How to make a semi-automatic machine from an inverter with your own hands. Homemade DC welding machine How to make DC welding from ordinary

Using a semi-automatic welding machine makes it easier to work with metals. This technique can easily join different alloys. You can make a semi-automatic welding machine with your own hands from an existing inverter, and homemade unit will be distinguished by its versatility and functionality in use, allowing you to save on the purchase of industrial equipment.

Design Features

A design feature of a semi-automatic welding machine is the constant supply of molten wire into the welding zone, which is used instead of metal electrodes. Wire feeding is carried out automatically, with the ability to change the speed of movement of flexible electrodes. The welding wire used will ensure constant contact of the surfaces being connected; such material, in comparison with standard electrodes, has less resistance, which improves the quality of the connection.

Semi-automatic welding is distinguished by its versatility, which allows using this technology to weld metals of various characteristics, including stainless steel, non-ferrous alloys, aluminum and others. Master correct technique semi-automatic welding is not difficult. Homemade devices are easy to use, so they can be recommended to ordinary homeowners. Depending on their type, semi-automatic machines may have an additional nozzle for supplying gas, and the metals are joined in a protective environment, which makes it possible to eliminate the subsequent formation of corrosion in the weld.

Welding inverters offered in stores today are distinguished by their versatility, and many of them have a two-in-one function. With low power and dimensions, a two-in-one semi-automatic machine can work with refractory metals and thick metal workpieces.

Many homeowners who often have to perform welding work, decide to manufacture such equipment themselves. The advantages of homemade semi-automatic machines from an inverter include the following:

Among the disadvantages of this technology and the equipment itself, one can note the high cost of semi-automatic machines, which, with characteristics similar to the inverter, can have a price two to three times higher. It is not surprising that many homeowners decide to make the equipment themselves, which allows them to significantly reduce costs without losing the quality of the device.

DIY making

The easiest way is to make a homemade semi-automatic machine from an inverter based on a powerful power unit. You can make an inverter yourself or use it from existing equipment. For semi-automatic devices, inverters with a capacity of at least 150 amperes should be used.

There are schemes for modifying equipment that allow you to set the power that will be enough to carry out semi-automatic welding. A device of this type will be difficult to implement, so the use of low-power power units can only be recommended to experienced radio amateurs who can produce truly complex equipment.

Make quality equipment It is possible if you have on hand the trigger circuit for a semi-automatic welding inverter. The characteristics of such a unit include the following:

Primary current - 8-12 A.
Supply voltage - 220 or 380 volts.
Voltage idle move- 36−42 Volts.
Welding current - 40−120 amperes.
Voltage adjustment in increments of plus or minus 20%.

These are the optimal parameters for household semi-automatic welding machine, which can handle metals with different refractoriness indices. Subsequently, using additional drawings for increasing the inverter power, you can change the basic characteristics, which allows the use of such equipment for domestic and industrial purposes.

Required Components

To make a semi-automatic garage welding machine with your own hands, you will need the following:

Burner attachment for inverter.
Wire feed mechanism.
Durable inner hose for welding wire.
Bobbin with wire.
Sealed gas supply hose.
Inverter control unit.

The easiest way is to place the inverter and mechanical control unit in a separate box, for which they use blocks from an old computer. The presence of power in the system unit can significantly simplify the manufacture of equipment.

The roller mechanism for the wire can be made from a motor from a car windshield wiper. For such a motor, a mechanism frame is designed, which is cut out of metal elements and welded or bolted together.

You can make the burner and hose yourself using a gun from polyurethane foam and silicone. You can also purchase ready-made kits, which will ensure the safety of working with a semi-automatic device and simplify its manufacture.

When making a wire feed mechanism, all used components must be placed opposite each other, which will subsequently ensure uniform feeding of flexible electrodes. The rollers should be centered relative to the fitting in one connector, in the future this will allow you to smoothly change the wire feed speed. A diagram of the wire feed speed regulator for a semi-automatic welding machine can be easily found on the Internet.

All used metal elements should be secured to a sheet of plywood, thick plastic or textolite. Since electricity is supplied to the metal elements used, the grounding of each node should be checked. This will eliminate the possibility short circuits, which can lead to serious equipment breakdowns.

Mechanical control circuit

A small electric motor and a drawing mechanism, the operation of which is controlled using a PWM controller, will be responsible for feeding the welding wire. The quality of the welding performed will directly depend on the uniformity of the welding wire feed into the work area. It is necessary to pay due attention to the correct manufacture of semiautomatic welding circuits.

A variable resistor of the controller is installed on the front panel of the inverter, after which they begin assembling the control relay for starting the motor and controlling the valve, which is responsible for supplying inert gas. The contact groups of the controllers must operate simultaneously when the start button on the burner is pressed.

The gas supply must be adjusted so that the valve opens a few seconds before the wire begins to flow into the welding zone. Otherwise, melting occurs in an atmospheric environment, after which the wire will begin to burn instead of melting. It will be impossible to achieve a high-quality connection and a reliable weld when the wire is burning.

To delay the switching on of the wire feed, you need to make a simple relay, which will require a capacitor and an 875 transistor. You can use a simple relay from a car, which connects to 12 Volts on the computer power supply.

The valve itself can be used from various automotive locking devices. Easiest to redo air valve from a GAZ-24 car. You can also choose an electric valve from a reducer from gas cylinders.

All available controls and the PWM wire feed regulator of the semi-automatic welding machine are located on the front panel of the system unit. A ready-made inverter with a power of at least 150 amperes is connected to the control unit and the wire feed controller with gas. All that remains is to perform a test run and, if necessary, make appropriate adjustments to the operation of the welding wire and shielding gas supply system.

In progress power block the inverter semi-automatic device will heat up, which can lead to damage to the inverter and control boards. Repairing the unit after such breakdowns will be extremely difficult. To avoid this, it is necessary to install thermal sensors and coolers inside the inverter and system unit that can effectively cool operating equipment.

You can use an optocoupler pair that connects to common block control of equipment operation. If the temperature inside the inverter is exceeded, the sensors will send corresponding signals to the executive relay, which turns off the power supply until the device has completely cooled down.

Additionally, to cool the system unit, you can use various coolers from old computers. Coolers will vary in size. You can choose a fan that will cope with high-quality cooling of the system unit, inside of which the inverter and other automation are located. The cooler used is connected to a 12-volt power supply directly or through a thermal sensor, which, when the temperature inside the case increases, will send a signal to supply voltage. The control unit will turn on the fan, which guarantees rapid cooling of the body of the semi-automatic device.

Assembling a semi-automatic welding machine is not particularly difficult, so every homeowner can handle this work. You just need to use a high-quality, powerful inverter, and it is best to take a burner with a drive from industrial factory semi-automatic devices. This will significantly simplify the production of equipment. On the Internet you can find various designs for semi-automatic welding machines, which will not be easy to implement. special labor. Such a device will be distinguished by its functionality and versatility in use..

If you decide to assemble a semi-automatic welding machine with your own hands from an inverter, diagram and detailed instructions will become indispensable companions on the way to achieving your goal. The easiest way is to purchase factory semi-automatic devices such as Kedr 160, Kaiser Mig 300 with the required Ampere rating. But many people strive to do everything themselves. It's not that easy, but if you want to, you can achieve a positive result.

Mig, Mag, MMA welding requires the use of appropriate devices. Mig Mag is a semi-automatic welding process that is performed in an inert argon gas environment. Sometimes Mig Mag is used for welding carbon dioxide. MMA welding is called manual arc processing with electrodes on which a special coating is applied. If you are working with stainless steel, then MMA welding is carried out only with direct current.

Since we are talking about how you can assemble a full-fledged semi-automatic machine based on an inverter with your own hands, you are not interested in MMA, but in Mig Mag welding.

To collect homemade apparatus, a worthy analogue for Kedr 160, Kaiser Mig 300, do it yourself, you will need a diagram, video instructions and necessary elements semi-automatic designs. These include:

Inverter. Determine its welding ability by selecting the supplied current. Typically, craftsmen assemble devices capable of delivering 150 Amps, 170 Amps or 190 Amps. The higher the Amps, the higher the ability of your welding device;
Feeding mechanism. We will tell you about it separately;
Burner;
Hose for supplying electrodes;
A spool of special wire. This attachment is easily attached to the structure in any way convenient for you;
Control unit for your welding unit.

Now regarding the feed mechanism for a semi-automatic machine and some important points.

He is responsible for supplying electrodes using a flexible hose to the welding point.
The optimal feeding speed of the electrode wire corresponds to the speed of its melting during do-it-yourself welding.
The quality of the seam you make with your own hands depends on the wire feed speed.
It is recommended to make a semi-automatic machine with the ability to adjust the speed. This will allow the semi-automatic machine to be adapted to different type electrodes used.
The most popular electrode wires have a diameter from 0.8 to 1.6 mm. It must be wound on a reel and charged the inverter.
If you provide fully automated feeding, you will not have to do it yourself, and therefore the time spent on welding activities will be significantly reduced.
The control unit is equipped with a control channel, which is responsible for stabilizing the current.
The behavior of Amperes, that is, the current of a semi-automatic device, is regulated by a special microcontroller. It performs its work in pulse-width operating mode. The voltage created in the capacitor directly depends on its filling. This affects the welding current parameters.

Preparing a semi-automatic transformer

For a self-made semi-automatic to work no worse than welding machine type Kedr 160, Kaiser Mig 300, it is necessary to understand the features of transformer preparation.

Wrap it with a copper strip. Its width should be 4 cm and thickness - 30;
Before this, the strip is wrapped with thermal paper. The material used in cash registers is suitable. It is not difficult to purchase such paper;
In this case, the circuit does not allow the use of ordinary thick wiring, otherwise it will begin to overheat;
The secondary winding must be made by using three layers of tin at once;
PTFE tape is used to isolate each layer of sheet metal from each other;
At the output, you will need to solder the contact ends from the secondary winding with your own hands. This is necessary in order to increase current conductivity;
Be sure to include a fan in the inverter housing. It will serve as a blowing mechanism that reduces equipment overheating.

Inverter setup

There are no problems with the operation of Kedr 160 and Kaiser Mig 300. Cedar 160 and Kaiser Mig 300 are factory equipment that have excellent specifications. These semi-automatic machines function perfectly and allow you to get required amount Ampere - 160 Ampere, 170, 190 Ampere, etc. It all depends on how you configure the device.

But if you decide to remake the inverter and make it a semi-automatic device, then the idea of buying Kedr 160, Kaiser Mig 300 should be thrown aside.

After completing work with the transformer, you should move on to the inverter. If you make the correct settings for the inverter itself, the modification will bring the desired result. Therefore, a homemade semi-automatic machine will function no worse than a ready-made Kedr 160 or Kaiser Mig 300 device.

Be sure to provide high-efficiency radiators used for rectifiers (input and output) and power switches. Without them, the device will not be able to work properly.
A temperature sensor should be installed inside the radiator housing, which heats up the most, to trigger it in case of overheating.
Connect the power part to the control unit and plug it into the working network.
When the indicator is activated, you should connect an oscilloscope to the wires.
Find bipolar impulses. Their frequency ranges from 40 to 50 kHz.
The time parameters between pulses are adjusted by changing the input voltage. The time indicator must correspond to 1.5 μs.
Make sure that the inverter produces square wave pulses on the oscilloscope. The edges should not exceed 500 ns.
When the device has passed the test, connect it to the power supply.
The indicator built into the semiautomatic device should produce 120 Amperes. Parameters can reach up to 170, 190 Amperes. But if the device does not show given value, you will have to go in search of the causes of low voltage in the wires.
Typically, this situation occurs when the voltage is less than 100 V.
Now we test the semi-automatic welding machine, starting the device with variable current. At the same time, constantly monitor the voltage on the capacitor.
We complete the testing by checking the temperature readings.
Check how the device behaves when loaded. Similar initial tests should be carried out with the Kedr 160 and Kaiser Mig 300. Although the Kedr 160 and Kaiser Mig 300 are factory semi-automatic machines from trusted manufacturers, it will never be superfluous to make sure of their professional suitability.
To test a homemade inverter or Kedr 160 with a Kaiser Mig 300, you need to connect a 0.5 Ohm load rheostat to the welding wires. Make sure that this element can withstand loads of more than 60 Amps. The current parameters are monitored with a voltmeter.
If checking the semi-automatic device shows that the specified current value and the controlled value are different, the resistance will need to be changed. Do this until you achieve a positive result.

Assembling a device that will act as a full-fledged analogue for the Kedr 160 and Kaiser Mig 300 is not so simple, but it is possible. You yourself determine whether the semi-automatic device will produce 120 or all 190 Amperes. Make choosing a factory model easier. But their price is appropriate. The price of the same semi-automatic Kedr 160 Mig is from 27 thousand rubles. But the decision is yours to make.

Modern manufacturers produce a large number welding inverters with a wide range of functions. These include semi-automatic machines operating in MIG/MAG mode, which means supplying inert or active gas and welding wire to the joint of the workpieces. Unfortunately, the cost of such units exceeds the financial capabilities of many people. Therefore, the desire to convert welding inverters into semi-automatic machines is finding more and more followers, since it is possible to save significant amounts. We will consider the possibility of such a modification and the necessary details for this.

Often, the master is faced with the question of choosing between an inverter or a semi-automatic welding machine, the difference between which lies in the quality of the seam and the types of metals being welded. If a conventional inverter allows welding in AC/DC mode, with piece electrodes of different thicknesses, then semi-automatic welding machines carry out the connection of parts. It is fed into the melting zone at a controlled speed and has different thicknesses, and to ensure best result, the process takes place in an inert or active gas environment (MIG/MAG).

Semi-automatic machines allow you to weld all kinds of metals of various thicknesses, while the size of the electrode does not change and work zone always at the same distance from the person. It contains an inverter, but also an adjustable wire feed unit and a special hose with a torch and a cylinder. This equipment can weld aluminum alloys, carbon and stainless steel, cast iron and titanium, and with special wire - brass and galvanized metal. When assembling a semi-automatic machine from an inverter with your own hands, you will need the following factory or home-made components:

welding machine with AC/DC modes, outputting adjustable currents from 10 to 200A, with variable pulse voltage;
a torch with the ability to supply welding wire and the corresponding gas to the place of welding work;
a hose reinforced with a spring to ensure uninterrupted supply of wire and gas;
gas cylinder with gearbox and pressure gauge;
reverse welding cable with clamp;
Control block;
reliable, adjustable unit for feeding welding wire of various thicknesses.

These elements can be purchased factory-made, and some of them can be made by hand. The inverter, burner and gas cylinder must be purchased from the manufacturer, since the technical requirements for these components require a quality certificate.

Of course, your own semi-automatic machine will cost much less, but it is important that home-made elements meet safety requirements when performing electric welding work.

Construction of a torch and hose for a semi-automatic welding machine

Using a semi-automatic welding machine, we can increase the speed of work by more than two and a half or three times, since there is no need for multiple passes of the seam, its cleaning and replacement of piece electrodes. To increase productivity, it is necessary to ensure an uninterrupted supply of inert gas, voltage and wire to the weld pool. For this purpose, use a device consisting of the following components:

a cylinder with a reducer, adjusted to a flow rate of 6-10 liters per minute and equipped with a gas supply hose;
Euro-sleeve, hose-cable 3 m long, through which current, wire and gas are supplied, as well as a control signal;
burner with tip, power button and nozzle under different diameter wire equipped with a nozzle for inert or active gas.

Creating a Euro-sleeve yourself is quite difficult; you need to take into account that the diameter of the wire used ranges from 0.8 to 1.6 mm, and it must pass through the welding hose without any hindrance. For this purpose, the channel is equipped with a spring, using a Teflon coating; in addition, a gas supply passes through the same hose. The control signal from the burner button also passes through the cable, and at the end there is usually a multi-pin Euro connector, through which all components are turned on and supplied.

The complex design of the burner and its operation in conditions high temperatures, implies the presence of refractory nozzles with holes for different diameters of welding wire. Gas is supplied through the torch, as well as the wire feeding mechanism to the weld pool is turned on. It consists of the following elements:

handle with control button;
burner;
gas nozzle;
calibrated current-carrying tip.

It is important to ensure the reliability of electrical contacts and tight connections of gas hoses.

Feeder design

The process of assembling a semi-automatic welding machine with your own hands can occur either using a factory feeder or its homemade version. In order to make it yourself, you need to understand what the factory product consists of, namely:

on the front panel there is a Euro connector for connecting a welding sleeve;
on the back of the case there is a toggle switch for turning on the power supply and connectors for connecting to the inverter and gas supply system;
inside the case there is a power supply unit for the feeding device;
feed unit with a fixed, freely rotating spool of wire;
Next there is a clamping, adjustable feeding device connected through a gearbox to the electric motor shaft;
circuit for adjusting the speed of the electric motor, ensuring the forward movement of the welding wire at a given speed;

a solenoid that provides or shuts off the gas supply to the burner through the valve;
gas supply tubes to the solenoid and Euro connector;
power cable, supply welding current to the wire feed unit;
a scheme for coordinating gas supply and wire movement with a delay of 1-2 seconds, preventing burnout or sticking of the wire when working in an aggressive oxygen environment;
cables connecting the inverter and the feeder.

It is important that the feed system be mounted on electrically insulating material, since the welding wire is energized and acts as an electrode, and electrical contact with the equipment frame must be prevented.

It is necessary to ensure effective adjustable pressure on the feed roller, since the wire has different section, depending on the thickness of the workpieces being welded. It is important to ensure the ratio of all nodes involved in ensuring the translational movement of the wire in order to avoid kinks that impede smooth feeding at the required speed. The material of the gas supply hose must be heat-resistant, and the connections must be provided with reliable clamps. It won’t be difficult to choose a power supply with suitable parameters that will ensure the operation of the electric motor and electronic circuits of the feeder.

Step-by-step assembly of a semi-automatic device

When converting inverters into semi-automatic machines, it is necessary to take into account some circumstances. When purchasing an inverter, it is desirable that it supports MMA+MIG/MAG mode. The device will not cost much more, but when switching to the MIG mode, it will provide a stable current-voltage characteristic at the output, which will ensure smooth operation of the semiautomatic device at a current below 40 A. Otherwise, you will have to make changes to electronic circuit inverter and use PWM to stabilize the voltage parameters. This can be done provided that you understand electronics and are good at using a soldering iron.

It is important to match the reference and output voltages by installing a divider and selecting the component values for supplying a signal to the controller inputs.

Further steps for assembling a semi-automatic machine from a welding inverter, a feeder and a Euro-sleeve with a torch are as follows:

switch the inverter to MIG mode and connect it to the feeder with a power and control cable;
connect a gas cylinder through a reducer and a pressure gauge to the supply device, and also adjust the flow of 6-10 liters per minute depending on the gas composition and welding conditions;
install and secure the wire reel into the feed unit;
using the speed control circuit, set the required feed speed of the welding wire and make sure that it moves unhindered;
connect the burner to the euro-sleeve, which, in turn, connects to the feeder;
turn on the inverter and feeding equipment and make sure there is a delay of 1-2 seconds between the arrival of gas and the movement of the wire.

Correct selection of wire thickness, composition of inert or active gas, as well as correct operation of radio-electronic components will ensure high speed and quality of welding work.

If difficulties arise, it is necessary to seek advice from specialists so as not to cause failure of expensive equipment, and also to avoid risk to life.

Let's sum it up

We looked at some ways to convert welding inverters into semi-automatic machines with our own hands. It's pretty difficult task, when studied closely, is not particularly difficult. It is only important to ensure reliable operation of the elements and electrical safety. The main thing is that these efforts and temporary losses will provide very significant savings.

Advantages of welding machines direct current before their “alternating current brothers” are well known. This includes soft arc ignition, the ability to connect thin-walled parts, less metal spattering, and the absence of unwelded areas. There is not even the annoying (and, as it turned out, harmful effect on people) crackling sound. And all because the main thing inherent in welding machines is missing alternating current feature - intermittent arc burning when the supply voltage sinusoid flows through zero

Rice. 1. Graphs explaining the welding process on alternating (a) and direct (b) current.

Moving from the graphs to real structures, it is also impossible not to note: in AC machines, to improve and facilitate welding, powerful transformers are used (the magnetic core is made of special electrical iron with a steeply falling characteristic) and a deliberately high voltage in the secondary winding, reaching up to 80 V, although for 25-36 V is sufficient to support arc combustion and metal deposition in the welding zone. You have to put up with the prohibitively large mass and dimensions of the apparatus, and increased energy consumption. By reducing the voltage transformed into secondary circuit, up to 36 V, you can lighten the weight of the “welder” by 5-6 times, bring its dimensions to the size of a portable TV while simultaneously improving other performance characteristics.

But how to light an arc with a low-voltage winding?

The solution was to introduce a diode bridge with a capacitor into the secondary circuit. As a result, the voltage at the output of the modernized “welder” was increased by almost 1.5 times. The opinion of experts has been confirmed in practice: when the 40-volt DC barrier is exceeded, the arc easily ignites and burns steadily, allowing you to weld even thin body metal.

Rice. 2. Fundamental electrical diagram DC welding machine.

The latter, however, is easily explained. With the introduction of a large capacity into the circuit, the characteristics of the welding machine also turn out to be steep (Fig. 3). The initial increased voltage created by the capacitor facilitates ignition of the arc. And when the potential on the welding electrode drops to U2 of the transformer (operating point “A”), a process of stable arc burning will occur with metal deposition in the welding zone.

Fig.3. Volt-ampere characteristics of a DC welding machine.

The “welder” recommended by the author can be assembled even at home, using a 220-36/42 V industrial power transformer as a basis (these are usually used in safe lighting systems and power supply for low-voltage factory equipment). After making sure that the primary winding, which usually contains 250 turns of insulated wire with a cross-section of 1.5 mm2, is intact, check the secondary windings. If their condition is unimportant, everything (with the exception of a serviceable network winding) is removed without regret. And in the freed space a new secondary winding is wound (until the “window” is filled). For a recommended transformer with a power of 1.5 kVA, this is 46 turns of a copper or aluminum bus with a cross-section of 20 mm2 with good insulation. Moreover, a cable (or several insulated single-core wires twisted into a bundle) with a total cross-section of 20 mm2 is quite suitable as a bus.

Selection of electrode cross-section depending on the power of the transformer.

The rectifier bridge can be assembled from semiconductor diodes with an operating current of 120-160 A, installing them on 100x100 mm heat sinks. It is most convenient to place such a bridge in the same housing with a transformer and a capacitor, bringing to the front textolite panel a 16-amp switch, an “On” signal light eye, as well as “plus” and “minus” terminals (Fig. 4). And to connect to the electrode holder and the “ground”, use a piece of single-core cable of the appropriate length with a copper cross-section of 20-25 mm2. As for the welding electrodes themselves, their diameter depends on the power of the transformer used.

Rice. 4. Homemade welding machine for DC welding.

And further. During testing, it is recommended to disconnect the device (10 minutes after welding) from the network and check the thermal conditions of the transformer, diode bridge and capacitor. Only after making sure that everything is normal can you continue working. After all, an overheated “welder” is a source of increased danger!

Among other requirements, it is worth noting, I think, that the welding machine must be equipped with a spark-protective mask, gloves and a rubber mat. The place where welding work is performed is equipped taking into account the requirements fire safety. In addition, you need to make sure that there are no rags or other flammable materials nearby, and connect the “welder” to the network in compliance with electrical safety rules through the powerful plug connector of the electrical panel at the entrance to the building.

V. Konovalov, Irkutsk
Mk 04 1998

Semi-automatic welding device for household needs can be purchased ready-to-use or completely assembled with your own hands. Homemade semi-automatic will cost the contractor much less, but its assembly will require certain skills in working with electrical equipment. Appearance Such a welded device is shown in the figure below.

We recommend that everyone who wants to make a semi-automatic machine from an inverter with their own hands first familiarize themselves with the structure of this unit and the operating features of the modules included in it.

What is needed to remake an inverter

Before making a semi-automatic welding machine with your own hands, you will need to prepare the following functional modules and spare parts that provide the required complete set of prefabricated equipment:

An old inverter unit designed for a welding current of about 150 Amps;
Another working unit of the future semi-automatic device is the so-called “burner”;
A special feeding mechanism, with the help of which it will be possible to organize the delivery of welding wire to the place of work;
Hoses that supply wire and shielding gas to a homemade welding unit (more precisely, to the area where work operations are performed);
A coil redesigned for new needs with a special wire placed on it;
A separate electronic module that controls the functioning of everything homemade device(including converter transformer).

The complete set of components and modules required for the semi-automatic machine can be found in the figure below.

Unit design

Let's look at the most important parts of units made by hand from an inverter in more detail.

Consumable supply unit and burner

When equipping with spare parts, special attention should be paid to a thorough modification of the wire feeder, which will have to move inside the flexible hose.

To obtain a high-quality and neat weld, the wire feed speed must be synchronized with the melting rate of its working part.

Since when welding semi-automatically it is allowed to use several types of wire made from various materials and having different diameters, the speed of its arrival must necessarily be a variable value. This is exactly what the so-called “feed” should provide. consumables, which is organized in accordance with general requirements to any inverter unit.

When setting up a semi-automatic circuit, consumable wire with sections of 0.8, 1.0, 1.2 and 1.6 mm is most often used. Immediately before starting work, it is wound on pre-prepared reels, which are fixed to the elements of the unit using simple fasteners. Semi-automatic welding involves feeding the wire “self-propelled”, which significantly reduces the time of all operations and increases the efficiency of these procedures.

The torch used in a semi-automatic machine can be taken entirely from a non-working welding unit of the same type or made independently at home. Let’s immediately make a reservation that making a burner with your own hands is a very difficult task, requiring the performer to have certain experience and skills in the manufacture of such devices.

Electronic control module

The electrical circuit of the semi-automatic welding machine is shown in the figure below.

The basic element of the semi-automatic control unit is the microcontroller, which is responsible for selecting the load mode and stabilizing the output current. In addition, the electronic unit includes the following mandatory components and parts:

Rectifier bridge on high power semiconductor diodes;
Key transistor circuits;
Additional winding transformer;
Correction chokes and inductors.

Particular attention in the composition of the electronic module should be paid to winding inductive products.

Famous simplified version inverter unit, which is usually called the “device from Sanych”. Its diagram is shown in the figure below.

Transformer

Another critical component of a semi-automatic machine, made with your own hands from an old welding device, is a transformer, which can be taken from the same inverter (subject to minor modifications).

To ensure the required characteristics of the inverter transformer, which are completely suitable for a semi-automatic device, it is necessary to rewind the old primary coil with a copper strip coated with a layer of heat-resistant paper.

Important! Such transformers cannot be wound with ordinary thick-section copper wire, since they will become very hot under high current loads.

The secondary winding of the old transformer product should also be slightly modified. To do this, you will need to perform the following operations:

First you need to wind a coil consisting of 3 layers of tin strips, each of which is insulated with fluoroplastic tape;
Next, the ends of the old and newly wound windings need to be soldered, which will ensure high conductivity of the entire coil;
It is also necessary to provide a small fan in the set of elements from which the semi-automatic design is assembled (it is intended for additional cooling of the device).

A fan from a failed old PC can be used as such a cooling device installed in welding units.

Assembly of the unit

Before making a semi-automatic machine with your own hands, be sure to check all necessary details old inverter. In addition, in order to improve the thermal conditions of the future device, it is necessary to provide additional radiators on which rectifiers and power diode switches are mounted (photo below).

Additional Information. In the spaces where radiator units are to be located, it is necessary to provide thermal sensors that record the temperature in this part of the device.

After completing all of the above procedures, you should begin mating the power module with the electronic control unit, after which you can try to connect it to the network and check its operation.

Inverter setup

To carry out this mandatory procedure, first of all, it is necessary to connect the probes of an oscilloscope to the output terminals of the inverter converter, through which it will be possible to examine the shape of the intermediate signals.

Note! Electrical pulses with a frequency of about 40-50 kHz should be observed on the screen of the oscilloscope device (see the figure below).

The time between individual bursts of such pulses should be equal to 1.5 μs (it can be adjusted by changing the input voltage). The amount of control potential supplied to the input of the converter is usually measured using an electronic voltmeter.

In the process of setting up the conversion system, it is also necessary to monitor the shape of the pulses observed at the output, which should approach rectangular with rises lasting no more than 500 ns. If all the above parameters comply with the standard values, you can proceed to setting up the load part of the inverter device.

The maximum current generated at the output of a working unit should have a value of about 120 Amperes (its value can be measured using special current clamps). In addition to the current component, after putting the device into operation, it is necessary to monitor the temperature sensors installed in the area where the radiators are located.

On final stage Before putting the device into operation, it is necessary to check its functionality under load. To do this, a sufficiently “powerful” rheostat with an active resistance of about 0.5 Ohm should be connected to the welding wires.

Important! This adjusting device must be designed for currents of at least 60 Amperes, which are controlled using an ammeter built into the device.

If the rheostat selected for adjustment does not provide the required current value, its nominal resistance should be selected experimentally.

Testing a semi-automatic device in operation

After starting the self-assembled semi-automatic device, its indicator panel should display a current value corresponding to the operating value of 120 Amperes. At the same time, you should check the readings of the sensors installed on the cooling radiators homemade product(the temperature in the area of their action should not exceed 100 degrees).

You will also need to check the adjustment range of the output (load) current, which cannot be less than 20-160 Amperes.

In conclusion, we note that a semi-automatic machine, made by hand in compliance with all the rules discussed in this review, will be able to serve its owner for quite a long time. Its performance and reliability will largely depend on the quality of the components used and the reliability of their assembly.