Do-it-yourself CNC plasma cutter diagrams and drawings

The technology of plasma cutting of sheet metal and various metal products is used with equal success in everyday life and in large industrial production.
Using special equipment, you can easily cut non-ferrous metals, as well as work efficiently with stainless steel, aluminum and other alloys. Cutting non-ferrous metals is carried out using special plasma cutters, which are at the same time easy to use, functional and reliable. Let's tell you more about this equipment and talk about how to make a plasma cutter with your own hands from an inverter. Industrial plasma cutters are productive equipment that allows for the most accurate cutting of metals with different refractoriness indices. Such industrial plasma cutters are designed primarily for operation under conditions of increased loads and are equipped with CNC, which makes it possible to manufacture parts in a serial manner.

Description of a homemade plasma cutter

If you need a plasma cutter for domestic use, as well as for the use of such equipment in construction, then such a cutter can be made with your own hands from a simple welding inverter . Subsequently, self-made equipment will be distinguished by its versatility in use and will allow you to effectively cut non-ferrous metals and thick sheet steel.

Making such a cutter with your own hands from an inverter will not be particularly difficult. You can easily find diagrams for the implementation of such devices on the Internet and, using the calculations obtained, make such an easy-to-use device. We can recommend that you make plasma cutters based on compact welding inverters, which will significantly simplify the design and guarantee the necessary efficiency of such devices.

Homemade plasma cutting machines are not equipped with CNC, so it will be impossible to use such equipment for work that is fully controlled by automation. You must understand that using such homemade plasma cutters it will be impossible to make two perfectly accurate parts.

A homemade plasma cutter will consist of the following elements:

Plasmatron.
DC source.
Compressor or gas cylinder.
Oscillator.
Power cables.
Connection hoses.

Electrodes used

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

Beryllium.
Zirconium.
Thorium.
Hafnium.

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

Principle of operation

The operating principle of such equipment is extremely simple:

The current source used, and in our case it is an inverter, generates voltage and supplies it through cables to the plasmatron.
The plasma torch contains two electrodes, between which a high-temperature arc is excited.
Through specially twisted channels under high pressure, a stream of air or gas is supplied to the working area with a ignited arc.
A work cable is pre-connected to the product being cut, which closes to the surface being cut and provides the ability to work with metal.

DC power supplies

Plasma cutting technology will invariably require high operating current power, the performance of which should be at the level of semi-professional and professional inverter welding machines. It is not recommended to use transformer welding machines as a power source, since such devices are bulky and inconvenient to use. But an inverter will be an excellent choice, since such devices combine compact dimensions and provide high-quality electric current.

Schemes and drawings of a plasma cutter with your own hands are simple, while the costs of manufacturing such equipment are significantly reduced. A hand-made compact plasma cutter made from a welding inverter will be able to cope with cutting metal whose sheet thickness will reach 30 mm. If we talk about the advantages of such home plasma cutters made using an inverter, we note the following:

No metal sparks.
Smooth edges.
Line accuracy.
Overheating problems resolved.

Important: making a homemade plasma cutter based on an inverter is not difficult. It is only necessary that the device generate an electric current with a force of at least 30 Amps.

The current source used must meet the following requirements:

Power supply from a network with a voltage of 220 Volts.
Ability to operate with a power of 4 kW.
The idle speed should be 220 Volts.
The current adjustment range is in the range of 20−40 Amperes.

Plasma torch design

The plasma torch is the second most important element of a metal cutter. Let's take a closer look at the design of the plasma torch and the principle of its operation. It consists of a main and auxiliary electrode. The main electrode is made of refractory metals, and the auxiliary electrode, which has the shape of a nozzle, is usually made of copper.

In a plasma torch, the cathode is the main electrode made of a refractory metal, and a copper electrode-nozzle is used as an anode, which makes it possible to provide high-quality electric current and a high-temperature arc for cutting metal.

The completed plasma torch is responsible for creating and maintaining an arc that is located between the workpiece and the cutter. The thickness of the cut, as well as the temperature created by such a cutter, will depend on the shape and design of the nozzle. The nozzle used can be hemispherical or conical, providing an operating temperature of 30,000 degrees Celsius.

During operation of the plasma torch, the main electrode and nozzle may wear out, which leads to a deterioration in the quality of metal cutting. If these elements become so worn, they should be replaced with new ones, which will ensure excellent quality of work with metal.

The plasma torch is supplied with working gas from a cylinder, using special heavy-duty gas hoses that can withstand high pressure. In each specific case, depending on the material being worked with, the gas used, which is necessary for cutting the metal, may differ.

The working gas is supplied through special channels, and the presence of numerous turns in the supply tube makes it possible to provide the necessary air turbulence, which, in turn, guarantees a high-quality cutting plasma arc that will have the correct shape. This improves the quality of metal cutting and welding and minimizes the thickness of the seam.

Oscillator

A special feature of plasma cutters is the fact that to start work, it is necessary to first ignite the arc , only after that gas is supplied to the plasma torch, the arc is created at the required temperature and the metal is cut. An oscillator is used as such a kind of starter, which serves to pre-ignite the arc. The implementation scheme of the oscillator is not difficult.

On the Internet you can find functional and electrical diagrams of oscillators, which will not be difficult to complete. It is only necessary to use high-quality electrical circuits and capacitors, which will be suitable in their parameters to the electric current generated by the inverter. Depending on its type, such a torch can be connected to the plasma torch power circuit in series or in parallel.

Transformer based cutter

Like other components of the system, the power supply is assembled or modified with your own hands. Detailed instructions help you easily cope with this task.

Device diagram

The electrical circuit of the device includes the following components:

welding transformer with rectifier;
start relay;
oscillator;
a resistor that reduces the pilot arc voltage;
start button;
a contactor that deactivates the initial arc;
compressor with controls.

A correctly compiled diagram should display all elements, regardless of their location.

What details will be needed

In addition to the welding inverter, to create the machine you will need:

Holder with replaceable rod. When the current is up to 100 A and the thickness of the workpiece is up to 5 cm, the element is made of copper. The holder of a more powerful unit is equipped with channels for liquid cooling. To ignite the arc, leave a distance of 2 mm between the nozzle and the electrode. The main rod is made movable.
PTFE insulator. Due to rapid wear, the part is replaceable.
Housing with nozzle.
Cables: power and for igniting the pilot arc.
Hoses. In liquid-cooled units, the bare wire is located in the tube that supplies water to the torch. You will also need a separate hose to remove gas to the nozzle.

Plasma cutter assembly

Work begins with remaking the welding transformer. The number of turns of the winding is selected taking into account the future characteristics of the equipment and the parts being cut.

With a sheet thickness of up to 1.2 cm, a current of 50 A and an open circuit voltage of 20 V, set the following values:

core cross-section - 107 mm²;
the number of turns of the primary winding is 225, the secondary is 205.

After remaking the transformer, other elements are connected:

Compressor with a capacity of 140-190 l per minute. The pressure generated by the unit must be more than 4.5 bar.
Cables and hoses for connecting components. The cross-section of the supply wire depends on the power of the plasma cutter. At a current of 50 A it is 6 mm². The wire cross-section for the pilot arc is 1.5 mm². The recommended diameter of the air hose is 1 cm.
Oscillator. When creating a plasma cutter from a transformer, you can use a car electronic ignition system as this block.

The air hose is connected to the compressor outlet. The start key wire is connected to the control unit.

Features of use

When working with a cutter from a transformer from a semi-automatic welding machine, carefully follow safety rules, which is explained by the influence of the following harmful factors:

Melt splash. Under the influence of plasma, the metal is heated to extreme temperatures. The air flow blows it out of the cut line. Splashing some materials will cause them to catch fire. Contact of the melt with human skin leads to deep burns. Therefore, the plasma jet is directed in the direction opposite to the welder and flammable materials.
Dust and air pollution with harmful gases. During plasma cutting, metal begins to burn. Smoke is dangerous to the human respiratory system. Therefore, a hood is installed above the desktop. The master puts on a respirator.
Bright light. The plasma torch is a powerful generator of ultraviolet radiation, which causes burns to the retina of the eye. Therefore, the carver puts on a protective mask and equips the work area with a mobile shield.
Temperatures. The edges of the resulting blanks retain heat for a long time. You can touch them only with gloves after the parts have cooled.

Working gas

Even before choosing a specific design for manufacturing a plasma cutter, you should decide on the scope of use of such equipment. If you plan to use the device exclusively for working with ferrous metals, you can exclude gas cylinders from the circuit and use only a compressor with compressed air. If you plan to use such equipment for brass, titanium and copper, then you need to choose a plasma cutter with a nitrogen cylinder. Aluminum cutting is performed using a special gas mixture with hydrogen and nitrogen.

Recommendations for working with devices for beginners

A correctly selected apparatus and the mode required for welding will help to carry out work without cracks and the formation of cavities, even with a metal such as aluminum, which is quite capricious for carrying out this kind of work.

Plasma welding. Video. Inexperienced welders may experience excessive metal spatter during the welding process due to high steam pressure. It is better for novice welders to select equipment that has a large nozzle and the largest hole diameter for the job.

Thanks to this, the steam pressure will not be so high, and the torch will be able to simultaneously cover both edges of the parts, which will increase the likelihood of obtaining a high-quality seam.

Features of using a plasma cutter

Let's figure out how plasma cutting of metal is done with our own hands. After turning on the inverter, the generated electric current enters the plasma cutter onto the electrode, and the oscillator ignites the electric arc. Its temperature can initially be 6-8 thousand degrees. Immediately after the arc is ignited, air or gas is supplied to the nozzle under high pressure, through which an electric charge passes. The air flow is heated and ionized by an electric arc, after which its volume can increase hundreds of times, and the gas and air itself begins to conduct electric current.

Read also: Fence and gates for a private house

A plasma cutter produces a thin jet of plasma, the temperature of which can reach 30,000 degrees. Subsequently, such a high-temperature plasma jet is supplied to the metal being processed, which makes it possible to cut heavy-duty metal elements.

One of the features of using plasma cutting is the fact that the metal being processed is cut and melted exclusively at the point where it is exposed to the plasma flow. It is extremely important to correctly position the plasma impact spot, which should be located strictly in the center of the working electrode. If this requirement is neglected, the air-plasma flow is disrupted, which deteriorates the quality of metal cutting.

The quality of work with such a plasma cutter will also depend on the air flow rate. It is recommended that all work be carried out with a current of 250 Amperes, while the speed of the air stream will be 800 meters per second. This will allow you to easily work with metals with different refractoriness characteristics, ensuring high-quality cutting without thermal effects on the structure of the alloy.

A plasma cutter is a special device that allows you to quickly, efficiently and effectively cut metal of various structures. You can either purchase plasma cutters that have already been manufactured in a factory, or make them yourself. You can easily find suitable schemes for making plasma cutters from an inverter or transformer welding machine, which will allow you to make such equipment yourself, saving on buying it in a store.

The advantage of a plasma cutter over a gas cutter

One of the simplest devices for cutting metal is a gas cutter. Such a device costs little money and consumables for it are also inexpensive. But when performing gas welding work, too large an area of metal is heated.

For this reason, materials with high thermal conductivity may warp and change color. Both at the point of metal melting and at a considerable distance from the thermal effects of the burner flame.

The advantage of a plasma cutter is that it is possible to obtain a very thin stream of hot gas, which will affect a small surface area, which will significantly reduce the heating of the part.

DIY plasma machine

Alex Kost » Jul 10, 2022 11:21 am

Gentlemen, help the amateur.

There’s a wild amount of money poured in, so there’s a risk of screwing it up somehow, tell me how to put it all together?

Thanks in advance to everyone who responded!

Re: DIY plasma machine

odekolon » Jul 10, 2022, 11:59 am

deliver the bottle to the electronics engineer!

I would take one power supply, 48 volt amperes at 20.

Where is the THC?

Re: DIY plasma machine

aftaev » Jul 10, 2022, 12:20 pm

You bought the slag, when you connect it you will understand why there are Nema 42 and 51 steppers on the plasma? The plasma must travel quickly, but it will crawl.

This is the source of problems.

They don’t install Nema 42 on heavy milling machines, but you’re about to screw it up on plasma. I have never seen such cruelty

Re: DIY plasma machine

odekolon » 10 Jul 2022, 13:16

Yeah, I didn’t even look at the sizes.

Right now I’m running homemade plasma 1700x2700. engines 23 x 110 x 2 pcs., Chinese nonname, excellent at carrying the portal 12 m/min. More is possible, I just don’t see the point for this project..

scheme (though without THC) here

Enable circuits are drawn “just in case” - in fact, they are wired, but not connected anywhere. Drivers are always enabled when power is applied.

Don’t worry, everyone makes mistakes, think about how to get out of the situation with the least losses.

for example, if the machine is on racks, put larger gears directly on the axis of the engine - everything will fly at amazing speed!

Re: DIY plasma machine

Alex Kost » 10 Jul 2022, 13:51

I don’t understand why it has to crawl, they will work on a rail, approximately 160 mm per revolution (portal 4x2 meters). Let me explain, I took it with a power reserve, because... The portal is planned to be multifunctional with the ability to change the working element on the Z axis. The X beam will ride on 1 drive (51), the portal will have a gusset, the weight will be stored there. Z will be on Ballscrew 2022.

I agree, the option is not the best, for the first time, there is no money left for “hypertherm”.

They were at a big discount.

Does a super board for 6 axes even support TNS? [/quote] What kind of beast is this? (I'm an electronics amateur) I planned to connect the board to a computer.

Thank you for not kicking too hard yet.

Re: DIY plasma machine

Alex Kost » 10 Jul 2022, 14:06

Thank you so much for the diagram!

Thanks to everyone who responded.

Re: DIY plasma machine

odekolon » 10 Jul 2022, 14:10

yes, it’s fine, it will fly, I think it will accelerate to 30 meters per minute easily

It’s a bit much, but it’s quite alright, in principle the engine can be changed to a weaker one, but the fact that it’s 20 mm per revolution is very good!

Please also note that some of your engines are pure steppers, and some are hybrid servos. But for you, it doesn't really matter

Yes, and put it on, it’s not scary, the dynamics will drop a little. When starting, set the current to a minimum, as the axes move in, something will start to work, you will increase it.

THC – search for “plasma thc” and read. Without it, the machine loses greatly in functionality. Although you can install a mechanical one

Re: DIY plasma machine

aftaev » 10 Jul 2022, 14:12

On plasma/gas cutting portals measuring 3x12 meters, on which there is a booth in which a person sits and rides along with the portal, there are often 400 watt servos (this is less than 2 Nm) + gearbox + rack. Look how many steps you have

If you buy steppers with a reserve that you don’t really need, then you won’t have enough money for normal plasma. As soon as this Chinese miracle burns out from the metal dust, the cut will be crooked/oblique; there will immediately be enough money for normal plasma

Re: DIY plasma machine

aftaev » 10 Jul 2022, 14:20

Re: DIY plasma machine

odekolon » 10 Jul 2022, 14:56

Re: DIY plasma machine

Alex Kost » 10 Jul 2022, 14:59

All the engines of the house are on the windowsill.

In the description they all say “hybrid”, tell me which one is a pure stepper. In the first message I confused the Z drive with the Y drive.

Re: DIY plasma machine

odekolon » 10 Jul 2022, 15:05

Re: DIY plasma machine

Alex Kost » 10 Jul 2022, 15:14

I don’t argue, maybe I didn’t do it quite right, you can scold me for this as much as you like, but it’s too late, the drives are at home. I ask for help given that they already exist.

I hope filters and careful operation will help, but then we’ll think about it.

Re: DIY plasma machine

aftaev » Jul 10, 2022, 03:23 pm

Re: DIY plasma machine

Alex Kost » 10 Jul 2022, 15:37

Re: DIY plasma machine

aftaev » Jul 10, 2022, 03:51 pm

Steppers have a property: the higher the speed, the lower the torque. That is, when the stepper is at its maximum torque, as soon as it starts to step (spinning) the torque drops. At some rpm the engine simply stops due to lack of torque. This depends on the inductance of the windings. The greater the motor, the greater the inductance. Nema 17 rotates at 3000 rpm, and Nema 42 at 150 rpm (that's approximately). Inductance can be thought of as a barrel into which you need to pour water. When the stream of water (voltage) is small, the barrel does not have time to fill quickly enough. And the faster the speed, the faster you need to manage to fill. This is how it is with motor windings, when the voltage is small and the inductance is large, the windings simply do not have time to be saturated with current. My drive was 80V constant, yours says 220V alternating. If the drive is really 220V, and not some clever way to cut the voltage in the drive, then it can rotate faster. Such large motors are more suitable for rotary axes.

The servo torque is small, but the same throughout the entire rev range.

Re: DIY plasma machine

Alex Kost » 10 Jul 2022, 20:25

Please tell me which of the engines is a clean stepper?

In addition to 6 axes, the board also allows you to connect pnp sensors. Does anyone have a software algorithm based on the sensor signal?

Re: DIY plasma machine

aftaev » July 10, 2022, 08:39 pm

What's the difference between clean/dirty/hybrid? The main thing is that it spins with the right torque, at the right speed.

This board works via USB. And cheap plasma has high-frequency ignition = strong interference = problems. And USB loves interference. These scarves work great on our plasmas https://www.ebay.com/itm/1pcs-5-Axis-CN. xyBjBTWMPR

What does algorithm mean? It is connected to the board, and then the signal is inverted in Mach3 if necessary.

Read also: DIY pipe cutter for plastic pipes

Alex Kost, to assemble a machine you don’t need to put all the problems together. The task needs to be split into parts. We screwed on one stepper and set it up in Mach3. We set up another one, then the third one can be installed with HOME sensors (although we work without them), and when everything is already absolutely super/perfectly working, install the TNS and metal detector sensor. We have been working fine without them for 5 years now, since a clumsy TNS creates more problems than it helps.

Re: DIY plasma machine

Alex Kost » 10 Jul 2022, 21:22

I would like not only power, but also a little precision. All the same, they will work on the rail.

Initially I wanted to build a map of the plane and work on jumping to the desired height. But I think the thermal deformation of the sheet during the cutting process will not allow such an algorithm.

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.

Why are shields needed?

Owners of homemade devices have heard a lot about expansion boards - Arduino cnc shield, the use of which expands the functionality of milling equipment.

Usually the shield is made to fit the form factor of the board. They also use several shields at the same time, installing them on the microcontroller (one on top of the other). Range of their application:

using the official Arduino device - Ethernet cnc shield, you can achieve independence of the project from the PC, and it is also used for hosting a web server;
4 Relay Shield – the ability to connect 4 peripheral devices;

IMPORTANT: You must be careful with the pins of this device so as not to damage the Arduino.

Protoshield is a very useful shield at the moment when the circuit is being assembled;
LCD Shield allows information from Arduino to be output directly to a peripheral screen;
Energy Shield - advanced power options for Arduino. Recharging mobile phones and gadgets is possible;
motor shield provides control and protection for a large number of motors;
SD Card Shield is used for processing and storing large amounts of information;

Wi-fi Shield connected to the serial port will provide remote control of the drives of robotic projects;
GPRS Shield is equipped with antennas for using the GSM/GPRS network;
E-Ink shield is a way to use electronic ink technology; the display needs a minimum of energy to power it;
Music Shield is capable of playing music through Arduino in excellent quality.

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.

Features of a homemade device

A homemade plasma cutter can easily perform various jobs. It can be used not only for industrial purposes, but also for everyday tasks, for example, for processing metal products, where the cut must be as precise, thin and high-quality as possible.

When manufacturing equipment, it is important to provide the appropriate current strength. This indicator is determined by the power source, in this case the inverter

Thanks to it, relatively stable operation is ensured; compared to a transformer, energy is consumed more economically, despite the fact that the thickness of the products with which it can work is several times smaller.

Another feature of the inverter is ease of use. It is compact and light weight. In addition, with low power consumption, its efficiency is almost ten percent greater than that of a transformer. All these nuances have a positive effect on the quality of his work. The only disadvantage of using an inverter plasma cutter is the difficulty in cutting workpieces of considerable thickness.

To assemble the design of homemade devices, you can use ready-made diagrams that are presented on the Internet

It is also important to prepare all components in advance

During the assembly process, you should follow the sequence of actions specified in the diagram as accurately as possible, paying attention to whether the structural elements correspond to each other

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.

How to make a welding transformer

The plasma power source is a welding transformer. Like some other elements, you can make it yourself.

Required parameters

A transformer for plasma cutting differs from a conventional welder in the no-load voltage and is 220-250V. This is necessary to create and maintain an arc between the electrode and the part being cut. The power and current of the secondary winding depend on the expected metal thickness:

20A, 2.5 kW – 6 mm;
50A, 6kW – 12 mm;
80A, 10kW – 18-25 mm.

A power source is required with a “soft” characteristic; the operating voltage is 70V. A current of 5A is sufficient to operate the pilot arc. It is limited to a resistance of 30-50 Ohms, made of thick nichrome wire.

How to calculate

The calculation of the supply transformer comes down to determining the required sections of the magnetic circuit, the primary and secondary windings and the number of turns.

For a device designed to cut metal up to 12 mm at a current of 50A, an open circuit voltage of 200V and a mains voltage of 220V, these parameters are:

magnetic core cross-section – 107 mm²
primary winding – 225 turns of copper wire Ø4.7 mm;
secondary winding – 205 turns of copper wire Ø5.04 mm².

Transformer manufacturing

Due to the fact that the transformer must have a “soft” characteristic, the coils are located separately from each other. When using an O-shaped core, they are located on different rods; on an W-shaped magnetic core, the windings are located along the middle part.

The coils are wound according to the calculated parameters on the frames of their electrical cardboard. The finished windings are wrapped with glass tape or keeper tape and coated with paint.

After winding the windings and assembling the magnetic circuit, a diode bridge of 4 diodes with radiators, assembled on a textolite platform, is attached and connected to the transformer. The assembled transformer is placed in the housing, and the outputs of the windings and diode bridge are connected to the terminals on the front panel. The connection is made according to the schematic diagram, taking into account the presence of ammeters, voltmeters, starters and other parts.

An oscillator connected in series with the welder has a high high frequency output voltage. Therefore, it is necessary to use high-frequency diodes in the rectifier or install a separate diode bridge, specifically for the pilot arc.

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.

You can read in detail about plasma cutting technology and working with equipment in the corresponding article.

Plasma torch

The second most important element is the plasmatron. A plasma cutter consists of a main and an additional electrode, the first is made of a refractory metal, and the second is a nozzle, usually copper

The main electrode serves as the cathode, and the nozzle serves as the anode, and during operation this is the current-conducting part being processed.

If we consider a direct plasma torch, the arc occurs between the workpiece and the cutter. Indirect plasma torches cut with a plasma jet. The inverter device is designed for direct action.

The electrode and nozzle are consumables and are replaced as they wear out. In addition to them, the housing has an insulator that separates the cathode and anode units, and there is also a chamber where the supplied gas vortexes. A thin hole is made in the nozzle, conical or hemispherical, through which gas escapes, heated to 3000-5000°C.

Gas enters the chamber from a cylinder or is supplied from a compressor through a hose, which is combined with power cables, forming a package of hoses and cables. The elements are connected in an insulating sleeve or connected by a harness. Gas enters the chamber through a straight pipe, which is located on top or on the side of the vortex chamber, which ensures the movement of the working medium in only one direction.

The principle of operation of the plasma torch

Gas entering under pressure into the space between the nozzle and the electrode passes into the working hole and is then released into the atmosphere. When the oscillator is turned on - a device that generates a pulsed high-frequency current - a preliminary arc appears between the electrodes and heats the gas in the limited space of the combustion chamber. Since the heating temperature is very high, the gas turns into plasma. In this state of aggregation, almost all atoms are ionized, that is, electrically charged. The pressure in the chamber rises sharply, and the gas rushes out in a hot stream.

When the plasma torch is brought to the part, a second, more powerful arc appears. If the oscillator current is 30-60 A, the working arc occurs at a force of 180-200 A. It additionally heats the gas, which accelerates under the influence of electricity to 1500 m/s. The combined effect of high temperature plasma and speed of movement cuts the metal along the finest line. The thickness of the cut is determined by the properties of the nozzle.

An indirect plasma torch works differently. The role of the main anode in it is played by the nozzle. Instead of an arc, a plasma jet erupts from the cutter, cutting non-conductive materials. Homemade equipment of this type works extremely rarely. Due to the complexity of the plasma torch design and fine adjustments, it is almost impossible to make it in artisanal conditions, although drawings are not difficult to find. It operates under high temperatures and pressures and becomes dangerous if not done correctly!

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.

Advantages and disadvantages of plasma cutting

Plasma metal cutting has advantages over other methods:

the ability to cut any metals and alloys;
high processing speed;
clean cut line without sagging or drips of material;
processing is carried out without heating the parts being cut;
Flammable materials such as oxygen and natural gas cylinders are not used.

The disadvantages of plasma cutting are:

complexity and high cost of installation;
each operator with a plasma torch requires a separate transformer and control panel;
cutting angle no more than 50°;
a lot of noise when working.

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:

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.

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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 increase 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, it is better to buy hafnium electrodes for household use.

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.

How to make a plasma cutter from an inverter - instructions

If desired, any owner can make such equipment with his own hands. However, in order for a homemade plasma cutter to do its job effectively, all the rules must be followed. In such a case, an inverter will be practically irreplaceable, since with the help of this device a reliable supply of current will be ensured. Due to this, there will be no interruptions in the operation of the plasma cutter, and it will also be possible to reduce energy consumption. However, it also has disadvantages: it is designed for cutting material of a smaller thickness than when using a transformer.

Selecting elements

If you decide to make a plasma cutter yourself, then you should prepare the necessary materials and equipment:

An inverter or transformer with the required power. In order not to make a mistake when purchasing this device, you need to tell the seller in the store about the thickness of the material you plan to use it for cutting. Based on this, the selection of a suitable mechanism will be made. Considering that cutting will be done manually, it is advisable to purchase an inverter, which is associated not only with its lightness, but also with its ability to reduce energy costs.

Plasma cutter or plasma torch point. When choosing it, you must rely on the same criteria as in the case of an inverter. The important point here is that direct impact equipment is designed to work with conductive materials, while an indirect impact plasma cutter is more suitable for working with products that are not capable of conducting electricity.

Compressor for air circulation

Here you should pay attention to its power, according to which it should be correlated with other selected components.

Cable-hose package. His task will be to combine all the above-described elements.

Assembly

Even before you start assembling a homemade plasma cutter, it doesn’t hurt to find out whether the components you purchased are compatible with each other. If you have never made a plasma cutting machine with your own hands before, it is advisable to seek help from more experienced craftsmen. After analyzing the power of each element needed, they will give you their recommendation. You should definitely make sure you have a protective set of clothing. You will have to use it when the time comes to test the performance of a homemade plasma cutter. If we talk about the procedure for assembling plasma cutting equipment, it includes the following steps:

At the first stage, it is necessary to prepare all the necessary elements for assembly and protective clothing.

Next, you should resolve the issue with an uninterruptible power supply.

Then you need to take an inverter or transformer, as well as a cable of suitable thickness and electrodes

Pay special attention to the last element, which should be made of beryllium, zirconium, thorium or hafnium. Such materials are considered the best choice for air plasma cutting

Hafnium may also be considered as an alternative because it will provide greater safety to the welder or craftsman who will be doing the work of separating the sheets. The listed elements must be connected to each other in order, the result should be an electric arc.

Next, a hose is connected to the compressor. It is through this that air will flow into the plasma cutting machine. The second edge must be connected to the plasma torch.

Take a small piece of aluminum and test the operation of the device you have made. Pay special attention to the security of connections.

Regardless of whether you plan to make a plasma cutter with your own hands or buy it in a store, you should first study all the models, get acquainted with the principles of their operation and design options. An important point is the type of material that is planned to be cut using this equipment in the future. You can simplify your selection task if you first watch a video that shows the operating principle of a manual plasma cutting machine and the technology for working with it.

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.

Safety rules when working with a plasma cutter

The plasma cutting process, if operating rules are not followed, is dangerous to the health and life of people. The main harmful factors are:

Splashes of molten metal. During the cut, the plasma stream melts the metal and blows it out of the part being cut. Contact of molten drops with flammable substances leads to their ignition, and contact with skin causes severe burns, up to IV degree (charring). For protection, it is necessary to direct the plasma flow away from people and flammable materials.
Harmful gases and dust. During cutting, the metal not only melts, but also burns. The resulting smoke is harmful to health. In addition, contaminants on the surface of parts burn. Therefore, the workplace must be equipped with exhaust ventilation and work in a respirator.
Bright light. During the operation of electric welding and cutting with plasma formed by an electric arc, in addition to visible light, ultraviolet radiation appears. This type of radiation causes burns to the retina of the eyes. For protection, the workplace is fenced with portable shields, and the cutter must use a protective shield.
Temperature. After completion of work, the edges of the part remain heated to a high temperature for some time and touching them can lead to burns. To avoid such injuries, cut parts should only be touched with protective gloves or after sufficient time for the edges to cool.

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.

What is needed to make a plasma cutter?

This question is asked most often. We have some unpleasant news for you. Making this device yourself would be impractical.

If you use an inverter as a power source. The cost of making it yourself, that is, on your own, will be much higher than usual. Let's explain why.

Approximately 400 Volts. In this case, a transformer is used. The plasma cutter has contact ignition of the arc, so independent production using an inverter is excluded.

It must be borne in mind that a high-quality plasma cutter cannot be made from a regular inverter. The monetary costs of making a homemade plasma cutter will not justify themselves.

The parts for its manufacture will cost more than half of a new plasma cutter. And considering that you will also need a valve and a plasmatron, the price will increase several times. Financially it will not be very profitable.

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.

Next, the supply of compressed air begins. When passing through the plasma torch nozzle, subjected to heating from the arc, the air will expand, turning into a plasma stream.

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.

Schemes of a plasma cutter using the example of the APR-91 device

When considering the electrical circuit diagram, we will use the APR-91 plasma cutting machine as a donor.

Power section diagram (click to enlarge)

Plasma cutter control circuit (click to enlarge)

Oscillator circuit (click to enlarge)

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.

Guides and controls

A do-it-yourself CNC plasma cutter is practically no different from a factory cutter in terms of capabilities.
The cutting head must be able to move in three axes. You can make a mobile frame with your own hands without much effort. You will only have to buy stepper motors and shielded cables. Cable protection is necessary - the signal from the CNC is very sensitive and interference even from the inverter can affect the operation of the system. If the machine operates from a transformer, then cable protection is doubly necessary. The software unit is also susceptible to the influence of extraneous electrical fields; it is best to install it in a grounded metal box. The scheme is simple, but very effective.

You can buy motors, a power supply and other components for the coordinate system in online stores. The cost of an average quality set of 5 motors, a power supply and a controller (five-axis) is about 20 thousand rubles (at eBay prices). Compared to the cost of a factory machine, the price is minuscule.

Lead screws, limit switches and other accessories will also have to be purchased. Automotive Hall sensors can be used as limit switches. They are an order of magnitude cheaper than standard industrial ones, although in terms of reliability and efficiency they are at the same level.

You can mount control boards yourself if you have the skills to work with a soldering iron and some knowledge of electronics. But it will be cheaper and faster to use a factory assembly, for example AVR ATmega16 or analogues. They are quite affordable in price, and in terms of performance, they are quite appropriate on industrial-level machines.

The complexity of the control circuit and settings makes it appropriate to purchase a ready-made system. It is quite difficult to adapt it to a ready-made desktop and plasma cutter; it is better to do the opposite - first purchase a control system, and then develop and implement executing mechanisms. It will be justified in any case.

What is Arduino

Arduino is a brand of hardware and software for building and prototyping simple systems, models and experiments in the fields of electronics, automation, process automation and robotics.

The software part consists of a free software shell (IDE) for writing programs, compiling them and programming hardware.

The hardware is a set of assembled printed circuit boards sold by both the official manufacturer and third-party manufacturers. The system's completely open architecture allows you to freely copy or expand the Arduino product line.

Most often, the term “Arduino” is used to refer to a controller with its own processor and memory. Arduino is very popular among novice engineers and experienced enthusiasts due to its low price and ease of setup.

The open architecture of Arduino boards allows people with minimal knowledge of electrical engineering to design microcontrollers. A significant advantage is the diagrams and codes available on the Internet, created for various types of machines.

The most popular Arduino controllers among engineers include UNI, R3, Mega 2560 and Nano.

Electronics development

You can assemble the board yourself or purchase a ready-made version, which is much more practical and profitable. The software is installed on it via a computer.

Programs are written using a simplified version of the C++ language.

But to create a CNC it is not necessary to know it, since there are already ready-made libraries in the public domain. In addition, there are many functions, classes, operators and methods for easier work.

CNC electronics include stepper motors, drivers for them, wires and the Arduino board itself.