We make a semi-automatic welding machine with our own hands. Do-it-yourself semi-automatic welding machines (diagram, video, including from an inverter) How to convert welding to direct current

With a good host without fail there should be a semi-automatic welding machine, especially for car owners and private property. You can always do small things with him. If you need to weld a part of the machine, make a greenhouse or create some kind of metal structure, then such a device will become indispensable assistant in personal business. Here the dilemma arises: buy or make yourself. If there is an inverter available, then it is easier to do it yourself. It will cost much less than buying in a retail network. True, you need at least basic knowledge on the basics of electronics, availability necessary tool and desire.

Creating a semiautomatic device from an inverter with your own hands

Structure

Convert the inverter into a semi-automatic welding machine for welding thin steel (low alloy and corrosion resistant) and aluminum alloys do it yourself is not difficult. It is only necessary to understand well the intricacies of the upcoming work and delve into the nuances of manufacturing. An inverter is a device for stepping down electrical voltage to the required level to power the welding arc.

The essence of the semi-automatic welding process in a protective gas environment is as follows. Electrode wire with constant speed is fed into the arc burning zone. Shielding gas is supplied to the same area. Most often it is carbon dioxide. This ensures that a high-quality weld is obtained, which is not inferior in strength to the metal being joined, while there are no slags in the joint, since the weld pool is protected from negative impact air components (oxygen and nitrogen) with protective gas.

The kit of such a semi-automatic device should include the following elements:

• current source;
• welding process control unit;
• wire feed mechanism;
• shielding gas sleeve;
• carbon dioxide cylinder;
• torch gun:
• wire spool.

Welding post device

Principle of operation

When connecting the device to network is being transformed alternating current into permanent. This requires a special electronic module, a high-frequency transformer and rectifiers.

For high-quality welding work, it is necessary that the future device has such parameters as voltage, current and welding wire feed speed in a certain balance. This is facilitated by the use of an arc power source having a rigid current-voltage characteristic. The length of the arc is determined by a fixed voltage. The wire feed speed controls the welding current. This must be remembered in order to achieve the best welding results from the device.

Easiest to use circuit diagram from Sanych, who has long made such a semi-automatic device from an inverter and successfully uses it. It can be found on the Internet. Many home craftsmen not only made a semi-automatic welding machine with their own hands according to this scheme, but also improved it. Here is the original source:

Scheme of a semi-automatic welding machine from Sanych

Semiautomatic Sanych

For the manufacture of the transformer, Sanych used 4 cores from the TS-720. wound the primary winding copper wireØ 1.2 mm (number of turns 180 + 25 + 25 + 25 + 25), for the secondary winding I used an 8 mm 2 bus (number of turns 35 + 35). The rectifier was assembled according to a full-wave circuit. For the switch, I chose a paired biscuit. I installed the diodes on the radiator so that they do not overheat during operation. The capacitor was placed in a device with a capacity of 30,000 microfarads. The filter inductor was made on the core from the TC-180. The power part is put into operation with the help of the TKD511-DOD contactor. The power transformer is installed TS-40, rewound to 15V. The roller of the broaching mechanism in this semi-automatic machine has a diameter of 26 mm. It has a guide groove 1 mm deep and 0.5 mm wide. The regulator circuit operates on a voltage of 6V. It is sufficient to ensure optimum welding wire feed.

How other craftsmen improved it, you can read messages on various forums devoted to this issue and delve into the nuances of manufacturing.

Inverter setting

To provide quality work semiautomatic device with small dimensions, it is best to use toroidal type transformers. They have the highest efficiency.

The transformer for the operation of the inverter is prepared as follows: it must be wrapped with a copper strip (40 mm wide, 30 mm thick), protected by thermal paper, of the required length. The secondary winding is made of 3 layers of sheet metal, isolated from each other. To do this, you can use fluoroplastic tape. The ends of the secondary winding at the output must be soldered. In order for such a transformer to work smoothly and at the same time not overheat, it is necessary to install a fan.

Transformer winding diagram

Work on setting up the inverter begins with a de-energization of the power unit. Rectifiers (input and output) and power switches must have heatsinks for cooling. Where the radiator is located, which heats up the most during operation, it is necessary to provide a temperature sensor (its readings during operation should not exceed 75 0 C). After these changes, the power section is connected to the control unit. When included in the email the network indicator should light up. Using an oscilloscope, you need to check the pulses. They must be rectangular.

Their repetition rate should be in the range of 40 ÷ 50 kHz, and they should have a time interval of 1.5 µs (the time is corrected by changing the input voltage). The indicator should show at least 120A. It will not be superfluous to check the device under load. This is done by including a 0.5 ohm load rheostat in the welding leads. It must withstand a current of 60A. This is checked with a voltmeter.

A correctly assembled inverter when performing welding operations makes it possible to regulate the current in a wide range: from 20 to 160A, and the choice of the operating current strength depends on the metal to be welded.

For making an inverter with my own hands you can take a computer unit, which must be in working order. The body needs to be reinforced by adding stiffeners. An electronic part is mounted in it, made according to the Sanych scheme.

Wire feed

Most often, in such home-made semi-automatic devices, it is possible to feed a welding wire Ø 0.8; 1.0; 1.2 and 1.6 mm. The feed rate must be adjustable. The feeder together with the welding torch can be purchased from the distribution network. If desired and the availability of the necessary details, it is quite possible to do it yourself. Savvy innovators for this use an electric motor from car wipers, 2 bearings, 2 plates and a Ø 25 mm roller. The roller is mounted on the motor shaft. Bearings are fixed on the plates. They stick to the roller. Compression is carried out using a spring. The wire, passing along special guides between the bearings and the roller, is pulled.

All components of the mechanism are installed on a plate with a thickness of at least 8-10 mm, made of textolite, while the wire should come out at the place where the connector connecting to the welding sleeve is installed. A coil with the necessary Ø and brand of wire is also installed here.

Broaching mechanism assy

A homemade burner can also be made with your own hands, using the figure below, where its components are shown clearly in disassembled form. Its purpose is to close the circuit, to provide the supply of shielding gas and welding wire.

Homemade burner device

However, those who want to make a semi-automatic device faster can buy a ready-made gun in the distribution network, along with sleeves for supplying shielding gas and welding wire.

Balloon

To supply shielding gas to the welding arc, it is best to purchase a standard type cylinder. If you use carbon dioxide as a protective gas, you can use a fire extinguisher cylinder by removing the mouthpiece from it. It must be remembered that it requires a special adapter, which is needed to install the reducer, since the thread on the cylinder does not match the thread on the fire extinguisher neck.

Semiautomatic do-it-yourself. Video

You can learn about the layout, assembly, testing of a home-made semiautomatic device from this video.

Do-it-yourself inverter welding semiautomatic device has undoubted advantages:

• cheaper than store counterparts;
• compact dimensions;
• the ability to cook thin metal even in hard-to-reach places;
• will become the pride of the person who created it with his own hands.

A semi-automatic welding machine can be homemade, made from an inverter. We must say right away that it is not easy to make a semi-automatic welding machine from an inverter with your own hands, but not impossible. Anyone who plans to make a semi-automatic device with their own hands from an inverter should study the principle of its operation, watch a video or photo on this topic if necessary, prepare necessary accessories and equipment.

How to convert an inverter into a semi-automatic

For work you will need:

FROMsemi-automatic welding circuit

Particular attention is paid to the alteration of the feeder, which feeds the wire into the welding zone, which moves along flexible hose. To obtain a high-quality, neat weld, the speed of wire feed through the flexible hose and the speed of its melting must match.

When welding semiautomatically, wires of different diameters and from different materials, so it should be possible to control the speed of its supply. This is what the feed mechanism does.

The most common wire diameters in our case: 0.8; one; 1.2 and 1.6 mm. Before welding, the wire is wound on coils, which are attachments fixed with simple fasteners. The wire is fed automatically during the welding process, which significantly reduces the time of the technological operation and increases efficiency.

The main element of the electronic circuit of the control unit is a microcontroller responsible for the stabilization and regulation of the welding current. The current parameters and the ability to regulate them depend on this element.

We remake the inverter transformer

Do-it-yourself semi-automatic welding can be done by altering the inverter transformer. To bring the characteristics of the inverter transformer in accordance with the required, it is wrapped with a copper strip wrapped with thermal paper. Ordinary thick wire is not used for these purposes, because it will get very hot.

The secondary winding is also being redone. For this you need:

• Wind the winding from three layers of tin, each of which is insulated with fluoroplastic tape.
• The ends of the windings are soldered to each other to increase the conductivity of the currents.

In the design diagram of the inverter used for inclusion in the semiautomatic device, a fan must be provided to cool the device.

Setting

When making a semiautomatic device from an inverter, first de-energize the equipment. To prevent the device from overheating, place its input and output rectifiers, as well as power switches, on heatsinks.

After completing the above procedures, connect the power section to the control box and connect it to the mains. When the mains indicator lights up, connect an oscilloscope to the outputs of the inverter. Use an oscilloscope to find electrical pulses at 40-50 kHz. Between the formation of pulses, 1.5 μs should pass, and this is regulated by changing the magnitude of the voltage supplied to the input.

Oscillogram of welding current and voltage: on reverse polarity - on the left, on straight polarity - on the right

Check that the pulses that are reflected on the oscilloscope screen are rectangular, and their front is no more than 500 ns. If the parameters being checked are as they should be, connect the inverter to the mains.

The current that comes from the output must be at least 120A. If this value is less, it is likely that a voltage not exceeding 100 V is going into the wires of the equipment. In this case, the equipment is tested by changing the current strength (plus the voltage on the capacitor is constantly monitored). The temperature inside the device is also constantly monitored.

After testing, check the machine under load: connect a rheostat with a resistance of at least 0.5 Ohm to the welding wires. It must withstand a current of 60 A. The current supplied to the welding torch is controlled by an ammeter. If it does not correspond to the required value, the resistance value is selected empirically.

Usage

After starting the device, the inverter indicator should show the current value - 120 A. If the value is different, something is done wrong. Eights may appear on the indicator. Most often this is due to insufficient voltage in the welding wires. It is better to immediately determine the cause of this malfunction and eliminate it. If everything is correct, the indicator will correctly show the strength of the current regulated by special buttons. The current adjustment interval that provides the inverters lies in the range of 20–160 A.

Checking the correct operation

For a semi-automatic to last long term, it is recommended to monitor all the time temperature regime inverter operation. In order to control at the same time two buttons are pressed, and then the temperature of the hottest of the inverter radiators will be displayed on the indicator. Normal working temperature- no more than 75 ° C.

If there is more, in addition to the information that is displayed on the indicator, the inverter will emit an intermittent sound, which should immediately alert. In this case (or when the temperature sensor closes) electronic circuit will automatically reduce the operating current to 20A, and the sound signal will go on until the equipment returns to normal. An error code (Err), which is displayed on the inverter indicator, can also indicate a malfunction of the equipment.

When is a semi-automatic welding machine used?

A semiautomatic device is recommended for use when accurate, neat connections of steel parts are needed. With such equipment thin metal is boiled, which is important, for example, when repairing car bodies. Qualified specialists or a training video will help you learn how to work with the device.

Most welding machines, especially homemade ones, are far from perfect. We offer a scheme for fine-tuning a home-made welding machine from "change" to "permanent" with your own hands and you can use electrodes of any type ( see fig. one).

Rice. 1 Scheme of a welding machine with a highly efficient inductive-capacitive filter that smooths out the ripple of the rectified voltage.

Let's go through the diagram.

Choke L.

The core for it is taken from the choke of urban lighting lamps 1N400N37-110. When removing the old windings, it is necessary to save the cardboard spacers, which provided a gap between the main and closing parts of the core (Fig. 2).

When reassembling, they are installed in place. The new winding is wound on only one side rod - three layers of a copper bus with a section of 4x6 mm, evenly spaced along the entire length of the core. The beginning of the inductor winding is connected to the block of capacitors C1 ... C6, and the end of the winding is connected to the “+” terminal (Fig. 1).

Rectifier and filter capacitor unit.

Diodes U01 ... U04 type D161-320 or similar, designed for average rectified current - above 250 A and reverse voltage - at least 200 V, are mounted on standard cast radiators-coolers, which must be isolated from each other and from the body of the welding apparatus with textolite plates. Capacitors 31 ... 56 - electrolytic, type K50-3 or K50-7 two-section 250/290 (150 + 150 microfarads). The total capacitance of the block of capacitors is 1800 microfarads. It is most convenient to install them in one row on a textolite plate 4 ... 6 mm thick.

Welding current regulator R (“ballast rheostat”).

Made from one section of the limiting resistance of the bridge crane DEK-256 (Fig. 3).

This resistance is a ceramic tube with a figured spiral groove on outer surface, in which a tire made of a material with high resistivity, with a cross section of about 20 mm2, is laid.

Any welder knows about the advantages of a semiautomatic device over manual electric welding. Due to their high prevalence and low cost, MMA inverters are in the arsenal of many craftsmen. But with MIG welding, the matter is different - these devices are more expensive. But, there is a way out - you can make a semi-automatic device from an inverter with your own hands. If you delve into this issue, the matter will not be so difficult.

There are fundamental differences between MMA and MIG welding. To operate the semiautomatic device, you need carbon dioxide (or a mixture of carbon dioxide and argon) and an electrode wire, which is supplied to the welding site through a special hose. Those. the very principle of semi-automatic welding is more complicated, but it is universal and its use is justified. What is needed for the operation of a semi-automatic device:

• wire feeder;
• burner;
• hose for wire and gas supply to the heating pad;
• current source with constant voltage.
• And to turn a welding inverter into a semiautomatic device, you need a tool, time and desire.

Training

Making a semi-automatic welding machine at home begins with work planning. There are two options for making MIG welding from an inverter:

1. Completely make a semi-automatic welding machine with your own hands.
2. To remake only the inverter - the feeding mechanism is ready to be purchased.

In the first case, the cost of parts for the feeder will be about 1000 rubles, excluding work, of course. If the factory semiautomatic device includes everything in one case, then the home-made one will consist of two parts:

1. Welding inverter.
2. Drawer with feeder and wire reel.

First, you need to decide on the case for the second part of the semiautomatic device. It is desirable that it be light and roomy. The feed mechanism must be kept clean, otherwise the wire will be jerky, in addition, periodically you need to change the spools and adjust the mechanism. Therefore, the box should be easy to close and open.

The ideal option is to use the old system unit:

1. neat appearance- it doesn’t really matter, but it’s much more pleasant when the insides of the homemade product do not stick out and the semi-automatic device from the MMA inverter looks good;
2. light, closed;
3. the case is thin - it is easy to make the necessary cutouts;
4. the gas valve and the wire feed drive operate on 12 volts. Therefore, a power supply from a computer is suitable, and it is already built into the case.

Now you need to estimate the size and location of future parts in the case. You can cut out approximate layouts from cardboard and check them mutual arrangement. After that, you can start work.

The best option for electrode wire is a coil weighing 5 kg. Her external diameter 200 mm, internal - 50 mm. For the axis of rotation, you can use a sewer pvc pipe. Its outer diameter is 50 mm.

Burner

Homemade semi-automatic must be equipped with a burner. You can make it yourself, but it's better to buy ready kit, which includes:

1. Burner with a set of tips of different diameters.
2. Supply hose.
3. Euro connector.

A normal burner can be purchased for 2-3 thousand rubles. Moreover, the device is homemade, so you can not chase expensive brands.

What to look for when choosing a kit:

• what welding current is the torch designed for;
• the length and rigidity of the hose is the main task of the hose, to ensure the free flow of the wire to the torch. If it is soft, any kink will slow down the movement;
• springs near the connector and burner - they prevent the hose from breaking.

Feeder

The electrode wire must be fed continuously and evenly - then the welding will turn out to be of high quality. The feed rate must be adjustable. There are three options for how to make a device:

1. Buy a fully assembled mechanism. Expensive, but fast.
2. Buy feed reels only.
3. Do everything with your own hands.

If the third option is chosen, you will need:

• two bearings, guide roller, tension spring;
• wire feed motor - a motor from wipers is suitable;
• metal plate for fastening the mechanism.

One pressure bearing - it must be adjustable, the second serves as a support for the roller. Manufacturing principle:

• holes are made on the plate for the motor shaft and for mounting bearings;
• the motor is fixed behind the plate;
• a guide roller is put on the shaft;
• bearings are fixed at the top and bottom;

Bearings are best placed on metal strips - one end is bolted to the main plate, and a spring with an adjusting bolt is connected to the other.

The made mechanism is placed in the body so that the rollers are located in line with the connector for the burner, i.e. so that the wire does not break. Before the rollers, you need to install a rigid tube to align the wire.

Implementation of the electrical part

For this you will need:

• two automotive relays;
• diode;
• PWM controller for the engine;
• capacitor with transistor;
• idle solenoid valve - for supplying gas to the burner. Any VAZ model will do, for example, from the eight;
• wires.

The wire and gas feed control scheme is quite simple and is implemented as follows:

• when the button on the burner is pressed, relay No. 1 and relay No. 2 are activated;
• relay No. 1 turns on the gas supply valve;
• relay No. 2 is paired with a capacitor and turns on the wire feed with a delay;
• wire pulling is done by an additional button bypassing the gas supply relay;
• to remove self-induction from solenoid valve, a diode is connected to it.
• It is necessary to provide for the connection of the burner to power cable from the inverter. To do this, next to the euro connector, you can install a quick connector and connect it to the burner.

The semi-automatic device has the following sequence of work:

1. The gas supply is turned on.
2. After a short delay, the wire feed is switched on.

Such a sequence is needed so that the wire immediately enters the protective environment. If you make a semi-automatic without delay, the wire will stick. To implement it, you will need a capacitor and a transistor through which the engine control relay is connected. Operating principle:

• voltage is applied to the capacitor;
• it is charging;
• current is applied to the transistor;
• the relay turns on.

The capacitance of the capacitor must be selected so that the delay is approximately 0.5 seconds - this is enough to fill the weld pool.

After assembly, the mechanism needs to be tested, and the manufacturing process can be seen on the video.

Alteration of the inverter

To make a semiautomatic device from a conventional inverter with your own hands, you will have to slightly redo its electrical part. If you connect the MMA inverter to the assembled case, you will be able to cook. But at the same time, the quality of welding will be far from the factory semiautomatic device. It's all about the CVC - current-voltage characteristics. The arc inverter produces a falling characteristic - the output voltage floats. And for the correct operation of the semiautomatic device, a rigid characteristic is required - the device maintains a constant voltage at the output.

Therefore, in order to use your inverter as a current source, you need to change its CVC (voltage characteristic). For this you will need:

• toggle switch, wires;
• variable resistor and two constant;

It is quite easy to get a hard characteristic on an inverter. To do this, you need to put a voltage divider in front of the shunt that controls welding current. For the divider, fixed resistors are used. Now you can get the necessary millivolts, which will be proportional to the output voltage, and not the current strength. There is only one minus in such a scheme - the arc turns out to be too rigid. To mitigate it, you can use a variable resistor, which is connected to the divider and the output of the shunt.

The advantage of this approach is that the arc stiffness adjustment appears - such a setting is only in professional semi-automatic machines. A toggle switch switches the inverter between MMA and MIG modes.

Thus, converting an MMA inverter into a semiautomatic device, although not an easy task, is quite feasible. At the output, it turns out a device that is not inferior to the factory ones in terms of its characteristics. But it is also much cheaper. The cost of such an alteration is 4-5 thousand rubles.

Comments:

Any tool shop nowadays can offer quite a few a large assortment a variety of welding machines of various price categories. Most welding units, up to 70%, occupy welding inverters, and other "welders" fall on transformer-type devices. Not all people can purchase an industrial product for the production of electric welding, and some want to do it themselves.

The home welding machine will not be able to perform challenging tasks, however, for small jobs, the power will be enough.

What is electric welding

Compound metal products between themselves by heating the metal with an electric arc and then fusing it into an integral seam is called electric welding. The main equipment in such a welding process is the welding machine, and the main tool for connecting metal things is the electrode. The welding unit serves as a source of alternating or direct current, which, by means of an electrode, ignites an arc that melts the metal. The quality of the welded joint when welding with direct currents is much higher than the same joint made by "change". The experience of an electric welder should not be discounted, although welding inverters that are popular today allow high-quality welding of metals almost the first time. That is why for most of the various welding work use welding machines that use a direct current type in their work.

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The simplest welding machine: instructions

For small home welding work, you can assemble a home-made compact machine with low power. It's not an inverter, of course, but necessary thing. When solving the problem of creating a welding "assistant", you can use various design features.

The simplest welding device is welding transformer with two windings: network and working. The network is calculated for the mains voltage, usually 220-240 volts, and the working one is calculated for a lower voltage from 70 to 45 volts, and the change in current usually occurs by changing the number of turns of the working winding, its taps. As iron for transformers, you can use old asynchronous motors or industrial step-down three-phase transformers of the TOZ type, etc.

The primary winding should be designed for 25 ampere current, the secondary or working one - for 160 A. This is reflected in the cross section of the wires used. For an approximate estimate of the current load per 1 sq. mm allow 10 A, for aluminum - 4 A. We determine the cross-sectional area of ​​\u200b\u200bthe window of transformer iron in square meters. cm, then we find the number of turns of the windings, if right amount for one volt is defined as 48 divided by the sectional area of ​​the iron window of the transformer. Calculating the device is half the battle, the main thing is to assemble it.

The product created according to the calculations is the simplest AC welding device, the design of the apparatus depends on the materials used.

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Let's make a DC welding machine with our own hands

In order for AC welding machines to turn into DC "welders", it is necessary to limit the rate of current change with a choke and rectify the alternating current with diodes or a rectifier bridge.

Diodes must be capable of 200A output current and have sufficient cooling so that the first welding does not damage them. This fully applies to the throttle. The use of these devices in conjunction with an AC welding machine turns it into a DC machine. It becomes possible to weld with DC electrodes, and the range of weldable metals is expanding. Becomes available for welding stainless steel and cast iron. The welding machine can cook like an inverter, although here the welder needs quite great experience work.