We make a semi-automatic welding machine from an inverter. We make a semi-automatic welding machine with our own hands How to make constant welding from a variable

Landscaping and planning 15.06.2019

Landscaping and planning

The advantages of DC welding machines over their "alternating current counterparts" are well known. This includes soft arc ignition, the ability to connect thin-walled parts, less metal spatter, and the absence of non-welding areas. There is not even an annoying (and, as it turned out, harmful to people) cod. And all because there is no main inherent in welding machines alternating current feature - intermittent arcing when the sinusoid of the supply voltage flows through zero

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

Moving from graphs to real designs, it should also be noted: in AC machines, to improve and facilitate welding, powerful transformers are used (the magnetic circuit is made of special electrical iron with a steeply falling characteristic) and a deliberately overestimated voltage in the secondary winding, reaching up to 80 V, although for 25-36 V is enough to support the arc burning and metal deposition in the welding zone. We have to put up with the prohibitively large mass and dimensions of the apparatus, increased power consumption. By reducing the voltage, which is transformed into secondary circuit, up to 36 V, it is possible to lighten the weight of the “welder” by 5-6 times, bring its dimensions to the size of a portable TV while improving other performance characteristics.

But how to ignite 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 output voltage of the modernized "welder" was increased by almost 1.5 times. The opinion of experts is confirmed in practice: when the 40-volt DC barrier is exceeded, the arc easily ignites and burns steadily, allowing even thin body metal to be welded.

Rice. 2. Fundamental circuit diagram DC welding machine.

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

Fig.3. Volt-ampere characteristic of the welding machine at direct current.

The "welder" recommended by the author can be assembled even at home, based on an industrial power transformer 220-36 / 42 V (these are usually used in systems for safe lighting and powering low-voltage factory equipment). After verifying the integrity of the primary winding, containing, as a rule, 250 turns insulated wire with a cross section of 1.5 mm2, check the secondary ones. If their condition is not important, everything (with the exception of a working network winding) is deleted without regret. And in the vacated space, a new secondary winding is wound (until the “window” is filled). For the recommended 1.5 kVA transformer, this is 46 turns of a 20 mm2 copper or aluminum bus 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.

The choice of the cross section of the electrodes depending on the power of the transformer.

The rectifier bridge can be assembled from semiconductor diodes with an operating current of 120-160 A by installing them on heat sinks-radiators 100x100 mm. 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-ampere 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 segment of a 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. When testing, it is recommended that, by disconnecting the device (10 minutes after welding) from the mains, check thermal regimes transformer, diode bridge and capacitor. Only after making sure that everything is in order, you can continue to work. After all, an overheated "welder" is a source of increased danger!

Of the 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 carried out is equipped in accordance with the requirements fire safety. In addition, it is necessary to ensure that there are no rags or other combustible materials nearby, and the connection of the “welder” to the network must be carried out in compliance with electrical safety rules through a powerful plug connector of the electrical panel at the entrance to the building.

V.Konovalov, Irkutsk
Mk 04 1998

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 "recession" 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.

The choice of household welding machines on modern market huge - from transformer and inverter to devices plasma cutting. The main area of use of this electrical equipment for domestic purposes is the repair of auto and motorcycle equipment, welding work on small construction sites (cottage construction). In this article, I propose to consider some points on the modernization of household transformer welding machines using the example of BlueWeld welding model Gamma 4.185.

Consider the circuit diagram of the device - as you can see, nothing complicated - an ordinary power transformer, with a primary winding of 220/400V, with thermal protection and a cooling fan.

The operating current of the device (from 25 to 160A) is regulated by means of the retractable part of the transformer core. The device is designed to work with coated electrodes from 1.5 to 4 mm in diameter. What was the prerequisite for the modernization of this device? First of all, the instability of the supply voltage in the area where the use of this device was planned - on other days it barely reached 170V (by the way, some inverter devices simply do not start at this supply voltage). In addition, the device is not originally intended for making welds with high aesthetic characteristics (for example, when using electric arc welding in the process of artistic cold forging metal or when welding thin-walled profile pipes) - in general, the main purpose of the device was to "solder" two iron blanks together. Among other things, it was very difficult to "ignite" the arc with this welding even at the rated supply voltage - there is no need to talk about low voltage at all. As a result, it was decided, first of all, to transfer the device to direct current (for the stability of the electric arc and, as a result, to increase the quality of the welded joint) and also to increase the output voltage for a more stable and easy ignition of the electrode. For these purposes, the rectifier / multiplier circuit designed by A. Trifonov was ideal - the circuit diagram (a) and current-voltage characteristics (b) are shown in the figure.

a special role in this technical solution It would seem that a conventional rectifier, jumper X1X3 plays - inserting it, we get a rectifier device from a conventional diode bridge VD1-VD4 with a low-pass filter C1C2L1, at the output of which we have twice the voltage in idle mode (compared to the option of operating the device without a jumper). Let's take a closer look at how the circuit works. A positive voltage half-wave enters the semiconductor valve VD1 and, having charged the capacitor C1 to the maximum, returns to the beginning of the transformer winding. In the other half-cycle, the charge passes to the capacitor C2, and from it to the valve VD2 and then to the winding. Capacitors C1 and C2 are connected in such a way that the resulting voltage is equal to the total (twice) voltage, which is supplied through the choke to the electrode holder and thus contributes to stable ignition of the arc. Valves VD3 and VD4 with a closed jumper X2X3 and the absence of a welding arc do not participate in the operation of the circuit. The main advantage of the scheme is that when using conventional scheme bridge, there is a sharp decrease in the rectified voltage with an increase in the load current at the moment of ignition of the arc - it is necessary to install electrolytic capacitors of huge capacity - 15000 microfarads, and all this despite the fact that at the moment the electrode touches the surfaces to be welded and the high-capacity capacitor is instantly discharged, a plasma microexplosion occurs with destruction electrode coating, and this worsens the ignition. Now a little about the design details.

Semiconductor diodes D161 or V200 with standard radiators for them are applicable as diode bridge valves.

If you have 2 D161 diodes and 2 V200 diodes, you can make the bridge more compact - the diodes are made with different conductivity and the radiators can be fastened with studs directly to each other without using gaskets. As capacitors, reinsured, I used a set of non-polar capacitors MBGO (you can MBGCH, MBGP).

The capacity of each turned out to be 400 microfarads, which was quite enough for the stable operation of the device. The current inductor L1 is wound on the core from the transformer TC-270 with a wire with a cross section of 10 mm square.

We wind until the window is completely filled. When assembling, between the halves of the transformer core we lay textolite plates with a thickness of 0.5 mm. Since it was planned to use the apparatus for welding thin-walled profile pipes, the negative terminal of the rectifier was connected to the electrode holder, and the positive one to the "crocodile" mass. The tests carried out showed the following results: stable ignition of the arc; confident maintenance of arc burning; excellent thermal conditions during long-term operation (10 electrodes in a row); good quality welds (compared to using a machine without a straightener). Conclusion - the modernization of the welding machine using the Trifonov rectifier significantly improves its performance in all respects.

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 converts alternating current to direct current. This requires a special electronic module, a high-frequency transformer and rectifiers.

For quality performance welding work it is necessary that for the future device such parameters as voltage, current strength and welding wire feed speed be 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. Wire feed speed adjusts 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 TS-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 during welding makes it possible to regulate the current in a wide range: from 20 to 160A, and the choice of the operating current 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 roller Ø 25 mm. 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 quickly make a semi-automatic 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 bottle 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.