Modern inverter welding machines cover most of the needs for producing permanent joints of metal workpieces. But in some cases, a device of a slightly different type will be much more convenient, in which the main role is played not by an electric arc, but by a flow of ionized gas, that is, a plasma welding machine. Purchasing it for occasional use is not very cost-effective. You can make such a welding machine with your own hands.
Equipment and components
The easiest way to make a microplasma welding machine is on the basis of an existing inverter welding machine. To complete this upgrade, you will need the following components:
- any inverter welding machine for TIG welding with or without a built-in oscillator;
- nozzle with a tungsten electrode from a TIG welder;
- argon cylinder with reducer;
- a small piece of tantalum or molybdenum rod with a diameter and length of up to 20 mm;
- fluoroplastic tube;
- copper tubes;
- small pieces of copper sheet 1-2 mm thick;
- electronic ballast;
- rubber hoses;
- sealed lead-in;
- clamps;
- wiring;
- terminals;
- car windshield wiper reservoir with electric pump;
- rectifier power supply for the electric windshield wiper pump.
Work on fine-tuning and manufacturing of new parts and assemblies will require the use of the following equipment:
- lathe;
- electric soldering iron;
- soldering torch with cylinder;
- screwdrivers;
- pliers;
- ammeter;
- voltmeter.
Return to contents
Theoretical basis
A plasma welding machine can be one of 2 main types: open and closed. The main arc of an open-type welding machine burns between the central cathode of the torch and the workpiece. Between the nozzle, which serves as the anode, and the central cathode, only a pilot arc burns to excite the main one at any time. A closed-type welding machine has only an arc between the central electrode and the nozzle.
It is quite difficult to make a durable one according to the 2nd principle. When the main welding current passes through the anode nozzle, this element experiences enormous thermal loads and requires very high-quality cooling and the use of appropriate materials. It is very difficult to ensure the heat resistance of the structure when making such a device yourself. When making a plasma device with your own hands, for durability it is better to choose an open circuit.
Return to contents
Practical implementation
Often, when making a homemade plasma welding machine, the nozzle is machined from copper. If there is no alternative, this option is possible, but the nozzle becomes a consumable even when only a standby current passes through it. It will have to be changed frequently. If you can get a small piece of molybdenum or tantalum round timber, it is better to make a nozzle from them. Then you can limit yourself to periodic cleaning.
The size of the central hole in the nozzle is selected experimentally. You need to start with a diameter of 0.5 mm and gradually bore it to 2 mm until the plasma flow is satisfactory.
The conical gap between the central tungsten cathode and the anode nozzle should be 2.5-3 mm.
The nozzle is screwed into a hollow cooling jacket, which is connected to the central electrode holder through a fluoroplastic insulator. Coolant circulates in the cooling jacket. As such, in the warm season you can use distilled water; in winter, antifreeze is better.
The cooling jacket consists of 2 hollow copper tubes. The inner one with a diameter and length of about 20 mm is located at the front end of the outer tube with a diameter of about 50 mm and a length of about 80 mm. The space between the ends of the inner tube and the walls of the outer tube is sealed with thin sheet copper. Copper tubes with a diameter of 8 mm are soldered into the jacket using a gas torch. Coolant flows in and out through them. In addition, a terminal must be soldered to the cooling jacket to supply a positive charge.
A thread is made in the inner tube into which a removable nozzle made of heat-resistant materials is screwed. An internal thread is also cut at the extended end of the outer tube. An insulating ring made of fluoroplastic is screwed into it. The central electrode holder is screwed into the ring.
An argon supply tube of the same diameter as for cooling is soldered through the wall of the outer tube into the space between the cooling jacket and the fluoroplastic insulator.
Liquid from the windshield wiper reservoir circulates through the cooling jacket. Power is supplied to the pump of its electric motor through a separate 12 V rectifier. There is already an outlet for the supply on the tank; the liquid return can be cut through the wall or lid of the tank. To do this, a hole is drilled in the lid and a piece of tube is inserted through the pressure seal. Rubber hoses for liquid circulation and argon supply are connected to their tubes with clamps.
The positive charge is taken from the main power source. A suitable electronic ballast is selected to limit the current through the nozzle surface. The supplied electric current must have a constant value in the region of 5-7 A. The optimal current value is selected experimentally. This should be the minimum current that ensures stable combustion of the pilot arc.
The pilot arc between the nozzle and the tungsten cathode can be excited in one of two ways. Using an oscillator built into the welding machine or, in the absence of one, using a contact method. The second option requires a more complex design of the plasma torch. During contact excitation, the central electrode holder is made spring-loaded relative to the nozzle.
When the rubber button of the rod connected to the electrode holder is pressed, the sharp end of the central tungsten cathode contacts the conical surface of the rod. During a short circuit, the temperature rises sharply at the point of contact, which allows an arc to be initiated when the cathode is pulled away from the anode by a spring. The contact must be very brief, otherwise the surface of the nozzle will burn.
Excitation of current by a high-frequency oscillator is preferable for the durability of the structure. But purchasing it or even manufacturing it makes it unprofitable for plasma welding.
During operation, the positive terminal of the welding machine is connected to the part without ballast. When the nozzle is within a few millimeters of the workpiece, electrical current is switched from the nozzle to the workpiece. Its value increases to that set on the welding machine, and the formation of plasma from argon intensifies. By adjusting the argon supply and welding current, you can achieve the required intensity of plasma flow from the nozzle.
Unlike, the inverter is compact, light weight and high efficiency, which explains its popularity in home workshops, small garages and workshops.
It allows you to cover most needs for welding work, but for high-quality cutting you need a laser machine or plasma cutter.
Laser equipment is very expensive, and a plasma cutter is also not cheap. small thickness has excellent characteristics that are unattainable when using electric welding. At the same time, the power unit of the plasma cutter has largely the same characteristics.
There is a desire to save money and, with a little modification, use it for plasma cutting. It turned out that this is possible, and you can find many ways to convert welding machines, including inverter ones, into plasma cutters.
A plasma cutting machine is the same welding inverter with an oscillator and a plasma torch, a work cable with a clamp and an external or internal compressor. Often the compressor is used externally and is not included in the package.
If the owner of a welding inverter also has a compressor, then you can get a homemade plasma cutter by purchasing a plasma torch and making an oscillator. The result is a universal welding machine.
Operating principle of the burner
The operation of a plasma welding and cutting apparatus (plasma cutter) is based on the use of plasma, the fourth state of matter, as a cutting or welding tool.
To obtain it, high temperature and gas under high pressure are required. When an electric arc is created between the anode and cathode of the burner, a temperature of several thousand degrees is maintained in it.
Plasma formation
If you pass a gas stream through an arc under such conditions, it will ionize, expand in volume several hundred times and heat up to a temperature of 20-30 thousand °C, turning into plasma. High temperature almost instantly melts any metal.
Unlike a cumulative projectile, the process of plasma formation in a plasmatron is adjustable.
The anode and cathode in a plasma cutter are located at a distance of several millimeters from each other. The oscillator generates a pulsed current of high magnitude and frequency, passes it between the anode and the cathode, which leads to the occurrence of an electric arc.
After this, gas is passed through the arc, which is ionized. Since everything happens in a closed chamber with one exit hole, the resulting plasma rushes out at tremendous speed.
At the output of the plasma cutter torch, it reaches a temperature of 30,000 ° and melts any metal. Before starting work, a ground wire is connected to the workpiece using a powerful clamp.
When the plasma reaches the workpiece, an electric current begins to flow through the mass cable and the plasma reaches maximum power. The current reaches 200-250 A. The anode-cathode circuit is broken using a relay.
cutting
When the main arc of the plasma cutter disappears, this circuit turns on again, preventing the plasma from disappearing. Plasma plays the role of an electrode in electric arc welding; it conducts current and, due to its properties, creates an area of high temperature in the area of contact with the metal.
The contact area between the plasma jet and the metal is small, the temperature is high, heating occurs very quickly, so there is virtually no stress or deformation of the workpiece.
The cut is smooth, thin and does not require further processing. Under the pressure of compressed air, which is used as a plasma working fluid, the liquid metal is blown out and a high-quality cut is obtained.
When using inert gases with a plasma cutter, you can carry out high-quality welding without the harmful effects of hydrogen.
DIY plasma torch
When making a plasma cutter from a welding inverter with your own hands, the most difficult part of the work is the production of a high-quality cutting head (plasma torch).
Tools and materials
If you make a plasma cutter with your own hands, it is easier to use air as a working fluid. For production you will need:
Plasma cutter consumables in the form of nozzles and electrodes should be purchased at a welding equipment store. They burn out during the cutting and welding process, so it makes sense to purchase several pieces for each nozzle diameter.
The thinner the metal to be cut, the smaller the plasma cutter torch nozzle hole should be. The thicker the metal, the larger the nozzle opening. The most commonly used nozzle is the one with a diameter of 3 mm; it covers a wide range of thicknesses and types of metals.
Assembly
The plasma cutter torch nozzles are attached with a clamping nut. Directly behind it there is an electrode and an insulating sleeve, which does not allow an arc to occur in an unnecessary place in the device.
Then there is a flow swirler that directs it to the desired point. The entire structure is placed in a fluoroplastic and metal case. A pipe for connecting an air hose is welded to the outlet of the tube on the plasma cutter torch handle.
Electrodes and cable
The plasma torch requires a special electrode made of refractory material. They are usually made from thorium, beryllium, hafnium and zirconium. They are used due to the formation of refractory oxides on the surface of the electrode during heating, which increases the duration of its operation.
When used at home, it is preferable to use electrodes made of hafnium and zirconium. When cutting metal, they do not produce toxic substances, unlike thorium and beryllium.
The cable from the inverter and the hose from the compressor to the plasma cutter torch must be laid in one corrugated pipe or hose, which will ensure cooling of the cable in case of heating and ease of operation.
The cross-section of the copper wire must be selected at least 5-6 mm2. The clamp at the end of the wire must ensure reliable contact with the metal part, otherwise the arc from the pilot arc will not transfer to the main arc.
The compressor at the outlet must have a reducer to obtain normalized pressure at the plasma torch.
Options for direct and indirect action
The design of a plasma cutter torch is quite complex; it is difficult to do at home, even with various machines and tools, without a highly qualified worker. That's why the manufacture of plasma torch parts must be entrusted to specialists, or even better, buy it in a store. The direct action plasma torch torch was described above; it can only cut metals.
There are plasma cutters with indirect action heads. They are also capable of cutting non-metallic materials. In them, the role of the anode is played by the nozzle, and the electric arc is located inside the plasma cutter torch; only the plasma jet comes out under pressure.
Despite the simplicity of the design, the device requires very precise settings; it is practically not used in amateur production.
Refinement of the inverter
To use an inverter power source for a plasma cutter, it needs to be modified. You need to connect an oscillator with a control unit to it, which will serve as a starter that ignites the arc.
There are quite a lot of oscillator circuits, but the principle of operation is the same. When the oscillator is started, high-voltage pulses pass between the anode and cathode, which ionize the air between the contacts. This leads to a decrease in resistance and causes an electric arc.
Then the gas electric valve is turned on and under pressure air begins to pass between the anode and cathode through an electric arc. Turning into plasma and reaching the metal workpiece, the jet closes a circuit through it and the mass cable.
A main current of approximately 200 A begins to flow through the new electrical circuit. This triggers the current sensor, which turns off the oscillator. The functional diagram of the oscillator is shown in the figure.
Functional diagram of the oscillator
If you have no experience working with electrical circuits, you can use a factory-made oscillator of the VSD-02 type. Depending on the connection instructions, they are connected in series or in parallel to the plasmatron power circuit.
Before making a plasma cutter, you must first determine what metals and what thickness you want to work with. A compressor is sufficient to work with ferrous metal.
Cutting non-ferrous metals requires nitrogen; high-alloy steel requires argon. In this regard, you may need a trolley for transporting gas cylinders and reduction gears.
Like any equipment and tool, a welding machine with a plasma head requires certain skill from the user. The movement of the cutter should be uniform, the speed depends on the thickness of the metal and its type.
Slow movement results in a wide cut with jagged edges. Moving quickly will result in the metal not being cut through in all places. With proper skill, you can get a high-quality and even cut.
Today the industry is developing at a fairly rapid pace. Every year new welding technologies appear, which are in great demand in private housing construction. Thanks to these techniques, construction work is greatly facilitated, while welding equipment becomes more productive and safe. These techniques include plasma welding.
The emergence of new types of metal alloys in modern technologies has forced specialists to develop new techniques and drawings of equipment for welding products made from them. Since many modern metals do not lend themselves well to traditional welding techniques. As a result, a new plasma method for welding metal samples has emerged, which is successfully used in various repair and installation processes.
The main differences between plasma welding technology
Plasma welding is somewhat reminiscent of argon welding, but there are characteristic differences. For example, it has an operating temperature that is much higher. The welding arc can have a temperature from 5 to 30 thousand degrees. Thanks to this quality, using plasma welding technology, it is possible to connect elements of building structures that cannot be welded with homemade and standard factory equipment, the arc temperature of which does not exceed 5 thousand degrees.
Operating principle of plasma welding
The essence of this welding: by exposing the metal surface to a flow of ionized gas conducting an electric current, the metal melts. When the arc is heated, the gas undergoes ionization, the level of which increases with increasing gas temperature. A plasma jet, which is characterized by ultra-high temperature and increased power, is formed from an ordinary arc after compression, injection into the arc formed by a plasma-forming gas, which is usually argon (hydrogen and helium are rarely used).
The kinetic energy of the chemical elements present in the gas during the ionization process significantly increases the thermal energy of the plasma arc. Moreover, the arc, when compared with a conventional one, has the ability to significantly increase the pressure on the metal surface due to a decrease in its own diameter.
Advantages of plasma technology
- Unlike gas welding, the cutting speed of metal 5-20 centimeters thick using the plasma method is three times higher.
- The high precision of the seams obtained as a result of melting and welding of metal, the quality of the work performed practically eliminates the need for subsequent processing of the edges of the products.
- Plasma cutting is used to process almost any type of metal. For example, you can cook samples from Zaporozhye steel, cast iron, copper, aluminum.
- When welding, the metal is not subject to deformation even when it is necessary to cut out complex shapes. The plasma welding technique makes it possible to cut on an unprepared metal surface, for example, rusty or coated with a layer of paint. In this case, the paint in the working area of the plasma arc does not ignite.
- There is no need for argon, acetylene, or oxygen. This significantly reduces financial costs.
- High degree of safety of work, since gas cylinders are not used. This indicator indicates the environmental friendliness of the process.
Types of plasma welding
Depending on the tools used, plasma welding can be:
- on currents of any polarity;
- with penetrating/non-penetrating arc;
- point, pulse;
- automatic, semi-automatic, manual;
- with and without filler wire.
In the case of using low currents, the connection technique is called microplasma, which is the most popular. This scheme is in demand in the production of structures up to 1.50 mm thick - this is usually the connection of thin-walled pipes, containers, welding of small elements to heavy structures, the manufacture of jewelry, thermocouples, as well as welding of foil samples. Thin-walled metal products are also welded using electric rivets.
If the connection is made using filler wire, then solid wire (cored wire) is used.
Features of microplasma connection
Plasma welding comes in three options, depending on the current used during operation:
- microplasma welding technology on currents - 0.1A-25A;
- connection with medium currents - 25A-150A;
- connection with high currents - 150A and above.
The first variation is more popular. In the process of connecting metal samples using a low-ampere current, a pilot arc is formed. It burns uninterruptedly between a water-cooling nozzle made of copper and a two-millimeter cross-section tungsten electrode.
The main arc is formed after bringing the plasmatron to the surface of the metal sample being processed. The gas that forms the plasma is supplied through a plasma nozzle, the diameter of which can be 0.5-1.5 millimeters.
The maximum diameter of the plasma arc is 2 millimeters. Thanks to this indicator, quite a large amount of thermal energy is generated on a relatively small element of the workpiece. This type of welding, like welding with electric rivets, is most effective for metal samples whose thickness is less than 1.5 millimeters.
Argon is used to form plasma, a protective gas environment, using this technology. Depending on what metal or alloy the sample is made of, additives can additionally be used to increase the efficiency of the “plasma”.
A plasma welding machine is capable of joining metal products in different modes. The range of welding uses is quite extensive:
- fastening membranes to large-scale structures;
- production of thin-walled pipes and containers;
- welding foil;
- jewelry manufacturing;
- many other connections.
DIY welding
This type of metal welding was not initially used at home, as it required a highly qualified welder. Today, thanks to the improvement of the methodology itself and the equipment used, there are welding units that can be used at home. The working method is very simple. To perform welding work, you need to purchase the appropriate equipment, filler wire, electrodes, and read the operating instructions for the device.
- The electrode must first be sharpened to a cone-shaped shape, and the sharpening angle should be a maximum of 30 degrees.
- Important! Correct installation of the electrode. Its axis must coincide with the axis of the nozzles for gas formation.
- The welding joint is subjected to similar processing as when welding with argon.
- It is imperative to clean and then degrease the edges of the workpiece.
- It is necessary to ensure that there are no gaps larger than 1.5 millimeters.
- Additionally, the tack areas are cleaned; they must be of the same quality as the weld.
- You can start welding work.
- Do-it-yourself welding is carried out using direct current. Its value must be within the specified range.
- Before welding the samples, gas is supplied 10-15 seconds, which is turned off after 15 seconds after the arc breaks.
- During operation, the plasma torch should be located from the workpiece at a distance of less than one centimeter.
- It is recommended to hold the welding arc until the seam connection is completely completed.
- Do not overheat the metal during welding. After reaching the critical point, welding is suspended, the metal sample is cooled, after which welding work can be resumed.
- The gun (torch) must be moved evenly, then you can count on obtaining a high-quality welded joint.
Welding machine "Gorynych"
Multifunctional welding "Gorynych" is one of the most popular welding units of domestic production. This is a really high-quality tool that allows you to do welding work at home with your own hands. It should be noted that the Gorynych line of equipment includes devices of various capacities (8,10,12A).
For household work, an 8A device is perfect; a 10-amp device is characterized by price/performance, but more powerful 12A equipment is already considered professional. The welding unit of the Gorynych brand is quite popular both in Russia and in Ukraine (in particular, in Zaporozhye), and in Belarus.
Home craftsmen involved in metal processing are faced with the need to cut metal blanks. This can be done using an angle grinder (grinder), oxygen cutter or plasma cutter.
- Bulgarian. The cut quality is very high. However, it is impossible to perform figured cutting, especially if it concerns internal holes with curved edges. In addition, there are restrictions on the thickness of the metal. It is impossible to cut thin sheets with a grinder. The main advantage is affordability;
- Oxygen cutter. Can cut a hole of any configuration. But achieving an even cut is impossible in principle. The edges turn out torn, with drops of melted metal. Thicknesses greater than 5 mm are difficult to cut. The device is not too expensive, but it requires a large supply of oxygen to work;
- Plasma cutter. This device cannot be called affordable, but the high cost is justified by the quality of the cut. After cutting, the workpiece practically does not need additional processing.
Considering the price that is prohibitive for most home craftsmen, many “Kulibina” craftsmen make a plasma cutter.
There are several ways - you can create a structure completely from scratch, or use ready-made devices. For example, from a welding machine, somewhat modernized for new tasks.
Making a plasma cutter with your own hands is a real task, but first you need to understand how it works.
The general diagram is shown in the illustration:
Plasma cutter device
Power unit.
It can be designed in different ways. The transformer has large dimensions and weight, but allows cutting thicker workpieces.
Electricity consumption is higher, this must be taken into account when choosing a connection point. Such power supplies are little sensitive to changes in input voltage.
Plasma cutting is actively used in many industrial fields. However, a plasma cutter is quite capable of being useful to a private master. The device allows you to cut any conductive and non-conductive materials with high speed and quality. The technology of work makes it possible to process any parts or create shaped cuts, which is carried out by a high-temperature plasma arc. The flow is created by basic components - electric current and air. But the benefits of using the device are somewhat overshadowed by the price of factory models. To provide yourself with the opportunity to work, you can create a plasma cutter with your own hands. Below we provide detailed instructions with the procedure and a list of equipment that is needed.
What to choose: transformer or inverter?
Due to the presence of features and parameters of plasma cutting devices, it is possible to divide them into types. Inverters and transformers have gained the most popularity. The cost of the device of each model will be determined by the declared power and operating cycles.
Inverters are lightweight, compact in size and consume minimal electricity. Disadvantages of the equipment include increased sensitivity to voltage changes. Not every inverter is able to function within the specific conditions of our electrical network. If the device’s protection system fails, you must contact a service center. Also, inverter plasma cutters have a rated power limitation of no more than 70 amperes and a short period of switching on the equipment at high current.
A transformer, traditionally, is considered more reliable than an inverter. Even with a noticeable drop in voltage, they lose only part of the power, but do not break. This property determines the higher cost. Plasma cutters based on a transformer can operate and be switched on for a longer period of time. Similar equipment is used in automatic CNC lines. The negative aspect of a transformer plasma cutter will be its significant weight, high energy consumption and size.
The maximum metal thickness that a plasma cutter can cut is from 50 to 55 millimeters. The average power of the equipment is 150 - 180 A.
Average cost of factory devices
The range of plasma cutters for manual cutting of materials is now truly huge. Price categories are also different. The price of devices is determined by the following factors:
- Device type;
- Manufacturer and country of production;
- Maximum possible cutting depth;
- Model.
Having decided to explore the possibility of purchasing a plasma cutter, you need to be interested in the cost of additional elements and components for the equipment, without which it will be difficult to fully operate. Average prices for devices, depending on the thickness of the metal being cut, are:
- Up to 6 mm – 15,000 – 20,000 rubles;
- Up to 10 mm – 20,000 – 25,000;
- Up to 12 mm – 32,000 – 230,000;
- Up to 17 mm – 45,000 – 270,000;
- Up to 25 mm – 81,000 – 220,000;
- Up to 30 mm – 150,000 – 300,000.
Popular devices are “Gorynych”, “Resanta” IPR-25, IPR-40, IPR-40 K.
As you can see the price range is wide. In this regard, the relevance of a homemade plasma cutter is increasing. Having studied the instructions, it is quite possible to create a device that is in no way inferior in technical characteristics. You can select an inverter or transformer at a price significantly lower than the prices presented.
Operating principle
After pressing the ignition button, the source of electricity starts, supplying high-frequency current to the working tool. An arc (pilot) occurs between the tip located in the cutter (plasma torch) and the electrode. Temperature range from 6 to 8 thousand degrees. It is worth noting that the working arc is not created instantly; there is a certain delay.
Then compressed air enters the cavity of the plasmatron. This is what a compressor is designed for. Passing through the chamber with a pilot arc on the electrode, it is heated and increases in volume. The process is accompanied by ionization of the air, which transforms it into a conductive state.
Through a narrow plasma torch nozzle, the resulting plasma flow is supplied to the workpiece. The flow speed is 2 – 3 m/s. Air in an ionized state can heat up to 30,000°C. In this state, the electrical conductivity of air is close to the conductivity of metal elements.
After the plasma contacts the surface being cut, the pilot arc is switched off and the working arc begins to operate. Next, melting is carried out at the cutting points, from which the molten metal is blown with supplied air.
Differences between direct and indirect devices
There are various types of devices that differ in operating principles. In direct acting equipment, the operation of an electric arc is assumed. It takes on a cylindrical shape and is directly connected to the gas stream. This equipment design makes it possible to provide a high arc temperature (up to 20,000°C) and a highly efficient cooling system for other components of the plasma cutter.
In indirect-acting devices, operation is assumed to be less efficient. This determines their lower distribution in production. The design feature of the equipment is that the active points of the circuit are placed on special tungsten electrodes or a pipe. They are used more often for heating and spraying, but are practically not used for cutting. Most often used in car repairs.
A common feature is the presence in the design of an air filter (extends the life of the electrode, ensures quick start-up of the equipment) and a cooler (creates conditions for long-term operation of the device without interruption). An excellent indicator is the ability of the device to operate continuously for 1 hour with a 20-minute break.
Design
With the proper desire and skill, anyone can create a homemade plasma cutter. But in order for it to function fully and effectively, certain rules must be followed. It is advisable to try on an inverter, because It is he who is able to ensure a stable current supply and stable arc operation. As a result, there are no interruptions and electricity consumption will be significantly reduced. But it is worth considering that an inverter-based plasma cutter can cope with a thinner metal thickness than a transformer.
Required components
Before starting assembly work, it is necessary to prepare a number of components, materials and equipment:
- Inverter or transformer with suitable power. To eliminate error, it is necessary to determine the planned cutting thickness. Based on this information, select the right device. However, taking into account manual cutting, it is worth choosing an inverter, because... it weighs less and consumes less electricity.
- Plasma torch or plasma cutter. There are also some peculiarities of choice. It is better to choose direct action for working with conductive materials, and indirect action for non-conductive materials.
- Compressed air compressor. It is necessary to pay attention to the rated power, because it must cope with the load imposed and match the other components.
Cable hose. Required for connecting all components of the plasma cutter and supplying air to the plasma torch.
Selection of power supply
The operation of the plasma cutter is ensured by the power supply. It generates the specified parameters of electric current and voltage and supplies them to the cutting unit. The main supply unit can be:
- Inverter;
- Transformer.
It is necessary to approach the choice of power supply taking into account the features of the devices described above.
Plasma torch
A plasma torch is a plasma generator. This is a working tool in which a plasma jet is formed that directly cuts materials.
The main features of the device are:
- Creation of ultra-high temperature;
- Simple adjustment of current power, start and stop of operating modes;
- Compact dimensions;
- Reliability of operation.
Structurally, the plasma torch consists of:
- Electrode/cathode containing zirconium or hafnium. These metals are characterized by a high level of thermionic emission;
- The nozzle is basically isolated from the electrode;
- A mechanism that swirls plasma-forming gas.
The nozzle and electrode are consumables of the plasma torch. If a plasma cutter processes a workpiece up to 10 millimeters in size, then one set of electrodes is consumed within 8 hours of operation. Wear occurs evenly, which allows you to change them at the same time.
If the electrode is not replaced in a timely manner, the cutting quality may be impaired - the geometry of the cut changes or waves appear on the surface. The hafnium insert in the cathode gradually burns out. If it has a production of more than 2 millimeters, then the electrode can burn and overheat the plasmatron. This means that electrodes replaced at the wrong time will lead to rapid failure of the remaining elements of the working tool.
All plasmatrons can be divided into 3 volume groups:
- Electric arc - has at least one anode and cathode, which are connected to a direct current power source;
- High-frequency - there are no electrodes and cathodes. Communication with the power supply is based on inductive/capacitive principles;
- Combined - operates when exposed to high-frequency current and arc discharges.
Based on the arc stabilization method, all plasmatrons can also be divided into gas, water and magnetic types. Such a system is extremely important for the operation of the instrument, because it forms a compression of the flow and fixes it on the central axis of the nozzle.
Currently, various modifications of plasma torches are available for sale. You may need to study the offers and buy a ready-made one. However, it is quite possible to make a homemade one at home. This requires:
- Lever. It is necessary to provide holes for wires.
- Button.
- An appropriate electrode designed for the current.
- Insulator.
- Flow swirler.
- Nozzle. Preferably a set with different diameters.
- Tip. Splash protection must be provided.
- Distance spring. Allows you to maintain a gap between the surface and the nozzle.
- Nozzle for removing carbon deposits and chamfering.
Work can be carried out with one plasma torch due to replaceable heads with different diameters that direct the plasma flow to the part. It is necessary to pay attention that they, like the electrodes, will melt during operation.
The nozzle is secured with a clamping nut. Directly behind it there is an electrode and an insulator that prevents the ignition of the arc in the wrong place. Next, a flow swirler is placed to enhance the arc effect. All elements are housed in a fluoroplastic casing. You can do some things yourself, but others will have to be purchased at the store.
The factory plasma torch will allow you to work without overheating for a longer time due to the air cooling system. However, for short-term cutting this is not an important parameter.
Oscillator
An oscillator is a generator that produces high-frequency current. A similar element is included in the plasma cutter circuit between the power source and the plasma torch. Capable of acting according to one of the following schemes:
- Creation of a short-term impulse that promotes the formation of an arc without touching the surface of the product. Externally, it looks like a small lightning bolt supplied from the end of the electrode.
- Constant voltage support with high voltage value superimposed on welding current. Ensures the preservation of stable arc maintenance.
The equipment allows you to quickly create an arc and start cutting metal.
For the most part they have a similar structure and consist of:
- Voltage rectifier;
- Charge storage unit (capacitors);
- Power unit;
- Pulse creation module. Includes an oscillatory circuit and a spark gap;
- Control block;
- Step-up transformer;
- Voltage monitoring device.
The main task is to modernize the incoming voltage. The frequency and voltage level increase, reducing the period of action to less than 1 second. The work sequence is as follows:
- The button on the cutter is pressed;
- In the rectifier, the current is leveled out and becomes unidirectional;
- Charge accumulates in capacitors;
- Current is supplied to the oscillatory circuit of the transformer windings, increasing the voltage level;
- The pulse is controlled by a control circuit;
- The pulse creates a discharge on the electrode, igniting an arc;
- The impulse ends;
- After stopping cutting, the oscillator purges the plasma torch for another 4 seconds. Due to this, cooling of the electrode and the treated surface is achieved.
Depending on the type of oscillator, it can be used in different ways. However, the general characteristic is an increase in voltage to 3000 - 5000 volts and a frequency from 150 to 500 kHz. The main differences are in the intervals of action of the high-frequency current.
For use in a plasma cutter, it is advisable to use an oscillator for non-contact ignition of the arc. Similar elements are used to work in argon welders. The tungsten electrodes in them will quickly become dull if they come into contact with the product. Including an oscillator in the apparatus circuit will allow you to create an arc without making contact with the plane of the part.
Using an oscillator can significantly reduce the need for expensive consumables and improve the cutting process. Properly selected equipment in accordance with the planned work allows you to improve its quality and speed.
Electrodes
Electrodes play an important role in the process of creating, maintaining an arc and direct cutting. The composition contains metals that allow the electrode not to overheat and not prematurely collapse when working with an arc at high temperatures.
When purchasing electrodes for a plasma cutter, it is necessary to clarify their composition. Beryllium and thorium contents create harmful fumes. They are suitable for work in appropriate conditions, with adequate protection for the worker, i.e. additional ventilation is required. Because of this, for application in everyday life it is better to buy hafnium electrodes.
Compressor and cable - hoses
The design of most homemade plasma cutters includes compressors and hose lines to direct air to the plasma torch. This design element allows you to heat the electric arc up to 8000°C. An additional function is to purge the working channels, clearing them of contaminants and removing condensate. In addition, compressed air helps cool the components of the device during long-term operation.
To operate the plasma cutter, it is possible to use a conventional compressed air compressor. Air exchange is carried out by thin hoses with suitable connectors. An electric valve is located at the inlet, which regulates the air supply process.
An electrical cable is placed in the channel from the apparatus to the burner. Therefore, it is necessary to place a hose with a large diameter here, which can accommodate the cable. The passing air also has a ventilation function, as it is able to cool the wire.
The mass must be made of cable with a cross-section of 5 mm2. There must be a clamp. If there is poor ground contact, switching the working arc to the standby arc will be problematic.
Scheme
Now you can find many schemes using which you can assemble a high-quality device. The video will help you understand the symbols in detail. A suitable schematic drawing of the equipment can be selected from those presented below.
Assembly
Before starting the assembly process, it is advisable to clarify the compatibility of the selected components. If you have never assembled a plasma cutter with your own hands before, you should consult with experienced craftsmen.
The assembly procedure assumes the following sequence:
- Prepare all assembled components;
- Electrical circuit assembly. In accordance with the diagram, an inverter/transformer and an electrical cable are connected;
- Connecting the compressor and air supply to the apparatus and plasma torch using flexible hoses;
- For your own safety net, you can use an uninterruptible power supply (UPS), taking into account the battery capacity.
Detailed equipment assembly technology is presented in the video.
Checking the plasma cutter
After all nodes are connected into a single structure, it is necessary to test for functionality.
Please note that testing and working with the plasma cutter must be carried out in protective clothing using personal protective equipment.
It is necessary to turn on all the units and press the button on the plasma torch, supplying electricity to the electrode. At this moment, an arc with a high temperature should form in the plasmatron, passing between the electrode and the nozzle.
If the assembled plasma cutting equipment is capable of cutting metal up to 2 cm thick, then everything is done correctly. It should be noted that a homemade device made from an inverter will not be able to cut parts with a thickness of more than 20 millimeters, since there is not enough power. To cut thick products, you will need to use a transformer as a power source.
Advantages of a homemade device
The benefits provided by an air plasma cutting machine are difficult to overestimate. It is capable of cutting sheet metal accurately. After work, there is no need to further process the ends. The main advantage is the reduction in work time.
These are already compelling reasons for assembling the equipment yourself. The circuit is not complicated, so anyone can cheaply remake an inverter or semi-automatic device.
In conclusion, let us draw your attention to the fact that it is necessary for an experienced specialist to work with a plasma cutter. It's best if it's a welder. If you have little experience, we recommend that you first study the technology of working with photos and videos, and then begin to complete the assigned tasks.
