How plasma cutting works. Completeness of manual cutting devices

Such devices are easy to distinguish - they are designated as "PAC" (Western classification). Plasma cutting It is the most modern technology, and not only metals, but also other materials, including those that do not conduct electric current, can be processed.

We will talk about the principle of operation of cutters of this type, their design and much more, which will be useful for a novice welder to know.

What is plasma?

This is a gas that, with a significant rise in temperature in working area(about 25,000 ºС) ionizes and becomes a conductive medium. He's under high pressure, jet, is fed to the workpiece. In fact, this cutting is an overlay (combination, combination) of two arcs; one of them is gas, the other is electric. The formation of a "working" arc occurs in a device called a plasma torch.

In practice, 2 methods of cutting materials are used, depending on what is being processed - metal or dielectric. Based on this, plasma cutters have a slight difference in design burners.

Direct impact cutters

They are used if the specimen to be cut is a good conductor of current. In this case, the part becomes one of the elements of the electric circuit, and a spark occurs between it and the burner. Such cutting is called plasma-arc, and it is used for.

Indirect cutters

This equipment is much more expensive, since it can be used to cut materials with extremely low electrical conductivity (including dielectrics). In such models, an electrode is placed in the cutter, which is “responsible” for the formation of a spark. The plasma column is slightly “carried out” beyond the dimensions of the nozzle, and the separation of the workpiece into parts is provided by its energy (jet cutting).

The device of the plasma torch may differ slightly, depending on the model and manufacturer, but general scheme practically does not change.

The principle of operation of a plasma cutter is that a jet of air formed in the gas supply channel, compressed to a specified limit, enters the working area, where a pre-ignited electric arc is already located. She converts it into plasma. What does it give?

• The current cuts the workpiece by melting the material.
• The plasma jet removes particles of molten metal from the cut area, that is, it cleans the working area.
• The heating of the part is insignificant and local.

The author considered only the simplest design flame cutting devices general information about the process. There are several modifications of devices. For example, according to the method of cooling the nozzle - air or liquid. According to the gases used, since in addition to air it can be pure oxygen, argon, water vapor or something else. But general principle work should already be clear to the reader. All the rest - design features which you can deal with yourself if you wish.

What are the benefits of plasma cutting?

• Increased speed of operation.
• Work with any alloys and metals.
• Ultimate purity and correct geometry edges.
• Probability thermal deformation parts is completely excluded, even if the cut is carried out by a person without practical experience in this area.
• Work safety.
• Performing figured cutting of samples.

Helpful information

Nozzle

Its cross section affects the accuracy of the cut. The smaller it is, the more complex technological operations can be performed. Including curly. But the speed of work depends on the length of the nozzle. When choosing a plasma cutter, it is necessary to look at the ratio of these parameters (L / d). Optimal value within 1.55 - 1.75.

electrodes

They are selected for cutters of indirect action. Samples made from hafnium are considered the best (by the way, most of these products are on sale).

Compressor

How well it works depends on the quality and speed of the cut. This device should supply to the working area not only heated to a high temperature and compressed air, but also dried and “clean”, without any impurities. If a PAC category machine is bought for plasma cutting of metals at home or for a small workshop, then preference should be given to cutters equipped with a built-in compressor. It already has both a dehumidifier and an airflow purification circuit.

How to choose a plasma cutter for domestic use

Nutrition

With regard to these devices, there is no difference, 1 phase or 3. But if we are talking about a household plasma cutter, then it is more advisable to take a model that can be powered from a conventional outlet.

Power

It is determined by the strength of the current in the arc. 60 A is enough to cut metals up to 30 mm thick. But as practice shows, it makes no sense to purchase plasma cutters with I ˃ 100 A for a home or a small specialized workshop. It is unlikely that anyone will cut samples thicker than 3 - 4 cm, if this is not a metalworking production, and the cost of such cutters is quite high. The principle of evaluating the feasibility is simple - such devices "for growth" are not bought.

Duration of continuous work

Denoted as PV, as a percentage. For domestic use 55 (±5)% torch is sufficient, which corresponds to approximately 5 to 6 minutes of continuous operation.

Nozzle

Its parameters have already been mentioned. Specific data is reflected in the documentation for the plasma cutter. It remains to add that you should immediately clarify whether it is possible to repair this product with your own hands and what of the necessary is included in the kit. In case of replacement, where can I buy this part of the cutter at retail.

Auto believes that a device for plasma cutting of metals will be extremely useful to any economic man. If you search, you can buy manual model costing about 18,000 - 20,000 rubles. Not too expensive for someone who often works with metals, considering how many problems it will save. Always breaking drills and hacksaw blades, grinding discs for angle grinders, dragging from place to place gas cylinders(which still need to be refueled regularly), the search for electrodes of a certain brand - all this is well known to home craftsmen.

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

1 Plasma metal cutting technology

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

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

Technologically, there are two cutting methods:

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

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

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

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

3 Plasma gases and their effect on cutting performance

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

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

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

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

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

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

4 Advantages and disadvantages of plasma cutting

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

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

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

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

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

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

Today it is difficult to imagine heavy industry without the use of welding and metal cutting. On most industrial enterprises engaged in the processing of metal products, a special cutting method is used - plasma.

Plasma cutting is a material processing process in which the cutting element is a plasma jet.

Few people know how do-it-yourself plasma cutting of metal is carried out and what are the main stages this process. Most often, the thickness of the processed products is less than 20 cm. It is for cutting metal of such thickness that plasma devices are used.

Characteristics of cutting products using plasma

Those who use an oxy-fuel cutting torch to cut metal know that plasma cutting differs in many ways from this method. Here, instead of cutting gas, a plasma jet is used. As with conventional welding, plasma cutting uses an electric arc. It is ignited directly between the surface of the object and the electrode. The supplied gas then becomes a plasma. An interesting fact is that the temperature of the latter can reach several tens of thousands of degrees (from 5 to 30 thousand). In this case, the jet velocity often reaches 1500 m/s. Plasma cutting of metal is suitable for products up to 20 cm thick. As for the gas supplied to the nozzle, it can be of several types: active and inactive.

The first category includes oxygen and air mixture, the second - nitrogen, hydrogen, and some inert gases, such as argon. The choice of one or another gas depends on the metal. If it is a ferrous metal, then it is recommended to use active gases. Inactive ones are more suitable for non-ferrous metals (aluminum, copper) and their alloys. Manual plasma cutting can be surface and separation. The latter is used much more frequently. You need to know that this method of cutting metal is the most automated. Plasma cutting involves the use of special automatic (programmable) machines.

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Positive and negative sides

Plasma cutting has its positive and negative sides. The advantages, firstly, include the possibility of using equipment for cutting any metal. This is achieved thanks to elevated temperature in the work area. Secondly, an important aspect is the high speed of work. This ensures the best performance. Thirdly, plasma cutting is great for cutting products of various geometric shapes. Simple gas method this is impossible to achieve. Fourth, great importance has the fact that such metal cutting is accurate and fast. Here, the probability of obtaining low-quality products is greatly reduced, since the work is automated.

Fifth, everyone knows that simple oxygen cutting can be dangerous to humans and others. Plasma cutting is the least dangerous. Sixthly, such work can be carried out both outdoors and under water. It is also important that the cost per 1 m of material is much less, because of all this, plasma cutting is increasingly being used at large industrial facilities. As for negative sides this process, the equipment is quite expensive, so this technique is rarely used at home.

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Which device to choose

Plasma cutting of metal begins with the preparation of equipment. To do this, you need to choose a quality device. There are 2 types of equipment: inverter and transformer. Inverters are familiar to many, since they are used for welding. They replaced the transformers. Inverter units are small in size, they are compact, aesthetic and consume less energy. When purchasing equipment, you need to pay attention to such characteristics as the duration of work in active mode and power. The disadvantage of such a unit is that it is quite sensitive to power surges in the network.

Equipment for cutting by the type of transformers is the most reliable and durable. A feature of transformers is that at high power they can be used for automated cutting. The manual method is also used. If metal cutting is supposed to be carried out in a private workshop or at industrial facilities, then it is more expedient to purchase a transformer-type apparatus. It is also widely used in the manufacture of automobiles. It must be remembered that any plasma cutting is an expensive pleasure.

The device will be expensive. An important criterion when choosing equipment is the maximum cutting thickness. For non-ferrous metals (copper) it is always less. If the technical data sheet indicates a maximum thickness of 10 mm, then this indicator refers to non-ferrous metals.

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Features of manual arc plasma cutting

For cutting metal products, a manual method is often used. Its peculiarity is that it does not require high qualifications to cut the product. Any person can perform the work, knowing all the main stages of the process. By purchasing a plasma cutter, you can cut not only metal, but also tiles, wood and other materials. Plasma cutting manually begins with inspection of the equipment, nozzle, electrodes. The nozzle and electrodes must be securely fastened. To save materials, it is advisable to strike the arc as infrequently as possible. In order for the device to start working, compressed air must be supplied to it.

For this purpose, you can use cylinders that are filled with air, a compressor or connect equipment to a central pipeline (if cutting is carried out in industrial environment). The most reliable devices are equipped with a special control device, with the help of which the incoming air is distributed in the device.

The next step is to set up the hardware. To do this, you need to choose the right current strength. It is preferable to start cutting at high current. In this case, several test cuts are made. An incorrectly selected mode can lead to overheating of the metal and its splashing. At optimal mode arcing, the cut line must be even, and the metal must not be deformed.

If it is required to cut sheet material, then the burner nozzle is placed close to the metal surface. To do this, turn on the power button on the device. Soon after this, the duty arc should light up, and after it the cutting one. The arc must be directed at an angle of 90° to the metal. The burner moves from top to bottom. If automatic plasma cutting is fast, then with the manual method, the torch must be moved slowly. At the end of the work, it is advisable to briefly stop the advance of the torch in order to complete the cutting.

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Cutting various metals

Cutting a particular metal may have its own characteristics. Today, cutting is more commonly used sheet material. It is usually represented by steel. Often you have to cut aluminum. If welding of this metal is difficult due to the formation of protective film in the form of aluminum oxide, cutting aluminum is quite simple. It is important to remember here that air and active gases do not need to be used.

Plasma cutting of aluminum is performed using argon or nitrogen.

Argon and nitrogen are chemically less active elements, therefore, in the process of cutting and heating the metal, an oxide film does not form on it. Another common material is steel. In this situation, cutting is carried out without the use of protective gases. Air-arc plasma cutting is excellent for products made of of stainless steel. This is the most affordable way cutting.

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Plasma jet cutting

Unlike the arc method, when cutting with a plasma jet, the metal does not participate in the formation electrical circuit. The electric arc itself is present, but it is formed directly between inside nozzle and electrode. Such an electric arc is necessary in order for the plasma to form. This makes it possible to cut materials that do not conduct electricity. The plasma in this situation is high-speed. Most often, this method is used to separate sheet material. With regard to the use of electrodes, electrodes based on various tungsten alloys are suitable for plasma cutting.

It must be remembered that in order to cut materials using a plasma flow, you need to have available necessary tools and materials. They include cutting machine, source electric current, overalls, footwear, a mask, mittens, a hammer, a chisel, a metal brush. Often, to carry out such work, a plasma cutting machine is made by hand. In terms of power, it may not be inferior to the factory one.

Metal cutting is necessary in many technological processes. Almost always, machining begins with cutting and cutting of the material. One of the most convenient and economical methods is plasma cutting of metal. It allows you to get blanks of any shape, which almost do not require further processing.

Principle of operation

For plasma cutting of metal, the action of a plasma jet on the workpiece is used. Plasma is a stream of ionized gas, heated to a temperature of thousands of degrees, which has electrical conductivity and moves with high speed. The formation of a plasma arc from an electric one is performed by a plasma cutter. The principle of operation of the plasma cutter and the stages of the cutting process:

• A standby electric arc is formed, which is ignited between the plasma cutter electrode 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 cuts it.

For metals and non-metal materials, different principles of plasma cutting are used. There are two ways to process materials:

• The arc burns between the plasma torch and the product. This is how a direct cutter works. The product must be conductive. If it is required to cut non-metal products, the indirect method is used.
• The arc is ignited in the plasma torch 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. Potential is not applied to the part and electrical conductivity is not required.

Plasma cutting equipment

For cutting metal with plasma, devices for industrial and domestic purposes are produced. All plasma cutting units include:

• source of power;
• plasma torch;
• compressor for injection of compressed gas;
• cables and hoses used to connect equipment elements.

The power source may be an inverter or a transformer. Inverter units are light, economical, have a high efficiency. They are often used in small industries. They have a current limit of 70 A, they are able to cut material only of small thickness up to 30 mm.

Transformer devices are more powerful, have more weight and dimensions. They are more resistant to voltage drops, capable of long continuous work and are often used in CNC machines. Equipment with a water cooling system is capable of cutting metal up to 100 mm thick. Power sources for cutting with 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. For steels and alloys, oxygen and air are used. Air-plasma cutting is used for processing low-alloy steels. When processing non-ferrous metals, plasma-forming gases can be argon, nitrogen, 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 more commonly used for cutting stainless steel and aluminum.

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

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

Processing in manual mode

Before starting work, the inverter or transformer is connected to the network alternating current. The workpiece is connected to a power source. The next stage is the convergence of the nozzle and the workpiece. There should be 40 mm between them. After that, you can light the duty arc. When the arc ignites, the nozzle is fed air flow, which ionizes and forms a plasma jet.

When working with a plasma cutter, safety precautions must be observed. You need to use a special suit and a protective face shield. Temperatures during plasma cutting reach thousands of degrees, and for a person it can be dangerous. Therefore, it is necessary to 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 metal and non-metal materials. This is due to the following advantages of cutting technology using a plasma arc:

But the method plasma cutting there are also disadvantages. These include:

Despite these shortcomings, plasma torches are increasingly being used 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 curvilinear figures make plasma cutters indispensable in many production processes.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Plasma cutter parameters

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Homemade plasma cutter - scheme of work.

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

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

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

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

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

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

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

Machine characteristics:

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

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

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

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

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

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

• The water table is being welded.

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

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

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

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

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

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

Everything, the CNC plasma cutting machine is ready.

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