How to make a plasma welding machine with your own hands? The principle of operation of a plasma cutter Do-it-yourself plasma cutter from an inverter

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

Design of an air plasma cutting machine

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

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

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

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

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

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

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

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

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

Operating principle of air plasma cutting machine

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

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

Plasma This is precisely what is called the heated ionized air escaping from the plasma torch nozzle. As soon as the plasma reaches the surface of the metal being processed, the working cutting arc is ignited, at which point the pilot arc goes out. The cutting arc heats up the workpiece at the point of contact, locally, the metal begins to melt, and a cut appears. The molten metal flows onto the surface of the workpiece and solidifies in the form of drops and small particles, which are immediately blown away by the plasma flow. This method 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 energy of one of the near-electrode arc spots, as well as the plasma of the column and the torch flowing from it, is used to cut the workpiece. Plasma arc cutting uses a direct current arc of straight polarity.

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

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

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

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

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

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

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

How to choose an air plasma cutting machine

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

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

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

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

Plasma cutter current and metal thickness

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

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

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

Table 1. Current required for cutting various metals.

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

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

Operating mode - ON duration (DS)

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

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

Do-it-yourself air plasma cutting - working technology

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

Take care of your safety

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

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

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

Preparing the air plasma cutting machine for operation

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

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

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

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

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

Now you can begin the cutting process itself.

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

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

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

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

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

Distance between plasmatron torch and metal

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

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

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

A plasma cutting machine is a fairly popular piece of equipment that allows cutting any metals in many areas of production. Plasma cutters are used not only in enterprises. Recently, they have begun to appear in home workshops. But, since almost every workshop already has welding machines, it would be wiser not to buy a ready-made plasma cutter, but to make it from an inverter with your own hands.

In some cases, a plasma cutter is an indispensable tool for processing metal products, since the temperature of the plasma leaving its torch reaches 25-30 thousand degrees. Thanks to these characteristics, the scope of application of plasma cutters is quite extensive:

• production of various types of metal structures;
• laying of pipelines;
• fast cutting of any metals, including high-alloy heat-resistant steels containing titanium, nickel and molybdenum, the melting point of which is above 3000°C;
• shaped cutting of thin-sheet materials (conductive) due to high cutting precision.

In addition, plasma cutters (as an alternative to laser cutters) are used as part of automatic lines at large enterprises for cutting parts of various configurations from sheet materials.

It is necessary to distinguish between concepts such as plasma cutting and plasma welding. The latter is available only on expensive, professional equipment, the cost of which starts from 100 thousand rubles.

Inverter or transformer

There are various methods, as well as drawings and diagrams, according to which you can make a plasma cutter. For example, if it is made on the basis of a transformer welder, then the plasma cutter diagram provided below is suitable, which describes in detail what parts are needed to manufacture this module.

If you already have an inverter, then in order to convert it into a plasma cutter, you will need a little modification, namely adding an oscillator to the electrical circuit of the device. It is connected between the inverter and the plasma torch in two ways, as shown in the following figure.

The oscillator can be soldered independently according to the diagram provided below.

If you make a plasma cutter yourself, then choosing a transformer as a current source is not recommended for several reasons:

• the unit consumes a lot of electricity;
• The transformer is heavy and inconvenient to transport.

Despite this, the welding transformer also has positive qualities, for example, insensitivity to voltage changes. It can also cut thick metal.

But advantages of an inverter plasma cutting machine in front of the transformer unit there is:

• light weight;
• high efficiency (30% higher than that of a transformer);
• low electricity consumption;
• High-quality cutting thanks to a more stable arc.

Therefore, it is preferable to make a plasma cutter from a welding inverter than from a transformer.

Typical plasma cutter design

To assemble a device that will make air plasma cutting of metals possible, you will need to have the following components available.

1. Power supply. Required to supply electric current to the burner electrode. The power source can be either a transformer (welding) that produces alternating current, or an inverter-type welding unit, the output of which is direct current. Based on the above, it is preferable to use an inverter, and with an argon welding function. In this case, it will have a connector for connecting the hose package and a place to connect the gas hose, which will simplify the modification of the device.
   
   
2. Plasma torch (cutter). It is a very important piece of equipment that has a complex design. In a plasma torch, a plasma jet is formed under the influence of an electric current and a directed air flow. If you decide to assemble a plasma cutter with your own hands, then it is better to purchase this element ready-made on Chinese websites.
   
   
3. . Required for effective arc ignition and stabilization. As mentioned above, it is soldered according to a simple scheme. But if you are not strong in radio, then this module can be bought in China for 1,400 rubles.
   
4. Designed to create an air flow entering the burner. Thanks to it, the plasma torch is cooled, the plasma temperature rises and the molten metal is blown away from the cut site on the workpiece. Any compressor to which a spray gun is usually connected is suitable for homemade work. But to remove water vapor from the air pumped by the compressor, you will need to install a filter drier.
   
   
   
5. . Through it, current flows into the burner, facilitating the ignition of the electric arc and ionization of gases. Compressed air is also supplied to the burner through this hose. You can make a hose cable yourself by placing an electrical cable and an oxygen hose inside, for example, a water hose of a suitable diameter. But it’s still better to buy a ready-made hose package, which will have all the elements for connecting to the plasmatron and to the unit.
   
   
6. Ground cable. It has a clamp at the end for attaching to the metal being processed.

Assembling the device

After all the necessary elements have been prepared, you can begin assembling the plasma cutter:

• connect a hose to the inverter through which air will be supplied from the compressor;
• connect the hose package and ground cable to the front side of the inverter;
• Connect the torch (plasma torch) to the hose package.

After assembling all the elements, you can begin equipment testing. To do this, connect the ground cable to the part or metal table on which it is placed. Turn on the compressor and wait until it pumps the required amount of air into the receiver. After the compressor automatically turns off, turn on the inverter. Bring the torch close to the metal and press the start button to create an electric arc between the torch electrode and the workpiece. Under the influence of oxygen, it will turn into a stream of plasma, and metal cutting will begin.

In order for a homemade plasma cutter from a welding inverter to work effectively and for a long time, you should listen to the advice of specialists related to the operation of the device.

1. Recommended to have a certain number of gaskets which are used to connect hoses. Their presence should especially be checked when the unit has to be transported frequently. In some cases, the absence of the necessary gasket will make the device impossible to use.
2. Because the cutter nozzle is exposed to high temperatures, it will wear out and fail over time. Therefore, you should worry about purchasing spare nozzles.
3. When selecting components for a plasma cutter, you should consider how much power you want to get from the unit. First of all, this concerns the choice of a suitable inverter.
4. When choosing an electrode for a burner, if you make it yourself, you need to give preference to a material such as hafnium. This material does not emit harmful substances during heating. But it is still strongly recommended to use ready-made cutters manufactured at the factory, in which all parameters for air flow swirl are observed. A homemade plasmatron does not guarantee high-quality cutting and quickly breaks down.

As for safety rules, work should be carried out in special clothing that protects against splashes of hot metal. You should also wear chameleon welding goggles to protect your eyes.

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:

1. Plasma cutters operating in an environment of inert gases, such as argon, helium or nitrogen.
2. Instruments operating in oxidizing agents, such as oxygen.
3. Equipment designed to work with mixed atmospheres.
4. Cutters operating in gas-liquid stabilizers.
5. 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 principle of operation 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:

1. 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.
2. 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:

1. Compressor.
   The part is necessary to supply air flow under pressure.
2. Plasmatron.
   The product is used for direct cutting of metal.
3. Electrodes.
   Used to ignite an arc and create plasma.
4. Insulator.
   Protects electrodes from overheating when performing plasma cutting of metal.
5. Nozzle.
   A part whose size determines the capabilities of the entire plasma cutter, assembled with your own hands from an inverter.
6. 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.

Drawings

There are many different drawings of a plasma cutter 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:

1. 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.
2. Nozzle.
   A component of an automatic plasma welding machine generates a jet of ionized gas and passes air to cool the electrode.
3. 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:

1. The first press of the start button turns on the relay that supplies power to the device control unit.
2. The second relay supplies current to the inverter and connects the electric burner purge valve.
3. A powerful air stream enters the burner chamber and cleans it.
4. After a certain period of time, set by resistors, the third relay is activated and supplies power to the electrodes of the installation.
5. 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.
6. When an arc is brought to a metal part, an arc is ignited between the plasma torch and the surface, called the working arc.
7. Turning off the current supply to ignite the arc using a special reed switch.
8. 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.
9. 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.

Pay attention! 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 handicraftsmen 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.

Metal cutting is carried out in several ways - mechanically, arc welding or exposure to high-temperature plasma. In the latter case, an inverter can be used as a power source. To make an effective plasma cutter with your own hands, you will need to familiarize yourself with the diagram and operating principle of the device.

Plasma cutter diagram

Processing of metal surfaces, their cutting and controlled deformation occurs using a jet of air or inert gas. Pressure and the presence of a flammable component (electrode) ensures the formation of a plasma region. It exerts high temperature and pressure on the workpiece area, resulting in its cutting.

Features of manufacturing a plasma cutter based on an inverter welding machine:

• Preliminary calculation of equipment power. The determining parameter is the thickness and properties of the material being cut.
• Mobility of the structure and its dimensions.
• Duration of continuous cutting.
• Budget.

The latter indicator should not affect the quality, and most importantly, the safety of operation of a homemade plasma cutter. It is recommended to use maximum factory-made components.

An inverter welding machine is a source of arc for igniting plasma. It is also used for its intended purpose - the formation of connecting seams. To complete the plasma cutter, you need to purchase only factory models, since homemade ones will not be able to ensure stable operation.

To ensure mobility, you need to buy an inverter with argon arc welding function. Its design provides space for connecting a hose from a source of air or inert gas. The average cost is 19,500 rubles.

Additionally you will need the following components:

• Cutter with the function of supplying electricity, wire (electrode) and air.
• Compressor. It is needed to pump gas; an alternative is refilled cylinders.
• Cable-hose package. These are lines for electricity, an air hose and a wire feeder.

Of the entire list, you can only make a handle for the cutter with your own hands. It is this that most often fails due to constant temperature exposure. The dimensions and performance properties of the remaining components must meet quality standards.

Step-by-step assembly instructions

In fact, the plasma cutter is not manufactured, but assembled from the elements described above. The possibility of connecting individual components is first checked, operating modes are specified - the amount of current supplied from the inverter, the intensity of the air stream, and the plasma temperature.

Additionally, you need to use a pressure gauge to monitor the pressure in the air line. The optimal location is on the body. On the holder it will interfere with the precise formation of the cut.

Operating procedure:

1. Check the inverter power supply.
2. Check the tightness of the air line.
3. Set the pressure of the inert gas jet to the required level.
4. Connect the negative electrode of the inverter to the workpiece.
5. Checking the arc, activating the air supply.
6. Plasma cutting.

The width of the cut should be small, without significant deformation of the metal at the edges. The maximum thickness of the processed material is up to 3 mm. When this parameter is increased, the inverter is replaced with a more powerful transformer.

During the cutting process, problems arise - lack of components, unstable installation mode. The likely consequences are the inability to continue work, poor-quality cutting. The solution is to carefully prepare for this event.

• Spare gaskets for the air line. Frequent switching leads to their abrasion and loss of tightness.
• Nozzle quality. With prolonged exposure to temperature, it can become clogged and change its geometry.
• Electrodes are made only from refractory materials.
• The reason for the breakdown of homemade cutters is the occurrence of 2 air vortices, which leads to deformation of the nozzle.
• Be sure to carry out work only in protective clothing.

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

Direct acting devices

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

Indirect action device

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

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

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

Hand tool design

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

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

Additional items

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

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

Parts selection

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

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

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

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

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

Operating principle

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

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

Cutter device

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

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

How to make a plasma cutter?

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

In addition, the inverter must meet several more requirements:

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

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

Plasma cutter diagram

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

Product circuit operation

Do-it-yourself assembly of a plasma cutter according to the drawing is the most important process that will ensure stable operation of the device in the future. The finished and correctly assembled circuit looks like this:

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

Plasma torch, electrodes, compressor

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

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

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