How to make a plasma cutter from a welding inverter. The principle of operation of a plasma cutter. Incorrect plasma cutter assembly

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 problems 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 the correct shape. 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 plasma torch 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 carried out with a current of 250 Amperes, while the speed of the air stream 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 is widely used in various industries: mechanical engineering, shipbuilding, advertising, utilities, metal structures and other industries. In addition, a plasma cutter can also be useful in a private workshop. After all, with the help of it you can quickly and efficiently cut any conductive material, as well as some non-conductive materials - plastic, stone and wood. You can cut pipes, sheet metal, make a shaped cut or make a part simply, quickly and conveniently using plasma cutting technology. The cut is performed using a high-temperature plasma arc, which requires only a power source, a torch and air to create. To make working with a plasma cutter easy and the cut to be beautiful and smooth, it doesn’t hurt to learn the operating principle of a plasma cutter, which will give you a basic understanding of how you can control the cutting process.

A device called a “plasma cutter” consists of several elements: power supply, plasma cutter/plasma torch, air compressor And cable-hose package.

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

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

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

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

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

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

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

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

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

Cable-hose package connects the power source, compressor and plasmatron. The electric cable supplies current from a transformer or inverter to initiate an electric arc, and the hose carries compressed air, which is necessary for the formation of plasma inside the plasma torch. We will describe in more detail what exactly happens in the plasmatron below.

As soon as the ignition button is pressed, the power source (transformer or inverter) begins to supply high-frequency currents to the plasmatron. As a result, a pilot electric arc appears inside the plasma torch, the temperature of which is 6000 - 8000 °C. The pilot arc lights up between the electrode and the nozzle tip for the reason that it is difficult to form an arc between the electrode and the workpiece being processed immediately. The pilot arc column fills the entire channel.

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

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

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

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

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

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

Plasma cutter parameters

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

Manual plasma cutters are used in everyday life, in small industries and in private workshops for the manufacture and processing of parts. Their main feature is that the plasma torch is held in the hands of the operator, he guides the cutter along the line of the future cut, holding it in weight. As a result, the cut is even, but not perfect. And the productivity of such technology is low. To make the cut more even, without sagging and scale, a special stop is used to guide the plasma torch, which is placed on the nozzle. The stop is pressed against the surface of the workpiece and all that remains is to guide the cutter, without worrying about whether the required distance is maintained between the workpiece and the nozzle.

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

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

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

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

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

For example, if you need to cut copper 2 mm thick, then you need to multiply 6 A by 2 mm, we get a plasma cutter with a current strength of 12 A. If you need to cut steel 2 mm thick, then multiply 4 A by 2 mm, you get a current strength of 8 A. Only Take a plasma cutting machine with a reserve, since the specified characteristics are maximum, not nominal. You can only work on them for a short time.

CNC plasma cutting machine used in manufacturing plants for the manufacture of parts or processing of workpieces. CNC stands for Computer Numerical Control. The machine operates according to a given program with minimal operator participation, which eliminates the human factor in production as much as possible and increases productivity significantly. The cutting quality of the machine is ideal; no additional edge processing is required. And most importantly - figured cuts and exceptional precision. It is enough to enter the cutting diagram into the program and the device can make any intricate shape with perfect accuracy. The price of a plasma cutting machine is significantly higher than that of a manual plasma cutter. First, a large transformer is used. Secondly, a special table, portal and guides. Depending on the complexity and size of the device, the price can be from 3000 USD. up to 20,000 USD

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

It would be most reasonable to purchase a ready-made, factory-made plasma cutter. In such devices, everything is taken into account, adjusted and works as perfectly as possible. But some “Kulibina” craftsmen manage to make a plasma cutter with their own hands. The results are not very satisfactory, since the quality of the cut is poor. As an example, we will give a stripped-down version of how you can make a plasma cutter yourself. Let us immediately make a reservation that the diagram is far from ideal and only gives a general concept of the process.

So, a transformer for a plasma cutter must have a falling current-voltage characteristic.

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

To operate, you need an air compressor, of course, a factory-made one. In this case, a unit with a capacity of 350 l/min was used.

Homemade plasma cutter - operation diagram.

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

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

Making a plasma cutter yourself at home makes it possible to save a lot, but there is no need to talk about the quality of the cut. Although if an engineer takes on the work, the result may be even better than the factory version.

Not every enterprise can afford a CNC plasma cutting machine, because its cost can reach 15,000 - 20,000 USD. Quite often, such organizations order plasma cutting work to be carried out at special enterprises, but this is also expensive, especially if the volume of work is large. But you really want your own new plasma cutting machine, but you don’t have enough money.

In addition to well-known specialized factories, there are enterprises that produce plasma cutting machines, purchasing only profile parts and assemblies, and producing everything else themselves. As an example, we will tell you how engineers make CNC plasma cutting machines on a production floor.

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

Table 1270x2540 mm;
Belting;
Step parts;
Linear guides HIWIN;
System that controls the height of the THC flame;
Control block;
The terminal stand in which the CNC control unit is located is separate.

Machine characteristics:

The speed of movement on the table is 15 m/min;
The accuracy of setting the plasma torch position is 0.125 mm;
If you use a Powermax 65 machine, the cutting speed will be 40 m/min for a 6 mm workpiece or 5 m/min for a 19 mm thick workpiece.

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

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

The base for welding the table is being prepared, it must be strictly horizontal, this is very important, it is better to check with a level.
The machine frame is welded in the form of a table. Square pipes can be used. The vertical “legs” must be reinforced with jibs.

The frame is coated with primer and paint to protect it from corrosion.

Supports for the machine are being manufactured. The material of the supports is duralumin, the bolts are 14 mm, it is better to weld the nuts to the bolts.

The water table is welded.

Fastenings for the slats are installed and the slats are installed. For slats, metal is used in the form of a 40 mm strip.
Linear guides are installed.
The table body is covered with sheet iron and painted.
The portal is installed on the guides.

A motor and end inductive sensors are installed on the portal.
The guide rails, rack and pinion and Y-axis motor are installed.

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

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

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

Next, the CNC terminal is manufactured. First, the body is welded.
A monitor, keyboard, TNS module and buttons for it are installed in the CNC terminal housing.

That's it, the CNC plasma cutting machine is ready.

Despite the fact that the plasma cutter has a fairly simple device, you still shouldn’t start making it without serious knowledge of welding and extensive experience. It’s easier for a beginner to pay for a finished product. But engineers who want to implement their knowledge and skills at home, as they say “on the knee,” can try to create a plasma cutter with their own hands from start to finish.

At industrial enterprises, small workshops, during construction and repair work, a manual plasma cutter is used when it is necessary to weld or cut metal products, as well as special equipment equipped with CNC systems. To perform small-scale work, you can use a plasma cutter assembled with your own hands from an inverter, which is capable of providing high quality cuts or seams, taking into account the operations being performed.

Operating principle of a plasma cutter

When the power source is turned on, current begins to flow into the working area into the internal chamber of the plasma cutter, where the electric pilot arc between the nozzle tip and the electrode is activated. The forming arc fills the nozzle channel, where an air mixture begins to flow under high pressure, which, due to the high temperature of 6000-8000 °C, heats up greatly and increases in volume from 50 to 100 times. Due to the internal shape of the tapering nozzle, which has the shape of a cone, the air flow is compressed, heating up to an outlet temperature of 25,000 - 30,000 °C, forming a plasma jet that cuts the processed blank. Moreover, the initially activated pilot arc goes out and the working arc between the electrode and the metal product is activated. The resulting products from the effects of plasma combustion and metal melting are removed due to the force of the jet.

Fig. 1 Carrying out metal cutting operations where cutting or welding of a product is necessary, using a hand-made homemade one or a professional plasma cutter.

The optimal indicators for the workflow are:

gas supply at speeds up to 800 m/sec;
The current indicator can be up to 250 - 400 A.

Scheme 1. Drawing of the plasma cutting process of the workpiece.

A manual plasma cutter assembled using an inverter is mainly used for processing workpieces and is characterized by its low weight and economical power consumption.

Selection of plasma cutter components

To assemble a plasma cutter using drawings (based on an inverter), you need the following units with your own hands:

pressure gas supply device - compressor;
plasma cutter;
electrical device - an inverter that provides current to form an electric arc;
high pressure working hoses for air supply and protected electrical cable.

To supply air, we select a compressor taking into account the output volume for 1 minute. Manufacturing companies produce 2 types of compressors:

piston apparatus;
screw device (which has lower power consumption, is lighter, but 40-50% more expensive).

Rice. 2 Plasma cutter (device) with a cable set for the cutter and connection to the workpiece (as an anode).

Piston compressors are divided into oil and non-oil based, based on the drive principle - with a belt or direct connection of elements.
When operating compressors, a number of rules must be observed:

at negative ambient temperatures, it is necessary to preheat the oil contained in the crankcase;
It is necessary to regularly change the air (inlet) filter;
strictly control the oil level in the crankcase;
At least once every six months it is necessary to completely clean the units from foreign impurities;
Upon completion of work, it is necessary to relieve pressure (using a regulator) in the system.

During repair work, products from ORLIK KOMRESSOR (Czech Republic) are often used. The ORL 11 device allows cutting workpieces using a current of 200-440 A and an air-gas flow coming under pressure.

The equipment set includes:

compressor;
block of main filters for the air-gas mixture;
gas dryers;
receiver.

At the outlet of the unit, purified air free of oil, dust and moisture arrives. An example of screw compressors is the CA series product from Atlas Copco (Sweden). The device is equipped with an automatic condensate removal system for air purification.

A plasmatron is a special device in which, using an electric current, an electric arc is formed that heats air supplied under pressure in a chamber to form a cutting plasma stream.

The cutter consists of elements:

special holder with electrode;
an insulating gasket separating the nozzle and the electrode assembly;
plasma generation chambers;
output nozzles for the formation of a plasma jet (see drawings);
supply systems;
tangential plasma supply elements (on some models) to stabilize the arc discharge.

According to the method of performing work (welding or cutting), cutters are divided into:

Double-flow, used in reducing, oxidizing and inert environments.
Gas inert (using helium, argon), reducing (hydrogen, nitrogen).
Gas oxidizing (the air-gas mixture includes oxygen).
Gas using a stabilizing (gas-liquid) arc.

The plasmatron cathode is made in the form of a rod or inserts made of tungsten, hafnium, and zirconium. Plasmatrons with a sleeve cathode, used for cutting using an air-gas flow under pressure, have become widespread.

To cut products in an oxidizing environment, a hollow cathode made of copper with a forced cooling system using water is used.

Rice. 3 Portable device (inverter) for plasma cutting.

Double-flow plasma cutters (inverter) are equipped with 2 coaxial nozzles, external and internal. The gas entering the internal nozzle is considered primary, and the external one is considered additional, and the gases can have different compositions and volumes.

A plasma cutter with arc stabilization due to the supply of a gas-liquid flow has a difference, which is the supply of water to the torch chamber to stabilize the state of the arc discharge.

To activate the working arc, a workpiece is used as an anode, which is connected to the inverter using clamps and a cable.

As a power plant for carrying out the plasma cutting process, a device (inverter) is used that provides the necessary current strength, which has a higher efficiency than a transformer, but the transformer’s metal processing capabilities are much higher.

Scheme 2. Drawing of the plasmatron power supply with your own hands.

Inverter advantages:

the ability to uniformly change parameters;
light weight;
stable state of the working arc;
high quality cutting or welding.

The equipment set also includes a set of high pressure hoses for connecting a stationary compressor and an electrical connecting cable.

To assemble a plasma cutter with your own hands, a device diagram is developed indicating the necessary units that meet the required characteristics, which should include all additions and changes used during assembly with the necessary calculations of the most important indicators. You can assemble a homemade plasma cutter with your own hands using ready-made blocks and assemblies produced by specialized companies; in this case, it is necessary to make accurate calculations and coordinate the output parameters of the ongoing processes.

Features of marking plasma cutters

Plasma cutters produced by industrial enterprises can be divided into 2 categories:

machine cutting units;
manual.

Hand cutters are more affordable if you need to do it yourself. Manufactured models have special markings:

MMA - the device is designed for arc welding using an individual electrode;
CUT - a device (plasma cutter) used for cutting metal;
TIQ - the device is used for work where argon welding is necessary.

Manufacturing enterprises produce equipment for metal cutting:

Profi CUT 40 (RT-31 burner, permissible cut thickness – 16 mm, air-gas mixture flow rate – 140 l/min, receiver volume 50 l);
Profi CUT 60 (P-80 burner, permissible workpiece cutting thickness - 20 mm, air-gas mixture flow rate - 170 l/min.);
Profi CUT 80 (burner R. – 80, permissible cutting thickness of the workpiece – 30 mm, air-gas mixture flow rate – 190 l/min.);
Pro CUT 100 (burner A-101, permissible cutting thickness of the workpiece - 40 mm, air-gas mixture flow rate - 200 l/min.), receiver with a volume of 100 l.

Making a CNC plasma cutter with your own hands

A CNC-equipped plasma cutter must have a unified assembly using drawings made on the basis of the prepared technical specifications for the product, which include:

work table;
belt transmission;
function control unit;
step elements;
linear guides;
cutting height adjustment system;
CNC control unit;

Scheme 3. Drawing of an inverter device for plasma cutting.

Drawings of all plasma cutter blocks can be purchased taking into account the required power and installation characteristics and financial capabilities, or you can do it yourself if you have experience and knowledge.

To complete and assemble a CNC machine, it is necessary to manufacture a number of elements using drawings:

table base for welding;
a durable frame is assembled and then painted;
support posts are attached;
the water table is assembled;
fastenings and the slats themselves are installed;
linear guides are mounted;
the table cover is installed;
guides are installed together with the portal;
the portal is equipped with a motor and signal sensors;
the guides, the Y guide motor and the positioning control rack are mounted;
a guide equipped with a motor is mounted;
a metal surface signal sensor is mounted;
a tap is installed to remove water from the table;
connecting cables-channels X.Z.Y are laid;
the wires are insulated and covered with cladding;
the working cutter is mounted;
The CNC device is assembled and installed.

Carrying out operations for the manufacture and assembly of a CNC plasma torch should only be carried out in the presence of qualified specialists. The device diagram (drawings) must include all the necessary elements to ensure high quality of work and safety of metal cutting. Equipping enterprises with CNC equipment can increase labor productivity and the complexity of operations. Make production processes performed using CNC equipment more economical by increasing labor productivity and reducing the processing speed of products.

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Plasma cutting is a fairly popular operation, especially when it comes to cutting thick metal parts or workpieces. The process happens quickly, 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 diagram is simple, the main thing is to choose the right devices according to the required technical characteristics.

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

Essentially, 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 blows away the molten metal and frees up the cutting space.

This means that to create plasma, you need gas and a source of electricity. And these two components must come together in one place. Therefore, plasma cutting equipment consists of a gas cylinder, a high-power source of electricity and a cutter in which the electrode is installed.

The design of the cutter is made in such a way that gas passes around the electrode and, when heated from the electrode, escapes out through a small hole. The small diameter of the hole and gas pressure create the necessary speed for the plasma. 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 strength at the electrode should not be less than 250 A.
Compressed air must be supplied to the cutter at a speed within 800 m/sec.

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, and you can begin assembling it. By the way, you don’t need special drawings for this.

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 energy 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. The compressor remains unchanged here. But which one? The main parameter is air pressure. You will need to pay attention to him. 2.0-2.5 atm. - it will be fine.
The cutter can be purchased at the store. And this will be the ideal solution. If you have a cutter for argon welding, then it can be converted for plasma cutting. To do this, you will have to make an attachment from copper in the form of a nozzle, 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 in the store as a single connecting element.

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

Auxiliary elements and materials

What else should you 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 to ensure maximum cutting quality? 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 it comes with a nozzle with such a hole.

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. This results in a neat metal cut, and the cutting process itself is quick and easy. But you shouldn’t buy a very long nozzle. Such a device quickly collapses under the influence of high temperatures.

As for choosing an electrode for a plasma cutter, you need to pay attention to the alloy from which it is made. For example, if the alloy contains beryllium, then it is a radioactive substance. It is not recommended to work with such electrodes for a long time. If the alloy contains thorium, it releases toxic substances at high temperatures. An ideal electrode for plasma cutting, the alloy of which includes 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 whether the assembled structure works. All units are turned on, the button on the cutter to supply electricity to the electrode is pressed. 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 this, compressed air begins to flow into the cutter. Passing through the nozzle and heated by an electric arc, it sharply expands tenfold and at the same time acquires conductive properties. That is, it turns out to be an ionized gas.

It passes through a narrowed nozzle, while acquiring a speed of 2-3 m/sec. But the plasma temperature rises to 25000-30000C. The most important thing is that the arc, with the help of 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 immediately the second, so-called working arc is turned on, which acts locally on the metal. Exactly in the cutting area. Therefore, metal is cut only in this zone.

If, when checking the operation of the plasma cutter, you were able to cut metal with a thickness of at least 20 mm, then all the elements of the new design, assembled with your own hands, were selected correctly. It is necessary to note that the plasma cutter cannot cut workpieces with a thickness of more than 20 mm from the inverter. 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 wearing 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 may not be enough for a large amount of work. The way out is to install a receiver on the compressor. It works like an accumulator that accumulates pressure in compressed air. For this purpose, you can use, for example, bolts from the brake systems of heavy vehicles. The option is actually simple. The volume of the cylinder is large, and it should be enough for a long period of time.
In order for the air pressure to be stable and uniform, a reducer must be installed at the receiver outlet.
Of course, the optimal 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 a plasma cutter are small 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 you can’t buy a ready-made hose-cable kit, you can make it yourself. You need to combine the welding cable and high-pressure hose into one sleeve and place them in a single sheath. For example, into a regular hose of larger diameter. A set 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 obtain the necessary information and study it; it is definitely recommended to watch the training video. And after that, correctly select all the elements exactly to 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.

Plasma cutters are widely used in workshops and enterprises related to non-ferrous metals. Most small businesses use a homemade plasma cutter.

It performs well when cutting non-ferrous metals, since it allows local heating of products and not deforming them. Self-production of cutters is due to the high cost of professional equipment.

In the manufacturing process of such a tool, components from other electrical appliances are used.

The inverter is used to perform work in both domestic and industrial environments. There are several types of plasma cutters for working with different types of metals.

There are:

Plasma cutters operating in an environment of inert gases, such as argon, helium or nitrogen.
Instruments operating in oxidizing agents, such as oxygen.
Equipment designed to work with mixed atmospheres.
Cutters operating in gas-liquid stabilizers.
Devices operating with water or magnetic stabilization. This is the rarest type of cutter, which is almost impossible to find on the open market.

Or a plasmatron is the main part of plasma cutting, responsible for direct cutting of metal.

Disassembled plasma cutter.

Most inverter plasma cutters consist of:

nozzles;
electrode;
protective cap;
nozzles;
hose;
cutter heads;
pens;
roller stop.

The operating principle of a simple semi-automatic plasma cutter is as follows: the working gas around the plasma torch is heated to very high temperatures, at which plasma appears that conducts electricity.

Then, a current passing through the ionized gas cuts the metal by local melting. After this, the plasma jet removes the remaining molten metal and a neat cut is obtained.

Based on the type of impact on metal, the following types of plasmatrons are distinguished:

Indirect action devices.
This type of plasmatron does not pass current through itself and is suitable only in one case - for cutting non-metallic products.
Direct plasma cutting.
Used for cutting metals by generating a plasma jet.

Making a plasma cutter with your own hands

DIY plasma cutting can be done at home. The prohibitive cost of professional equipment and the limited number of models on the market force craftsmen to assemble a plasma cutter from a welding inverter with their own hands.

A homemade plasma cutter can be made provided you have all the necessary components.

Before making a plasma cutting installation, you need to prepare the following components:

Compressor.
The part is necessary to supply air flow under pressure.
Plasmatron.
The product is used for direct cutting of metal.
Electrodes.
Used to ignite an arc and create plasma.
Insulator.
Protects electrodes from overheating when performing plasma cutting of metal.
Nozzle.
A part whose size determines the capabilities of the entire plasma cutter, assembled with your own hands from an inverter.
Welding inverter.
DC power source for installation. Can be replaced with a welding transformer.

The power source of the device can be either transformer or inverter.

Scheme of operation of a plasma cutter.

Transformer DC sources are characterized by the following disadvantages:

high electrical energy consumption;
large dimensions;
inaccessibility.

The advantages of such a power source include:

low sensitivity to voltage changes;
more power;
high reliability.

Inverters can be used as a power supply for a plasma cutter if necessary:

construct a small apparatus;
assemble a high-quality plasma cutter with a high efficiency and a stable arc.

Due to the availability and lightness of the inverter power supply, plasma cutters based on it can be constructed at home. The disadvantages of the inverter include only the relatively low power of the jet. Because of this, the thickness of the metal workpiece cut by an inverter plasma cutter is seriously limited.

One of the most important parts of a plasma cutter is the manual cutter.

This element of metal cutting equipment is assembled from the following components:

handle with cuts for laying wires;
gas plasma burner start button;
electrodes;
flow swirl system;
a tip that protects the operator from splashes of molten metal;
a spring to ensure the required distance between the nozzle and the metal;
nozzles for removing scale and carbon deposits.

Cutting metal of various thicknesses is carried out by changing the nozzles in the plasma torch. In most plasmatron designs, the nozzles are secured with a special nut, with a diameter that allows you to pass the conical tip and clamp the wide part of the element.

After the nozzle, electrodes and insulation are located. To be able to strengthen the arc, if necessary, an air flow swirler is included in the design of the plasmatron.

Do-it-yourself plasma cutters based on an inverter power source are quite mobile. Thanks to its small dimensions, such equipment can be used even in the most inaccessible places.

Blueprints

There are many different plasma cutter drawings available on the Internet. The easiest way to make a plasma cutter at home is to use a DC inverter source.

Electrical circuit of a plasma cutter.

The most common technical drawing of a plasma arc cutter includes the following components:

Electrode.
This element is supplied with voltage from a power source to ionize the surrounding gas. As a rule, refractory metals are used as an electrode, forming a strong oxide. In most cases, welding machine designers use hafnium, zirconium or titanium. The best choice of electrode material for home use is hafnium.
Nozzle.
A component of an automatic plasma welding machine generates a jet of ionized gas and passes air to cool the electrode.
Cooler.
The element is used to remove heat from the nozzle, since during operation the plasma temperature can reach 30,000 degrees Celsius.

Most plasma cutting machine circuits imply the following operating algorithm for the cutter based on a jet of ionized gas:

The first press of the start button turns on the relay that supplies power to the device control unit.
The second relay supplies current to the inverter and connects the electric burner purge valve.
A powerful air stream enters the burner chamber and cleans it.
After a certain period of time, set by resistors, the third relay is activated and supplies power to the electrodes of the installation.
The oscillator is started, thanks to which the working gas located between the cathode and anode is ionized. At this stage, a pilot arc occurs.
When an arc is brought to a metal part, an arc is ignited between the plasma torch and the surface, called the working arc.
Turning off the current supply to ignite the arc using a special reed switch.
Carrying out cutting or welding work. In the event of an arc loss, the reed switch relay turns on the current again and ignites the standby plasma jet.
When work is completed after the arc is turned off, the fourth relay starts the compressor, the air of which cools the nozzle and removes the remains of burnt metal.

The most successful plasma cutter schemes are the APR-91 model.

What do we need?

Plasma cutter drawing.

To create a plasma welding machine you need to acquire:

DC source;
plasmatron.

The latter includes:

nozzle;
electrodes;
insulator;
compressor with a capacity of 2-2.5 atmospheres.

Most modern craftsmen make plasma welding connected to an inverter power supply. A plasmatron designed using these components for manual air cutting works as follows: pressing the control button ignites an electric arc between the nozzle and the electrode.

After completion of work, after pressing the shutdown button, the compressor supplies a stream of air and knocks off the remaining metal from the electrodes.

Inverter assembly

If a factory inverter is not available, you can assemble a homemade one.

Inverters for cutters based on gas plasma, as a rule, have the following components:

power unit;
power switch drivers;
power block.

Plasma torch in section.

Plasma cutters or welding equipment cannot do without the necessary tools in the form of:

set of screwdrivers;
soldering iron;
knife;
hacksaws for metal;
threaded type fasteners;
copper wires;
PCB;
mica.

The power supply for plasma cutting is assembled on the basis of a ferrite core and must have four windings:

primary, consisting of 100 turns of wire, 0.3 millimeters thick;
the first secondary of 15 turns of cable with a thickness of 1 millimeter;
second secondary of 15 turns of 0.2 mm wire;
the third is secondary from 20 turns of 0.3 mm wire.

Note! To minimize the negative consequences of voltage surges in the electrical network, winding should be carried out across the entire width of the wooden base.

The power unit of a homemade inverter must consist of a special transformer. To create this element, you need to select two cores and wind copper wire 0.25 millimeters thick on them.

Special mention should be made of the cooling system, without which the inverter power supply of the plasma torch can quickly fail.

Plasma cutting technology drawing.

When working with the device, to achieve the best results, you must follow the recommendations:

regularly check the correct direction of the gas plasma jet;
check the correct choice of equipment in accordance with the thickness of the metal product;
monitor the condition of plasma torch consumables;
ensure that the distance between the plasma jet and the workpiece is maintained;
always check the cutting speed used to avoid dross;
from time to time diagnose the condition of the working gas supply system;
eliminate vibration of the electric plasmatron;
Maintain a clean and tidy work area.

Conclusion

Plasma cutting equipment is an indispensable tool for accurately cutting metal products. Thanks to their thoughtful design, plasma torches provide fast, even and high-quality cuts of metal sheets without the need for subsequent surface treatment.

Most crafters from small workshops prefer to assemble mini cutters with their own hands for working with thin metal. As a rule, a self-made plasma cutter does not differ in characteristics and quality of work from factory models.