Plasma cutting is widely used in various industries: mechanical engineering, shipbuilding, advertising, utilities, metal structures and other industries. In addition, a plasma cutter can also be useful in a private workshop. After all, with the help of it you can quickly and efficiently cut any conductive material, as well as some non-conductive materials - plastic, stone and wood. You can cut pipes, sheet metal, make a shaped cut or make a part simply, quickly and conveniently using plasma cutting technology. The cut is performed using a high-temperature plasma arc, which requires only a power source, a torch and air to create. To make working with a plasma cutter easy and the cut to be beautiful and smooth, it doesn’t hurt to learn the operating principle of a plasma cutter, which will give you a basic understanding of how you can control the cutting process.
A device called a “plasma cutter” consists of several elements: power supply, plasma cutter/plasma torch, air compressor And cable-hose package.
Power supply for plasma cutter supplies a certain current to the plasmatron. May be a transformer or inverter.
Transformers They are heavier, consume more energy, but are less sensitive to voltage changes, and they can be used to cut workpieces of greater thickness.
Inverters lighter, cheaper, more economical in terms of energy consumption, but at the same time they allow cutting workpieces of smaller thickness. Therefore, they are used in small industries and private workshops. Also, the efficiency of inverter plasma cutters is 30% greater than that of transformer ones, and their arc burns more stable. They are also useful for working in hard-to-reach places.
Plasma torch or whatever they call it "plasma cutter" is the main element of the plasma cutter. In some sources you can find a mention of a plasma torch in such a context that one might think that “plasma torch” and “plasma cutter” are identical concepts. In fact, this is not so: a plasma torch is directly a cutter with which the workpiece is cut.
The main elements of a plasma cutter/plasma torch are nozzle, electrode, cooler/insulator between them there is a channel for supplying compressed air.
The plasma cutter diagram clearly demonstrates the location of all plasma cutter elements.
Inside the plasma torch body there is electrode, which serves to excite an electric arc. It can be made of hafnium, zirconium, beryllium or thorium. These metals are suitable for air plasma cutting because during operation, refractory oxides are formed on their surface, which prevent the destruction of the electrode. However, not all of these metals are used because the oxides of some of them can be harmful to the operator's health. For example, thorium oxide is toxic, and beryllium oxide is radioactive. Therefore, the most common metal for the manufacture of plasmatron electrodes is hafnium. Less commonly, other metals.
Plasma torch nozzle compresses and forms a plasma jet, which escapes from the output channel and cuts the workpiece. The capabilities and characteristics of the plasma cutter, as well as the technology for working with it, depend on the size of the nozzle. The dependence is as follows: the diameter of the nozzle determines how much air volume can pass through it in a unit of time, and the width of the cut, the cooling rate and the operating speed of the plasma torch depend on the volume of air. Most often, the plasma torch nozzle has a diameter of 3 mm. The length of the nozzle is also an important parameter: the longer the nozzle, the more accurate and better the cut. But you need to be more careful with this. A nozzle that is too long will break down faster.
Compressor for a plasma cutter it is necessary for air supply. Plasma cutting technology involves the use of gases: plasma-forming and protective. Plasma cutting machines, designed for currents up to 200 A, use only compressed air, both to create plasma and for cooling. This machine is sufficient for cutting workpieces 50 mm thick. An industrial plasma cutting machine uses other gases - helium, argon, oxygen, hydrogen, nitrogen, as well as their mixtures.
Cable-hose package connects the power source, compressor and plasmatron. The electric cable supplies current from a transformer or inverter to initiate an electric arc, and the hose carries compressed air, which is necessary for the formation of plasma inside the plasma torch. We will describe in more detail what exactly happens in the plasmatron below.
As soon as the ignition button is pressed, the power source (transformer or inverter) begins to supply high-frequency currents to the plasmatron. As a result, a pilot electric arc appears inside the plasma torch, the temperature of which is 6000 - 8000 °C. The pilot arc lights up between the electrode and the nozzle tip for the reason that it is difficult to form an arc between the electrode and the workpiece being processed immediately. The pilot arc column fills the entire channel.
After the pilot arc occurs, compressed air begins to flow into the chamber. It breaks out of the pipe, passes through an electric arc, as a result of which it heats up and increases in volume by 50 - 100 times. In addition, the air is ionized and ceases to be a dielectric, acquiring conductive properties.
The plasma torch nozzle, narrowed to the bottom, compresses the air, forms a flow from it, which escapes from the nozzle at a speed of 2 - 3 m/s. The air temperature at this moment can reach 25,000 - 30,000 °C. It is this high-temperature ionized air that is in this case plasma. Its electrical conductivity is approximately equal to the electrical conductivity of the metal being processed.
At the moment when the plasma escapes from the nozzle and comes into contact with the surface of the metal being processed, the cutting arc is ignited, and the pilot arc goes out. The cutting/working arc heats up the workpiece being processed at the cutting site - locally. The metal melts, a cut appears. Particles of just molten metal appear on the surface of the metal being cut, which are blown away from it by a stream of air escaping from the nozzle. This is the simplest plasma metal cutting technology.
Cathode spot The plasma arc must be located strictly in the center of the electrode/cathode. To ensure this, the so-called vortex or tangential supply of compressed air is used. If the vortex feed is disrupted, then the cathode spot moves relative to the center of the electrode along with the plasma arc. This can lead to unpleasant consequences: the plasma arc will burn unstably, two arcs may form simultaneously, and in the worst case, the plasma torch may fail.
If you increase the air flow, the speed of the plasma flow will increase, and the cutting speed will also increase. If you increase the diameter of the nozzle, the speed will decrease and the width of the cut will increase. The speed of the plasma flow is approximately 800 m/s at a current of 250 A.
Cutting speed is also an important parameter. The larger it is, the thinner the cut. If the speed is low, the cutting width increases. If the current increases, the same thing happens - the width of the cut increases. All these subtleties relate directly to the technology of working with a plasma cutter.
Plasma cutter parameters
All plasma cutting machines can be divided into two categories: manual plasma cutters and machine cutting machines.
Manual plasma cutters are used in everyday life, in small industries and in private workshops for the manufacture and processing of parts. Their main feature is that the plasma torch is held in the hands of the operator, he guides the cutter along the line of the future cut, holding it in weight. As a result, the cut is even, but not perfect. And the productivity of such technology is low. To make the cut more even, without sagging and scale, a special stop is used to guide the plasma torch, which is placed on the nozzle. The stop is pressed against the surface of the workpiece and all that remains is to guide the cutter, without worrying about whether the required distance is maintained between the workpiece and the nozzle.
For a manual plasma cutter, the price depends on its characteristics: maximum current, thickness of the workpiece being processed, and versatility. For example, there are models that can be used not only for cutting metals, but also for welding. They can be distinguished by their markings:
- CUT - cutting;
- TIG - argon arc welding;
- MMA - arc welding with a stick electrode.
For example, the FoxWeld Plasma 43 Multi plasma cutter combines all of the listed functions. Its cost is 530 - 550 USD. Characteristics related to plasma cutting: current strength - 60 A, workpiece thickness - up to 11 mm.
By the way, the current strength and the thickness of the workpiece are the main parameters by which a plasma cutter is selected. And they are interconnected.
The higher the current, the stronger the plasma arc, which melts the metal faster. When choosing a plasma cutter for specific needs, you need to know exactly what metal will have to be processed and what thickness. The table below shows how much current is needed to cut 1 mm of metal. Please note that processing non-ferrous metals requires high amperage. Keep this in mind when you look at the characteristics of a plasma cutter in a store; the thickness of the ferrous metal workpiece is indicated on the device. If you plan to cut copper or other non-ferrous metal, it is better to calculate the required amperage yourself.
For example, if you need to cut copper 2 mm thick, then you need to multiply 6 A by 2 mm, we get a plasma cutter with a current strength of 12 A. If you need to cut steel 2 mm thick, then multiply 4 A by 2 mm, you get a current strength of 8 A. Only Take a plasma cutting machine with a reserve, since the specified characteristics are maximum, not nominal. You can only work on them for a short time.
CNC plasma cutting machine used in manufacturing plants for the manufacture of parts or processing of workpieces. CNC stands for Computer Numerical Control. The machine operates according to a given program with minimal operator participation, which eliminates the human factor in production as much as possible and increases productivity significantly. The cutting quality of the machine is ideal; no additional edge processing is required. And most importantly - figured cuts and exceptional precision. It is enough to enter the cutting diagram into the program and the device can make any intricate shape with perfect accuracy. The price of a plasma cutting machine is significantly higher than that of a manual plasma cutter. First, a large transformer is used. Secondly, a special table, portal and guides. Depending on the complexity and size of the device, the price can be from 3000 USD. up to 20,000 USD
Machine plasma cutting machines use water for cooling, so they can work the entire shift without interruption. The so-called PV (on duration) is 100%. Although for manual devices it can be 40%, which means the following: the plasma cutter works for 4 minutes, and it needs 6 minutes to cool down.
It would be most reasonable to purchase a ready-made, factory-made plasma cutter. In such devices, everything is taken into account, adjusted and works as perfectly as possible. But some “Kulibina” craftsmen manage to make a plasma cutter with their own hands. The results are not very satisfactory, since the quality of the cut is poor. As an example, we will give a stripped-down version of how you can make a plasma cutter yourself. Let us immediately make a reservation that the diagram is far from ideal and only gives a general concept of the process.
So, a transformer for a plasma cutter must have a falling current-voltage characteristic.
Example in the photo: the primary winding is from below, the secondary winding is from above. Voltage - 260 V. Winding cross-section - 45 mm2, each bus 6 mm2. If you set the current to 40 A, the voltage drops to 100 V. The inductor also has a cross-section of 40 mm2, wound with the same bus, about 250 turns in total.
To operate, you need an air compressor, of course, a factory-made one. In this case, a unit with a capacity of 350 l/min was used.
Homemade plasma cutter - operation diagram.
It is better to purchase a plasma torch from the factory; it will cost about 150 - 200 USD. In this example, the plasma torch was made independently: a copper nozzle (5 cu.) and a hafnium electrode (3 cu.), the rest is “handicraft”. Due to this, the consumables quickly failed.
The circuit works like this: there is a start button on the cutter, when it is pressed, the relay (p1) supplies voltage to the control unit, the relay (p2) supplies voltage to the transformer, then releases air to purge the plasma torch. The air dries the plasma torch chamber from possible condensation and blows out all excess, it has 2 - 3 seconds for this. It is with this delay that the relay (p3) is activated, which supplies power to the electrode to ignite the arc. Then the oscillator is turned on, which ionizes the space between the electrode and the nozzle, as a result, the pilot arc lights up. Next, the plasma torch is brought to the workpiece and the cutting/working arc lights up between the electrode and the workpiece. The reed switch switches off the nozzle and ignition. According to this scheme, if the cutting arc suddenly goes out, for example, if the nozzle gets into a hole in the metal, then the reed switch relay will turn on the ignition again and after a few seconds (2 - 3) the pilot arc will light up, and then the cutting arc. All this is provided that the “start” button is not released. Relay (p4) releases air into the nozzle with a delay, after the “start” button is released and the cutting arc goes out. All these precautions are necessary in order to extend the life of the nozzle and electrode.
Making a plasma cutter yourself at home makes it possible to save a lot, but there is no need to talk about the quality of the cut. Although if an engineer takes on the work, the result may be even better than the factory version.
Not every enterprise can afford a CNC plasma cutting machine, because its cost can reach 15,000 - 20,000 USD. Quite often, such organizations order plasma cutting work to be carried out at special enterprises, but this is also expensive, especially if the volume of work is large. But you really want your own new plasma cutting machine, but you don’t have enough money.
In addition to well-known specialized factories, there are enterprises that produce plasma cutting machines, purchasing only profile parts and assemblies, and producing everything else themselves. As an example, we will tell you how engineers make CNC plasma cutting machines on a production floor.
Components of a do-it-yourself plasma cutting machine:
- Table 1270x2540 mm;
- Belting;
- Step parts;
- Linear guides HIWIN;
- System that controls the height of the THC flame;
- Control block;
- The terminal stand in which the CNC control unit is located is separate.
Machine characteristics:
- The speed of movement on the table is 15 m/min;
- The accuracy of setting the plasma torch position is 0.125 mm;
- If you use a Powermax 65 machine, the cutting speed will be 40 m/min for a 6 mm workpiece or 5 m/min for a 19 mm thick workpiece.
For a similar metal plasma cutting machine, the price will be about 13,000 USD, not including the plasma source, which will have to be purchased separately - 900 USD.
To manufacture such a machine, components are ordered separately, and then everything is assembled independently according to the following scheme:
- The base for welding the table is being prepared, it must be strictly horizontal, this is very important, it is better to check with a level.
- The machine frame is welded in the form of a table. Square pipes can be used. The vertical “legs” must be reinforced with jibs.
- The frame is coated with primer and paint to protect it from corrosion.
- Supports for the machine are being manufactured. The material of the supports is duralumin, the bolts are 14 mm, it is better to weld the nuts to the bolts.
- The water table is welded.
- Fastenings for the slats are installed and the slats are installed. For slats, metal is used in the form of a 40 mm strip.
- Linear guides are installed.
- The table body is covered with sheet iron and painted.
- The portal is installed on the guides.
- A motor and end inductive sensors are installed on the portal.
- The guide rails, rack and pinion and Y-axis motor are installed.
- The guides and motor are installed on the Z axis.
- A metal surface sensor is installed.
- A tap is installed to drain water from the table, and limiters for the portal are installed so that it does not move off the table.
- Cable channels Y, Z and X are installed.
- All wires are hidden in corrugation.
- A mechanized burner is installed.
- Next, the CNC terminal is manufactured. First, the body is welded.
- A monitor, keyboard, TNS module and buttons for it are installed in the CNC terminal housing.
That's it, the CNC plasma cutting machine is ready.
Despite the fact that the plasma cutter has a fairly simple device, you still shouldn’t start making it without serious knowledge of welding and extensive experience. It’s easier for a beginner to pay for a finished product. But engineers who want to implement their knowledge and skills at home, as they say “on the knee,” can try to create a plasma cutter with their own hands from start to finish.
Assembling a plasma cutter with your own hands from an inverter is a relatively simple matter.
A plasma cutter can be used not only for cutting various parts, but also for welding.
Before assembling a homemade plasma cutter with your own hands, you should prepare in advance some of the components included in the design of the plasma cutter. The plasma cutter design includes the following elements:
- plasma cutter;
- power source, which can be an inverter or transformer;
- a compressor device for supplying an air flow and forming a plasma flow;
- cable hoses for assembling all components into a single complex.
A homemade plasma cutter can be used to carry out a variety of technical operations not only in production, but also in the home.
At home, these devices can be used for processing metal products if thin and precise cutting is required.
The industry offers consumers devices that can be used to weld metals in a protective gas environment. The inert gas argon is used as protection during welding.
When assembling a homemade device, special attention should be paid to the current strength. The value of this parameter depends on the power source used.
It is best to use an inverter as a source of electric current. This device ensures stable operation of the plasma cutting machine. In addition, the use of an inverter allows for more economical energy consumption than when using a transformer as a power source.
The disadvantage of using an inverter power source in the design of a plasma cutter is the small thickness of the workpieces that can be processed using such a device.
The advantages of a plasma cutter based on the use of an inverter are the relatively small weight of the device and low electrical energy consumption. In addition, the efficiency of a device based on an inverter power supply is 10% higher than that of a device with a transformer unit, which affects the quality of operations.
When assembling a device, attention should be paid to the accuracy and quality of the assembly in accordance with the design, as well as the integration of elements in the system.
When assembling the device in a structure, you need to use a nozzle of sufficient length, which should not be too long, otherwise it will have to be replaced frequently.
Selection of structural elements for assembling the fixture
When making a device with your own hands, you need to choose the right components.
Power supply for equipment. An inverter is used as this element - this is a device that supplies voltage with predetermined characteristics for the operation of the equipment. In addition to the inverter, a transformer can be used. If a transformer is used as a power supply, then when designing the equipment, the large weight of the welding transformer must be taken into account. In addition, it should be remembered that when using a transformer, the device consumes a large amount of electrical energy.
To assemble the tool, you need to prepare a plasma cutter, which is the main element of the device that ensures the execution of work operations. You will also need to purchase an air flow injection device - a compressor and a cable-hose package.
Using an inverter power supply is more profitable, since this device is more economical and its cost is much lower. A device whose operation is based on the use of an inverter power supply is easier to use. This device can be used when carrying out work at home and in small factories. When using this type of power supply, voltage stability is achieved, which allows for high-quality work in hard-to-reach places where the use of transformer devices is impossible.
The plasma torch is the main element of the cutter. The design of this device consists of a nozzle, an air flow channel that ensures cutting of metal workpieces, an electrode and an insulator, which simultaneously plays the role of a cooler.
Plasma cutter assembly
To assemble the plasma torch, you need to select the appropriate electrode. The most commonly used electrodes are made using thorium, beryllium, zirconium or hafnium. Such materials are considered optimal for cutting metal with an air-flame flow. During the operation of the installation, refractory oxides are formed on the surface of the electrode material, which prevent destruction of the electrode material. When choosing the type of electrode, it should be remembered that some of the materials used to make the electrode body are hazardous to the worker. For example, beryllium in the electrode during operation causes the formation of radioactive oxides, and the use of thorium causes the formation of toxic compounds with oxygen. The best material is hafnium, which is absolutely safe for the worker carrying out the work.
During the assembly process, special attention should be paid to the nozzle, which generates the jet for cutting. The quality of the working jet depends on the technical characteristics of this element. It is optimal to use a device with a diameter of 3 cm. The length should be sufficient so that the cut has a neat and high-quality appearance. If the nozzle is too long, it may quickly be destroyed during operation.
To supply air flow, a compressor is used in the design of the plasma cutter. A special feature of the cutter’s operation is the use of gases for protection and plasma formation during the operation of the equipment. The work of cutting metal is carried out at a current of 200 A. When operating the device, compressed air is used, which is required to cool the operating equipment and form a plasma jet. The use of this design during operation allows cutting metal workpieces with a metal thickness of up to 50 mm.
A cable-hose package is used to connect all elements of the installation. When assembling the installation, a certain order of work must be followed. First, the inverter is connected to the electrode using a cable to supply voltage to it. A hose is used to supply a compressed air flow from the compressor unit to the plasma torch, where a plasma jet is formed.
Operating principle of the cutter
After the installation for cutting metal has been assembled, it is necessary to check its functionality. When started, the inverter supplies high-frequency electric current to the plasmatron. After applying voltage to the electrode, an electric arc is formed; its temperature at the moment of occurrence varies in the range from 6 to 8 thousand degrees Celsius. Arc formation occurs between the electrode and the nozzle tip. Next, a stream of compressed air is supplied, which, when passing through the electric arc, heats up and increases in volume a hundred times, while the flow is ionized, and it acquires conductive properties.
Using a nozzle, a narrow plasma stream is formed. The speed of the plasma flow is 2-3 meters per second. At the moment of expiration of the plasma jet, its temperature increases significantly and reaches 25-30 thousand degrees. At the exit from the nozzle, a stream of high-temperature plasma is formed, which is used to carry out the cutting process. At the moment of contact of the plasma jet with the metal of the workpiece, the initial arc is extinguished and the cutting arc is ignited, with the help of which the workpiece is processed. Melting of the metal occurs locally, at the point of exposure to the plasma flow.
At industrial enterprises, small workshops, during construction and repair work, a manual plasma cutter is used when it is necessary to weld or cut metal products, as well as special equipment equipped with CNC systems. To perform small-scale work, you can use a plasma cutter assembled with your own hands from an inverter, which is capable of providing high quality cuts or seams, taking into account the operations being performed.
Operating principle of a plasma cutter
When the power source is turned on, current begins to flow into the working area into the internal chamber of the plasma cutter, where the electric pilot arc between the nozzle tip and the electrode is activated. The forming arc fills the nozzle channel, where an air mixture begins to flow under high pressure, which, due to the high temperature of 6000-8000 °C, heats up greatly and increases in volume from 50 to 100 times. Due to the internal shape of the tapering nozzle, which has the shape of a cone, the air flow is compressed, heating up to an outlet temperature of 25,000 - 30,000 °C, forming a plasma jet that cuts the processed blank. Moreover, the initially activated pilot arc goes out and the working arc between the electrode and the metal product is activated. The resulting products from the effects of plasma combustion and metal melting are removed due to the force of the jet.
Fig. 1 Carrying out metal cutting operations where cutting or welding of a product is necessary, using a hand-made homemade one or a professional plasma cutter.
The optimal indicators for the workflow are:
- gas supply at speeds up to 800 m/sec;
- The current indicator can be up to 250 - 400 A.
Scheme 1. Drawing of the plasma cutting process of the workpiece.
A manual plasma cutter assembled using an inverter is mainly used for processing workpieces and is characterized by its low weight and economical power consumption.
Selection of plasma cutter components
To assemble a plasma cutter using drawings (based on an inverter), you need the following units with your own hands:
- pressure gas supply device – compressor;
- plasma cutter;
- electrical device - an inverter that provides current to form an electric arc;
- high pressure working hoses for air supply and protected electrical cable.
To supply air, we select a compressor taking into account the output volume for 1 minute. Manufacturing companies produce 2 types of compressors:
- piston apparatus;
- screw device (which has lower power consumption, is lighter, but 40-50% more expensive).
Rice. 2 Plasma cutter (device) with a cable set for the cutter and connection to the workpiece (as an anode).
Piston compressors are divided into oil and non-oil based, based on the drive principle - with a belt or direct connection of elements.
When operating compressors, a number of rules must be observed:
- at negative ambient temperatures, it is necessary to preheat the oil contained in the crankcase;
- It is necessary to regularly change the air (inlet) filter;
- strictly control the oil level in the crankcase;
- At least once every six months it is necessary to completely clean the units from foreign impurities;
- Upon completion of work, it is necessary to relieve pressure (using a regulator) in the system.
During repair work, products from ORLIK KOMRESSOR (Czech Republic) are often used. The ORL 11 device allows cutting workpieces using a current of 200-440 A and an air-gas flow coming under pressure.
The equipment set includes:
- compressor;
- block of main filters for the air-gas mixture;
- gas dryers;
- receiver.
At the outlet of the unit, purified air free of oil, dust and moisture arrives. An example of screw compressors is the CA series product from Atlas Copco (Sweden). The device is equipped with an automatic condensate removal system for air purification.
A plasmatron is a special device in which, using an electric current, an electric arc is formed that heats air supplied under pressure in a chamber to form a cutting plasma stream.
The cutter consists of elements:
- special holder with electrode;
- an insulating gasket separating the nozzle and the electrode assembly;
- plasma generation chambers;
- output nozzles for the formation of a plasma jet (see drawings);
- supply systems;
- tangential plasma supply elements (on some models) to stabilize the arc discharge.
According to the method of performing work (welding or cutting), cutters are divided into:
- Double-flow, used in reducing, oxidizing and inert environments.
- Gas inert (using helium, argon), reducing (hydrogen, nitrogen).
- Gas oxidizing (the air-gas mixture includes oxygen).
- Gas using a stabilizing (gas-liquid) arc.
The plasmatron cathode is made in the form of a rod or inserts made of tungsten, hafnium, and zirconium. Plasmatrons with a sleeve cathode, used for cutting using an air-gas flow under pressure, have become widespread.
To cut products in an oxidizing environment, a hollow cathode made of copper with a forced cooling system using water is used.
Rice. 3 Portable device (inverter) for plasma cutting.
Double-flow plasma cutters (inverter) are equipped with 2 coaxial nozzles, external and internal. The gas entering the internal nozzle is considered primary, and the external one is considered additional, and the gases can have different compositions and volumes.
A plasma cutter with arc stabilization due to the supply of a gas-liquid flow has a difference, which is the supply of water to the torch chamber to stabilize the state of the arc discharge.
To activate the working arc, a workpiece is used as an anode, which is connected to the inverter using clamps and a cable.
As a power plant for carrying out the plasma cutting process, a device (inverter) is used that provides the necessary current strength, which has a higher efficiency than a transformer, but the transformer’s metal processing capabilities are much higher.
Scheme 2. Drawing of the plasmatron power supply with your own hands.
Inverter advantages:
- the ability to uniformly change parameters;
- light weight;
- stable state of the working arc;
- high quality cutting or welding.
The equipment set also includes a set of high pressure hoses for connecting a stationary compressor and an electrical connecting cable.
To assemble a plasma cutter with your own hands, a device diagram is developed indicating the necessary units that meet the required characteristics, which should include all additions and changes used during assembly with the necessary calculations of the most important indicators. You can assemble a homemade plasma cutter with your own hands using ready-made blocks and assemblies produced by specialized companies; in this case, it is necessary to make accurate calculations and coordinate the output parameters of the ongoing processes.
Features of marking plasma cutters
Plasma cutters produced by industrial enterprises can be divided into 2 categories:
- machine cutting units;
- manual.
Hand cutters are more affordable if you need to do it yourself. Manufactured models have special markings:
- MMA - the device is designed for arc welding using an individual electrode;
- CUT - a device (plasma cutter) used for cutting metal;
- TIQ - the device is used for work where argon welding is necessary.
Manufacturing enterprises produce equipment for metal cutting:
- Profi CUT 40 (RT-31 burner, permissible cut thickness – 16 mm, air-gas mixture flow rate – 140 l/min, receiver volume 50 l);
- Profi CUT 60 (P-80 burner, permissible workpiece cutting thickness - 20 mm, air-gas mixture flow rate - 170 l/min.);
- Profi CUT 80 (burner R. – 80, permissible cutting thickness of the workpiece – 30 mm, air-gas mixture flow rate – 190 l/min.);
- Pro CUT 100 (burner A-101, permissible cutting thickness of the workpiece - 40 mm, air-gas mixture flow rate - 200 l/min.), receiver with a volume of 100 l.
Making a CNC plasma cutter with your own hands
A CNC-equipped plasma cutter must have a unified assembly using drawings made on the basis of the prepared technical specifications for the product, which include:
- work table;
- belt transmission;
- function control unit;
- step elements;
- linear guides;
- cutting height adjustment system;
- CNC control unit;
Scheme 3. Drawing of an inverter device for plasma cutting.
Drawings of all plasma cutter blocks can be purchased taking into account the required power and installation characteristics and financial capabilities, or you can do it yourself if you have experience and knowledge.
To complete and assemble a CNC machine, it is necessary to manufacture a number of elements using drawings:
- table base for welding;
- a durable frame is assembled and then painted;
- support posts are attached;
- the water table is assembled;
- fastenings and the slats themselves are installed;
- linear guides are mounted;
- the table cover is installed;
- guides are installed together with the portal;
- the portal is equipped with a motor and signal sensors;
- the guides, the Y guide motor and the positioning control rack are mounted;
- a guide equipped with a motor is mounted;
- a metal surface signal sensor is mounted;
- a tap is installed to remove water from the table;
- connecting cables-channels X.Z.Y are laid;
- the wires are insulated and covered with cladding;
- the working cutter is mounted;
- The CNC device is assembled and installed.
Carrying out operations for the manufacture and assembly of a CNC plasma torch should only be carried out in the presence of qualified specialists. The device diagram (drawings) must include all the necessary elements to ensure high quality of work and safety of metal cutting. Equipping enterprises with CNC equipment can increase labor productivity and the complexity of operations. Make production processes performed using CNC equipment more economical by increasing labor productivity and reducing the processing speed of products.
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Plasma cutting is a fairly popular operation, especially when it comes to cutting thick metal parts or workpieces. The process happens quickly, the edges of the metal remain smooth. But such a device is not cheap. Therefore, many craftsmen make a plasma cutter for themselves with their own hands from different types of equipment, combining them into one design. Their connection diagram is simple, the main thing is to choose the right devices according to the required technical characteristics.
Plasma cutting is based on ionized gas, which flies out of the torch nozzle at high speed. This gas is that same plasma. What is she doing.
- Essentially, this ionized medium is an excellent conductor of electric current, which flows from the electrode to the metal workpiece.
- The plasma heats the metal to the required temperature.
- It blows away the molten metal and frees up the cutting space.
This means that to create plasma, you need gas and a source of electricity. And these two components must come together in one place. Therefore, plasma cutting equipment consists of a gas cylinder, a high-power source of electricity and a cutter in which the electrode is installed.
The design of the cutter is made in such a way that gas passes around the electrode and, when heated from the electrode, escapes out through a small hole. The small diameter of the hole and gas pressure create the necessary speed for the plasma. When making homemade plasma cutting, you just need to purchase a ready-made cutter and not think about creating it. Because everything is already thought out in it, plus the factory version is a guarantee of safety.
As for gas, all options have long been abandoned, leaving compressed air. You can get it today very simply - purchase and install a compressor.
There are certain conditions that guarantee the quality of plasma cutting.
- The current strength at the electrode should not be less than 250 A.
- Compressed air must be supplied to the cutter at a speed within 800 m/sec.
How to make a plasma cutter with your own hands
The basics of plasma cutting are clear, the design of the plasma cutter is also clear, and you can begin assembling it. By the way, you don’t need special drawings for this.
So what will be needed.
- We need to find a source of electricity. The simplest option is a welding transformer or inverter. For many reasons, an inverter is better. For example, it has a stable current value, without drops. It is more economical in terms of energy consumption. You will have to pay attention to the current that the welding machine produces. Its value should not be less than 250 amperes.
- Source of compressed air. The compressor remains unchanged here. But which one? The main parameter is air pressure. You will need to pay attention to him. 2.0-2.5 atm. - it will be fine.
- The cutter can be purchased at the store. And this will be the ideal solution. If you have a cutter for argon welding, then it can be converted for plasma cutting. To do this, you will have to make an attachment from copper in the form of a nozzle, which is inserted into the argon welding cutter.
- A set of hoses and cables for connecting all parts of a homemade plasma cutter. Again, the kit can be purchased in the store as a single connecting element.
Here are the four elements with which a homemade plasma cutter is assembled.
Auxiliary elements and materials
What else should you pay attention to when assembling a plasma cutting machine with your own hands? As mentioned above, the main characteristic of a plasma cutter is the diameter of its hole. What size should it be to ensure maximum cutting quality? Experts believe that a diameter of 30 mm is the optimal size. Therefore, when buying a cutter in a store, you need to pay attention to whether it comes with a nozzle with such a hole.
In addition, it is necessary to select a nozzle with a significant length. It is this size that allows the jet of compressed air to gain the required speed. This results in a neat metal cut, and the cutting process itself is quick and easy. But you shouldn’t buy a very long nozzle. Such a device quickly collapses under the influence of high temperatures.
As for choosing an electrode for a plasma cutter, you need to pay attention to the alloy from which it is made. For example, if the alloy contains beryllium, then it is a radioactive substance. It is not recommended to work with such electrodes for a long time. If the alloy contains thorium, it releases toxic substances at high temperatures. An ideal electrode for plasma cutting, the alloy of which includes hafnium.
Checking the plasma cutter
So, the hoses connect the cutter and the compressor, the cable cutter and the inverter. Now you need to check whether the assembled structure works. All units are turned on, the button on the cutter to supply electricity to the electrode is pressed. In this case, an arc is formed with a temperature of 6000-8000C. It slips between the metal of the electrode and the nozzle.
After this, compressed air begins to flow into the cutter. Passing through the nozzle and heated by an electric arc, it sharply expands tenfold and at the same time acquires conductive properties. That is, it turns out to be an ionized gas.
It passes through a narrowed nozzle, while acquiring a speed of 2-3 m/sec. But the plasma temperature rises to 25000-30000C. The most important thing is that the arc, with the help of which the compressed air was heated and turned into plasma, goes out as soon as the plasma begins to act on the metal workpiece prepared for cutting. But immediately the second, so-called working arc is turned on, which acts locally on the metal. Exactly in the cutting area. Therefore, metal is cut only in this zone.
If, when checking the operation of the plasma cutter, you were able to cut metal with a thickness of at least 20 mm, then all the elements of the new design, assembled with your own hands, were selected correctly. It is necessary to note that the plasma cutter cannot cut workpieces with a thickness of more than 20 mm from the inverter. It just doesn't have enough power. To cut thicker metal, you will have to use a transformer.
Attention! Any work related to the use of plasma cutting must be carried out wearing protective clothing and gloves.
There are many points that necessarily affect the operation of the unit.
- There is no need to purchase, for example, a large compressor. But 2-2.5 atmospheres may not be enough for a large amount of work. The way out is to install a receiver on the compressor. It works like an accumulator that accumulates pressure in compressed air. For this purpose, you can use, for example, bolts from the brake systems of heavy vehicles. The option is actually simple. The volume of the cylinder is large, and it should be enough for a long period of time.
- In order for the air pressure to be stable and uniform, a reducer must be installed at the receiver outlet.
- Of course, the optimal solution is to purchase a compressor complete with a receiver. It costs more than usual, but if this unit is used for other things, for example, for painting, then you can increase its functionality and thereby cover the costs.
- To make a mobile version of the machine, you can make a small trolley. After all, all the elements of a plasma cutter are small devices. Of course, you will have to forget about mobility if the machine is made on the basis of a welding transformer. It's too big and heavy.
- If you can’t buy a ready-made hose-cable kit, you can make it yourself. You need to combine the welding cable and high-pressure hose into one sleeve and place them in a single sheath. For example, into a regular hose of larger diameter. A set made in this way simply will not get in the way, which is very important when cutting metals.
Making your own plasma cutter is not difficult at all. Of course, you will need to obtain the necessary information and study it; it is definitely recommended to watch the training video. And after that, correctly select all the elements exactly to the required parameters. By the way, the assembled plasma cutter based on a serial inverter makes it possible not only to carry out plasma cutting of metals, but also plasma welding, which increases the functionality of the unit.
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.
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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.
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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 at the contact point rises sharply, which makes it possible to initiate an arc 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.
