If you need to perform some simple welding work for domestic needs, it is not at all necessary to purchase an expensive factory unit. After all, if you know some subtleties, you can easily assemble a welding machine with your own hands, which will be discussed below.
Welding machines: classification
Any welding machines can be electric or gas. It’s worth saying right away that homemade welding machines should not be gas. Since they include explosive gas cylinders, you should not keep such a unit at home.
Therefore, in the context self-assembly designs will be discussed exclusively about electrical options . Such units are also divided into varieties:
- Generator units are equipped with their own current generator. Distinctive feature- large weight and dimensions. This option is not suitable for home needs, and it will be difficult to assemble it yourself.
- Transformers - such installations, especially the semi-automatic type, are very common among those who make welding equipment themselves. They are powered from a 220 or 380 V network.
- Inverters - such installations are easy to use and ideal for home use; the design is compact and lightweight, but the electronic circuit is quite complex.
- Rectifiers - these devices are easy to assemble and use for their intended purpose. With their help, even a beginner can make high-quality welds.
To assemble an inverter at home, you will need a circuit that will allow you to comply with the necessary parameters. It is recommended to take parts from old Soviet devices:
The following parameters can be selected for the device:
- It must work with electrodes whose diameter does not exceed 5 mm.
- The maximum operating current is 250 A.
- Voltage source - household network at 220 V.
- The welding current adjustment varies from 30 to 220 A.
The tool includes the following components:
- power unit;
- rectifier;
- inverter
Begin from winding transformer and proceed in the following sequence:
- Take a ferrite core.
- Perform the first winding (100 turns using 0.3 mm PEV wire).
- The second winding is 15 turns, wire with a cross section of 1 mm).
- The third winding is 15 turns of 0.2 mm PEV wire.
- The fourth and fifth - respectively 20 turns of wires with a cross section of 0.35 mm.
- To cool the transformer, use a computer fan.
In order for transistor switches to operate continuously, voltage should be applied to them after the rectifier and capacitors. Assemble the rectifier block according to the diagram on the board, and secure all components of the device in the housing. Can be used old radio casing, or you can do it yourself.
Installed from the front of the case led indicator, which shows that the device is connected to the network. Here you can install an additional switch, as well as a protective fuse. It can also be installed on the back wall and even in the case itself.
It all depends on its size and design features. Variable resistance is installed on the front part of the housing, with its help you can adjust operating current. When you have assembled all the electrical circuits, check the device with a special device or tester and you can test it.
The assembly of the transformer version will be slightly different from the previous one. This unit operates on alternating current, but for welding with direct current you need to assemble a simple attachment for it.
To work you will need transformer iron for the core, as well as several tens of meters of thick wire or thick copper busbar. All this can be found at the metal collection point. The core is best made U-shaped, toroidal or round. Many also take the stator from an old electric motor.
The assembly instructions for the U-shaped core look like this:
- Take transformer iron with a cross-section from 30 to 55 cm2. If the figure is higher, the device will be too heavy. And if the cross section is less than 30, the device will not be able to work correctly.
- Take a copper winding wire with a cross-section of about 5 mm 2, equipped with heat-resistant fiberglass or cotton insulation. Insulation is important because during operation the winding can heat up to 100 degrees or more. The winding wire has a square cross-section or rectangular section. However, such an option is difficult to find. An ordinary one with a similar cross-section will do, but you will only need to remove the insulation from it, wrap it in fiberglass and thoroughly soak it with electrical varnish, and then dry it. The primary winding has 200 turns.
- The secondary winding will require about 50 turns. There is no need to cut the wire. Connect the primary winding to the network, and on the secondary wires find a place where the voltage is about 60 V. To find such a point, unwind or wind additional turns. The wire can be aluminum, but the cross-section must be 1.7 times larger than for the primary winding.
- Install the finished transformer into the housing.
- To bring out the secondary winding, copper terminals are required. Take a tube with a diameter of 10 mm and a length of about 4 cm. Rivet its end and drill a hole with a diameter of 10 mm, and insert the end of the wire, previously cleared of insulation, into the other end. Next, crimp it with light hammer blows. To strengthen the contact of the wire with the terminal tube, apply notches to it with a core. Screw homemade terminals to the body with nuts and bolts. It is best to use copper parts. When winding the secondary winding, it is advisable to make taps every 5-10 turns, they will allow you to change the voltage on the electrode in steps;
- To make an electrical holder, take a pipe with a diameter of about 20 mm and a length of about 20 cm. At the ends, about 4 cm from the end part, cut out recesses to half the diameter. Insert the electrode into the recess and press it with a spring based on a welded bush of steel wire with a diameter of 5 mm. Attach the same wire that was used for the secondary winding to the second terminal using a nut and screw. Place a rubber tube with a suitable inner diameter onto the holder.
It is best to connect the finished device to the network using wires with a cross-section of 1.5 cm2 or more, as well as a switch. The current in the primary winding usually does not exceed 25 A, and in the secondary winding it fluctuates between 6-120 A. When working with electrodes with a diameter of 3 mm every 10-15 make stops to allow the transformer to cool down. If the electrodes are thinner, this is not necessary. More frequent breaks are needed if you are working in cutting mode.
Do-it-yourself mini-welding
To assemble a miniature welding machine yourself, you will only need a few hours and the following materials:
First carefully disassemble the old battery and extract from it graphite rod. Sharpen the end with sandpaper and wipe with a dry cloth. Clean a piece of thick wire 4-5 cm from the end from the insulation and use pliers or side cutters to bend a loop. Insert a carbon electrode into it.
Remove the secondary winding from the transformer and replace it with wind thick wire for 12-16 turns. Now all this is inserted into a suitable housing - and the device is ready.
Its wires are connected to the terminals of the secondary winding, carbon the rod is inserted into the loop and crimps well. Connect the positive terminal to the electrode holder, and the negative terminal to the twist of the working parts. The holder handle can be adapted for an electrode.
You can use a soldering iron handle or something similar. Connect the device to a household network and perform joining parts using graphite. A flame should appear, and a spherical weld seam will form at the end of the parts.
For a home workshop, having a welding machine is very important. Such devices have different designs and modifications. Both beginners and experienced craftsmen often prefer not factory ones, but homemade devices, which can be modified in your own way.
20 years ago, at the request of a friend, I built him a reliable welder to work on a 220-volt network. Before this, he had problems with his neighbors due to a voltage drop: an economical mode with current regulation was required.
After studying the topic in reference books and discussing the issue with colleagues, I prepared electrical diagram control on thyristors, mounted it.
This article is based on personal experience I’m telling you how I assembled and configured a DC welding machine with my own hands based on a homemade toroidal transformer. It came out in the form of a small instruction.
I still have the diagram and working sketches, but I can’t provide photographs: there were no digital devices then, and my friend moved.
Versatile capabilities and tasks performed
A friend needed a machine for welding and cutting pipes, angles, sheets different thicknesses with the ability to work with electrodes 3÷5 mm. Welding inverters were not known at that time.
We settled on the DC design, as it is more universal and provides high-quality seams.
Thyristors removed the negative half-wave, creating a pulsating current, but did not smooth out the peaks to an ideal state.
The welding output current control circuit allows you to adjust its value from small values for welding up to 160-200 amperes required when cutting with electrodes. She:
- made on a board from thick getinax;
- covered with a dielectric casing;
- mounted on the housing with the output of the adjusting potentiometer handle.
The weight and dimensions of the welding machine were smaller compared to the factory model. We placed it on a small cart with wheels. To change jobs, one person rolled it freely without much effort.
The power cord was connected through an extension cord to the connector of the input electrical panel, and the welding hoses were simply wound around the body.
Simple design of DC welding machine
Based on the installation principle, the following parts can be distinguished:
- homemade transformer for welding;
- its power supply circuit is from network 220;
- output welding hoses;
- power unit of thyristor current regulator with electronic circuit control from a pulse winding.
Pulse winding III is located in power zone II and is connected through capacitor C. The amplitude and duration of the pulses depend on the ratio of the number of turns in the capacitor.
How to make the most convenient transformer for welding: practical tips
Theoretically, you can use any model of transformer to power the welding machine. The main requirements for it:
- provide arc ignition voltage at idle speed;
- reliably withstand the load current during welding without overheating the insulation from prolonged operation;
- meet electrical safety requirements.
In practice, I have come across different designs of homemade or factory-made transformers. However, they all require electrical engineering calculations.
I have been using a simplified technique for a long time, which allows me to create fairly reliable transformer designs of medium accuracy class. This is quite enough for household purposes and power supplies for amateur radio devices.
It is described on my website in the article This is an average technology. It does not require clarification of the grades and characteristics of electrical steel. We usually don’t know them and cannot take them into account.
Features of core manufacturing
Craftsmen make magnetic wires from electrical steel of various profiles: rectangular, toroidal, double rectangular. They even wind coils of wire around the stators of burnt-out powerful asynchronous electric motors.
We had the opportunity to use decommissioned high-voltage equipment with dismantled current and voltage transformers. They took strips of electrical steel from them and made two donut rings out of them. The cross-sectional area of each was calculated to be 47.3 cm 2 .
They were insulated with varnished cloth and secured with cotton tape, forming a figure of a reclining figure eight.
They began to wind the wire on top of the reinforced insulating layer.
Secrets of the power winding device
The wire for any circuit must have good, strong insulation, designed to withstand long work when heated. Otherwise, it will simply burn during welding. We proceeded from what was at hand.
We received a wire with varnish insulation, covered with a fabric sheath on top. Its diameter - 1.71 mm is small, but the metal is copper.
Since there was simply no other wire, they began to make the power winding out of it with two parallel lines: W1 and W’1 with the same number of turns - 210.
The core donuts were mounted tightly: this way they have smaller dimensions and weight. However, the flow area for the winding wire is also limited. Installation is difficult. Therefore, each power half-winding was separated into its own magnetic circuit rings.
In this way we:
- doubled cross section power winding wires;
- saved space inside the donuts to accommodate the power winding.
Wire alignment
You can get a tight winding only from a well-aligned core. When we removed the wire from the old transformer, it turned out to be bent.
We figured out the required length in our minds. Of course it wasn't enough. Each winding had to be made from two parts and spliced with a screw clamp directly on the donut.
The wire was stretched along its entire length on the street. We picked up the pliers. They clamped the opposite ends and pulled with force in different directions. The vein turned out to be well aligned. They twisted it into a ring with a diameter of about a meter.
Technology of winding wire on a torus
For the power winding, we used the rim or wheel winding method, when a ring is made from the wire large diameter and is wound inside the torus by rotating one turn at a time.
The same principle is used when putting a winding ring on, for example, a key or keychain. After the wheel is inserted inside the donut, they begin to gradually unwind it, laying and fixing the wire.
This process was well demonstrated by Alexey Molodetsky in his video “Winding a torus on a rim.”
This work is difficult, painstaking, and requires perseverance and attention. The wire must be laid tightly, counted, the process of filling the internal cavity must be monitored, and the number of turns wound must be recorded.
How to wind a power winding
For it, we found a copper wire of a suitable cross-section - 21 mm 2. We estimated the length. It affects the number of turns, and the voltage depends on them idle move necessary for good ignition of the electric arc.
We made 48 turns with the middle terminal. In total, there were three ends on the donut:
- middle - for direct connection of the “plus” to the welding electrode;
- the extreme ones - to the thyristors and after them to ground.
Since the donuts are fastened together and the power windings are already mounted on them along the edges of the rings, the winding of the power circuit was carried out using the “shuttle” method. The aligned wire was folded like a snake and pushed through the holes of the donuts for each turn.
The midpoint has been desoldered screw connection with its insulation with varnished fabric.
Reliable welding current control circuit
The work involves three blocks:
- stabilized voltage;
- formation of high-frequency pulses;
- separation of pulses into circuits of thyristor control electrodes.
Voltage stabilization
An additional transformer with an output voltage of about 30 V is connected from the power winding of the 220 volt transformer. It is rectified by a diode bridge based on D226D and stabilized by two zener diodes D814V.
In principle, any power supply with similar electrical characteristics current and voltage at the output.
Pulse block
The stabilized voltage is smoothed by capacitor C1 and supplied to the pulse transformer through two bipolar transistor direct and reverse polarity KT315 and KT203A.
Transistors generate pulses to the primary winding Tr2. This is a toroidal type pulse transformer. It is made of permalloy, although a ferrite ring can also be used.
Winding of three windings was carried out simultaneously with three pieces of wire with a diameter of 0.2 mm. Made 50 turns. The polarity of their inclusion matters. It is shown by dots in the diagram. The voltage on each output circuit is about 4 volts.
Windings II and III are included in the control circuit for power thyristors VS1, VS2. Their current is limited by resistors R7 and R8, and part of the harmonic is cut off by diodes VD7, VD8. Appearance We checked the pulses with an oscilloscope.
In this chain, the resistors must be selected for the voltage of the pulse generator so that its current reliably controls the operation of each thyristor.
The unlocking current is 200 mA, and the unlocking voltage is 3.5 volts.
With this simple welding machine you can cut thin metals, weld copper wires, and engrave metal surfaces. Other applications can be found without any problems. This mini welding machine can be powered with a voltage of 12-24 V.
The welding machine is based on a high-voltage, high-frequency converter. Built on the principle of a blocking oscillator with deep transformer feedback. The generator generates short-term electrical pulses, repeated at relatively large intervals. The clock frequency is in the range of 10-100 kHz.
The transformation ratio of this circuit will be 1 to 25. This means that if you apply a voltage of 20 V to the circuit, then the output should be about 500 V. This is not entirely true. Since any pulse transformer source or generator without load has powerful high-voltage pulses reaching a voltage of 30,000 V! Therefore, if you disassemble any Chinese pulse charger, you will see a soldered resistor parallel to the output capacitor. This is also a network load; without a resistor, the output capacitor will quickly leak due to excess voltage, or worse than that will explode.
Therefore, attention! The voltage at the transformer output is dangerous to life!
Mini welding machine diagram
Required parts:
- The transformer is homemade, the manufacturing procedure is described below.
- Resistors - 0.5-2 W power.
- The transistor used was FP1016, but it is difficult to find due to its specificity. Can be replaced with transistor 2SB1587, KT825, KT837, KT835 or KT829 by changing the polarity of the power supply. Another transistor with a collector current of 7 A, a collector-emitter voltage of 150 V, and a high gain (composite transistor) is also suitable.
Transformer manufacturing
The transformer is wound on a piece of ferrite rod from a radio receiver.- The collector winding is 20 turns of 1 mm wire.
- Base winding - 5 turns with a 0.5-1 mm rein.
- High-voltage winding - 500 turns with a drive of 0.14-0.25 mm.
Let's put together a diagram. If everything is in order, everything should start without problems. Since the operating frequency of the generator exceeds the sound frequency, you will not hear a squeak during operation, so you should not touch the output of the transformer with your hands.
Start the generator with a voltage of 12 Volts and increase if necessary.
The arc is ignited from a distance of 1 cm, indicating a voltage of 30 kV. High frequency prevents the burning arc from breaking, as a result of which the arc burns very stably. When using a copper electrode in close contact with another electrode, a plasma medium (copper plasma) is formed, resulting in an increase in the temperature of arc welding and cutting.
Welding machine testing by cutting and welding
We cut the razor blade with an arc.
We fuse copper wires up to 1 mm thick.
Thick copper wire was used as an electrode. It is clamped in a wooden match, as dry wood It is also a good insulator.
If you liked this small welding machine, then you can make it larger in size and power. But be extremely careful.
Also, to increase power, you can assemble a generator using a push-pull circuit, and even on field effect transistors, as here - . In this case, the power will be decent.
Also, do not look at the bright arc discharges with the naked eye; use special safety glasses.
Watch a video of making a welding machine using a blocking generator
Many households would benefit from a device for electric welding of parts made of ferrous metals. Since commercially produced welding machines are quite expensive, many radio amateurs are trying to make welding inverter with your own hands.
We already had an article about that, but this time I offer an even simpler version of a homemade welding inverter from available parts with your own hands.
Of the two main design options for the apparatus - with a welding transformer or based on a converter - the second was chosen.
Really, welding transformer- this is a large cross-section and heavy magnetic circuit and a lot copper wire for windings, which is inaccessible to many. Electronic components for the converter with their making the right choice not in short supply and relatively cheap.
How I made a welding machine with my own hands
From the very beginning of my work, I set myself the task of creating the simplest and cheapest possible welding machine using widely used parts and assemblies.
As a result of quite lengthy experiments with various types of converters using transistors and thyristors, the circuit shown in Fig. 1.
Simple transistor converters turned out to be extremely capricious and unreliable, while thyristor converters can withstand output shorting without damage until the fuse trips. In addition, SCRs heat up much less than transistors.
As you can easily see, the circuit design is not original - it is an ordinary single-cycle converter, its advantage is its simplicity of design and the absence of scarce components; the device uses many radio components from old TVs.
And finally, it requires virtually no setup.
The diagram of the inverter welding machine is presented below:
The type of welding current is constant, regulation is smooth. In my opinion, this is the simplest welding inverter that you can assemble with your own hands.
When butt welding steel sheets 3 mm thick electrode with a diameter of 3 mm, the steady current consumed by the device from the network does not exceed 10 A. The welding voltage is turned on with a button located on the electrode holder, which allows, on the one hand, to use an increased arc ignition voltage and increase electrical safety, on the other hand, since When the electrode holder is released, the voltage on the electrode is automatically switched off. The increased voltage makes it easier to ignite the arc and ensures its burning stability.
A little trick: a self-assembled welding inverter circuit allows you to connect parts made of thin sheet metal. To do this, you need to change the polarity of the welding current.
The mains voltage rectifies the diode bridge VD1-VD4. The rectified current, flowing through lamp HL1, begins to charge capacitor C5. The lamp serves as a charging current limiter and an indicator of this process.
Welding should only begin after lamp HL1 goes out. At the same time, battery capacitors C6-C17 are charged through inductor L1. The glow of the HL2 LED indicates that the device is connected to the network. SCR VS1 is still closed.
When you press the SB1 button, a pulse generator with a frequency of 25 kHz, assembled on a unijunction transistor VT1, is started. The generator pulses open the thyristor VS2, which, in turn, opens the thyristors VS3-VS7 connected in parallel. Capacitors C6-C17 are discharged through inductor L2 and the primary winding of transformer T1. The inductor circuit L2 - the primary winding of the transformer T1 - capacitors C6-C17 is an oscillatory circuit.
When the direction of the current in the circuit changes to the opposite, current begins to flow through the diodes VD8, VD9, and the thyristors VS3-VS7 close until the next generator pulse on the transistor VT1.
The pulses arising on winding III of transformer T1 open the thyristor VS1. which directly connects the mains rectifier based on diodes VD1 - VD4 with a thyristor converter.
LED HL3 serves to indicate the generation process impulse voltage. Diodes VD11-VD34 rectify the welding voltage, and capacitors C19 - C24 smooth it out, thereby facilitating the ignition of the welding arc.
Switch SA1 is a batch or other switch with a current of at least 16 A. Section SA1.3 closes capacitor C5 to resistor R6 when turned off and quickly discharges this capacitor, which allows you to inspect and repair the device without fear of electric shock.
Fan VN-2 (with electric motor M1 according to the diagram) provides forced cooling of the device components. It is not recommended to use less powerful fans, or you will have to install several of them. Capacitor C1 - any one designed to operate at an alternating voltage of 220 V.
Rectifier diodes VD1-VD4 must be designed for a current of at least 16 A and a reverse voltage of at least 400 V. They must be installed on plate corner heat sinks with dimensions of 60x15 mm, 2 mm thick, made of aluminum alloy.
Instead of a single capacitor C5, you can use a battery of several connected in parallel with a voltage of at least 400 V each, and the battery capacity may be greater than that indicated in the diagram.
Choke L1 is made on a steel magnetic core PL 12.5x25-50. Any other magnetic circuit of the same or larger cross-section is also suitable, provided that the condition of placing the winding in its window is met. The winding consists of 175 turns of PEV-2 1.32 wire (wire of a smaller diameter cannot be used!). The magnetic core must have a non-magnetic gap of 0.3...0.5 mm. Inductance of the choke is 40±10 µH.
Capacitors C6-C24 must have a small dielectric loss tangent, and C6-C17 must also have an operating voltage of at least 1000 V. The best capacitors I have tested are K78-2, used in televisions. You can also use more widely used capacitors of this type with a different capacitance, bringing the total capacitance to that indicated in the circuit, as well as imported film capacitors.
Attempts to use paper or other capacitors designed to operate in low-frequency circuits usually lead to their failure after some time.
It is advisable to use thyristors KU221 (VS2-VS7) with the letter index A or, in extreme cases, B or D. As practice has shown, during operation of the device the cathode terminals of the thyristors noticeably heat up, which is why it is possible that the solder joints on the board may be destroyed and even fail SCR.
Reliability will be higher if either tube-pistons made of tinned copper foil with a thickness of 0.1...0.15 mm, or bandages in the form of a tightly rolled spiral of tinned copper wire with a diameter of 0.2 mm are put on the terminal of the SCR cathode and soldered along the entire length. The piston (bandage) should cover the entire length of the terminal almost to the base. You need to solder quickly so as not to overheat the thyristor.
You will probably have a question: is it possible to install one powerful one instead of several relatively low-power SCRs? Yes, this is possible when using a device that is superior (or at least comparable) in its frequency characteristics to the KU221A thyristors. But among those available, for example, from the PM or TL series, there are none.
The transition to low-frequency devices will force the operating frequency to be lowered from 25 to 4...6 kHz, and this will lead to the deterioration of many the most important characteristics machine and a loud piercing squeak when welding.
When installing diodes and SCRs, the use of heat-conducting paste is mandatory.
In addition, it has been established that one powerful thyristor is less reliable than several connected in parallel, since it is easier for them to provide Better conditions heat removal. It is enough to install a group of SCRs on one heat sink plate with a thickness of at least 3 mm.
Since current equalizing resistors R14-R18 (C5-16 V) can become very hot during welding, before installation they must be freed from the plastic shell by firing or heating with a current, the value of which must be selected experimentally.
Diodes VD8 and VD9 are installed on a common heat sink with thyristors, and diode VD9 is isolated from the heat sink with a mica spacer. Instead of KD213A, KD213B and KD213V are suitable, as well as KD2999B, KD2997A, KD2997B.
Choke L2 is a frameless spiral of 11 turns of wire with a cross-section of at least 4 mm2 in heat-resistant insulation, wound on a mandrel with a diameter of 12...14 mm.
The choke gets very hot during welding, so when winding the spiral, a gap of 1...1.5 mm should be provided between the turns, and the choke should be positioned so that it is in the air flow from the fan. 
Rice. 2 Transformer magnetic core
T1 is made up of three PK30x16 magnetic cores folded together from 3000NMS-1 ferrite (the horizontal transformers of old TVs were made on them).
The primary and secondary windings are divided into two sections each (see Fig. 2), wound with PSD1.68x10.4 wire in glass fabric insulation and connected in series according to. The primary winding contains 2x4 turns, the secondary winding contains 2x2 turns.
The sections are wound on a specially made wooden mandrel. The sections are protected from unwinding of the turns by two bands made of tinned copper wire with a diameter of 0.8...1 mm. Bandage width - 10...11 mm. A strip of electrical cardboard is placed under each bandage or several turns of fiberglass tape are wound.
After winding, the bandages are soldered.
One of the bands of each section serves as the output of its beginning. To do this, the insulation under the bandage is performed so that inside it was in direct contact with the beginning of the section winding. After winding, the bandage is soldered to the beginning of the section, for which purpose the insulation is removed from this section of the coil in advance and it is tinned.
It should be borne in mind that winding I operates in the most severe thermal conditions. For this reason, when winding its sections and during assembly, air gaps should be provided between the outer parts of the turns, placing short fiberglass inserts lubricated with heat-resistant glue between the turns.
In general, in the manufacture of transformers for inverter welding With your own hands, always leave air gaps in the winding. The more of them, the more effective the heat removal from the transformer and the lower the likelihood of burning the device.
It is also appropriate to note here that winding sections made with the mentioned inserts and gaskets with wire of the same cross-section 1.68x10.4 mm 2 without insulation will be cooled better under the same conditions.
The contacting bands are connected by soldering, and it is advisable to solder a copper pad in the form of a short piece of wire from which the section is made to the front ones, which serve as the sections’ leads.
The result is a rigid, one-piece primary winding of the transformer.
The secondary one is made in the same way. The only difference is the number of turns in the sections and the fact that it is necessary to provide an outlet from the middle point. The windings are installed on the magnetic circuit in a strictly defined manner - this is necessary for proper operation rectifier VD11 - VD32.
The winding direction of the upper section of winding I (when looking at the transformer from above) should be counterclockwise, starting from the upper terminal, which must be connected to inductor L2.
The winding direction of the upper section of winding II, on the contrary, is clockwise, starting from the upper terminal, it is connected to the diode block VD21-VD32.
Winding III is a turn of any wire with a diameter of 0.35...0.5 mm in heat-resistant insulation that can withstand a voltage of at least 500 V. It can be placed in last resort anywhere in the magnetic circuit on the side of the primary winding.
To ensure the electrical safety of the welding machine and effective cooling of all transformer elements by air flow, it is very important to maintain the necessary gaps between the windings and the magnetic core. When assembling a welding inverter with their own hands, most DIYers make the same mistake: they underestimate the importance of cooling the trance. This cannot be done.
This task is performed by four fixing plates, placed in the windings when final assembly node. 
The plates are made of fiberglass laminate with a thickness of 1.5 mm in accordance with the drawing in the figure.
After final adjustment, it is advisable to secure the plates with heat-resistant glue. The transformer is attached to the base of the device with three brackets bent from brass or copper wire with a diameter of 3 mm. The same brackets fix the relative position of all elements of the magnetic circuit.
Before installing the transformer on the base between the halves of each of the three sets of magnetic circuits, it is necessary to insert non-magnetic gaskets made of electrical cardboard, getinax or textolite with a thickness of 0.2...0.3 mm.
To manufacture a transformer, you can use magnetic cores of other standard sizes with a cross-section of at least 5.6 cm 2. For example, W20x28 or two sets of W 16x20 made of 2000NM1 ferrite are suitable.
Winding I for the armored magnetic circuit is made in the form of a single section of eight turns, winding II is similar to that described above, from two sections of two turns. The welding rectifier on diodes VD11-VD34 is structurally a separate unit, made in the form of a shelf: 
It is assembled in such a way that each pair of diodes is placed between two heat sink plates measuring 44x42 mm and 1 mm thick, made of sheet aluminum alloy.
The entire package is tightened with four steel threaded rods with a diameter of 3 mm between two flanges 2 mm thick (of the same material as the plates), to which two boards forming the rectifier terminals are attached with screws on both sides.
All diodes in the block are oriented in the same way - with the cathode terminals to the right in the figure - and the terminals are soldered into the holes of the board, which serves as the common positive terminal of the rectifier and the device as a whole. The anode leads of the diodes are soldered into the holes of the second board. Two groups of terminals are formed on it, connected to the extreme terminals of winding II of the transformer according to the diagram.
Given the large total current flowing through the rectifier, each of its three terminals is made of several pieces of wire 50 mm long, each soldered into its own hole and connected by soldering at the opposite end. A group of ten diodes is connected by five segments, of fourteen - by six, the second board with a common point of all diodes - by six.
It is better to use a flexible wire with a cross-section of at least 4 mm.
In the same way, high-current group leads from the main printed circuit board of the device are made.
The rectifier boards are made of foil fiberglass laminate 0.5 mm thick and tin-plated. Four narrow slots in each board help reduce the load on the diode leads during thermal deformation. For the same purpose, the leads of the diodes must be molded, as shown in the figure above.
In the welding rectifier you can also use more powerful diodes KD2999B, 2D2999B, KD2997A, KD2997B, 2D2997A, 2D2997B. Their number may be smaller. Thus, in one of the variants of the device, a rectifier consisting of nine 2D2997A diodes worked successfully (five in one arm, four in the other).
The area of the heat sink plates remained the same, but it was possible to increase their thickness to 2 mm. The diodes were not placed in pairs, but one in each compartment.
All resistors (except R1 and R6), capacitors C2-C4, C6-C18, transistor VT1, thyristors VS2 - VS7, zener diodes VD5-VD7, diodes VD8-VD10 are mounted on the main printed circuit board, and SCRs and diodes VD8, VD9 are installed on a heat sink screwed to a board made of foil PCB 1.5 mm thick: 
Rice. 5. Board drawing
The scale of the board drawing is 1:2, however, the board is easy to mark, even without using photo enlargements, since the centers of almost all holes and the boundaries of almost all foil pads are located on a grid with a pitch of 2.5 mm.
The board does not require great precision in marking and drilling holes, but remember that the holes in it must coincide with the corresponding holes in the heat sink plate.
The jumper in the circuit of diodes VD8, VD9 is made of copper wire with a diameter of 0.8...1 mm. It is better to solder it from the print side. The second jumper made of PEV-2 0.3 wire can also be placed on the parts side.
Group output of the board, indicated in Fig. 5 letters B, connected to inductor L2. Conductors from the anodes of the thyristors are soldered into the holes of group B. Terminals G are connected to the bottom terminal of transformer T1 according to the diagram, and Terminal D is connected to inductor L1.
The wire pieces in each group must be the same length and the same cross-section (at least 2.5 mm2). 
Rice. 6 Heatsink
The heat sink is a 3 mm thick plate with a bent edge (see Fig. 6).
The best material for a heat sink is copper (or brass). As a last resort, in the absence of copper, you can use an aluminum alloy plate.
The surface on the installation side of the parts must be smooth, without nicks or dents. The plate has threaded holes drilled for assembly with printed circuit board and fastening elements. Leads of parts are passed through holes without threads and connecting wires. The anode terminals of the thyristors are passed through the holes in the bent edge. Three M4 holes in the heat sink are intended for its electrical connection with printed circuit board. For this, three brass screws with brass nuts were used.Fig. 8. Placement of nodes
The unijunction transistor VT1 usually does not cause problems, however, some instances, in the presence of generation, do not provide the pulse amplitude necessary for the stable opening of the thyristor VS2.
All components and parts of the welding machine are installed on a base plate made of getinax 4 mm thick (textolite 4...5 mm thick is also suitable) on one side. There is a round window cut in the center of the base for mounting a fan; it is installed on the same side.
Diodes VD1-VD4, thyristor VS1 and lamp HL1 are mounted on angle brackets. When installing transformer T1 between adjacent magnetic cores, an air gap of 2 mm should be provided. Each of the clamps for connecting welding cables is an M10 copper bolt with copper nuts and washers.
The head of the bolt presses a copper square to the base from the inside, which is additionally secured against turning with an M4 screw and nut. The thickness of the angle shelf is 3 mm. An internal connecting wire is connected to the second shelf by bolting or soldering.
The printed circuit board-heatsink assembly is mounted in parts to the base on six steel posts bent from a strip 12 mm wide and 2 mm thick.
On the front side of the base there is a toggle switch handle SA1, a fuse holder cover, LEDs HL2, HL3, a handle variable resistor R1, clamps for welding cables and cable to button SB1.
In addition, to front side four bushing posts with a diameter of 12 mm are attached to internal thread M5, machined from textolite. A false panel with holes for the device controls and a protective fan grille is attached to the racks.
The false panel can be made from sheet metal or dielectric with a thickness of 1... 1.5 mm. I cut it out of fiberglass. On the outside, six posts with a diameter of 10 mm are screwed to the false panel, onto which the network and welding cables are wound upon completion of welding.
Holes with a diameter of 10 mm are drilled in the free areas of the false panel to facilitate the circulation of cooling air. 
Rice. 9. External view of an inverter welding machine with laid cables.
The assembled base is placed in a casing with a lid made of sheet textolite (getinax, fiberglass, vinyl plastic can be used) 3...4 mm thick. Cooling air outlets are located on the side walls.
The shape of the holes does not matter, but for safety it is better if they are narrow and long.
The total area of the outlet openings should not be less than the area of the input opening. The casing is equipped with a handle and a shoulder strap for carrying.
The electrode holder can be of any design, as long as it provides ease of operation and easy replacement of the electrode.
On the handle of the electrode holder, you need to mount the button (SB1 according to the diagram) in such a place that the welder can easily hold it pressed even with a mitten hand. Since the button is under mains voltage, it is necessary to ensure reliable insulation of both the button itself and the cable connected to it.
P.S. The description of the assembly process took a lot of space, but in reality everything is much simpler than it seems. Anyone who has ever held a soldering iron and a multimeter in their hands will be able to assemble this welding inverter with their own hands without any problems. 
When performing simple and small-scale welding work at home, anyone can assemble.
You don’t have to spend a lot of money, effort and time to assemble. There is also no need to purchase unreasonably expensive models of such equipment.
To make a mini welding machine with your own hands from available materials, without special financial costs and effort, you need to understand how the equipment functions, after which you can start producing it at home.
First of all, it is worth determining the required power current supply homemade equipment for welding. Connecting parts of a massive structure requires a higher current intensity, and welding work with thin metal surfaces requires minimal current.
The current value is related to the selected electrodes that will be used in the process. When welding products up to 5 millimeters, it is necessary to use rods up to 4 millimeters, and in a structure with 2 millimeters thick, rods should be 1.5 millimeters.
When using electrodes of 4 millimeters, the current is regulated up to 200 amperes, for 3 millimeters up to 140 amperes, for 2 millimeters - up to 70 amperes, and for the smallest ones up to 1.5 millimeters - up to 40 amperes.
Form an arc for welding process you can do it yourself using mains voltage, which is obtained due to the operation of the transformer.
This equipment includes:
- magnetic circuit;
- winding – primary and secondary.
You can also make a transformer yourself. For the magnetic circuit, plates made of steel or other durable material. Windings are necessary to directly perform welding work and be able to connect the welding unit to a 220 volt network.
Transformer for welding work.
Specialized equipment has additional devices that improve the quality and power of the arc, which makes it possible to independently regulate the current values.
There is no need to go deep enough into this topic, since one of the easiest ways to assemble a welding machine with your own hands is.
Its peculiarity is that it works with alternating current, which ensures high-quality seam when welding metal surfaces. Such equipment can cope with any household work where it is necessary to weld metal or steel structures.
To make it you need to prepare:
- Several meters of cable with great thickness.
- Material for the core that will be located in the transformer.
The material itself must have increased permeability with magnetization.
The best option is when the rod-shaped core has the letter “P”. In some cases, it is allowed to use this part in a more modified form, for example, a round stator made from a damaged electric motor.
Diagram of a welding transformer.
However, it is worth paying attention that it is more difficult to wind windings onto this shape. It is best when the core cross-section for classic welding equipment, made by hand and used for domestic purposes, had an area of about 50 cm2.
In order for the equipment to have an accessible weight, it is not necessary to increase the cross-section in volume, however, the technical effect will not be top level. If the cross-sectional area does not suit you, then you can calculate it yourself using special diagrams and formulas.
The primary winding must be made of copper wire, which will have increased characteristics: thermal resistance, since during operation of the structure this part heats up very much.
Such a part must have cotton or fiberglass insulation. As a last resort, it is possible to use rubber insulated wire or rubber cloth, but beware of PVC winding.
The insulation is also made by hand, using cotton or fiberglass, or rather parts of it 2 cm wide. Thanks to these pieces, you can wrap the wire and then impregnate it with any varnish for electrical purposes. This insulation will not overheat after regular use.
Similar to the above calculations, it will be possible to calculate which cross-sectional area of the winding - primary and secondary - will be the most optimal. Often the secondary winding has an area of about 30 mm2, and the primary winding up to 7 mm2, using a rod of 4 millimeters in diameter.
Besides in a simple way you need to determine how far a piece of copper wire will stretch and how many turns will be needed to wind two windings. After this, the coils are wound, and the frame is made using geometric parameters magnetic circuit.
The main thing is to ensure that there are no difficulties when putting on the magnetic core. First of all, you need to choose the correct core size. It is best made using electrical cardboard or textolite.
Using the same analogue, it will be possible to make a structure for welding small parts. For home use, you can use a small mini welding machine.
Manufacturing of welding machine
Today it is almost impossible and quite difficult to weld metal or process it in the proper way without using welding equipment. After you make a welding machine with your own hands, you will be able to perform any work with metal products.
Transformer circuit with a separate choke.
To produce a high-quality unit, you must have knowledge and skills that will help you understand the circuit of a DC or AC welding machine, which are two options for assembling equipment.
With the aim of home use It's best to learn how to do mini welding.
It is more convenient to call a specialist or purchase a ready-made unit, but sometimes this can be too expensive, since it is quite difficult to determine the choice of model based on various parameters, such as the weight of the welding machine, and the number of volts per welding machine.
There are several types of welding machines: operating on alternating current, direct current, having three phases or inverter. To choose one of the options and start assembling, you need to consider each circuit of the first 2 types. During preparatory process You need to pay attention to the voltage stabilizer.
AC
To make homemade welding machines, you need to select a voltage indicator, the best is 60 volts, the current is best adjusted from 120 to 160 amperes.
You can independently determine the cross-sectional value of the required wire for the manufacture of the primary winding of the transformer, which must be connected to a 220-volt network.
The cross-section according to the area parameters should not be more than 7 mm2, since it is worth noting the possible voltage drop and possible additional load.
Based on the calculations, optimal size The diameter of the copper core for the primary winding, which reduces the action of the mechanism, is 3 millimeters. When choosing aluminum for the wire, the cross-section is multiplied by 1.6.
It is worth noting that the wires need to be wrapped with a rag, since they must be insulated. The fact is that when the temperature increases, the wire can melt and a short circuit may occur.
If the necessary wire is not available, it is possible to replace it with a slightly thinner wire, winding it in pairs. However, it must be remembered that the thickness of the winding will increase, which is why the dimensions of the welding equipment will be larger. Used for the secondary winding large thickness wire with a large number of copper cores.
DC
Electrical circuit of a DC welder.
Some welding machines operate using direct current. Thanks to this unit, you can weld cast iron products and stainless steel structures.
It may take no more than half an hour to create a DC welding machine with your own hands. In order to convert a homemade product with alternating current, it is necessary that the secondary winding be connected, which is assembled on a diode.
In turn, the diode must withstand a current of 200 amperes and have good cooling. To equalize the current value, you can use capacitors that have certain characteristics and voltage characteristics. After this, the unit is assembled sequentially according to the scheme.
Chokes are used to regulate current, and contacts are used to attach a holder. Additional parts are used to transmit current from an external carrier to the welding site.
In order to operate the welding machine for its intended purpose, it is necessary, first of all, to ignite the electric arc. This the process is easy and is performed by the following steps: we bring the tip of the electrode at a certain angle from the side of the metal coating and scratch it along the surface of the structure.
If the action is performed correctly and successfully, a flash occurs small sizes, and the material melts, after which the necessary elements can be welded.
When making a mini welding machine with your own hands, you must follow the recommendations for working with it. To weld elements, you need to hold the rod in such a position that it is at a certain distance from each other of the parts being welded. This distance may be equal to the section selected electrode.
Often a metal such as carbon steel connects with direct polar current. However, some alloys can only be welded using reverse current polarity. In addition, it is necessary to carefully monitor the quality of the seam and how the structure is fused.
Diagram of a simple welding machine.
It is worth emphasizing that alternating current located can be adjusted efficiently and smoothly. Often, no difficulties arise in setting up the unit to the required parameters.
With a small current indicator, the seam will turn out to be of poor quality, but you should not set an increased value, since there is a risk of burning the surface.
If it is necessary to weld surfaces of small thickness, then rods with a size of 1 to 3 millimeters are suitable, while the current strength should vary from 20-60 A. Using large cross-section electrodes, you can weld hardware up to 5 millimeters, but in this case the current should be 100 A.
Upon completion of the welding process, using a homemade product, it is necessary to carefully remove the scale that appears on the seam with light movements, after which it is cleaned with a special brush.
Thanks to this action, you can maintain a pleasant aesthetic appearance of your device. Don’t worry if cleaning the equipment isn’t very successful in the first couple of days. This skill is developed through experience and subject to following all recommendations for proper operation of the structure.
Bottom line
To summarize, it is worth noting that DC welding machines are much easier to assemble and they are also easy to use, due to their low power.