DIY semi-automatic - detailed video

Created plan

Any scheme homemade device provides a separate sequence of work:

• On entry level It is necessary to ensure preparatory purging of the system. It will accept the subsequent supply of gas;
• The arc power source must then be started;
• Feed wire;
• Only after all actions have been completed will the inverter begin to move at the specified speed.
• At the final stage, the seam should be protected and the crater welded;

Control board

To create an inverter, a special control board is required. This device must have the following components installed:

• A master oscillator including a galvanic isolation transformer;
• The node with which the relay is controlled;
• Blocks feedback, responsible for the mains voltage and supply current;
• Thermal protection block;
• Antistick block;

Case selection

Before assembling the unit, you need to select the housing. You can choose a box or box with suitable dimensions. It is recommended to choose plastic or thin sheet material. Transformers are built into the housing and connected to the secondary and primary bobbins.

Coil alignment

The primary windings are made according to parallel circuit. Secondary bobbins are connected in series. According to a similar circuit, the device is capable of accepting a current of up to 60 A. In this case, the output voltage will be equal to 40 V. These characteristics are ideal for welding small structures at home.

Cooling system

During continuous operation homemade inverter may overheat greatly. Therefore, such a device needs special system cooling. The most simple method To create cooling is to install fans. These devices must be attached to the sides of the case. Fans should be installed opposite transformer device. The mechanisms are attached in such a way that they can work for extraction.

Selection of household welding machines for 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 automobiles and motorcycles, welding work on small construction sites ( country house 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.

Let's consider schematic diagram The device - as you can see, is 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 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 it was planned to use this device - 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 initially designed 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 “light” the arc with this welding even at the rated supply voltage - there is no need to talk about reduced voltage at all. As a result, it was decided first of all to transfer the device to direct current (for stability electric arc and as a consequence of increasing the quality of the welded joint) as well as increasing the output voltage for more stable and easier ignition of the electrode. For these purposes, the rectifier/multiplier circuit designed by A. Trifonov was ideal - fundamental electrical diagram(a) and current-voltage characteristics (b) are shown in the figure.

A special role in this technical solution seemingly ordinary rectifier, the jumper X1X3 plays - by inserting it, a rectifier device is obtained from a conventional diode bridge VD1-VD4 with a low-frequency filter C1C2L1, at the output of which in idle mode we have double the voltage (compared to the version of the device without a jumper). Let's take a closer look at the operation of the circuit. A positive half-wave of voltage is supplied to the semiconductor valve VD1 and, having charged 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 further to the winding. Capacitors C1 and C2 are connected in such a way that the resulting voltage is equal to the total (double) voltage, which is supplied through the inductor to the electrode holder and thus contributes to stable ignition of the arc. When the X2X3 jumper is closed and there is no welding arc, valves VD3 and VD4 do not participate in the operation of the circuit. The main advantage of the circuit is that when using a conventional bridge circuit, 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 welded surfaces and instantaneous discharge of a large capacitor, a microexplosion of the plasma occurs with destruction of the electrode coating, and this impairs ignition. Now a little about the design details.

Semiconductor diodes D161 or B200 with standard radiators for them are used as diode bridge valves.

If you have 2 D161 diodes and 2 B200 diodes, you can make the bridge more compact - the diodes are made with different conductivities and the radiators can be fastened with pins directly to each other without using gaskets. As capacitors, to play it safe, I used a set of non-polar capacitors MBGO (you can use MBGCh, MBGP).

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

We wind until the window is completely filled. When assembling, we place 0.5mm thick textolite plates between the halves of the transformer core. 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 terminal to the “crocodile” of the mass. The tests carried out showed the following results: stable arc ignition; reliable maintenance of the arc; excellent thermal conditions for long-term operation (10 electrodes in a row); good quality of welds (compared to using a machine without a rectifier). Conclusion - modernizing a welding machine using a Trifonov rectifier significantly improves its performance in all respects.

A semi-automatic welding device is a fairly popular device among professional and home craftsmen, especially those who deal body repair. This unit can be purchased ready-made. But many welding machine owners inverter devices They are wondering: is it possible to convert the inverter into a semi-automatic device, so as not to buy another welder? Making a semi-automatic device from an inverter with your own hands is a rather difficult task, but when strong desire quite feasible.

To assemble the unit you will need the following elements:

• inverter welding machine;
• burner, as well as a special flexible hose, inside which there are a gas pipeline, a wire guide, power cable and electrical control cable;
• mechanism for uniform automatic wire feeding;
• control module, as well as motor speed controller (PWM controller);
• cylinder with protective gas (carbon dioxide);
• solenoid valve for gas cut-off;
• coil with electrode wire.

To assemble a homemade semi-automatic machine from welding inverter, the latter must generate a welding current of at least 150 A. But it will have to be slightly modernized, since the current-voltage characteristics (CV) of the inverter are not suitable for welding with electrode wire in a shielding gas environment.

But more on that later. First you need to make the mechanical part of the semi-automatic machine, namely the wire feed mechanism.

Electrode wire feeding mechanism

Since the feeding mechanism will be placed in a separate box, it is ideal for this purpose computer system case. Plus, there is no need to throw away the power supply. It can be adapted to the operation of the broaching mechanism.

To begin with, you need to measure the diameter of the coil of wire or, having outlined it on paper, cut out a circle and insert it into the body. There should be enough space around the reel to accommodate other components (power supply, hoses and wire pulling mechanism).

The wire drawing device is made from a windshield wiper mechanism from a car. It is necessary to design a frame for it, which will also hold the pressure rollers. The layout must be drawn on thick paper in real scale.

Advice! The connector for connecting the burner hose and the hose with the burner itself can be made by yourself. But it would be better to buy ready set, which has an affordable price.

The feeder should be installed in the housing so that the connector is located in a convenient location.

In order for the wire to be fed evenly, all components must be fixed exactly opposite each other. The rollers must be centered relative to the hole for the inlet fitting, which is located in the connector for connecting the hose.

As roller guides you can Use bearings of suitable diameter. on them with the help lathe a small groove is machined along which the electrode wire will move. For the mechanism body, you can use 6 mm thick plywood, textolite or durable sheet plastic. All elements are fixed to the base, as shown in the following photo.

Used as a primary wire guide bolt drilled along the axis. The result is something like a wire extruder. At the inlet of the fitting, a cambric reinforced with a spring (for rigidity) is put on.

The rods on which the rollers are attached are also spring-loaded. The clamping force is set using a bolt located below, to which the spring is attached.

Advice! If for some reason you do not have the opportunity to make a mechanism for drawing wire with your own hands, then you can buy it in China. 12 V and 24 V mechanisms are available for sale. In this case, since a power supply from a computer is used, a device powered by 12 V is required.

Base for securing the bobbin can be made from a small piece of plywood or PCB and trim plastic pipe suitable diameter.

Mechanical control circuit

To achieve good quality seam when welding, it is necessary to ensure wire feed at a certain and constant speed. Since the motor from the windshield wiper is responsible for the feed speed of the equipment, a device is needed that can change the speed of rotation of its armature. Suitable for this already ready-made solution, which can also be purchased in China, and it’s called

Below is a diagram from which it becomes clear how the speed controller is connected to the engine. The controller regulator with a digital display is located on the front panel of the case.

Next, you need to install relay control gas valve . It will also control the engine start. All these elements must be activated when the start button located on the burner handle is pressed. In this case, the gas supply to the welding site should be ahead (by about 2-3 seconds) of the start of wire feeding. Otherwise, the arc will ignite in the surrounding atmospheric air, and not in a protective gas environment, causing the electrode wire to melt.

Delay relay for homemade semi-automatic can be assembled based on an 815 transistor and capacitor. To get a pause of 2 seconds, a capacitor of 200-2500 uF will be enough.

Advice! Since the power comes from a computer power supply, which produces a voltage of 12 V, instead of self-made module, you can use a car relay.

It is placed in any place where it will not interfere with the operation of the moving units, and is connected to the circuit according to the diagram. You can use an air valve from GAZ 24 or buy a special one designed for semi-automatic machines. The valve is responsible for automatic feeding protective gas to the torch. It turns on after pressing the start button located on the semi-automatic burner. The presence of this element significantly saves gas consumption.

But as already noted, the current-voltage characteristics (VC) of the inverter are not suitable for full-fledged operation of a semiautomatic device. Therefore, in order for a semi-automatic attachment to work in tandem with an inverter, minor changes need to be made to its electrical circuit.

Changing the current-voltage characteristic of the inverter

To change the I-V characteristic of an inverter, there are many circuits, but the simplest way to do this is as follows:

• assemble the device using choke from fluorescent lamp according to the diagram below;

• to connect the assembled device, you will need to assemble another block according to the following diagram;

• To prevent the overheating sensor from triggering on the inverter, an optocoupler must be soldered to it (in parallel), as shown in the following diagram.

But if the welding current is controlled in the inverter using a shunt, then you can collect simple diagram of three resistors and a mode switch as shown below.

As a result, converting a welding inverter into a semi-automatic machine will cost 3 times less than a ready-made unit. But of course, for self-assembly To operate the device, you will need to have some knowledge of radio technology.

Advantages of welding machines DC 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 feature inherent in AC welding machines is missing - 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. Schematic diagram of a 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) is quite suitable as a bus. general cross section 20 mm2.

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 themselves welding electrodes, then their diameter depends on the power of the transformer used.

Rice. 4. Homemade welding machine for DC welding.

And one more thing. 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 fire safety requirements. 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