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Do-it-yourself plasma torch scheme drawings. Do-it-yourself plasma cutter from a welding inverter

Plasma cutting is actively used in many industrial areas. However, a plasma cutter is quite capable of being useful to a private master. The device allows you to cut any conductive and non-conductive materials with high speed and quality. The technology of work creates the possibility of processing any parts or creating curly cuts, which is carried out by a high-temperature plasma arc. The flow is created by the basic components - electric current and air. But the benefits of using the device are somewhat overshadowed by the price of factory models. To provide yourself with the opportunity to work, you can create a plasma cutter with your own hands. Next, we provide detailed instructions with the procedure and a list of equipment that is needed.

What to choose: transformer or inverter?

Due to the presence of features and parameters of devices for plasma cutting, it is possible to divide them into types. The most popular are inverters and transformers. The cost of the device of each model will be determined by the declared power and work cycles.

The inverters are lightweight, compact and consume minimal electricity. The disadvantages of the equipment include increased sensitivity to voltage drops. Not every inverter is able to function in the features of the mode of our electrical network. If the protection system of the device fails, then it is necessary to contact the service center. Also, inverter plasma cutters have a limitation in rated power - no more than 70 amperes and a short period of switching on equipment at high current.

The transformer is traditionally considered more reliable than the inverter. Even with a noticeable voltage drop, they lose only part of the power, but do not break. This property determines the higher cost. Plasma cutters based on a transformer can work and be included in the operating mode for a longer period. Such equipment is used in automatic lines with CNC. The negative point of the transformer plasma cutter will be a significant mass, high power consumption and dimensions.

The largest value of the thickness of the metal that the plasma cutter is capable of cutting is from 50 to 55 millimeters. The average power of the equipment is 150 - 180 A.

Average cost of factory devices

The range of plasma cutters for manual cutting of materials is now truly huge. Price categories are also different. The price of devices is determined by the following factors:

Device type;
Manufacturer and country of production;
Maximum possible cutting depth;
Model.

Having decided to study the possibility of buying a plasma cutter, you need to be interested in the cost of additional elements and components for equipment, without which it will be difficult to fully work. The average prices for devices, depending on the thickness of the metal being cut, are:

Up to 6 mm - 15,000 - 20,000 rubles;
Up to 10 mm - 20,000 - 25,000;
Up to 12 mm - 32,000 - 230,000;
Up to 17 mm - 45,000 - 270,000;
Up to 25 mm - 81,000 - 220,000;
Up to 30 mm - 150,000 - 300,000.

Popular devices are "Gorynych", "Resanta" IPR-25, IPR-40, IPR-40 K.

As you can see the price range is wide. In this regard, the relevance of a homemade plasma cutter is increasing. Having studied the instructions, it is quite possible to create an apparatus that is in no way inferior in terms of technical characteristics. You can pick up an inverter or transformer at a price significantly lower than the prices presented.

Operating principle

After pressing the ignition button, the source of electricity is started, supplying high-frequency current to the working tool. There is an arc (on duty) between the tip located in the cutter (plasma torch) and the electrode. Temperature range from 6 to 8 thousand degrees. It is worth noting that the working arc is not created instantly, there is a certain delay.

Then compressed air enters the cavity of the plasma torch. This is what the compressor is for. Passing through the chamber with a pilot arc on the electrode, it is heated and increases in volume. The process is accompanied by ionization of the air, which transforms it into a conductive state.

Through the narrow nozzle of the plasma torch, the resulting plasma flow is fed to the workpiece. The flow velocity is 2 - 3 m/s. Air in an ionized state can heat up to 30,000°C. In this state, the electrical conductivity of air is close to the conductivity of metal elements.

After the contact of the plasma with the surface being cut, the pilot arc is switched off and the working one starts to operate. Next, melting takes place at the cutting points, from which the molten metal is blown by the supplied air.

Differences between direct and indirect devices

There are various types of devices that differ in the principles of operation. In direct action equipment, an electric arc is expected to work. It acquires a cylindrical shape and is directly connected to the gas jet. Such a design of the equipment makes it possible to provide a high arc temperature (up to 20,000°C) and a highly efficient cooling system for other components of the plasma cutter.

In devices of indirect action, work is expected with a lower efficiency. This determines their lesser distribution in production. The design feature of the equipment is that the active points of the circuit are placed on special tungsten electrodes or a pipe. They are used more often for heating and spraying, but they are practically not used for cutting. Most often used in car repairs.

A common feature is the presence of an air filter in the design (prolongs the life of the electrode, provides quick start-up of the equipment) and a cooler (creates conditions for long-term operation of the device without interruption). An excellent indicator is the possibility of continuous operation of the device for 1 hour with a 20-minute break.

Design

With due desire and skill, a homemade plasma cutter can be created by anyone. But in order for it to fully and effectively function, certain rules must be observed. It is advisable to try on the inverter, because. it is he who is able to provide a stable current supply and stable operation of the arc. As a result, there are no interruptions and the consumption of electricity is significantly reduced. But it is worth considering that an inverter-based plasma cutter is able to cope with a thinner metal thickness than a transformer.

Required accessories

Before starting assembly work, it is necessary to prepare a number of components, materials and equipment:

Inverter or transformer with suitable capacity. To eliminate the error, it is necessary to determine the planned cutting thickness. Based on this information, select the desired device. However, taking into account manual cutting, it is worth choosing an inverter, because. it weighs less and consumes less electricity.
Plasma torch or plasma cutter. It also has its own choices. It is better to choose direct action for working with conductive materials, and indirect action for non-conductive materials.
Compressed air compressor. It is required to pay attention to the rated power, because it must cope with the load imposed and comply with the rest of the components.
Cable-hose. Required to connect all components of the plasma cutter and supply air to the plasma torch.

Selection of a power supply

The plasma cutter is powered by a power supply. It generates the specified parameters of electric current, voltage and supplies them to the cutting unit. The main supply node can be:

inverter;
Transformer.

It is necessary to approach the choice of a power supply element, taking into account the features of the devices described above.

Plasmatron

The plasma torch is a plasma generator. This is a working tool in which a plasma jet is formed that directly cuts materials.

The main features of the device are:

Creation of ultra-high temperature;
Easy adjustment of current power, start and stop working modes;
Compact dimensions;
Work reliability.

Structurally, the plasma torch consists of:

Electrode/cathode containing zirconium or hafnium. These metals are distinguished by a high level of thermionic emission;
The nozzle is mainly insulated from the electrode;
A mechanism that swirls the plasma gas.

Nozzle, electrode are consumables of the plasma torch. If a workpiece up to 10 millimeters is processed with a plasma cutter, then one set of electrodes is consumed within 8 hours of operation. Wear occurs evenly, which allows you to change them at the same time.

If the electrode is not replaced in time, the quality of the cut may be impaired - the geometry of the cut changes or waves appear on the surface. The hafnium insert gradually burns out in the cathode. If it has a production of more than 2 millimeters, then the electrode can burn and overheat the plasma torch. This means that electrodes that are not replaced in time will lead to a quick failure of the remaining elements of the working tool.

All plasma torches can be divided into 3 volume groups:

Electric arc - has at least one anode and a cathode, which are connected to a DC power source;
High-frequency - there are no electrodes and cathodes. Communication with the power supply is based on inductive/capacitive principles;
Combined - operates when exposed to high-frequency current and burning arc discharges.

Based on the method of arc stabilization, all plasma torches can also be divided into gas, water and magnetic types. Such a system is extremely important for the operation of the tool, because. it forms the compression of the flow and fixes it on the central axis of the nozzle.

Currently, there are various modifications of plasma torches on sale. It may be necessary to study the offers, and buy ready-made. However, it is quite possible to make homemade at home. This requires:

Lever. It is necessary to provide holes for wires.
Button.
Appropriate electrode, rated for current.
Insulator.
Flow swirler.
Nozzle. Preferably a kit with different diameters.
Tip. Splash protection must be provided.
remote spring. Allows you to maintain the gap between the surface and the nozzle.
Nozzle for removal of a deposit and chamfering.

It is possible to carry out work with one plasma torch due to interchangeable heads with different diameters, directing the plasma flow to the part. It should be noted that they, like the electrodes, will melt during operation.

The nozzle is fixed with a clamping nut. Directly behind it is an electrode and an insulator that prevents the ignition of the arc in the wrong place. Next, a flow swirler is placed to enhance the arc effect. All elements are placed in a fluoroplastic housing. Some things you can do yourself, and some you will have to buy in the store.

The factory plasma torch will allow to work without overheating for a longer time due to the air cooling system. However, for short-term cutting, this is an unimportant parameter.

Oscillator

An oscillator is a generator that generates a high frequency current. A similar element is included in the plasma cutter circuit between the power source and the plasma torch. Able to act according to one of the schemes:

Creation of a short-term impulse, which contributes to the occurrence of an arc without touching the surface of the product. Outwardly, it is a small lightning supplied from the end of the electrode.
Constant voltage support with a high voltage value superimposed on the welding current. Ensures the safety of stable maintenance of the arc.

The equipment allows you to quickly create an arc and start cutting metal.

For the most part, they have a similar structure and consist of:

Voltage rectifier;
Charge storage unit (capacitors);
Power unit;
Impulse generation module. Includes an oscillatory circuit and a spark gap;
Control block;
step-up transformer;
Voltage control device.

The main task is to upgrade the input voltage. There is an increase in frequency and voltage level, reducing the period of action to less than 1 second. The sequence of work is as follows:

The button on the cutter is pressed;
In the rectifier, the current levels out and becomes unidirectional;
Capacitors store charge;
The current is supplied to the oscillatory circuit of the transformer windings, increasing the voltage level;
The impulse is controlled by the control circuit;
The impulse creates a discharge on the electrode, igniting the arc;
The action of the impulse ends;
After cutting is stopped by the oscillator, the plasma torch is purged for another 4 seconds. Due to this, cooling of the electrode and the treated surface is achieved.

Depending on the type of oscillator, it can be used in different ways. However, a common characteristic is the increase in voltage to 3000 - 5000 volts and frequency from 150 to 500 kHz. The main differences are in the intervals of action of high-frequency current.

For use in a plasma cutter, it is advisable to use an oscillator for non-contact ignition of the arc. Similar elements are used to work in argon welders. In them, tungsten electrodes will quickly become dull if they make contact with the product. The inclusion of an oscillator in the circuit of the apparatus will allow creating an arc without making contact with the plane of the part.

The use of an oscillator can significantly reduce the need for expensive consumables and improve the cutting process. Properly selected equipment in accordance with the planned work can improve its quality and speed.

electrodes

Electrodes play an important role in the process of creating, maintaining the arc and direct cutting. The composition contains metals that allow the electrode not to overheat and not prematurely collapse when working with an arc in high-temperature conditions.

When buying electrodes for a plasma cutter, it is necessary to clarify their composition. With the content of beryllium and thorium, harmful vapors are created. They are suitable for work in appropriate conditions, with proper protection of the worker, i.e. additional ventilation is required. Because of this, for the application in everyday life it is better to buy hafnium electrodes.

Compressor and cable - hoses

The design of most homemade plasma cutters includes compressors and hose routes to direct air to the plasma torch. This structural element allows heating the electric arc up to 8000°C. An additional function is to purge the working channels, cleaning them from dirt and removing condensate. In addition, compressed air contributes to the cooling of the components of the apparatus during prolonged operation.

A conventional compressed air compressor can be used to operate the plasma cutter. Air exchange is carried out by thin hoses with suitable connectors. An electric valve is placed at the inlet, which regulates the process of air supply.

An electric cable is placed in the channel from the apparatus to the burner. Therefore, it is necessary to place a hose with a large diameter in which the cable can be accommodated. The passing air also has a ventilation function, as it is able to cool the wire.

The ground must be made from a cable with a cross section of 5 mm2 or more. There must be a clamp. If the ground contact is poor, switching the working arc to the standby one will be problematic.

Scheme

Now you can find many schemes by which you can assemble a high-quality device. The video will help you understand the conventions in detail. A suitable principal drawing of the equipment can be selected from the following.

Assembly

Before starting the assembly process, it is desirable to clarify the compatibility of the selected components. If you have not previously had to assemble a plasma cutter with your own hands, then you need to consult with experienced craftsmen.

The assembly procedure assumes the following sequence:

Prepare all assembled components;
Assembly of an electrical circuit. In accordance with the diagram, an inverter / transformer, an electric cable are connected;
Connection of the compressor and air supply to the apparatus and plasma torch using flexible hoses;
For your own safety net, you can use an uninterruptible power supply (UPS), given the capacity of the battery.

Detailed equipment assembly technology is presented in the video.

Checking the plasma cutter

After all nodes are connected into a single structure, it is necessary to test for operability.

Please note that checking and working with a plasma cutter should be carried out in protective clothing using personal protective equipment.

It is necessary to turn on all the units and press the button on the plasma torch, supplying electricity to the electrode. At this moment, an arc with a high temperature should form in the plasma torch, slipping between the electrode and the nozzle.

If the assembled plasma cutting equipment is capable of cutting metal up to 2 cm thick, then everything is done correctly. It should be noted that a home-made apparatus from an inverter will not be able to cut parts with a thickness of more than 20 millimeters, since there is not enough power. For cutting thick products, you will need to use a transformer as a power source.

Advantages of a homemade device

The benefits provided by the air-plasma cutting machine are difficult to overestimate. It is able to accurately cut sheet metal. After work, it is not required to additionally process the ends. The main advantage is the reduction in working time.

These are already weighty arguments for self-assembly of equipment. The circuit is not complicated, so it is cheap to remake an inverter or a semiautomatic device for everyone.

In conclusion, let's pay attention to the fact that it is necessary for an experienced specialist to work with a plasma cutter. Best if it's a welder. If there is little experience, then we recommend that you first study the technology of working with photos and videos, and then proceed with the tasks.

Increasingly, in small private workshops and small enterprises, plasma cutting machines are used instead of grinders and other devices. Air-plasma cutting allows you to perform high-quality straight and figured cuts, align the edges of sheet metal, make openings and holes, including figured ones, in metal blanks and other more complex work. The quality of the resulting cut is simply excellent, it turns out to be even, 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, plastics and wood. All work is carried out quickly, the workpiece is heated locally, only in the cut area, so the workpiece metal 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 plasma cutter device, understand its principle of operation, and also study the technology of how to work with an air-plasma cutting machine.

The device of the air-plasma cutting machine

Knowledge of the plasma cutter device will allow not only to work more consciously, but also to create a home-made analogue, which requires not only deeper knowledge, but also engineering experience is desirable.

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

Power supply;
Plasmatron;
Cable-hose package;
Air compressor.

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

Plasmatron- the main element of the air-plasma cutting machine, it is in it that the processes occur, due to which the plasma appears. The plasma torch consists of a nozzle, an electrode, a housing, an insulator between the nozzle and the electrode, and air channels. Items 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 plasma torches are made is hafnium.

Nozzle has a conical shape, compresses the plasma and forms a plasma jet. Escaping from the outlet channel of the nozzle, 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 itself. The width of the cut, as well as the speed of the plasma cutter and the cooling rate of the plasma torch, depend on the amount of air. 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 prone to destruction, so the length is optimally increased by a size equal to 1.3 - 1.5 of the nozzle diameter. It should be taken into account that each current value corresponds to the optimal nozzle size, which ensures stable arcing and maximum cutting parameters. It is not advisable to reduce the nozzle diameter and make it less than 3 mm, since the resource of the entire plasma torch is significantly reduced.

Compressor supplies compressed air to the plasma torch for the formation of 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 electric cable connecting the power source and the plasma torch, as well as a hose for supplying air from the compressor to the plasma torch. What exactly happens inside the plasma torch, we will consider below.

The principle of operation of the 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, a high-frequency current is supplied from the power source to the plasma torch. As a result, a standby electric arc lights up. Due to the fact that the formation of an electric arc between the electrode and the workpiece is directly 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 ignition of the pilot arc, compressed air begins to flow into the plasma torch chamber. It passes through the standby electric arc, ionizes, heats up and increases in volume by 50 - 100 times. The shape of the plasma torch nozzle is narrowed down, due to which the air is compressed, a stream is formed from it, which breaks out of the nozzle at a speed close to sonic - 2 - 3 m / s. The temperature of the ionized heated air escaping from the outlet of the nozzle 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 just called the heated ionized air escaping from the nozzle of the plasma torch. As soon as the plasma reaches the surface of the metal being processed, the working cutting arc is ignited, at this moment the pilot arc goes out. The cutting arc heats the workpiece at the point of contact, locally, the metal begins to melt, a cut appears. The molten metal flows to 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 of 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 workpiece is cut using the energy of one of the near-electrode spots of the arc, as well as the plasma of the column and the torch flowing from it. Plasma arc cutting uses a direct current arc of direct polarity.

Plasma-arc cutting of metal is used in such cases: if it is necessary to produce parts with curly contours from sheet metal, or to produce parts with straight contours, but so that it is not necessary to process the contours additionally, for cutting pipes, strips and rods, for cutting holes and openings in details and more.

But there is also another way of plasma cutting - plasma jet cutting. In this case, the cutting arc ignites between the electrode (cathode) and the nozzle tip (anode), and the workpiece is not included in the electrical circuit.. Part of the plasma is taken out of 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 plasma torch of direct action and indirect action is performed in different ways. Plasma arc cutting requires axial air supply (direct). And for plasma jet cutting, tangential air supply.

Tangential or vortex (axial) air supply to the plasma torch is necessary to ensure that the cathode spot is located strictly in the center. If the tangential air supply is disturbed, the displacement of the cathode spot is inevitable, and with it the plasma arc. As a result, the plasma arc does not burn stably, sometimes two arcs ignite simultaneously, and the entire plasma torch fails. Homemade air plasma cutting is not able to provide tangential air supply. Since to eliminate turbulences inside the plasma torch, nozzles of a special shape, as well as liners, are used.

Compressed air is used for air-plasma cutting of such 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 it is absolutely impossible to use air for cutting titanium. We will consider in more detail the subtleties of working with a manual air-plasma cutting machine below.

How to choose an air plasma cutting machine

To make the right choice of a plasma cutter for private household needs or a small workshop, you need to know exactly for what purposes it will be used. What blanks will you have to work with, what material, what thickness, what is the intensity of loading the device and much more.

For a private workshop, an inverter may well fit, 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 drops, 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 blanks, then you need a direct-acting device.

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 strength.

Plasma cutter current and metal thickness

The current strength and the maximum thickness of the workpiece are the main parameters for choosing an air-plasma cutting machine. They are interconnected. The more current the plasma cutter power supply can supply, the thicker the workpiece can be processed with this machine.

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

Cutting different metals requires different amperages. 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 2.5 mm thick, then a current 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 should be 15 A. To make a high quality cut , 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 output current. The greater the current, the more expensive the device.

Operating mode - duty cycle (PV)

The operating mode of the apparatus is determined by the intensity of its loading. On all devices, such a parameter as the duration of inclusion or duty cycle is indicated. What does she mean? For example, if PV = 35% is indicated, then 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 duty cycle is designed for 10 minutes. There are devices with PV 40%, 45%, 50%, 60%, 80%, 100%. For household needs, where the device will not be used constantly, devices with PV from 35% to 50% are sufficient. For CNC machine cutting, plasma cutters with duty cycle = 100% are used, as they provide continuous operation throughout the entire shift.

Please note that in the process of 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 are counted towards the cooling time. Also, the duration of the inclusion depends on the load of the device. For example, from the beginning of the shift, even a plasma cutter with PV = 35% can work without interruption for 15 - 20 minutes, but the more often it is used, the shorter the time of continuous operation will be.

Do-it-yourself air-plasma cutting - work technology

We chose a plasma cutter, familiarized ourselves with the principle of operation and the device, it's time to get to work. In order not to make mistakes, for starters, it does not hurt to get acquainted with the technology of working with an air-plasma cutting machine. How to comply with all safety measures, how to prepare the device for operation and choose the right current strength, and then how to ignite the arc and maintain the necessary distance between the nozzle and the surface of the workpiece.

Take care of safety

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

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

The fact that the network must be designed for the voltage indicated on the device (220 V or 380 V) is a matter of course. Otherwise, compliance with safety precautions will help to avoid injuries and occupational diseases.

Preparing the air plasma cutting machine for operation

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

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

In order for the cut to turn out to be even, 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. The force and speed of cutting with the help of an air-plasma cutting machine for workpieces from various metals.

At first, it will be difficult to select the cutting speed, experience is required. Therefore, at first, you can focus on the following rule: it is necessary to guide the plasma torch in such a way that sparks are visible on the reverse side of the workpiece. If sparks are not visible, then the workpiece is not cut through. Also note that too slow a torch lead will negatively affect the quality of the cut, dross and sagging will appear on it, and the arc may burn unstable and even go out.

Now you can start the cutting process itself.

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

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

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 it was not possible to ignite the working arc the first time, it is necessary to 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 malfunctions.

In the process of work, there are also cases when the cutting arc goes out. The reason, most likely, is the wear of the electrode or the non-observance of the distance between the plasma torch and the surface of the workpiece.

Distance between plasma torch and metal

Handheld air plasma cutting is fraught with the difficulty that the distance between the torch/nozzle and the metal surface must be maintained. When working with your hand, this is quite difficult, since even breathing knocks your hand, and the cut is uneven. The optimal distance between the nozzle and the workpiece is 1.6 - 3 mm; special distance stops are used to maintain it, because the plasma torch itself cannot be pressed against the surface of the workpiece. The stops are put on top of the nozzle, then the plasma torch rests on the workpiece with the stop and the cut is performed.

Please note that it is necessary to keep the plasma torch strictly perpendicular to the workpiece. Permissible deflection angle 10 - 50 °. If the workpiece is too thin, then the cutter can be held at a slight angle, this will avoid strong deformations of thin metal. Molten metal should not fall on the nozzle.

Do-it-yourself work with air-plasma cutting can be done on your own, it is only important to remember safety precautions, as well as the fact that the nozzle and electrode are consumables that require timely replacement.

Plasma cutting is a fairly popular operation, especially when it comes to cutting thick metal parts or blanks. The process is fast, the edges of the metal remain smooth. But such a device is not cheap. Therefore, many craftsmen make a plasma cutter for themselves with their own hands from different types of equipment, combining them into one design. Their connection scheme is simple, the main thing is to choose the right devices according to the necessary technical characteristics.

Plasma cutting is based on ionized gas, which flies out of the torch nozzle at high speed. This gas is the same plasma. What is she doing.

In fact, this ionized medium is an excellent conductor of electric current, which flows from the electrode to the metal workpiece.
The plasma heats the metal to the required temperature.
It also blows off the molten metal, freeing up the cutting space.

This means that in order to create a plasma, a gas and a source of electricity are needed. And these two components must be connected in one place. Therefore, plasma cutting equipment consists of a gas cylinder, a high-power electric power source, and a torch in which an electrode is installed.

The design of the cutter is made in such a way that gas passes around the electrode and, in the form heated from the electrode, bursts out through a small hole. The small diameter of the hole and the gas pressure create the required plasma velocity. When making homemade plasma cutting, you just need to purchase a ready-made cutter and not think about creating it. Because everything is already thought out in it, plus the factory version is a guarantee of safety.

As for gas, all options have long been abandoned, leaving compressed air. You can get it today very simply - purchase and install a compressor.

There are certain conditions that guarantee the quality of plasma cutting.

The current on the electrode should not be less than 250 A.
Compressed air must be supplied to the torch at a speed within 800 m/s.

How to make a plasma cutter with your own hands

The basics of plasma cutting are clear, the design of the plasma cutter is also clear, you can start assembling it. By the way, this does not require special drawings.

So what will be needed.

We need to find a source of electricity. The simplest option is a welding transformer or inverter. For many reasons, an inverter is better. For example, it has a stable current value, without drops. It is more economical in terms of electricity consumption. You will have to pay attention to the current that the welding machine produces. Its value should not be less than 250 amperes.
Source of compressed air. Here, the compressor is unchanged. But what? The main parameter is air pressure. It will be necessary to pay attention to it. 2.0-2.5 atm. - will be fine.
The cutter can be purchased at the store. And that would be the perfect solution. If there is a cutter for argon welding, then it can also be converted to plasma cutting. To do this, you will have to make a nozzle in the form of a nozzle from copper, which is inserted into the argon welding cutter.
A set of hoses and cables for connecting all parts of a homemade plasma cutter. Again, the kit can be purchased at the store as a single connecting element.

Here are four elements with which a homemade plasma cutter is assembled.

Auxiliary elements and materials

What else you need to pay attention to when assembling a plasma cutting machine with your own hands. As mentioned above, the main characteristic of a plasma cutter is the diameter of its hole. What size should it be in order for the quality of the cut to be maximum. Experts believe that a diameter of 30 mm is the optimal size. Therefore, when buying a cutter in a store, you need to pay attention to whether there is a nozzle with such a hole in its kit.

In addition, it is necessary to select a nozzle with a significant length. It is this size that allows the jet of compressed air to gain the required speed. From what the metal cut turns out to be neat, and the cutting process itself is quick and easy. But you should not buy a nozzle that is too long. Such a device is quickly destroyed under the influence of high temperatures.

As for the choice of an electrode for a plasma cutter, then it is necessary to pay attention to the alloy from which it is made. For example, if beryllium is included in the alloy, then this is a radioactive substance. It is not recommended to work with such electrodes for a long time. If thorium is included in the alloy, then at high temperatures it releases toxic substances. The ideal electrode for plasma cutting, which alloy contains hafnium.

Checking the plasma cutter

So, the hoses connect the cutter and the compressor, the cable cutter and the inverter. Now you need to check if the assembled structure works. All units are turned on, the button for supplying electricity to the electrode is pressed on the cutter. In this case, an arc is formed with a temperature of 6000-8000C. It slips between the metal of the electrode and the nozzle.

After that, compressed air begins to flow into the cutter. Passing through the nozzle and heating up from the electric arc, it expands sharply tenfold and at the same time acquires conductive properties. That is, an ionized gas is obtained.

It passes through a narrowed nozzle, while acquiring a speed in the range of 2-3 m/s. But the plasma temperature rises to 25000-30000C. The most important thing is that the arc, with which the compressed air was heated and turned into plasma, goes out as soon as the plasma begins to act on the metal workpiece prepared for cutting. But then the second, so-called working arc, which acts locally on the metal, turns on. Right in the cut zone. Therefore, the metal is cut only in this zone.

If, when checking the operation of a plasma cutter, you managed to cut metal with a thickness of at least 20 mm, then all the elements of the new design, assembled by yourself, were selected correctly. It should be noted that the plasma cutter from the inverter does not cut workpieces with a thickness of more than 20 mm. It just doesn't have enough power. To cut thicker metal, you will have to use a transformer.

Attention! Any work related to the use of plasma cutting must be carried out in protective clothing and gloves.

There are many points that necessarily affect the operation of the unit.

There is no need to purchase, for example, a large compressor. But 2-2.5 atmospheres with a large amount of work may not be enough. The way out is to install a receiver on the compressor. It works like an accumulator that accumulates pressure in compressed air. For this case, you can adapt, for example, bolts from the brake system of heavy vehicles. The option is really simple. The volume of the balloon is large, and it should be enough for a long period of time.
In order for the air pressure to be stable and the same, a reducer must be installed at the outlet of the receiver.
Of course, the best solution is to purchase a compressor complete with a receiver. It costs more than usual, but if this unit is used for other things, for example, for painting, then you can increase its functionality and thereby cover the costs.
To make a mobile version of the machine, you can make a small trolley. After all, all the elements of the plasma cutter are small-sized devices. Of course, you will have to forget about mobility if the machine is made on the basis of a welding transformer. It's too big and heavy.
If it is not possible to buy a ready-made hose-cable kit, then you can make it yourself. It is necessary to combine the welding cable and the high pressure hose into one sleeve and place them in a single sheath. For example, in a regular hose of a larger diameter. A kit made in this way simply will not get in the way, which is very important when cutting metals.

Making your own plasma cutter is not difficult at all. Of course, you will need to get the necessary information, study it, it is definitely recommended to watch the training video. And after that, correctly select all the elements exactly for the required parameters. By the way, the assembled plasma cutter based on a serial inverter makes it possible not only to carry out plasma cutting of metals, but also plasma welding, which increases the functionality of the unit.

Until recently, when at home there was a need to cut metal blanks for various needs, the home master did not have a very large choice. Either an angle grinder (angle grinder, in the common people "Bulgarian"), or a gas cutter.

But progress does not stand still, and relatively recently a fundamentally different tool for cutting metal, more efficient and easy to use, has become available to the masses. We are talking about or, as it is sometimes called, a plasma cutter. Considering the high cost of home-made factory-made plasma cutters, it seems quite rational to try to assemble this device at home. And in order to verify the feasibility of this idea, you can compare the technological features of the work performed using the above devices.

Homemade plasma cutter

Assembling a plasma cutter at home is very similar to assembling a designer. The fact is that without exception, all the constituent elements of a plasma cutter are quite complex technological products. Making these elements at home from scratch not only requires very deep knowledge in this subject and the corresponding expensive equipment, but is also unsafe in terms of the health of the home master.

For example, the temperature inside the combustion chamber of a plasma torch is about 20,000–30,000 degrees. Therefore, it is better to buy the elements that make up the plasma cutter, ready-made, with a guarantee of high reliability, than trying to make houses from improvised means and thereby endangering not only your life, but also the lives of your loved ones.

Those who understand nothing at all in metalworking need to know at least elementary things, for example, that a laser cutter for metal and a plasma cutter for metal are not the same thing.

Constituent elements

Any plasma cutter consists of the following elements:

Inverter or transformer

Both have both positive and negative sides. Ultimately, the choice is made in favor of a specific device based on the technical tasks that are set for the future plasma cutter.

Welding inverter-semiautomatic

The most optimal solution for a personal garage or a small workshop.

welding transformer

More suitable for stationary conditions of large workshops or factories.

Based on these comparative characteristics, home craftsmen most often lean towards a plasma cutter from an inverter assembled with their own hands based on a welding inverter.

Plasma torch or cutter

The main components of the plasma cutter are: two electrodes, an insulator separating the cathode and anode units, and a gas mixture swirl chamber.

The principle of operation of the plasma torch

Under pressure, the gas enters the space between the nozzle and the electrode. At the moment the oscillator is turned on, as a result of the occurrence of a high-frequency pulsed current, an electric arc occurs between the two electrodes. This arc is called preliminary, and its task is to heat up the gas in the combustion chamber. The temperature of the heated gas in the chamber is relatively low - about 5000−7000 degrees.

After the preliminary arc fills the entire nozzle, with the help of a compressor, the pressure of the supplied compressed air is increased, as a result, gas ionization begins to occur. As a consequence of this, the gas expands in volume, becomes superconductive and heats up to prohibitively high temperatures of the order of 20,000-30,000 degrees. In other words, gas turns into plasma.

Under high pressure, the plasma escapes through a narrow nozzle opening to the outside. At the moment of contact of the plasma flow with the metal surface, a second arc arises - the main, or classical. The role of the second electrode in this case is assumed by the plasma itself. The plasma arc instantly melts the metal at the point of contact. Under a strong pressure of compressed air, the molten metal is instantly blown out, and the result is a clean cut.

There are two basic conditions under which high-quality plasma cutting is obtained:

The current supplied to the electrode must be at least 250 A.
Compressed air is supplied to the combustion chamber at a speed of at least 800–900 m/s.

The complexity of manufacturing a plasma torch

Diagrams, drawings for making a plasma cutter with your own hands are very easy to find on the Internet. But the plasma cutter is very complex and, in addition, requires very fine adjustments before direct operation. Despite the abundance of relevant recommendations, drawings and videos on the Internet, it is technically extremely difficult to make a plasma torch at home. And given that this idea is also extremely dangerous for health, it is better to completely abandon it and use the services of Ali Express or the nearest specialized store.

Assembly from prefabricated components

It is necessary to connect the plasma cutter nozzle to the inverter and compressor. This is done by means of a so-called cable-hose package. It would be optimal to use special clamps and clamps for these purposes, which are easily fixed and also easily removed.

Before assembly begins, you must finally make sure that all components are compatible.

The assembly order is quite simple:

The inverter is connected to the plasma cutter electrode by means of an electric cable.
The compressor is connected to the working chamber of the plasma cutter using a special hose.

Even when assembled from ready-made components, the price of the final product will be several orders of magnitude less than if you buy a ready-made plasma cutter. After the device is assembled and the machine is ready to work, you need to take care of consumables and some aspects of operating the device.

You can learn how to choose a plasma cutter.

You can learn how to choose a plasma cutter.

In organizations whose work is related to non-ferrous types of metals, one cannot do without such a device as a plasma cutter. In domestic conditions, this tool is also often applicable, and it is not necessary to buy a ready-made tool, because you can make a plasma cutter with your own hands from an inverter.

About the work of the plasma cutter

It will be possible to make a welding fixture with high efficiency only if a person understands the welding process and the rules for operating all mechanisms. The action of the tool is based on the following:

voltage is supplied to the plasma torch through the cables, which creates a current source;
an arc is electrified between the cathode and anode located in the burner;
a stream of air passes through the screwed channels under a certain pressure, which increases the temperature of the electric arc, directing it outward;
in some cases, a liquid is used for this, which, when evaporated, forms an outlet pressure, and a high-temperature flame acts as a plasma;
the plasma cutter enters the active phase due to the supply of mass by an electric wire, which contributes to closing the arc in the section being cut;
during welding, argon or other inert mixtures are used.

A jet of air can raise the temperature of the arc over 7 thousand degrees, and the welder can quickly heat up the desired area of \u200b\u200bmetal in a pointwise manner.

Power supply

Homemade plasma cutter should start designing with a search for a current generator. As such, a familiar inverter can serve, the cost of which will be much less than ordinary cutting equipment. The big plus of his work is the high-frequency stable voltage, due to which the arc will burn constantly, providing a first-class cut.

The convenience of the welding inverter is also in its dimensions, which allows for on-site manipulations with a plasma cutter. Mandatory conditions for the operation of a welding plasma cutter are:

mains supply 220 V;
work productivity - 4 kW;
idling - 220 V;
with a 10-minute cycle of operation, the design mode of operation is 60%;
width of current stabilization - from 20 to 40 A.

You can also use an AC welding transformer, but it is better to use an inverter machine with argon welding.

Features of the plasma cutter circuit

There are various drawings and video tutorials for the manufacture of welding plasma cutters. To get the right, and, most importantly, a working unit, you need the skills and ability to understand the schematic material and drawings. To convert an existing welding inverter into a homemade plasma cutter, you need to add an oscillator to the electrical circuit of the device.

The circuit works like this:

There is a start button on the torch, by pressing it, voltage is applied to the control section.
The relay provides air supply for cleaning the plasma torch, freeing its chamber from condensate in a couple of seconds.
The oscillator ionizes the area between the nozzle and the electrode, causing the arc to ignite.
A plasma torch is directed to the product and the working arc is ignited.
The reed relay switches off the nozzle and ignition.

Do-it-yourself plasma torch assembly

To construct a plasma cutter from an inverter, you will need to purchase all related parts and prepare tools. The main components are:

compressor;
plasma torch;
electrodes;
nozzle;
flow swirler;
insulator;
shutter button;
handle with holes for cables;
cable-hose;
distance spring to ensure the same gap between the nozzle and the metal.

First, you need to attach a hose to the welding inverter, which is the air conductor from the compressor. The mass cable and the hose package are mounted on the front side, and the plasma torch is connected to the hose package. The burner nozzle must be attached with a clamping nut. Behind the plasma cutter is an electrode and an insulating sleeve that prevents arcing in an undesirable area.

The flow swirler directs it to the target, and the entire structure is placed in a metal or fluoroplastic housing. After assembling the welding plasma cutter, you need to check the unit for operability. When switched on, the inverter supplies high-frequency current to the plasma torch.

Applicable electrodes

Electrodes occupy a significant place in the assembly of the inverter plasma cutter. In the plasma torch, you need to select a special electrode from the appropriate material. For these purposes, parts from the following refractory substances are used:

Beryllium.
Zirconium.
Thorium.
Hafnium.

These electrodes are characterized by the ability to create a refractory oxide film during heating, which protects the instruments from damage and increases the level of protection. If you choose between these materials, then for domestic welding it is optimal to stop at hafnium and zirconium electrodes, because the other two elements produce toxic fumes.

About cable hoses and compressor

An important part of the welding plasma cutter from the inverter is the compressor, which allows the electric arc to warm up to 8 thousand degrees and is responsible for the cutting process itself. The function of the compressor also includes blowing the plasma torch and the channels of the unit, due to which debris and condensate are removed. Compressed air passing through the burner cools the working units.

For a welding plasma cutter, an ordinary compressor used during painting with a spray gun is suitable. It is connected to the equipment using a thin hose with an appropriate connector. At the inlet, you need to attach an electrovalve that is responsible for regulating the air supply. The compressor at the outlet must have a reducer to obtain a normalized pressure on the plasma torch.

The hose from the compressor to the burner and the cable from the inverter are laid in one corrugated hose, due to which the cable can be cooled during overheating, and also make work more convenient. The copper wire must have a cross section of 5–6 mm2, and the clamp at the output must guarantee safe contact with the inverter part.

A do-it-yourself plasma cutter from a welding inverter is an achievable goal. It will be faster to achieve it with the help of technical recommendations and a stock of necessary parts and tools.