Do-it-yourself plasma cutting of metal. Making a homemade plasma cutter from a welding inverter

Both experts and novice craftsmen often use plasma cutting in their work. This is understandable: after all, this is an indispensable process for a wide variety of construction and production processes. There is only one drawback: devices produced by various companies cost a lot of money, and not everyone can afford them. Therefore, a variety of working people, be it construction crews or individual craftsmen, are thinking about how to create a plasma cutter from an inverter, relying only on their own hands and on available equipment, thereby saving a significant amount.

Video: Homemade plasma cutter, plasma cutter made in a month

The main purpose of a manual plasma cutter is cutting different types metals Such actions are necessary during the construction of various structures. After all, you don't need to use other tools. The use of all kinds of electrodes with which the welding process is carried out is also possible if you have a homemade plasma cutter.

In this unit, the fundamental principle by which metals are joined is soldering. It is thanks to the high temperature of the solder that a manual plasma cutter allows you to reliably bond a variety of metals - this is its main advantage, which is why this equipment is so necessary for many.

In addition to standard construction activities, this convenient tool is also used for blacksmithing. After all, with his direct participation, it is possible to perform various manipulations with both non-ferrous and ferrous metals. In addition to their welding: also thermal cleaning, hardening, and annealing. For this reason, the presence of a manual plasma cutter for such work is mandatory, this ensures both product quality and significant time savings.

Design features

Before you start assembling a plasma cutter from an inverter yourself, you need to accurately determine its configuration and how it will be arranged. It should be understood that it is better to purchase individual parts of the future device ready-made rather than assemble it yourself, because such an assembly will be fraught with certain difficulties.

Typically, the assembled apparatus consists of the following main components, without which its operation is impossible: an air compressor, a hose-cable package, a power source and a cutter, which is officially called a plasma torch.

The peculiar “heart” of a manual plasma cutter is the power source. It is he who supplies the current of the required power. The technical characteristics of the unit are determined precisely by this component.

If we compare the cutter (or “plasma torch”) used on this device, we can see that its design is significantly different from similar components used in welding units. However, it is no less important than the power source. It is the cutter (plasma cutter) that is the part whose independent creation from an inverter is associated with significant problems. It’s better to buy a cutter ready-made in a store. This will save you from many problems in the future.

In powerful units for hot metal cutting, internal cooling functions are required. There, various gas mixtures are used for this. Cooling is also necessary in a manual plasma cutter, but here only timely air supply is sufficient. For this purpose, a compressor is used, the operation of which requires a current of 200 A.

The connecting part, through which current from the source flows to the cutter, and air is also forced through the compressor, is a cable and hose package.

About using a transformer or inverter

Most often, when you plan to assemble a plasma cutter, either an inverter or a special transformer is used as the power source. Each of these options has its own advantages, but in order to understand which one is suitable, you need to know exactly which specifications should be possible with your plasma cutter; accordingly, you need to know the features of the inverter and transformer.

The advantages of a plasma cutter made on the basis of an inverter are as follows: on average, its efficiency is one third higher than that of analogues that contain a transformer; they are the most efficient and economical. This device ensures arc stability. The disadvantages include the fact that the work is carried out exclusively with materials of insignificant thickness.

If a transformer is used as a basis, then such a unit will certainly be bulky and require an additional platform for use. But a significant advantage is that it allows you to work with fairly massive and thick parts. Such devices are installed either in rooms specially equipped for them or on mobile platforms.

Therefore, if you do not plan to cut particularly large objects, then it is recommended to use a plasma cutter made from an inverter. The principle is simple: you need to connect the power source you already have at your disposal and other parts, following a certain sequence.

What equipment will you need?

Of course, before you begin directly assembling a device for plasma cutting of metal, you will need to purchase all the parts that will make up the final product. But if you want the intended functions to be performed at a high level, without breakdowns, then some of the components must be purchased ready-made.

Inverter

This is the “heart” of our future unit, and you can take it from any welding machine. In most cases, this is the main material investment in the project being described. In order to choose a suitable inverter, you need to know exactly what work will be performed by the plasma cutter, its volume, etc. Then it will no longer be difficult to select the power of the inverter.

We have heard that some craftsmen assemble the inverter on their own. To do this, they painstakingly select parts and use the materials at their disposal. But in practice it turns out that such home-made designs are less reliable than purchased options. In addition, it is difficult to achieve the same standards at home as in production. Therefore, a purchased inverter option is still preferable.

Cutter

When craftsmen or amateurs make a plasma cutter on their own, they often make the mistake of trying to completely assemble the cutter with the supply of electricity and air. The components of the cutter are: nozzle, supply elements and handle. Moreover, the handle, due to its intensive use, wears out in a short period of time and has to be replaced frequently. Therefore, the best choice would be to buy a factory nozzle, but you can assemble the remaining components yourself. But the opinion that spending a large amount of money and effort on independently assembling this component is not productive is also quite reasonable. It is better to buy a factory product.

Compressor

According to the instructions, using a compressor implies that oxygen or inert gas will be used. In practice, more often it is connected to cylinders containing a special mixture. It is this mixture that provides a strong plasma beam with decent cooling. If the plasma cutter is used at home, then for economy and simplicity of the matter it is recommended to use a simple compressor. This component can be assembled on your own, where the role of a receiver will be played by a regular cylinder. The compressor is often taken from a refrigerator or from a ZIL car. It is important not to make mistakes with pressure regulation. This is done experimentally, by masters, on initial stage works

Cable-hose package

This component of the plasma cutter can be purchased either individually or together with the main equipment. The main thing is to know some characteristics of the unit, namely: what pressure there will be during operation, as well as what cross-section of the cable - the characteristics of the hoses also depend on this. The conductor is selected according to the strength of the inverter. Otherwise, it will overheat and may catch fire and even cause electric shock.

Build process

This is a fairly simple assembly sequence. The plasma cutter nozzle is connected to the inverter and compressor. For such purposes, a cable-hose package is needed. You will need a set of terminals and clamps. With their help, you can quickly assemble and disassemble the plasma cutter. If everything is done correctly, the output will be a device with very compact parameters. It is easy to transport it to the place where the next work will be carried out.

First of all, you must ensure that you have sufficient spare gaskets on hand. After all, plasma cutting occurs when using gas, and gaskets are necessary to connect the hoses. And if the unit is planned to be transported quite often, then this element cannot be avoided; moreover, the lack of gaskets can cause the entire work to stop.
Particularly high temperatures affect the cutter nozzle. Therefore, in the long term of long-term use of the device, it is this part that wears out more quickly than others. So there should be a spare nozzle available.
The price range for inverters is very wide: from very cheap to really expensive. The main thing that affects the price is the power of the inverter. So, before you buy, decide how much power you need. And based on your real needs, choose one model or another. This way, you’ll save money and create a plasma cutter that’s right for your job.
You cannot do without electrodes made of refractory metals. There is quite a wide choice on the market. For example, products made from zirconium, beryllium or thorium. But with significant heating, hazardous components are released from certain metals. Electrodes made of hafnium are considered the safest, and therefore preferable.
During work, the plasma in such a device heats up to 30 thousand degrees. This means that all safety measures must be observed. Without this, a fire may occur, or harm may be caused to both the welder and others. For this reason, beginners who have not undergone any training should not work on such equipment. Ideally, a specialist with significant experience should work.
The reason why experts recommend using only factory-made cutters when working is that homemade variations can disrupt the vortex air flow. And this is unacceptable, because... the formation of 2 arcs is possible, which will cause damage to the product. Therefore, it is better to spend money once than to invest additional money and effort into repairing the unit later.
If you plan to perform only one type of work with the help of an inverter, then it is possible to make some modifications designed to facilitate this particular type of work. For example, some craftsmen introduce their own modifications to the nozzle or create a special casing to protect their hands. The main principle of any such addition: they should not contradict safety rules.

conclusions

So, having familiarized yourself with this material, it becomes clear that to assemble a plasma cutter with an inverter you will need to purchase ready-made components from different manufacturers. As for making a plasma cutter, it’s a simple assembly. But still, the selection of individual parts will allow you to save money, because... If you take a complete ready-made kit from one manufacturer, it will be much more expensive.

Video: How to turn an inverter for manual welding semi-automatic

Making a plasma cutter from an inverter with your own hands is a task that almost any good owner can do. One of the main advantages of this device is that after cutting with such a device there will be no need for additional processing edges of metal sheets.

Direct acting devices

Currently, there are many options for manual plasma cutters, as well as many different options for how they work. One such setup is the direct action cutter. The operation of this type of device is based on the use of an electric arc. This arc has the form of a cylinder to which a gas stream is supplied. It is due to this unusual design that this device can reach a colossal temperature of approximately 20,000 degrees. In addition, this device is capable of not only developing enormous temperatures, but also quickly cooling other working elements.

Indirect action device

Indirect installations are not used as often as direct ones. The thing is that they are characterized by a lower efficiency, that is, efficiency.

The design of these tools is also quite specific and consists in the fact that the active points of the circuit are placed either on a pipe or on a special tungsten electrode. These devices have become quite widely used when it is necessary to spray or heat metal parts. However, this type of equipment is not used as a plasma cutter. Most often they are used to repair automotive components without removing them from the body.

The peculiarities of the operation of such cutters also include the fact that they can only work if there is an air filter, as well as a cooler. The presence of air filters in this device ensures a longer service life of elements such as the cathode and anode, and also affects the acceleration of the process of starting the mechanism.

Hand tool design

In order to ensure that a plasma cutter from an inverter performs all the necessary functions with your own hands, you need to understand the basic principle of operation. The entire functionality of the device depends on the supply of highly heated air from the cutter to the sheet of metal. The temperature conditions that need to be created are several tens of thousands of degrees. When oxygen is heated to such limits, it is supplied under pressure from the cutter to the surface that needs to be cut. It is this work process that is fundamental. Metal sheets are cut using highly heated oxygen under high pressure.

In order to speed up this process, it is necessary to take into account ionization by electric current. It is also important to note that you can increase the service life of a plasma cutter made with your own hands from an inverter if the device contains some additional parts.

Additional items

There are a total of five main elements that must be included in the design of a plasma cutter.

The first and main part is the plasmatron. It is this element that is responsible for performing all the main functions of the cutter.
Next comes the plasma cutter. The design of this element can be done in two ways - direct or indirect. The difference between these designs is described above.
It is also important to have electrodes as consumables for a plasma cutter.
One of the most important parts was the nozzle. The configuration of this particular element allows the master to understand what kind of metal sheet this cutter is intended for cutting.
Compressor. The need for this detail is quite understandable. Since cutting requires oxygen to be supplied under high pressure, the presence of this device is vital for the functioning of the device as a whole.

Parts selection

In order to make a plasma cutter with your own hands from an inverter, you need to decide which elements to create it from.

The part that will create required power for cutting, there may be an inverter or transformer. When choosing this element of the device, it is very important to understand exactly what thickness of metal will need to be cut. It is the thickness of the metal that will be the fundamental factor that will influence the choice of this part. Since a manual cutter is being assembled, it is, of course, better to purchase a welding inverter. Its power is slightly less than that of a transformer, but it is much lighter and will save a large number of electricity.

Second important detail There will be a choice between a plasma cutter or a plasma point. The main selection criterion here will be the same factor as when selecting a welding inverter, that is, the thickness of the metal. However, one more nuance needs to be taken into account. Direct impact equipment is designed to work with elements capable of conducting current. The indirect element is most often installed if it is necessary to do without things that use current in the work.

Another important element is the compressor. Its choice is already simpler, since the only important requirement is power, which must fit the previously selected parts.

The last piece is the cable-hose package. Designed to connect all the parts given above.

Operating principle

In order to create a good working tool of this type, it is very important to understand the operating principle and design of the plasma cutter. This device works as follows:

When the equipment starts up, it begins to generate the required voltage, which is transmitted through the cable to the torch-torch.
There are two main elements in a plasmatron (cutter-torch) - a cathode and an anode. An arc will be initiated between these two parts.
A powerful stream of air, which moves under high pressure, and also overcomes special twisted cables, brings the arc out. At the same time, the supplied air greatly increases the arc temperature.
Next, the ground cable comes into play, which is always connected to the device in advance. It creates an arc closure on the working surface, which ensures stable operation of the plasma cutter.
It is important to note that when converting an inverter into a plasma cutter, welding remains possible. That is, the cutter can also be used as a welding machine. In this case, it is best to use argon as the main gas or another inert mixture that can protect the weld pool from environmental influences.

Cutter device

Since the temperature of the arc is artificially increased by supplying hot air, its temperature in a homemade plasma cutter can reach 8,000 degrees. This is a very high temperature indicator, which allows for spot cutting of metal without heating other parts of the sheet. Like any other technical devices, plasma cutters made from an inverter with your own hands will differ from each other in their power, which will determine how thick a sheet of steel the device can cut. Hand cutters can most often cut sheets up to 10 mm thick. Industrial units are capable of handling metal 100 mm thick. A homemade plasma cutter made on your own will be able to cut sheets with a thickness of up to 12 mm.

Such products can be used for figure cutting, as well as welding alloy steels with filler wire. The simplest cutters include four main parts - a plasma torch, a compressor, and a mass.

How to make a plasma cutter?

Assembling this device should always start with the power source. In industrial units, a transformer is used to achieve more power and, therefore, cut thicker metal. For a manual home cutter, a regular inverter is perfect, as it can provide such indicators as stable voltage and high frequency. The advantage of using an inverter will be its light weight, which will make the device more convenient for transportation, and it is also quite capable of ensuring stable burning of the torch arc and the quality of the cutting itself.

In addition, the inverter must meet several more requirements:

Its power supply must be supplied from a 220V network.
The cutter should operate with a power of 4 kW.
The current adjustment range for a manual device should be from 20 to 40 A.
Idling is also 220V.
The nominal operating mode for a 10-minute cycle should not exceed 60%.

In order to achieve all these parameters, it is necessary to use certain additional equipment.

Plasma cutter diagram

In order to make a working device, it is necessary to consult the diagram of this device. You can easily find such a diagram on the Internet, but you still need to read it. To do this, you need to have the most minimal knowledge in electrical engineering. It is the correct assembly according to the diagram that ensures the actual operation of the unit.

Product circuit operation

Do-it-yourself assembly of a plasma cutter according to a drawing is the most important process that will ensure stable operation of the device in the future. Ready and correct assembled circuit as follows:

The plasma torch has a button that starts the entire workflow. Pressing this button will activate relay P1. The function of this element is to supply current to the control unit.
Next, relay P2 is switched on. It performs tasks such as starting current to the inverter and simultaneously turning on the solenoid valve, which purges the burner. This blowing is necessary in order to dry the burner chamber and clean it of possible debris or scale.
After a three second delay, relay P3 is turned on, which supplies current to the electrodes.
Together with the activation of this relay, an oscillator is started, which ionizes the air between the cathode and the anode, thereby exciting a pilot electric arc.
When the flame is brought to the product, an arc is ignited between the sheet and the plasma torch, which is called the working arc.
At this moment, the current supply that operates for ignition is cut off.
Next, work is carried out on cutting or welding the metal.
Upon completion of work and pressing the button on the plasma torch, relay P4 is activated, which turns off both arcs and also turns on the air supply to the burner chamber for a short period of time to remove burnt elements.

Plasma torch, electrodes, compressor

Cutting or welding of metal is carried out by an element such as a plasma torch. Making it water-based on your own is very problematic, and therefore it is better to buy it. Plasmatrons with an air system are most often made with their own hands.

For this, a compressor is required, which is responsible for blowing and heating the arc to the required 8,000 degrees. This element also performs a cleaning function in the cutter, drying it and clearing it of unwanted elements and debris. As a compressor, you can use a part used in a conventional spray gun.

An important part of a homemade cutter will be the electrodes used. When purchasing them, it is important to clarify what material they are made of. Beryllium and thorium emit harmful fumes when used. It is better to use them only in a special environment where human safety is guaranteed. Best choice for a home cutter, electrodes will be made of hafnium.

The technology of various metal products is used with equal success in everyday life and in large industrial production. Using special equipment, you can easily cut non-ferrous metals, as well as work efficiently with stainless steel, aluminum and other alloys. Cutting non-ferrous metals is carried out using special plasma cutters, which are at the same time easy to use, functional and reliable. Let's tell you more about this equipment and talk about how to make a plasma cutter with your own hands from an inverter.

Industrial plasma cutters are productive equipment that allows for the most accurate cutting of metals with different refractoriness indices. Such industrial plasma cutters are designed primarily for operation under conditions of increased loads and are equipped with CNC, which makes it possible to manufacture parts in a serial manner.

If you need a plasma cutter for domestic use, as well as for the use of such equipment in construction, then such a cutter you can make it yourself from a simple welding inverter. Subsequently, self-made equipment will be distinguished by its versatility in use and will allow you to effectively cut non-ferrous metals and thick sheet steel.

Making such a cutter with your own hands from an inverter will not be particularly difficult. You can easily find diagrams for the implementation of such devices on the Internet and, using the calculations obtained, make such an easy-to-use device. We can recommend that you make plasma cutters based on compact welding inverters, which will significantly simplify the design and guarantee the necessary efficiency of such devices.

Homemade plasma cutting machines are not equipped with CNC, so it will be impossible to use such equipment for work that is fully controlled by automation. You must understand that using such homemade plasma cutters it will be impossible to make two perfectly accurate parts.

A homemade plasma cutter will consist of the following elements:

Plasmatron.
DC source.
Compressor or gas cylinder.
Oscillator.
Power cables.
Connection hoses.

Principle of operation

The operating principle of such equipment is extremely simple:

The current source used, and in our case it is an inverter, generates voltage and supplies it through cables to the plasmatron.
The plasma torch contains two electrodes, between which a high-temperature arc is excited.
Through specially twisted channels under high pressure, a stream of air or gas is supplied to the working area with a ignited arc.
A work cable is pre-connected to the product being cut, which closes to the surface being cut and provides the ability to work with metal.

DC power supplies

Plasma cutting technology will invariably require high operating current power, the performance of which should be at the level of semi-professional and professional inverter welding machines. It is not recommended to use transformer welding machines as a power source, since such devices are bulky and inconvenient to use. But an inverter will be an excellent choice, since such devices combine compact dimensions and provide high-quality electric current.

Schemes and drawings of a plasma cutter with your own hands are simple, while the costs of manufacturing such equipment are significantly reduced. A hand-made compact plasma cutter made from a welding inverter will be able to cope with cutting metal whose sheet thickness will reach 30 mm. If we talk about the advantages of such home plasma cutters made using an inverter, then we note the following:

No metal sparks.
Smooth edges.
Line accuracy.
Overheating issues resolved.

Important: making a homemade plasma cutter based on an inverter is not difficult. It is only necessary that the device generate an electric current with a force of at least 30 Amps.

The current source used must meet the following requirements:

Power supply from a network with a voltage of 220 Volts.
Ability to operate with a power of 4 kW.
The idle speed should be 220 Volts.
The current adjustment range is in the range of 20−40 Amperes.

Plasma torch design

The plasma torch is the second most important element of a metal cutter. Let's take a closer look at the design of the plasma torch and the principle of its operation. It consists of a main and auxiliary electrode. The main electrode is made of refractory metals, and the auxiliary electrode, which has the shape of a nozzle, is usually made of copper.

In a plasma torch, the cathode is the main electrode made of a refractory metal, and a copper electrode-nozzle is used as an anode, which makes it possible to provide high-quality electric current and a high-temperature arc for cutting metal.

The completed plasma torch is responsible for creating and maintaining an arc that is located between the workpiece and the cutter. The thickness of the cut, as well as the temperature created by such a cutter, will depend on the shape and design of the nozzle. The nozzle used can be hemispherical or conical, providing an operating temperature of 30,000 degrees Celsius.

During operation of the plasma torch, the main electrode and nozzle may wear out, which leads to a deterioration in the quality of metal cutting. If these elements become so worn, they should be replaced with new ones, which will ensure excellent quality of work with metal.

The plasma torch is supplied with working gas from a cylinder, using special heavy-duty gas hoses that can withstand high pressure. In each specific case, depending on the material being worked with, the gas used, which is necessary for cutting the metal, may differ.

The working gas is supplied through special channels, and the presence of numerous turns in the supply tube makes it possible to provide the necessary air turbulence, which, in turn, guarantees a high-quality cutting plasma arc that will have correct form. This improves the quality of metal cutting and welding and minimizes the thickness of the seam.

Oscillator

A special feature of plasma cutters is the fact that To start work, preliminary ignition of the arc is required, only after this gas is supplied to the plasmatron, the arc is created at the required temperature and the metal is cut. An oscillator is used as such a kind of starter, which serves to pre-ignite the arc. The implementation scheme of the oscillator is not difficult.

On the Internet you can find functional and electrical diagrams of oscillators, which will not be difficult to complete. It is only necessary to use high-quality electrical circuits and capacitors, which will be suitable in their parameters to the electric current generated by the inverter. Depending on its type, such a torch can be connected to the plasmatron power circuit in series or in parallel.

Working gas

Even before choosing a specific design for manufacturing a plasma cutter, you should decide on the scope of use of such equipment. If you plan to use the device exclusively for working with ferrous metals, you can exclude gas cylinders from the circuit and use only a compressor with compressed air. If you plan to use such equipment for brass, titanium and copper, then you need to choose a plasma cutter with a nitrogen cylinder. Aluminum cutting is performed using a special gas mixture with hydrogen and nitrogen.

Let's figure out how plasma cutting of metal is done with our own hands. After turning on the inverter, the generated electric current enters the plasma cutter onto the electrode, and the oscillator ignites the electric arc. Its temperature can initially be 6-8 thousand degrees. Immediately after the arc is ignited, air or gas is supplied to the nozzle under high pressure, through which an electric charge passes. The air flow is heated and ionized by an electric arc, after which its volume can increase hundreds of times, and the gas and air itself begins to conduct electric current.

A plasma cutter produces a thin jet of plasma, the temperature of which can reach 30,000 degrees. Subsequently, such a high-temperature plasma jet is supplied to the metal being processed, which makes it possible to cut heavy-duty metal elements.

One of the features of using plasma cutting is the fact that the metal being processed is cut and melted exclusively at the point where it is exposed to the plasma flow. It is extremely important to correctly position the plasma impact spot, which should be located strictly in the center of the working electrode. If this requirement is neglected, the air-plasma flow is disrupted, which deteriorates the quality of metal cutting.

The quality of work with such a plasma cutter will also depend on the air flow rate. It is recommended that all work be performed with a current of 250 Amperes, while the speed air jet will be 800 meters per second. This will allow you to easily work with metals with different refractoriness characteristics, ensuring high-quality cutting without thermal effects on the structure of the alloy.

A plasma cutter is a special device that allows you to quickly, efficiently and effectively cut metal of various structures. You can either purchase plasma cutters that have already been manufactured in a factory, or make them yourself. You can easily find suitable schemes for making plasma cutters from an inverter or transformer welding machine, which will allow you to make such equipment yourself, saving on buying it in a store.

Plasma cutting of sheet metal is usually used in large industries for the production of complex parts. You can cut any metals on industrial machines - regular and stainless steel, aluminum, copper, brass, super-hard alloys. You can also make a plasma cutter with your own hands, and it’s a completely workable design, albeit with somewhat limited capabilities.

It will not be suitable for large-scale production, but cutting out several parts in a metalworking workshop, metalworking shop or at home, in a garage, for example, will always work. At the same time, there are practically no restrictions on the complexity of the configuration and hardness of the metal being processed. Limitations relate to metal thickness, sheet size and cutting speed.

The easiest way to build a plasma cutting machine is based on an inverter welding machine. A do-it-yourself plasma cutter made from an inverter is distinguished by its relatively simple design, operability, and accessibility of main components and parts. Those that cannot be purchased can be made independently in a workshop with average equipment.

A homemade plasma cutting machine is not equipped with a CNC - this is its disadvantage and advantage. The disadvantage is that it is difficult to produce two absolutely precise parts when operated manually. Even small series of blanks will differ in some way.

The advantage is that you don’t have to buy one of the most expensive units. Not every highly qualified engineer can make it, and assembling it from ready-made components is the same as buying a new device. A mobile cutter does not need a CNC due to the other tasks it performs.

The main components of a homemade plasma cutter are:

DC source;
plasmatron;
oscillator
compressor or compressed gas cylinder;
connection hoses;
power cable.

As you can see, the device does not include anything particularly complicated. But difficulties begin upon closer examination of the characteristics of a particular unit.

Current source

The characteristics of plasma cutting require that the current be at least at the level of a medium-power welding machine. This current is generated by ordinary welding transformer and an inverter device. In the first case, the installation will be conditionally mobile - the large weight and dimensions of the transformer will make it difficult to move. In combination with a compressed gas cylinder or compressor, the system will turn out to be quite cumbersome.

In addition, transformers are characterized by low efficiency, which will lead to increased energy consumption when cutting metal. The circuit using an inverter is somewhat simpler and more convenient to use, as well as more energy efficient. A welding inverter will produce a fairly compact plasma cutter that can easily handle cutting metal up to 25-30 mm thick. It is for these thicknesses that industrial installations are used. the transformer will be able to process thicker workpieces, but this is required less frequently. All the advantages of plasma cutting are manifested precisely on thin and ultra-thin sheets. This:

line accuracy;
smooth edges;
no metal splashes;
there are no overheated zones near the interaction between the arc and metal.

A homemade plasma cutter is assembled on the basis of any inverter welding machine. The number of operating modes does not matter - only direct current with a power of more than 30A is needed.

Plasma torch

The second most important element of the plasma cutter. Let's briefly consider the principle of its operation. A plasma cutter consists of two electrodes, one of which, the main one, is made of refractory metal, the second is the nozzle. It is usually made from copper. The main electrode serves as the cathode, the nozzle as the anode, and during operation, the current-conducting part being processed.

In this case, we are considering a direct plasma torch for cutting metals. An arc occurs between the cutter and the workpiece. There are also indirect plasma torches that cut with a plasma jet, but they will be discussed below. The inverter plasma cutter is designed for direct action.

In addition to the electrode and nozzle, which are consumables and can be replaced as they wear out, the plasma torch body contains an insulator that separates the cathode and anode units and a small chamber in which the supplied gas swirls. A thin hole is made in the conical or hemispherical nozzle, through which gas heated to a temperature of 5000-3000 0 C escapes.

Gas is supplied to the chamber from a cylinder or from a compressor through a hose combined with power cables, which form a hose-cable package. They are connected in one insulating sleeve, or connected in the form of a bundle. Gas enters the chamber through a straight pipe located on top or side of the vortex chamber, which is needed so that the working medium moves only in one direction.

How does a plasma torch work?

Gas, entering under pressure into the space between the nozzle (anode) and the electrode (cathode), quietly passes into the working hole and escapes into the atmosphere. When the oscillator, a device that generates a pulsed high-frequency current, is turned on, an arc appears between the electrodes, which is called a preliminary arc and heats the gas located in the limited space of the combustion chamber. The heating temperature is so high that it turns into another type of physical state - plasma.

This type of material state is distinguished by the fact that almost all atoms are ionized, that is, electrically charged. In addition, the pressure in the chamber increases sharply and the gas rushes out in the form of a hot jet. When the plasma torch is brought to the part, a second arc appears, more powerful. If the current from the oscillator is 30-60 A, then the working arc occurs at 180-200 A.

This arc additionally heats the gas, which accelerates under the influence of electrical forces to an extremely high speed - up to 1500 m/s. The combined effect of the high temperature of the plasma and the speed of movement cuts the metal in a very fine line. The thickness of the cut depends on the properties of the nozzle.

An indirect plasma torch works differently, in which a nozzle acts as the main anode. It is not an arc that escapes from the cutter, but a stream of plasma - a jet that cuts non-conductive substances. Homemade equipment with such plasma torches very rarely works.

Due to the complexity and subtle settings, it is almost impossible to make it yourself, despite the simple drawings that are available on the Internet. It operates under high pressures and temperatures and becomes downright dangerous if done incorrectly. You can assemble a plasma cutter according to the drawings yourself from ready-made parts that are sold in welding equipment stores. But, like most machines and mechanisms, assembly from components costs more than a complete cutter.

Oscillator

This is a kind of starter that serves to start the preliminary arc. For those versed in electronics, its circuit is simple. The functional diagram looks like this:

And the electric one is something like this (one of the options):

You can see how the homemade oscillator looks and works in the video. If you don’t have time to assemble electrical circuits and search for parts, use factory-made oscillators, for example VSD-02. Its characteristics are best suited to work with an inverter. The plasmatron power supply is connected in parallel or in series, depending on the requirements of the instructions for a particular device.

Working gas

Before making a plasma cutter, you should outline the preliminary scope of its application. If you are going to work only with ferrous metals, then you can only get by with a compressor. Copper, titanium and brass require nitrogen, and occurs in a mixture of nitrogen and hydrogen. High alloy steels are cut in an argon atmosphere. In this case, the device is also designed for compressed gas.

Assembling the device

Due to the rather complex and numerous components of a plasma cutting machine, it is difficult to place it in a portable case or box. It is best to use a warehouse cart to transport goods. On it you can compactly place an inverter, cylinders or compressor, cable and hose group. It is very easy to move them within a workshop or workshop. If you need to travel to another site, everything can be loaded into a car trailer.

Increasingly, small private workshops and small enterprises use plasma metal cutting devices instead of grinders and other devices. Air plasma cutting allows you to perform high-quality straight and shaped cuts, align the edges of sheet metal, make openings and holes, including shaped ones, in metal workpieces and other more complex work. The quality of the resulting cut is simply excellent; it turns out smooth, clean, practically free of scale and burrs, and also neat. Air plasma cutting technology can process almost all metals, as well as non-conductive materials such as concrete, ceramic tiles, plastic and wood. All work is performed quickly, the workpiece is heated locally, only in the cutting area, so the metal of the workpiece does not change its geometry due to overheating. Even a beginner without welding experience can handle a plasma cutting machine or, as it is also called, a plasma cutter. But so that the result does not disappoint, it still does not hurt to study the device of a plasma cutter, understand its operating principle, and also study the technology of how to operate an air plasma cutting machine.

Design of an air plasma cutting machine

Knowledge of the design of a plasma cutter will allow you not only to carry out work more consciously, but also to create a home-made analogue, which requires not only more in-depth knowledge, but also preferably engineering experience.

An air plasma cutting machine consists of several elements, including:

Power supply;
Plasma torch;
Cable-hose package;
Air compressor.

Power supply for a plasma cutter, it serves to convert voltage and supply a certain current strength to the cutter/plasma torch, due to which an electric arc lights up. The power source can be a transformer or an inverter.

Plasma torch- the main element of an air plasma cutting machine, it is in it that the processes take place due to which plasma appears. The plasma torch consists of a nozzle, an electrode, a housing, an insulator between the nozzle and the electrode, and air channels. Elements such as the electrode and nozzle are consumables and require frequent replacement.

Electrode in the plasma torch it is the cathode and serves to excite the electric arc. The most common metal from which electrodes for plasmatrons are made is hafnium.

Nozzle has a cone-shaped shape, compresses the plasma and forms a plasma jet. Escaping from the nozzle exit channel, the plasma jet touches the workpiece and cuts it. The dimensions of the nozzle affect the characteristics of the plasma cutter, its capabilities and the technology of working with it. The most common nozzle diameter is 3 - 5 mm. The larger the diameter of the nozzle, the greater the volume of air per unit time it can pass through. The width of the cut depends on the amount of air, as well as the operating speed of the plasma cutter and the cooling rate of the plasma torch. The most common nozzle length is 9 - 12 mm. The longer the nozzle, the more accurate the cut. But a nozzle that is too long is more susceptible to destruction, so the optimal length is increased by a size equal to 1.3 - 1.5 times the nozzle diameter. It should be taken into account that each current value corresponds to the optimal nozzle size, which ensures stable arc burning and maximum cutting parameters. Reducing the nozzle diameter to less than 3 mm is not advisable, since the service life of the entire plasma torch is significantly reduced.

Compressor supplies compressed air to the plasmatron to form plasma. In air plasma cutting machines, air acts as both a plasma-forming gas and a protective gas. There are devices with a built-in compressor, as a rule, they are low-power, as well as devices with an external air compressor.

Cable-hose package consists of an electrical cable connecting the power source and the plasmatron, as well as a hose for supplying air from the compressor to the plasmatron. What exactly happens inside the plasma torch will be discussed below.

Operating principle of air plasma cutting machine

The air plasma cutting machine operates according to the principle described below. After pressing the ignition button, which is located on the handle of the plasma torch, high-frequency current begins to be supplied to the plasma torch from the power source. As a result, the pilot electric arc lights up. Due to the fact that the formation of an electric arc between the electrode and the workpiece directly is difficult, the nozzle tip acts as the anode. The temperature of the pilot arc is 6000 - 8000 °C, and the arc column fills the entire nozzle channel.

A couple of seconds after the pilot arc is ignited, compressed air begins to flow into the plasma torch chamber. It passes through a duty electric arc, is ionized, heated and increases in volume by 50 - 100 times. The shape of the plasma torch nozzle is narrowed downwards, due to which the air is compressed and a flow is formed from it, which escapes from the nozzle at a speed close to sound - 2 - 3 m/s. The temperature of the ionized heated air escaping from the nozzle outlet can reach 20,000 - 30,000 °C. The electrical conductivity of the air at this moment is approximately equal to the electrical conductivity of the metal being processed.

Plasma This is precisely what is called the heated ionized air escaping from the plasma torch nozzle. As soon as the plasma reaches the surface of the metal being processed, the working cutting arc, at this moment the pilot arc goes out. The cutting arc heats up the workpiece at the point of contact, locally, the metal begins to melt, and a cut appears. The molten metal flows onto the surface of the workpiece and solidifies in the form of drops and small particles, which are immediately blown away by the plasma flow. This method air plasma cutting is called a sharp plasma arc (direct arc), since the metal being processed is included in the electrical circuit and is the anode of the cutting arc.

In the case described above, the energy of one of the near-electrode arc spots, as well as the plasma of the column and the torch flowing from it, is used to cut the workpiece. Plasma arc cutting uses a direct current arc of straight polarity.

Plasma arc cutting of metal is used in the following cases: if it is necessary to produce parts with shaped contours from sheet metal, or to produce parts with straight contours, but so that the contours do not have to be processed additionally, for cutting pipes, strips and rods, for cutting holes and openings in details and more.

But there is also another method of plasma cutting - plasma jet cutting. In this case, the cutting arc lights up between the electrode (cathode) and the nozzle tip (anode), and the workpiece is not included in the electrical circuit. Part of the plasma is removed from the plasma torch in the form of a jet (indirect arc). Typically, this cutting method is used to work with non-metallic, non-conductive materials - concrete, ceramic tiles, plastic.

The air supply to the direct-acting and indirect-acting plasmatrons is carried out differently. Plasma arc cutting requires axial air supply (direct). And for cutting with a plasma jet you need tangential air supply.

Tangential or vortex (axial) air supply to the plasmatron is necessary to ensure that the cathode spot is located strictly in the center. If the tangential air supply is disrupted, the cathode spot will inevitably shift, and with it the plasma arc. As a result, the plasma arc does not burn stably, sometimes two arcs light up at the same time, and the entire plasma torch fails. Homemade air plasma cutting is not capable of providing a tangential air supply. Since to eliminate turbulence inside the plasma torch, specially shaped nozzles and liners are used.

Compressed air is used for air plasma cutting of the following metals:

Copper and copper alloys - no more than 60 mm thick;
Aluminum and aluminum alloys - up to 70 mm thick;
Steel up to 60 mm thick.

But air should absolutely not be used to cut titanium. We will consider in more detail the intricacies of working with a manual air plasma cutting machine below.

How to choose an air plasma cutting machine

To do right choice plasma cutter for private household needs or a small workshop, you need to know exactly for what purpose it will be used. What workpieces will you have to work with, from what material, what thickness, what is the load intensity of the machine and much more.

An inverter may well be suitable for a private workshop, since such devices have a more stable arc and a 30% higher efficiency. Transformers are suitable for working with workpieces of greater thickness and are not afraid of voltage surges, but at the same time they weigh more and are less economical.

The next gradation is plasma cutters of direct and indirect action. If you plan to cut only metal workpieces, then a direct-action machine is needed.

For a private workshop or home needs, it is necessary to purchase a manual plasma cutter with a built-in or external compressor, designed for a certain current.

Plasma cutter current and metal thickness

Current strength and maximum workpiece thickness are the main parameters for choosing an air plasma cutting machine. They are interconnected. The higher the current the power source of the plasma cutter can supply, the thicker the workpiece can be processed using this device.

When choosing a machine for personal needs, you need to know exactly how thick the workpiece will be processed and from what metal. The characteristics of plasma cutters indicate both the maximum current strength and the maximum metal thickness. But please note that the thickness of the metal is indicated based on the fact that ferrous metal will be processed, and not non-ferrous or stainless steel. And the current strength indicated is not the nominal, but the maximum; the device can operate at these parameters for a very short time.

Different metals require different amounts of current to cut. The exact parameters can be seen in the table below.

Table 1. Current required for cutting various metals.

For example, if you plan to cut a steel workpiece with a thickness of 2.5 mm, then a current strength of 10 A is required. And if the workpiece is made of non-ferrous metal, for example, copper 2.5 mm thick, then the current strength must be 15 A. In order for the cut to be of high quality , it is necessary to take into account a certain power reserve, so it is better to purchase a plasma cutter designed for a current of 20 A.

The price of an air plasma cutting machine directly depends on its power - the current output. The higher the current, the more expensive the device.

Operating mode - ON duration (DS)

The operating mode of the device is determined by the intensity of its load. All devices indicate a parameter such as on-time or duty cycle. What does it mean? For example, if PV = 35% is indicated, this means that the plasma cutter can be operated for 3.5 minutes, and then it must be allowed to cool for 6.5 minutes. The cycle duration is 10 minutes. There are devices with PV 40%, 45%, 50%, 60%, 80%, 100%. For domestic needs, where the device will not be used constantly, devices with a duty cycle of 35% to 50% are sufficient. For CNC machine cutting, plasma cutters with duty cycle = 100% are used, as they ensure continuous operation throughout the entire shift.

Please note that when working with manual air plasma cutting, there is a need to move the plasma torch or move to the other end of the workpiece. All these intervals count towards the cooling time. Also, the duration of activation depends on the load of the device. For example, from the beginning of a shift, even a plasma cutter with a duty cycle of 35% can work for 15 - 20 minutes without a break, but the more often it is used, the shorter the continuous operation time will be.

Do-it-yourself air plasma cutting - working technology

We have chosen the plasma cutter, familiarized ourselves with the principle of operation and the device, and it’s time to get to work. To avoid making mistakes, it won’t hurt to start by familiarizing yourself with the technology of working with an air plasma cutting machine. How to comply with all safety measures, how to prepare the device for work and select the correct current strength, and then how to ignite the arc and maintain the required distance between the nozzle and the surface of the workpiece.

Take care of your safety

Air plasma cutting involves a number of hazards: electric current, heat plasma, hot metal and ultraviolet radiation.

It is necessary to work in special equipment: dark glasses or a welder's shield (glass darkening class 4 - 5), thick gloves on your hands, thick fabric pants on your feet and closed shoes. When working with a cutter, gases can be generated that pose a threat to the normal functioning of the lungs, so you must wear a mask or respirator over your face.
The plasma cutter is connected to the network via an RCD.
Sockets, work stand or table, and surrounding objects must be well grounded.
Power cables must be in perfect condition and windings must not be damaged.

It goes without saying that the network must be designed for the voltage indicated on the device (220 V or 380 V). Otherwise, following safety precautions will help avoid injuries and occupational diseases.

Preparing the air plasma cutting machine for operation

How to connect all the elements of an air plasma cutting machine is described in detail in the instructions for the device, so let’s immediately move on to further nuances:

The device must be installed so that there is access to air. Cooling the plasma cutter body will allow you to work longer without interruption and less often turn off the device for cooling. The location should be such that drops of molten metal do not fall on the device.
The air compressor is connected to the plasma cutter through a moisture and oil separator. This is very important, since water or drops of oil that get into the plasma torch chamber can lead to failure of the entire plasma torch or even its explosion. The pressure of air supplied to the plasmatron must correspond to the parameters of the device. If the pressure is insufficient, the plasma arc will be unstable and will often go out. If the pressure is excessive, some elements of the plasma torch may become unusable.
If there is rust, scale or oil stains on the workpiece you are going to process, it is better to clean and remove them. Although air plasma cutting allows you to cut rusty parts, it is still better to play it safe, since when the rust is heated, toxic fumes are released. If you plan to cut containers in which flammable materials were stored, they must be thoroughly cleaned.

In order for the cut to be smooth, parallel, without scale and sagging, it is necessary to correctly select the current strength and cutting speed. The tables below show the optimal cutting parameters for various metals of various thicknesses.

Table 2. Force and cutting speed using an air plasma cutting machine for workpieces made of various metals.

At first it will be difficult to select the cutting speed; experience is required. Therefore, at first you can follow this rule: it is necessary to drive the plasma torch in such a way that sparks are visible from the back of the workpiece. If no sparks are visible, it means the workpiece is not cut all the way through. Please also note that moving the torch too slowly negatively affects the quality of the cut; scale and sagging appear on it, and the arc may burn unstably and even go out.

Now you can begin the cutting process itself.

Before igniting the electric arc, the plasma torch should be purged with air to remove any accidental condensation and foreign particles. To do this, press and then release the arc ignition button. So the device goes into purge mode. After about 30 seconds, you can press and hold the ignition button. As has already been described in the principle of operation of the plasma cutter, a pilot (auxiliary, pilot) arc will light up between the electrode and the nozzle tip. As a rule, it burns for no longer than 2 seconds. Therefore, during this time it is necessary to light the working (cutting) arc. The method depends on the type of plasmatron.

If the plasma torch is direct-acting, then it is necessary to make a short circuit: after the formation of a pilot arc, you must press the ignition button - the air supply stops and the contact closes. Then the air valve opens automatically, a stream of air escapes from the valve, ionizes, increases in size and removes a spark from the plasmatron nozzle. As a result, a working arc lights up between the electrode and the metal of the workpiece.

Important! Contact ignition of the arc does not mean that the plasma torch must be applied or leaned against the workpiece.

As soon as the cutting arc lights up, the pilot arc goes out. If you fail to ignite the working arc the first time, you must release the ignition button and press it again - a new cycle will begin. There are several reasons why the working arc may not ignite: insufficient air pressure, incorrect assembly of the plasma torch, or other problems.

During operation, there are also cases when the cutting arc goes out. The reason is most likely a worn electrode or failure to maintain the distance between the plasma torch and the surface of the workpiece.

Distance between plasmatron torch and metal

Manual air plasma cutting is fraught with the difficulty that it is necessary to maintain the distance between the torch/nozzle and the metal surface. When working with your hand, this is quite difficult, since even breathing confuses your hand, and the cut turns out uneven. The optimal distance between the nozzle and the workpiece is 1.6 - 3 mm; to maintain it, special distance stops are used, because the plasma torch itself cannot be pressed against the surface of the workpiece. The stops are placed on top of the nozzle, then the plasma torch is supported by the stop on the workpiece and the cut is made.

Please note that the plasma torch must be held strictly perpendicular to the workpiece. Permissible deviation angle 10 - 50 °. If the workpiece is too thin, the cutter can be held at a slight angle, this will avoid severe deformation of the thin metal. Molten metal should not fall on the nozzle.

It is quite possible to do the work with air plasma cutting yourself, but it is important to remember about safety precautions, as well as the fact that the nozzle and electrode are consumables that require timely replacement.