. These include:

• ordinary air;
• technical oxygen;
• nitrogen;
• hydrogen;
• argon;
• steam produced by boiling water.

Metal cutting technology using plasma involves cooling the equipment nozzle and removing particles of molten material from the processing zone. These requirements are ensured by the flow of gas or liquid supplied to the area where cutting is carried out. Characteristics of a plasma jet formed on special equipment, allow you to use it to cut metal parts whose thickness reaches 200 mm.

Plasma cutting machines are successfully used at enterprises in various industries. With their help, cutting not only metal parts, but also plastic and natural stone. Thanks to such unique capabilities and its versatility, this equipment is widely used in machine-building and shipbuilding plants, in advertising and repair enterprises, and in the public utilities sector. A huge advantage of using such installations is that they allow you to obtain a very smooth, thin and accurate cut, which is important requirement in many situations.

Plasma cutting equipment

On modern market There are two main types of devices available for cutting metal using plasma:

• indirect action devices - cutting is performed in a non-contact manner;
• devices direct action- contact cutting.

The first type of equipment, in which an arc is ignited between the electrode and the torch nozzle, is used for processing non-metallic products. Such installations are mainly used in various enterprises; you will not find them in a workshop home craftsman or in a repairman's garage.

In devices of the second type, an electric arc is ignited between the electrode and the part itself, which, naturally, can only be made of metal. Due to the fact that the working gas in such devices is heated and ionized throughout the entire gap (between the electrode and the part), the plasma jet in them has a higher power. This type of equipment can be used to perform manual plasma cutting.

Any plasma cutting machine operating on the contact principle consists of standard set components:

• power supply;
• plasma torch;
• cables and hoses used to connect the plasma torch to the power source and the working gas supply source;
• gas cylinder or compressor to obtain a jet of air at the required speed and pressure.

The main element of all such devices is the plasmatron; it is this that distinguishes such equipment from conventional welding equipment. Plasma torches or plasma cutters consist of the following elements:

• working nozzle;
• electrode;
• an insulating element that is highly heat resistant.

The main purpose of the plasma torch is to convert the energy of the electric arc into thermal energy plasma. The gas or air-gas mixture coming out of the plasma torch nozzle through a small diameter hole passes through a cylindrical chamber in which the electrode is fixed. It is the nozzle of the plasma cutter that provides the required speed and shape of the flow of the working gas, and, accordingly, the plasma itself. All manipulations with such a cutter are performed manually by the equipment operator.

Considering the fact that the operator has to hold the plasma cutter by weight, it can be very difficult to ensure high quality metal cutting. Often, parts produced using manual plasma cutting have uneven edges, traces of sagging and jerking. In order to avoid similar shortcomings, apply various devices: stands and stops that allow for smooth movement of the plasma torch along the cutting line, as well as a constant gap between the nozzle and the surface of the part being cut.

Air or nitrogen can be used as the working and cooling gas when using manual equipment. This air-gas jet is also used to blow molten metal out of the cutting zone. When using air, it is supplied from a compressor, and nitrogen comes from a gas cylinder.

Required Power Sources

Although all plasma cutter power supplies operate on AC power, some can convert it to DC power, while others can amplify it. But those devices that operate on DC. Installations operating on alternating current are used for cutting metals with a relatively low melting point, for example, aluminum and alloys based on it.

In cases where too high power of the plasma jet is not required, conventional inverters can be used as power sources. It is these devices, characterized by high efficiency and ensuring high stability of the electric arc, that are used to equip small industries and home workshops. Of course, it will not be possible to cut a piece of metal of considerable thickness using a plasma torch powered by an inverter, but it is optimal for solving many problems. A big advantage of inverters is their compact dimensions, which makes them easy to carry and use for work in hard-to-reach places.

Transformer-type power supplies have higher power, with the use of which both manual and mechanized cutting of metal using a plasma jet can be carried out. Such equipment is distinguished not only by high power, but also by higher reliability. They are not afraid of power surges that can damage other devices.

Any power source has one important characteristic, as the on-duration (DS). For transformer power supplies, the duty cycle is 100%, which means that they can be used the whole working day, without a break for cooling or rest. But, of course, such power supplies also have disadvantages, the most significant of which is their high energy consumption.

How is manual plasma cutting performed?

The first thing you need to do in order to start using a machine for plasma cutting of metal is to put together all its component elements. After this, the inverter or transformer is connected to the metal workpiece and to the alternating current network.

Metal cutting - technological process dividing a monolithic part into separate parts. Operation in progress mechanically(cutting, sawing), waterjet (suspension of water and abrasive material) or thermal (heating).

The last type is oxygen gas, laser and plasma cutting of metal.

What is plasma cutting? This is the processing of metal products, where a plasma jet serves as a cutter.

Plasma is a stream of ionized gas heated to several thousand degrees. Contains particles with positive and negative charges. Has quasi-neutral properties. That is, in an infinitesimal volume, the total charge is balanced and equal to zero.

However, the presence of free radicals means that plasma is a conductor of electricity. The combination of high temperature, electrical conductivity and high flow speed (greater than the speed of sound) made it possible in the last century to develop and create plasma equipment for cutting metal.

Operating principle

How plasma works - two methods of processing metal parts are used:

• direct action cutting, or plasma-arc cutting of metals;
• by indirect influence.

Direct cutter

An electric arc is ignited between the cutter (cathode unit) and the product (anode). The cathode (electrode) is placed inside a housing that has a nozzle. Gas, under pressure, passing by the electrode, heats up to high temperatures and is ionized. High flow speed is created when passing the nozzle. An electric arc melts metal. The hot gas ensures removal from the heating zone.

Indirect cutter

This method makes it possible to process ordinary metals, but also those with low electrical conductivity and dielectrics. Unlike the previous scheme, the source of the electric spark is placed in the cutter. Therefore, only the plasma flow has an impact on the processed products. Such equipment costs much more than direct-acting models.

Both types of cutters have a common scientific and technical name - plasmatron (literally, plasma generator).

Benefits of Plasma Treatment

Compared to other types of metal processing, this method has a number of consumer properties:

• the ability to process workpieces made of various metals, as well as non-metallic products;
• the processing speed of small thicknesses (up to 50 mm) is 25 times higher than with;
• local heating of the part occurs only at the point of impact, which contributes to the absence of thermal stress and deformation of the product;
• high-quality and clean metal cutting, - low surface roughness at the processing site;
• absence of explosive substances and objects - flammable gases, pressure cylinders, etc.;
• The method allows you to produce complex geometric cuts.

What equipment is used

For cutting metal with plasma, units of industrial and household use. The first are a complex multifunctional complex with an automated process (CNC machines). The second are small devices operating from a 220V or 380 V network.

The source of plasma cutting in household appliances is an inverter (welding generator) or transformer. The first type is smaller in size and more convenient to use. The second one has high reliability and a long service life. The working fluid is prepared atmospheric air.

The power of the manual unit is enough to cut metal up to 15–20 mm thick. Some models are equipped with a non-contact arc ignition function. The package includes a plasma torch and an air preparation device.

Used in home workshops, conditions professional production and construction:

• sheet metal plasma river;
• processing of cylindrical products, including steel pipes;
• cutting complex geometric shapes, including holes;
• processing of ceramic and stone products and other types of crafts.

This type of equipment is significantly superior in functionality and ease of use to conventional oxy-fuel cutting. Not only in terms of size, but also in terms of safety.

A model of a household plasmatron is shown in the photo.

Technology properties

Industrial and Appliances unite general principles plasma cutting work:

• creating an electric arc;
• formation of ionized gas;
• creation of a high-speed plasma flow;
• the effect of this active medium on the material being processed.

Plasma arc cutting is characterized by:

• Flow temperature. The values ​​are in the range of 5000–30000°C. Determined by the type of material being processed: lower values used for non-ferrous metals, upper ones - for refractory steels.
• Flow rate. Values ​​range from 500–1500 m/s. Configured for a specific type of processing:
  • workpiece thickness;
  • type of material;
  • type of cut (straight or curved);
  • duration of operation of the plasmatron.
• Gas used for plasma cutting. When processing ferrous metals (steels), the active group used is oxygen (O2) and air. For non-ferrous metals and alloys, - inactive: nitrogen (N2), argon (Ar), hydrogen (H2), water vapor. This is explained by the fact that non-ferrous metals are oxidized by oxygen (they begin to burn), so a protective gas environment is used. In addition, combining the composition gas mixture, the processing quality can be improved.
• Cut width. There is a direct sequence here: as the indicators increase, the cutting width increases. Its value is influenced by:
  • metal thickness and type;
  • nozzle diameter;
  • current strength;
  • gas consumption;
  • cutting speed.
• Performance. Determined by processing speed. For example, for household units and according to GOST, the value does not exceed 6.5–7 m/min (~0.11 m/sec). Depends on the thickness, type of metal, gas jet speed. Naturally, as the size increases, the processing speed decreases.

Processing quality

The quality of the cut is an important factor when processing metal, especially if it is plasma cutting of pipes. Determined by the mode of operation and the skill of the performer. Plasma arc cutting is regulated by GOST 14792-80. International quality standard - ISO 9013-2002.

The documents define the main criteria:

1. Tolerance for perpendicularity or angularity. Shows deviations from the perpendicular and cutting plane to the surface of the workpiece.
2. Melting of the top edge. Cracks at processing points are not allowed. The upper edge can be sharp, melted, melted-overhanging.
3. Roughness. According to GOST, it is divided into three classes, 1, 2 and 3.

Types of plasma cutting

Metal plasma cutting technology is a set of several methods. Plasma arc cutting is divided into:

1. air-plasma method of metal cutting;
2. gas plasma;
3. laser-plasma cutting method.

The first two types are similar in principle of operation - an electric arc plus an ionized flow of hot gas. The difference is in the working fluid. In the first case - air, in the second - some kind of gas or water vapor.

According to the method of processing workpieces up to 200 mm thick, combined equipment is used. Modern industrial installation combines heat treatment with a gas jet or the use of a plasma torch. The cutting machines are equipped with a CNC module (numerical software control). They cut sheet metal along a straight or curved path.

Manual plasma cutting is a classic plasma arc cutting. Portable units (household level) cut ferrous metal using an ionized air jet. Expanding the range of gases entails a significant complication of equipment and an increase in its cost.

Laser-plasma

It is a combination on one machine. Laser cutting is used for work with thicknesses up to 6 mm. Larger sheets are processed using plasma arc cutting.

Laser and flame cutting, combined on one CNC machine, increases productivity. Allows you to create various cutting lines, including cutting holes.

Laser or plasma cutting, combined on one device, significantly saves production space. Plasma arc cutting is used on large workpieces. Laser - during processing small parts With increased requirements to cutting accuracy.

The fundamental difference between the laser method and the plasma method is the heating source. In a laser, it is a focused beam of light. The contact area is extremely small, so it is possible to obtain a local impact on the part. Thanks to this, the cutting width is small, and the cutting quality is higher than with a plasmatron.

Because of this, plasma pipe cutting is gradually losing ground where it is required high accuracy cutting and increased quality is presented to the edge of the product.

Titanium processing

Titanium and its alloys are gaining great popularity in the space, aviation, medical and other industries. The combination of strength and low density are the main advantages of this substance. But this metal is chemically active and refractory.

Due to these characteristics, it is difficult to subject to mechanical and thermal processing. You can't use a cutting tool - the metal will burn. Hence, titanium cutting is well mastered using a plasmatron and laser method.

In addition to conventional direct cutting, the plasma-laser method allows for spatial processing of complex geometric shapes, for example, mating several holes.

An example of plasma cutting of metal using a plasmatron can be seen in the video.

Cutting materials using plasma flow is high-tech, effective way their quality processing. Manual plasma cutting, carried out with appropriate equipment, expands the scope of this type of work.

2 Basic classification of plasma cutting equipment

All devices for plasma cutting are divided into:

• indirect action – for non-contact cutting;
• direct action - for contact.

The first type of cutters are used for processing non-metallic materials. This technique is specific and is not in demand outside of production. In the non-contact method, an electric arc is ignited between the electrode and the nozzle of the plasma torch.

Direct acting devices cut various metals. When working with them, the part to be cut is included in electrical diagram plasma apparatus, and an electric arc is ignited between it and the electrode located in the nozzle. The flow of ionized gas is heated throughout the entire area between its exit point and the surface of the workpiece - the plasma jet has greater power than in devices of the first type. Manual plasma is performed only with the help of equipment of this type, contact method.

3 Devices for manual plasma cutting of metals

They consist of a plasma torch, a power source, a set of cables and hoses with which the plasma torch is connected to the power source and gas cylinder or a compressor. Plasma torch (plasma cutter) – main element such equipment. Sometimes the entire apparatus is called this by mistake. This may be due to the fact that the power sources used for plasma cutters do not differ from similar devices and can be used together with welding equipment. And the only element that distinguishes plasma apparatus from another device, and is a plasmatron. Its main components:

• nozzle;
• electrode;
• heat-resistant insulator located between them.

A plasma torch is equipment that converts the energy of an electric arc into thermal energy of plasma. Inside its body there is a cylindrical chamber with an output channel (nozzle) of a very small diameter. An electrode is installed in the back of the chamber, which serves to form an electric arc. The nozzle is responsible for the speed and shape of the plasma flow. A manual plasma cutting machine is used for cutting metal manually - the operator holds the plasma torch in his hands and moves it over the cutting line.

Since the working tool is suspended all the time, and therefore can be subject to movement due to involuntary movements of the performer, this invariably affects the quality of cutting. The cut may be uneven, with sagging, traces of jerks, and so on. To facilitate and improve the quality of work, there are special stands and stops that are placed on the plasma torch nozzle. They allow you to place the equipment directly on the workpiece and guide it along the cutting line. In this case, the gap between the metal and the nozzle will always meet the requirements.

At manual cutting The plasma-forming and protective (for cooling the nozzle and removing cutting products) gas can be air or nitrogen. They are supplied from the main line, a cylinder or a compressor built into the equipment.

4 Power sources for hand-held plasma cutting machines

All power sources for hand-held devices operate from alternating current mains. Most of them convert the received electricity into direct current voltage, while the rest only serve to amplify alternating current. This distribution is due to the fact that plasma torches operating on direct current have a higher efficiency. Alternating current used in a number of cases - for example, for cutting aluminum and its alloys.

The power source can be an inverter or transformer that supplies a high current to the plasmatron. Inverters are usually used in small industries and at home. They have smaller dimensions, weight and are much more energy efficient than transformers. Inverters are most often included in manual apparatus For . To the advantages inverter devices include efficiency, which is 30% higher than that of transformers, and stable combustion of the electric arc, as well as compactness and the ability to carry out work in any hard-to-reach places.

The disadvantages are the power limitation (the maximum current is usually 70–100 A). As a rule, inverter machines are used when cutting workpieces of relatively small thickness.

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

The switching duration (DS) has a direct impact on the specifics of working with the equipment. For example, if manual plasma cutting of metal, the equipment for which has a duty cycle of 40%, lasted 4 minutes without a break, then the device must then be given 6 minutes of rest in order for it to cool down. Devices with 100% duty cycle are used in production, where the device is operated throughout the entire working day. Significant disadvantage transformer equipment – ​​high energy consumption.

5 Operating principle of manual plasma cutting machines

After the manual plasma cutting installation has been assembled (all connections and connections of its elements have been made), the metal workpiece is connected to the device (inverter or transformer) with the cable provided for this purpose. The equipment is connected to the electrical network, the plasma torch is brought to the material being processed at a distance of up to 40 mm and the pilot (initiating ionization) electric arc is ignited. Then the gas supply is turned on.

After receiving a plasma jet, which has high electrical conductivity, at the moment of its contact with the metal, a working (cutting) electric arc is formed. At the same time, the attendant switches off automatically. The working arc maintains the continuity of the process of ionization of the supplied gas and the formation of a plasma flow. If for some reason it goes out, then you need to stop the gas supply, turn on the plasma device again and light the pilot arc, and then turn on the gas.

Several are used for cutting metals various methods differing from each other in cost and efficiency. Some methods are used exclusively for industrial purposes, others can also be used in everyday life.

The latter includes plasma cutting of metals. The effectiveness of plasma cutting is limited by the experience of the master and the correct choice of installation.

• What is plasma metal cutting?
• What is the principle of work based on?
• What areas of application does this method of cutting materials have?

Plasma Metal Cutting Basics

To understand the basics of cutting metal using the plasma method, you should first understand what plasma is? The quality of the final result depends on a correct understanding of how the plasmatron works and the principles of working with it.

Thermal plasma processing of metals depends on the parameters of the working jet of gas or liquid directed under pressure onto the surface being treated. To achieve the required results, the jet is adjusted to the following characteristics:

• Speed ​​- the jet is directed under high pressure onto the surface of the material. We can say that plasma cutting of metal is based on heating the metal to its melting point and quickly blowing it out. The operating speed of the jet is from 1.5 to 4 km per second.
• Temperature - for plasma to form, it is necessary to almost instantly heat the air to 5000-30000°C. The high temperature is achieved by creating an electric arc. Upon reaching required temperature air flow ionizes and changes its properties, acquiring electrical conductivity. Plasma metal cutting technology involves the use of air injection systems, as well as dehumidifiers that remove moisture.
• Presence of an electrical circuit. Everything about cutting metal with plasma can only be learned through practice. But some features must be taken into account even before purchasing the unit. Thus, there are plasmatrons of indirect and direct influence. And if for the latter it is necessary that the material being processed transmits electricity and is included in the general electrical network(acting as an electrode), then for the former there is no such need. In this case, plasma for cutting metal is obtained using a built-in electrode inside the holder. This method is used for metals and other materials that do not conduct electricity.

Another important point to consider is that plasma cutting of thick metal is practically not performed, as it leads to increased material costs and is ineffective.

Characteristics and principle of metal cutting with plasma

The basic operating principle of metal plasma cutting can be described as follows:

Since the process is associated with instant heating of the material being cut to a liquid state, the thickness of the metal during cutting is:

• aluminum up to 120 mm;
• copper 80 mm;
• carbon and alloy steel up to 50 mm;
• cast iron up to 90 mm.

There are two main methods of processing materials, which determine the characteristics of plasma cutting. Namely:

1. Plasma arc - the method is suitable for all types of metal that are able to conduct electric current. Typically, plasma arc cutting is used for industrial equipment. The essence of the method is that plasma is formed due to an arc that appears directly between the surface of the material being processed and the plasma torch.
2. Plasma-jet - in this case, the arc occurs in the plasma torch itself. The plasma jet processing option is more versatile and allows cutting non-metallic materials. The only drawback is the need to periodically replace the electrodes.

Plasma cutting of metal works like a regular arc, but without the use of conventional electrodes. But the effectiveness of the processing method is directly proportional to the thickness of the material being processed.

Speed ​​and accuracy of metal cutting with plasma

As with any other type of heat treatment, when plasma cutting of metal a certain melting of the metal occurs, which affects the quality of the cut. There are other features that are characteristic of this method. Namely:

The quality of the work largely depends on the professionalism of the master. Clean and precise cut with minimal deviation from required sizes can only be performed by an employee with specialized education. Without appropriate preparation, it is unlikely that you will be able to perform figure cutting.

Plasma cutting of non-ferrous metals

When processing non-ferrous metals they are used different ways cutting depending on the type of material, its density and other technical characteristics. To cut non-ferrous alloys, the following recommendations must be observed.

Where is plasma metal cutting used?

It is not for nothing that the use of plasma torches is so popular. With relatively simple operation and low cost of manual installation (compared to other cutting equipment), it is possible to achieve high levels of cut quality.

The use of plasma cutting of metal has become widespread in the following areas of production:

The use of plasma cutting machines has not replaced manual installations. Thus, artistic cutting of metal with plasma allows you to make unique parts that exactly match the artist’s plan, for use as decorative decorations for fences and stairs, as well as railings, fences, etc.

Metal cutting with plasma - advantages and disadvantages

Almost nothing can do without metal cutting industrial enterprise, one way or another connected with rolled metal. Quick cutting of sheet material into blanks, decorative figure cutting metal with plasma, cutting out precise holes - all this can be done quite quickly using a plasma torch. The advantages that the method has are as follows:

• High productivity and speed of processing parts. Compared to the conventional electrode method, it is possible to perform 4 to 10 times more work.
• Cost-effective - the plasma method is much better compared to standard methods materials processing. The only restrictions are related to the thickness of the metal. It is impractical and uneconomical to cut steel thicker than 5 cm using plasma.
• Accuracy - deformations from heat treatment are almost invisible and do not require additional processing afterwards.
• Safety.

All these advantages of plasma cutting of metal explain why the method is so widely popular not only for industrial but also for domestic purposes.

But speaking about the advantages, it is necessary to note some negative aspects:

• Limitations related to cut thickness. Even with powerful installations, the maximum density of the processed surface cannot be higher than 80-100 mm.
• Strict requirements regarding the processing of parts. The master is required to strictly adhere to the angle of inclination of the cutter from 10 to 50 degrees. Failure to comply with this requirement will compromise the quality of the cut and accelerate the wear of components.

Comparison of plasma and laser cutting of metal

The difference between laser cutting of metal and plasma cutting lies in the methods used to influence the surface of the material.

Laser systems provide greater productivity and speed of processing parts, while after the operation there is a lower percentage of melting. Minus laser equipment is his high price, and also that the thickness of the material being cut should be less than 20 mm.

Compared to a laser, a plasmatron has a lower cost, more wide scope applications and functionality.