Home-made apparatus for spot welding circuit design. We assemble the machine for spot welding with our own hands. The device and operation of the control circuit

Spot welding can be found not only in production, but also in domestic conditions. The advantages of choosing this type of welding is its reliability. With this fastening method, it is easy to connect different carbon steels, non-ferrous metal. In this case, you can build almost any configuration and combination with metals.

Allows you to create a product for any imagination and need.

Range of applications

Most often, spot welding has been widely used in the repair of cables and household appliances. allows you to repair batteries and other mobile portable devices.

Welding technology

Battery welding technology is quite simple, an example can be seen in the video below.

The whole welding process consists in heating the working metal surface to a plastic state. In this condition, the products are easily deformed and connected.

To ensure quality, a continuous melting process is required. Continuity and a certain speed of the working pace, pressing force are key in the work. In the future, these parameters characterize the quality of products.

The basis of the principle of operation of this welding is the conversion of electrical energy into heat. Under the influence of heat, the metal surface is melted.

The contact of the electrodes should be placed at the junction of 2 working surfaces of the parts necessary for fixing.

The solidification of the molten mass occurs when the current is turned off. This eliminates the effect of spreading the surface of the seams. Therefore, this type of welding is called spot.

Ticks

Joining parts of parts is carried out by fixing the surface using special pliers. Which are divided into pendant and manual.

• Outboard.  Got wide application in the conditions of the plant and industrial enterprises, are subject to repeated use.
• Tame.  The main function is the transmission of electric current to the electrodes.

Several advantages

• High speed;
• The highest degree of electrical safety;
• Providing a quality connection;
• You can make a device for welding manually.

Technical process

The whole system is built on the elementary transfer of heat in order to melt the metal in the places of fixation. The quality of welding can be affected by poor surface cleaning, visible oxides.

Using the law of thermal conductivity, this parameter should be taken into account for most common metals. The thermal conductivity parameters for some of them are presented in the table below.

Metal name	Melting point, Сᵒ
Iron (mild steel)
Aluminum

The electrodes must also meet some parameters:

• Thermal conductivity;
• Electrical conductivity;
• Mechanical strength;
• Processing speed.

The electrodes are short-lived and require careful handling. With constant exposure to temperature, it is necessary to interrupt. This feature allows you to cool the electrodes and the welded surface. Thus, the life of the electrodes is extended.

The diameter of the electrodes affects the characteristic of the current strength, and accordingly the quality of the seam. The diameter of the electrode cross section is selected based on the thickness of the working surface. The electrode should be approximately two times thicker than the fixed products.

contact welding

Resistance weldingand allows you to carry out work in ordinary home conditions. But, most often, this method is widely used in industry.

Manufacturers made sure that bulky spot welding machines were not present at home. Compact mobile devices have been invented for a long time. Their purpose is to repair home appliances.

Such a device is called spotter. The device is equipped with two terminals designed to fix one of them to the working surface of the product. The second conclusion is brought to the electrode.

This configuration is not necessary. The current source should be located at a fairly close distance from the place of work.

Do not pay to a small-sized device, it is quite functional for its size.

The simplest devices use single-phase current. But it is not worth hoping to fix a part of more than one millimeter. The fixing of more complex parts is carried out using an additional transformer.

Cost

The cost of spotters is quite small. In the most expensive category are inverter.

As a rule, household devices do not require large capacities. Therefore, you can do with a homemade device.

Spot welding is distinguished by its weld quality. In most cases, to destroy it requires the use of serious mechanical stress. Most often, drills are used for this.

Apparatus diagram

If there is such a need, there is a desire to make the device yourself, then it is quite possible to assemble it at home.

The dimensions of the spot welding machine depend primarily on the needs. The most convenient devices are medium-sized.

Picture. The scheme of the welding machine for spot welding.

The operation of the device is based on the Lenz-Joule principle. The requirements of the physical law states that the conductor must generate heat in an amount equal to the proportion with the resistance of the conductor, as well as the square of the current and the time spent.

The installation of a rectifier bridge is mandatory for such a circuit design. A capacitor charges through the thyristor bridge. The first thyristor acts as a cathode.

The capacitor unit is a kind of protection and serves as a current release. The principle of a swing, constant charging and discharging of capacitors is created. This principle allows you to create the effect of spot soldering. The seam cools evenly and in a timely manner, not allowing the metal to blur.

To increase power in the circuit, an additional thyristor with an off relay is also added.

Homemade machine

An important part of the welding machine is a transformer. The minimum power value should be 750 watts.

Video on creating a hand-held device.

You can create a device using an inverter. Before proceeding to the goal, it is necessary to have some skills in the field of electrical engineering.

A simpler circuit is considered using a transformer instead of an inverter. But such devices are not powerful enough to work with metals of sufficient thickness more than 1 mm.

Device creation steps

• Remove transformer from unnecessary microwave;
• Get rid of the secondary winding, mounts, shunts;
• Make the secondary winding with a thicker wire than in the primary;
• Check the assembled device for current leakage;
• Leaks should be repaired by insulation with tape;
• Check current strength. The value should be no more than 2 kA.

Copper wire of considerable thickness is most suitable as tips or electrodes. Tips are sharpened and fixed.

The resistance welding machine is not only simple to operate, but it is still not difficult to manufacture. The main thing is that it is not necessary to possess the skills of this work. Even a beginner will figure out how to make home-made contact welding with your own hands and from available devices. What is a contact connection?

Types of resistance welding:

• point;
• embossed;
• butt and suture.

Design

The machine of spot resistance welding made in domestic conditions can be designed to solve simple problems that arise in everyday life. With its help, it is easy to suture, necessary for the repair or manufacture of products. Contact spot welding is obtained by heating individual elements with electric current and provides a reliable connection, and the repaired product will last for some time.

The device operates in direct dependence on the dimensions of the material, its thermal conductivity and the power of the equipment.

The operating parameters are as follows:

1. Low voltage from 1 to 10V.
2. The production time takes a few seconds.
3. Current strength from 1000 Amperes.
4. Small melting area.
5. The pressure to the place of the repaired sample must be strong.

Automatic resistance welding made in the home, subject to all parameters, takes into account quality requirements. To simplify the task, it is recommended to choose alternating current. In this case, the duration of exposure will allow to make high-quality seams, while the time interval will be increased. In such devices there is a relay that provides time control.

Do-it-yourself resistance welding is easy to do. It is quite simple to manufacture. For these purposes, current converters from an old TV can be used as an autotransformer. Contact welding from a microwave, as well as welding from an inverter or from LATR, will also function well.

When choosing the most suitable transformer, the windings are wound again based on the parameters of voltage and current. Designation of spot resistance welding according to the requirements of GOST 14098.

A control scheme for a technical device is being developed, or you can use an existing one located on Internet pages, again based on the parameters that are set. The resistance welding machine is made in accordance with the types of proposed work. In many cases, tongs for resistance welding are performed.

The connection must be made correctly so that direct contact is ensured, including the passage of the current strength of one parameter. Special attention is given to a transformer for resistance welding and electrodes for resistance welding, mounted on pincers.

On aggregates with insufficient attention to this criterion arcing occurs, and the final result is not achieved. A good solution is also seam resistance welding with your own hands from the inverter or the execution of the unit with your own hands from the microwave, as well as a microwave oven.

The resistance welder can cook all types of materials in accordance with the types of certification. Jobs always include initial training. Arc welding makes connections for more massive structures.

Do it yourself

Flash butt welding machines must be safe during operation, and it is also necessary to know for what purposes the device will be used. Homemade contact welding is made in the domestic environment. For this, it is taken into account that the metal thickness should be no more than 1 mm, and the cross-section of wire electrodes not more than 4 mm.

The welding machine operates at 220 V and 50 Hz, while the output voltage is from 4 to 7 V. The pulse current indicator is up to 1.5 thousand A. The contact welding control unit can be made after watching the video.

The electrical circuits in the drawing combine the following designs:

• circuit breaker operating in automatic mode;
• chains to control the work;
• power unit;
• resistance welding transformer;
• single-phase thyristor for connecting power to the network.

The winding circuit includes a primary, having six outputs for switching on and providing current regulation in the secondary. In this case, the first is connected to the network, and 5 regulate the process parameters.

The starter circuit in the MTT4 drawing includes:

1. Thyristor key.
2. Through two contacts, the load is redistributed simultaneously to the other 2 contacts through a transformer.

The control scheme consists of:

• power supply from a transformer;
• relay for closing contacts when voltage is applied;
• diode bridge, performing the function of a rectifier.

Resistance Welding Accessories:

1. Case, not passing current.
2. The transformer on which the wire is wound.
3. Ticks
4. Electrodes
5. Wiring diagrams.
6. A number of safety devices: pressure gauges for gas at the pressure inlet.

Automation of the process is performed using all components. The resistance welder must have certain skills when joining with a seam or in places. Jobs in this specialty can often be found on the Internet.

Blueprints

Transformer manufacturing

Resistance welding, the main structural element of which is a transformer, is done by yourself. You can remove transformer equipment from any device, most importantly, take into account the calculation of the transformer so that the current strength is at least 2.5 A. The old winding should be removed, and the rings should be installed on the magnetic circuit from thin conductive cardboard. This wire is wrapped with varnish in more than 3 layers.

For the manufacture of the primary winding, wires insulated with a cloth for better impregnation should be used, with a diameter of 1.5 mm. For the secondary, it is better to use a stranded wire of 20 mm in diameter in silicone insulation. Calculate the number of turns from the calculation of the power of the device. After winding the pepper, a cotton tape is wound, then a secondary is applied to it. Everything is saturated with varnish.

The resistance welder of a manual machine must know all the structural elements. Jobs in this specialty are in demand. Arc welding also has a transformer in its design solution.

Tick \u200b\u200bMaking

The resistance welding machine is equipped with tongs. Hand clamps for contact docking can be:

• remote;
• stationary.

The second option provides good insulation and excellent contact with the electrodes. To do this, you need to make the remote lever long. Handles of the appropriate length are easier to make on a remote structure. The insulation of the movable joint must be reliable, as a rule, washers and bushings made of PCB are used for this.

Pincers for resistance welding are made with a given parameter of the electrode extension in the form of points, which is also important, the distance from the edge to the junction of the parts depends on it. Electrodes are made of copper or beryllium bronze. Also, welding pliers can be made from the working part of soldering irons. This is convenient when connecting polyethylene pipes.

The welder on resistance welding machines must be certified, but if he works in production. Doing spot welding with your own hands is a simple task, like arc welding. In everyday conditions, everyone can handle it.

Performance of work

Arc welding is not suitable for brewing individual points.

Before performing work, sharpening of the electrodes for resistance welding is necessary, every welder on resistance welding machines knows this.

Flash butt welding is performed as follows:

1. Parts are installed between the electrodes.
2. Under the action of the clamping force, a friction force is created between the electrode and the surface.
3. The maximum clearance is set before applying voltage. In the process of current flow, contact resistance is created.
4. A voltage is applied and the electrode moves, capturing the joints, forming a seam.

Aluminum structures are joined by flash butt welding. Resistance welding of aluminum can be seam and spot. The welder on resistance welding machines can have the same qualifications as when working on inverters. Electric arc is considered the most dangerous.

Quality control of seams is carried out by the state standard. The standard is GOST 14098, which OTK employees are guided by and based on laboratory tests.

About equipment

General engineering standards of the time for resistance welding are necessary to perform production tasks in a given period of time. For production needs, equipment is purchased, for example, tecna resistance welding, which forms joints in the form of dots.

PF Contact Welding LLC manufactures, repairs and retrofits inverter units. A plan of enterprises aimed at manufacturing products in mechanical engineering should be implemented with the availability of modern devices.

Multipoint resistance welding machines, including their technology on the principle of welding the mesh and rods in a stationary state. Roller welding by these machines combines the methods of performing work in both intermittent and continuous steps.

Butt welding, made by hand, is needed for the repair of products made of thin metal, polyethylene, including polyethylene pipes, carried out end-to-end.

Today 91 welding units for resistance spot welding are on sale. Contact spot welding machine MT 1928 LM by LLC PF resistance welding company, manufactured on the basis of semiconductors and on capacitors, the kit includes:

• contact welding controller PKC 502 or contact welding controller PKC 801;
• resistance welding pliers foxweld ktr 8 3097;
• the pic16f628 controller is installed on the winding.

The machine performs single-point connections, it is also possible to connect polyethylene pipes. Contact welding MT is sufficient for welding fittings.

Using this unit, flash butt welding of wire is performed.

Video: spot welding do-it-yourself (spotter).

The Ax 2M device is used for welding copper and non-ferrous alloys, spot welding of batteries is performed. DIY welding for batteries is simple by technology.

The sunkko spot welding machine is used to assemble a battery of cells. Sunkko 709a does not overheat the metal plate during operations, which can happen when products are sealed. It is supplied complete with a soldering iron, and nickel is used during operation. Suture work is done for end-to-end polyethylene pipes on pipelines, and plastic products can also be joined.

A professional contact welding welder receives a specialty in an educational institution. Vacancies for gas and gas welders, including a welder in resistance welding machines or a resistance welding welder, are always open at enterprises.

Today it is difficult to imagine the construction and creation of various metal structures without the use of welding transformers. High reliability of structural connections and ease of work allowed the welding machine to firmly take its place in the arsenal of any builder. You can purchase such a transformer in any hardware store. But not always the factory model can meet certain needs and requirements. Therefore, many are trying to make a transformer for welding on their own. The manufacture of a home-made welding transformer takes place in several stages, from calculations to installation.

To understand the whole process of making a transformer for DIY welding, you need to understand the principle of its operation, which consists in converting a voltage of 220 volts to a lower voltage of up to 80 volts. In this case, the current increases from 1.5 Amperes to 160 - 200 Amperes, and in industrial ones up to 1000 Amperes. This dependence for a welding transformer is also called a lowering current-voltage characteristic and is one of the fundamental characteristics of the apparatus. It is on the basis of this dependence that the entire construction of the welding transformer is built and all the necessary calculations are performed, and various models of welding machines are created.

  Types of homemade transformers for welding

More than two hundred years have passed since the discovery of the electric arc phenomenon and the creation of the first welding machine. During all this time, the welding transformer and welding methods have been improved. Today you can see several different designs of welding machines, of varying complexity and principle of operation. Among them, the most popular for DIY manufacture are a welding transformer for resistance welding and for arc welding.

The most common among craftsmen were arc welding transformers. There are several reasons for this popularity. Firstly, the simple and reliable design of the device. Secondly, a wide range of applications. Thirdly, simplicity and mobility. But in addition to the advantages described above, manual arc welding has several disadvantages, among which the main ones are low efficiency and the dependence of the quality of the weld on the skill of the welder.

Manual arc welding is most often widely used for various repair and construction works, the manufacture of metal structures and structural parts, and pipe welding. With the help of arc welding, both cutting and welding of metal of various thicknesses is possible.

The design of such transformers is quite simple. The apparatus consists of the transformer itself, a current regulator, an electrode holder and a mass clamp. Separately, it is worth highlighting the central element - the transformer. Its design can be of several types, but the most popular are home-made welding transformers with a toroidal and U-shaped magnetic circuit. Around the magnetic circuit there are two windings of copper or aluminum wire - primary and secondary. Depending on the operating characteristics, the thickness of the wire on the windings, as well as the number of turns, changes.

This type of welding is also called contact welding, and contact welding transformers are somewhat different from arc welding machines. The key difference is the welding method. So, if during arc welding, melting occurs using an electric arc arising between the electrode and the surface being welded, then in spot welding, the spot is heated by electric welding using two sharpened copper electrodes and high pressure for connection. As a result, the metal of the workpieces at the point of impact melts and merges.

Spot welding is widely used in the automotive industry, in construction, when creating a frame of reinforcement for reinforced concrete structures, welding thin sheets of aluminum, stainless steel, copper and other metals that require special conditions for welding.

The design of spot welding transformers also has certain differences. Firstly, this concerns the lack of surfaced electrodes. Instead, pointed copper contacts are used, between which are welded elements. Secondly, the transformers in such devices are less powerful and are made with a U-shaped core. Thirdly, contact welding machines have a set of capacitors in their design, which is not necessary for arc welding.

But regardless of whether you plan to make an arc welding transformer or a contact transformer, you need to know their performance. And understand what each of them is responsible for and how one or another characteristic can be changed.

The operation of the welding transformer is determined by its performance. Knowing and understanding what this or that characteristic is responsible for, it is possible to calculate the welding transformer without any problems and assemble the machine with your own hands.

  Mains voltage and number of phases

This characteristic indicates the mains voltage from which the welding transformer will be powered. Most often, home-made welding transformers are designed for a voltage of 220 V, but sometimes it can be 380 V. When performing calculations and creating a circuit, this parameter is one of the main ones.

  Rated welding current of the transformer

This feature is fundamental to any welding transformer. The possibility of welding and cutting a metal billet depends on the value of the nominal welding current. In home-made and household welding transformers, the value of the nominal current does not exceed 200 A. But this is more than enough, especially since the higher this indicator, the higher the weight of the transformer itself. For example, in industrial welding transformers, the welding current can reach 1000 A, and the weight of such devices will be more than 300 kg.

  Welding current control limits

When welding metal of various thicknesses, a certain current strength is necessary, otherwise the metal will not melt. For this, a regulator is provided in the design of welding transformers. Most often, the limits of adjustment are set based on the need to use electrodes of a certain diameter. For home-made arc welding machines, the adjustment limits range from 50 A to 200 A. For resistance welding welding transformers, the regulation limits start from 800 A to 1000 A or more.

  Electrode diameter

To weld metal of various thicknesses using the same arc welding machine, it is necessary to regulate the nominal welding current, as well as use electrodes of different diameters. It must be clearly understood that for welding with thin electrodes, a low current strength is required, and for thicker ones, on the contrary, a large one. The same goes for the thickness of the metal. The table below summarizes the diameters of the electrodes used, depending on the thickness of the metal and the current strength of the transformer.

Important! For resistance welding transformers, the diameter of the electrodes is also important. But this uses two parameters - the diameter of the electrode itself and the diameter of its cone-shaped part.

  Rated operating voltage

As we already know, the welding transformer works to lower the input voltage to a lower value. The output voltage is called rated and does not exceed 80 volts. For arc welding transformers, the rated voltage range is between 30 - 70 Volts. Moreover, this characteristic is not adjustable and is set initially. Transformers for spot welding, unlike arc ones, have an even lower rated voltage of the order of 1.5 - 2 Volts. Such indicators are quite natural, given the relationship between voltage and current strength. The higher the current should be, the lower the voltage.

  Rated operating mode

This performance is one of the key. The nominal operating mode indicates how much time you can work continuously and how much you need to let it cool. For home-made welding transformers, the nominal mode is within 30%. That is, from 10 minutes 3 can be cooked continuously and 7 minutes left to rest.

  Power input and output

In fact, these two indicators have little effect. But knowing both of these indicators, you can calculate the efficiency of the welding transformer. The smaller the difference between power input and output, the better. It should be noted that when performing calculations, the value of power consumption must be known and taken into account.

  Open circuit voltage

This indicator is important for arc welding transformers. He is responsible for the appearance of the arc. The higher this indicator, the easier it is to cause a welding arc. But the open circuit voltage is limited by safety rules and should not exceed 80 volts.

  Welding transformer circuit

Creating a transformer for welding with your own hands, you can not do without its circuit diagram. In fact, there are no particular difficulties in this, especially since the device of the transformer itself is quite simple. The diagram below shows the simplest arc welding transformer.

Important! Those who are poorly versed or not at all versed in electrical circuits should first familiarize themselves with GOST 21.614 “Conventional graphic images of electrical equipment and wiring in the original”. And only then go on to create a circuit for a welding transformer.

With the development of electrical engineering and technology, the welding transformer circuit has been improved. Today, in home-made devices for welding, you can see diode bridges and various regulators of the welding current strength. The diagram below the arc welding transformer shows how the diode bridge is integrated into it.

Important! The most popular among home-made arc welding transformers is toroidal. Such a device has excellent performance characteristics, which are an order of magnitude higher than that of transformers with a U-shaped core. This applies primarily to high efficiency and nominal current strength, which favorably affects the overall weight of the device.

Unlike the ones described above, the spot welding transformer circuit is more complex and may include capacitors, thyristors and diodes. This filling allows you to more finely adjust the current strength, as well as the time of resistance welding. An example circuit of a resistance welding transformer can be seen below.

In addition to the above diagrams of welding machines, there are others. Finding them is not difficult. They are posted both on the Internet and in various magazines and books on electrical engineering. Having acquired the most liked circuit, you can proceed to the calculations and assembly of the welding transformer.

As already described, the transformer consists of a core and two windings. It is these structural elements that are responsible for the main operating characteristics of the transformer for welding. Knowing in advance what should be the nominal current strength, voltage on the primary and secondary windings, as well as other parameters, a calculation is performed for the windings, core and cross-section of the wire.

When performing calculations of a transformer for welding, the following data are taken as a basis:

• primary winding voltage U1. In fact, this is the voltage of the network from which the transformer will operate. It can be 220 V or 380 V;
• rated voltage of the secondary winding U2. The voltage of electricity, which should be after lowering the incoming and not exceeding 80 V. Required to excite the arc;
• nominal current strength of the secondary winding I. This parameter is selected from the calculation which electrodes will be welded and what maximum thickness the metal can be welded;
• core cross-sectional area Sс. The reliability of the device depends on the area of \u200b\u200bthe core. The optimal sectional area is from 45 to 55 cm2;
• window area So. The window area of \u200b\u200bthe core is selected from the calculation of good magnetic scattering, removal of excess heat and the convenience of winding the wire. The optimal parameters are from 80 to 110 cm2;
• current density in the winding (A / mm2). This is a rather important parameter responsible for the electrical losses in the transformer windings. For home-made welding transformers, this figure is 2.5 - 3 A.

As an example of calculations, we take the following parameters for a welding transformer: mains voltage U1 \u003d 220 V, secondary voltage U2 \u003d 60 V, rated current 180 A, core cross-sectional area Sс \u003d 45 cm2, window area So \u003d 100 cm2, current density in winding 3 A.

P \u003d 1.5 * Sс * So \u003d 1.5 * 45 * 100 \u003d 6750 W or 6.75 kW.

Important! In this formula, a coefficient of 1.5 is applicable for transformers with a core of type P, W. For toroidal transformers, this coefficient is 1.9, and for cores of a type PL, SH 1.7.

Important! As in the first formula, a coefficient of 50 is used for transformers with a core of type P, W. For toroidal transformers it will be 35, and for cores of type PL, SH 40.

Now we carry out the calculation of the maximum current strength on the primary winding according to the formula: Imax \u003d P / U \u003d 6750/220 \u003d 30.7 A. It remains on the basis of the data obtained to perform the calculation of the turns.

To calculate the turns, we use the formula Wх \u003d Uх * K. For the secondary winding, this will be W2 \u003d U2 * K \u003d 60 * 1.11 \u003d 67 turns. For the primary calculation, we will perform a little later, since a different formula is used there. Quite often, especially for toroidal transformers, the calculation of the current regulation steps is performed. This is done to output the wire at a certain turn. The calculation is performed according to the following formula: W1st \u003d (220 * W2) / Ust.

Ust - output voltage of the secondary winding.

W2 - turns of the secondary winding.

W1st - turns of the primary winding of a certain stage.

But first you need to calculate the voltage of each stage Ust. To do this, we use the formula U \u003d P / I. For example, we need to make four steps with adjustment to 90 A, 100 A, 130 A and 160 A for our transformer with a power of 6750 W. Substituting the data in the formula, we obtain U1st1 \u003d 75 V, U1st2 \u003d 67.5 V, U1st3 \u003d 52 V, U1st4 \u003d 42.2 V.

The obtained values \u200b\u200bare substituted in the calculation form of turns for the adjustment steps and we obtain W1st1 \u003d 197 turns, W1st2 \u003d 219 turns, W1st3 \u003d 284 turns, W1st4 \u003d 350 turns. Adding another 5% to the maximum value of the obtained turns for the 4th stage, we obtain the actual number of turns - 385 turns.

Finally, we calculate the cross section of the wire on the primary and secondary windings. To do this, divide the maximum current for each winding by the current density. As a result, we get Sper \u003d 11 mm2 and S second \u003d 60 mm2.

Important! The calculation of the resistance welding transformer is performed in a similar way. But there are a number of significant differences. The fact is that the nominal current strength of the secondary winding for such transformers is about 2000 - 5000 A for low-power and up to 150,000 A for powerful. In addition to such transformers, adjustment is made up to 8 steps using capacitors and a diode bridge.

  Welding Transformer Installation

Having all the calculations and the scheme in hand, you can proceed to the assembly of the transformer. All work will be not so much complicated as painstaking, as you will have to consider the number of turns and not get off the count. Despite the fact that the toroidal transformer for welding is the most popular among home-made devices, we consider installation using an example of a transformer with a U-shaped core. This type of transformer is somewhat easier to assemble, in contrast to the toroidal and the second most popular among homemade products.

We start work with creating frames for windings. For this we use textolite plates. This material is used to create stamped circuit boards. From the plates we cut out parts for two boxes. Each box will consist of two top covers with slots for four walls. The area of \u200b\u200bthe internal slots will correspond to the cross-sectional area of \u200b\u200bthe core with a slight increase for the walls of the box. An example of what the parts of the box should look like can be seen in the photo.

Having assembled the frames for the windings, we isolate them with heat-resistant insulation. Then we begin to wind the windings.

It is advisable to take wires for windings with heat-resistant glass insulation. This, of course, will be slightly more expensive compared to conventional wiring, but as a result there will be no headache regarding possible overheating and breakdown in the windings. After one layer of wiring is wound, we isolate it and only after that we begin to wind the next one. Do not forget to make bends on a certain number of skeins. At the end of the creation of the windings, we wind the layer of upper insulation. At the ends of the bends we fix the copper bolts.

Important! Before installing and securing the bolts at the ends of the wires, we extend the latter through additional holes cut into the upper plate of the PCB frame.

Now we begin to assemble and charge the magnetic circuit of the welding transformer. For it, iron is used, created specifically for this. The metal has certain indicators of magnetic induction, and an inappropriate grade can ruin everything. The metal plates for the core can be removed from old transformers or purchased separately. The plates themselves have a thickness of about 1 mm, and the assembly of the entire core will require only patient connection of all the plates into a single whole. Upon completion, all windings of the tester should be checked for errors.

Upon completion of the transformer assembly, we do diode bridgeand set the current regulator. For the diode bridge we use diodes of type B200 or KBPC5010. Each diode is designed for 50 A, so for a welding transformer with a nominal current of 180 A, 4 such diodes are required. All diodes are fixed to an aluminum radiator and connected in parallel with the inductor to the taps from the windings. It remains only assemble the case  and place the welding transformer there.

A good welding transformer with your own hands may not work the first time. There are many reasons for this, starting with errors in the calculations and ending with the lack of experience in the assembly and installation of electrical equipment. But everything comes with experience, and once or twice rewinding the transformer windings, you can get the desired result.

Do-it-yourself spot welding will interest those who need a welding machine, but who do not want to spend a lot of money on it.

In this case, contact spot welding is the best option, as you can literally assemble such an apparatus from improvised means.

In the article you will learn about how to assemble the device at home, what tools and tools will be required for this, as well as the pros and cons of this type of welding.

The diagram and video will help you complete the whole process yourself and get a quality product that will last for more than one year.

How does this type of welding work?

Spot welding is not at all amateurish type of work, which is used only in home use - it is widespread both on an industrial scale and in private production.

Spot welding is the contact work of connecting two elements in the desired position. This type of welding is similar to suture and analog, but still has its own differences and nuances.

The most significant plus of spot welding is that to make an apparatus for it (including from old microwave parts) is possible for anyone who is more or less familiar with electrical engineering.

In addition, such a device will not be inferior in any way to machines manufactured at the factory - the difference is that the home can only be used locally, but for personal needs more is not needed.

If resistance welding is a new process for you, it is best to first dig deeper into this process and understand how the machine works. In this case, it will be much easier to assemble it.

Welding of elements is as follows: first you need to fix the metal parts in the position that you need and place them between the electrodes of the device.

Then the parts are heated so that they become plastic and then are connected to each other.

Parts are heated by an impulse of electricity, the duration of which is no more than 1 second.

Its task is to melt parts of the parts and make in the place where it is directed, something like a liquid bath, whose diameter is 12 mm.

After completing the pulse, the parts should remain locked in the position you need for some time to cool down and better connect with each other.

The advantages of spot welding are obvious: this is a low price for the production of the apparatus itself (it is assembled practically from improvised means and with one's own hands), significant savings in electricity, high strength of joints and automation of the process (apparatuses capable of producing up to 600 dots / min are used in production).

There is only one minus for this type of welding - you cannot make a tight seam, although the resulting options will be quite strong and durable.

The welding pattern will help you better understand how this works.

As can be seen from the process, the main task of the apparatus is to heat the parts to the melting point.

The power of heating of different devices is different and you need to know what power and duration you need.

For example, it is better to use short heating for stainless steel, and vice versa for carbon steel.

In addition, the welding machine must provide significant pressure to the parts to be joined, the peak of which is achieved at the end of heating. Without this, a quality connection of the parts will not work.

Good spot welding electrodes imply high heat and electrical conductivity and do not have problems with machining, so not every material is suitable for manufacturing.

You can use: bronze mixed with cobalt or cadmium, electrolytic copper and alloys based on it with tungsten and chromium.

To assemble the device with your own hands, it is best to use EV alloys of copper.

When manufacturing it is important to remember that the diameter of the thinnest element of the apparatus should not exceed the size of the melting point (its diameter should be 2-3 times smaller).

Watch a video on how to use spot welding for home use.

Stages of creation

As already mentioned, spot welding with your own hands can be assembled literally from improvised means.

You need to start work with the inverter assembly. Using an inverter will make it possible for the entire device to function.

For its assembly, use parts made in the USSR:

• diodes;
• capacitors;
• chokes;
• transformers.

In the case of using these parts, complex additional configuration is not required.

Most often, the device is made from the details of an old microwave, which you may have in your house or with friends. Such spot welding from old microwave parts has a power of about 800 amperes.

It is enough to weld sufficiently thin sheets of metal. As a rule, for home use, more power is not needed.

Try to choose large rather than small microwaves, as large models have a more powerful transformer, which will be the basis of your welding machine.

The transformer is as follows: this is a core with two windings, the first of which is made of a thick wire with fewer turns.

The transformer is held by welds, so to get to its windings, you need to remove them (this can be done with a hacksaw or grinder).

The extracted transformer must contain an intact winding and a core divided into 2 parts, cleaned of paper and glue that fixed the windings.

The transformer needs to be attached to the base, it can be done with epoxy resin - to do this, squeeze the mechanism with a vice and leave it for a while so that the material can stick together.

The video below shows welding on a microwave transformer.

Thanks to the secondary winding, the power of the transformer will be approximately 2 watts.

If you want the power of the device to be higher, then you will need another microwave transformer, which will need to be connected to the first.

This is how the transformer circuit looks.

When both windings of the device are connected, it is necessary to check the current strength.

It should not be higher than 2000 Amps, otherwise significant power surges are possible not only in your apartment, but also in all neighbors.

You can connect the transformer using the secondary winding.

In this case, the amount of welding current will double - if it was 220, then it will be about 500.

Use 10 mm diameter wires for connection. The connection diagram will help you do everything right; if the technology is disrupted, then a short circuit is likely.

The voltage will go to the first winding, and at the output you need to turn on a voltmeter that can work with alternating voltage.

It is necessary to choose the direction of winding operation based on the following options: is there voltage in the device or is it absent.

In the primary circuit, one can observe the presence of windings having opposite conclusions.

The voltage of these windings is usually equal to ½ of the input voltage, its increase and transformation will occur in the subsequent windings, but the coefficients will be the same.

Below is a diagram of how to make a gun for spot welding.

After turning on the secondary windings, you need to add the difference of the obtained potentials - then the voltmeter will show twice the difference value for each of the windings.

If the device displays “0”, then the resulting values \u200b\u200bwill be equal, but with opposite signs.

Therefore, each connected pair of windings will have similar findings.

Check out the video on how to remove and assemble a spot welding transformer.

Transformer Pliers

For the device to work, you need not only a transformer, but also pincers. Pliers are the mechanical part of the machine.

Therefore, spot welding necessarily requires making pincers and electrodes, without which the operation of the apparatus is impossible.

To make pincers, you need to sharpen the rods of the electrodes that you will use, because otherwise they are deformed. Electrodes cannot work forever and lose their properties over time.

The wire that connects the electrodes and the current transducer does not need to be made long, otherwise it will be inconvenient to work. Also, there should not be many connections, because each of them will take power.

At the ends of the wire, it is best to make copper lugs that can connect the electrodes to the wire.

The tips are soldered so that the fit is as tight as possible. a poorly soldered connection will cause a significant loss of power of the device and even its breakdown.

Soldering the tip and the wire with your own hands will not be so simple because of the significant diameter, so when working, use the tips for soldering, they will facilitate the work.

It will also help when the time comes to replace the electrodes, as replacing old rods with new ones is not very convenient.

A connection made using a solder tip is easier to remove from oxide sites.

Electrodes can be bought in any market with electrical appliances. They look like small rods (a little more than 1 cm in diameter). The circuit of the electrode is below in the photo.

If the microwave transformer has poor welding, you can use the electrodes from the soldering irons - for this you need to remove the tips from them.

Connect the electrodes with a short cord without unnecessary connections.

To make the connection between the electrode and the transformer, drill a hole with a drill or drill, but you can also use a copper tip.

For tight fastening, tighten the bolt as much as possible, and to avoid the oxidation process, solder the wire with the ferrule.

The simplest to manufacture are welding machines for contact spot welding of alternating current with unregulated current strength. The welding process is controlled by changing the duration of the electric pulse - using a time relay or manually using a switch.

Before considering the designs of home-made resistance spot welding machines, we should recall the Lenz-Joule law: when an electric current passes through a conductor, the amount of heat released in the conductor is directly proportional to the square of the current, the resistance of the conductor and the time during which the electric current flowed through the conductor ( Q \u003d I 2 R t). This means that at a current of 1000A, poorly made connections and thin wires lose about 10,000 times more energy than at a current of 10A. Therefore, the quality of the electrical circuit cannot be neglected.

Transformer. The main component of any resistance spot welding equipment is a power transformer with a large transformation ratio (to ensure a large welding current). Such a transformer can be made from a transformer from a powerful microwave oven (transformer power should be about 1 kW or higher) supplying a magnetron.

These transformers are distinguished by their availability and high power. Such a transformer is enough for a precision welding machine capable of welding steel sheets 1 mm thick. If you need a more powerful spot welding machine, you can use two (or more) transformers (as described below).

In the microwave, a magnetron requires a very high voltage (about 4000V). Therefore, the transformer feeds the magnetron, not lowering, but increasing. Its primary winding has fewer turns than the secondary, and the thickness of the winding wire is greater.

The output of such transformers is up to 2000V (voltage doubled by a doubler is applied to the magnetron), so it is not worth checking the operability of the transformer including it in the network and measuring the output voltage.

From such a transformer, a magnetic circuit and a primary winding (one with fewer turns and a thicker wire) are needed. The secondary winding is cut with a hacksaw or chopped off with a chisel (if the magnetic circuit is firmly welded, but not glued), knocked out with a rod or drilled and picked out. The need for drilling arises when the winding is stuffed into the window very tightly and an attempt to knock it out can lead to the destruction of the magnetic circuit.

When removing the secondary winding, care must be taken not to damage the primary winding.

In addition to the two windings, shunts that limit the current can be mounted in the transformer, they must also be removed.

After removing unnecessary elements from the transformer, a new secondary winding is wound. To ensure a large current close to 1000A, a thick copper wire with a cross-sectional area of \u200b\u200bmore than 100 mm 2 (wire with a diameter of more than 1 cm) is required. This can be either a single stranded wire, or a bundle of several wires of small diameter. If the insulation of the wire is thick and makes it difficult to make a sufficient number of turns, then it can be removed, and the wire should be wrapped with fabric tape. The length of the wire should be the shortest possible so as not to create additional resistance.

2-3 turns are made. The output should be about 2V, this will be enough. If it is possible to shove more turns into the windows of the transformer, then the output voltage will be more, therefore, the current will be longer (in comparison with fewer turns of wire of the same diameter) and the power of the device.

If there are two identical transformers, then they can be combined into one, more powerful, current source. This may be required when there are two transformers with insufficient power, or when you want to make a do-it-yourself spot welding machine for working with thicker metal.

For example, in the case of insufficiently powerful transformers, each of the transformers with a power of 0.5 kW has an input voltage of 220V, the output voltage is 2V at nominal  current 250A (the value is taken as an example, let the short-term welding current be 500A). Connecting the same name  the conclusions of the primary and secondary windings, we get a device in which at the same voltage value (2V) nominal  the value of the output current will be 500A (the welding current will also almost double, there will be more loss due to resistances).

At the same time, the connections shown in the circuit in the secondary circuit must be on the electrodes, that is, in the case of two transformers with a power of 0.5 kW, there will be two identical wires with a diameter of 1 cm, the ends of which are connected to the electrodes.

If you make a mistake in connecting the terminals of the primary or secondary windings, then there will be a short circuit.

If there are two sufficiently powerful transformers and you need to increase the voltage, and the dimensions of the magnetic circuit window do not allow you to make the required number of turns with a thick wire on one transformer, then the secondary windings of two transformers are connected in series (one wire is drawn through two transformers), with the same number of turns on each transformer . The direction of the turns should be consistent so that the antiphase does not turn out and, as a result, the output voltage is close to zero (you can first experiment with thin wires).

Usually in transformers, the same winding leads are always indicated. If for some reason they are unknown, then they can be determined by setting a simple experiment, the scheme of which is shown below.

Here, the input voltage is applied to the primary windings of two identical transformers connected in series, and an alternating voltage voltmeter is connected at the output formed by the serial connection of the secondary windings. Depending on the direction of turning on the windings, there can be two cases: a voltmeter shows some voltage or the output voltage is zero. The first case indicates that in the primary and secondary circuits the opposite conclusions of the corresponding windings are combined. In fact, the voltage on each of the primary windings is equal to half the input and is transformed in the secondary windings with the same transformation ratios. With the indicated inclusion of the secondary windings, the voltages on them are summed up and the voltmeter gives twice the voltage value of each of the windings. The zero reading of the voltmeter indicates that the voltage equal in value to the secondary windings of the transformers connected in series have opposite signs and, therefore, any of the pairs of windings is connected by the terminals of the same name. In this case, changing, for example, the connection sequence of the terminals of the primary windings as shown in Figure (b), we obtain at the output a double value of the output voltage of each of the secondary windings and it can be assumed that the transformer windings are connected opposite  conclusions. Obviously, the same result can be obtained by changing the sequence of connection of the terminals of the secondary windings.

To make a more powerful spot welding machine with your own hands, you can connect more transformers in the same way, if only this allows you to make a network. Too powerful a transformer will cause a large voltage drop in the network, lead to fuses tripping, blinking of bulbs, neighbors' complaints, etc. Therefore, the power of home-made spot welding machines is usually limited to values \u200b\u200bthat provide a welding current of 1000-2000A. The lack of current is compensated by an increase in the welding cycle time.

Electrodes. Copper rods (rods) are used as electrodes. The thicker the electrode, the better, it is desirable that the diameter of the electrode is not less than the diameter of the wire. For small power devices, tips from powerful soldering irons are suitable.

Electrodes must be periodically grinded, as they lose shape. Over time, they grind completely and require replacement.

As already mentioned, the length of the wire going from the transformer to the electrodes should be minimal. There should also be a minimum of connections, as power loss occurs on each connection. Ideally, copper ends are put on both ends of the wire, through which the wire connects to the electrodes.

The lugs must be soldered to the wire (the cores of the wire must also be soldered). The fact is that over time (possibly at the first start-up), copper oxidation occurs at the point of contact, leading to an increase in resistance and a large loss of power, due to which the apparatus can stop welding. Plus, when crimping the tips, the contact area is less than when soldering, which also increases the contact resistance.

Due to the large diameter of the wire and the tip for it, it is not easy to solder them, however, tinned soldered tips for sale can facilitate this task.

Unsoldered connections of tips with electrodes also create additional resistance and are oxidized, but since the electrodes should be removable, it is inconvenient each time when replacing, to unsolder the old ones and solder the new ones. Moreover, this connection is much easier to clean from oxides than the end of a stranded wire crimped by a ferrule.

Governing bodies. The only controls can be a lever and a switch.

The compression force between the electrodes should be sufficient to ensure contact of the parts to be welded with honey electrodes, and the thicker the sheets to be welded, the greater should be the compression force. On industrial devices, this force is measured in tens and hundreds of kilograms, so the lever should be made more authentic and stronger, and the base of the device is more massive and can be clamped to the table.

A large clamping force for home-made spot welding machines can be created not only by a lever, but also by a lever-screw clamp (screw tie between the lever and the base). Other methods are possible, requiring various equipment.

The circuit breaker must be installed in the primary winding circuit, because the current in the secondary circuit is very high and the circuit breaker will create additional resistance, in addition, the contacts in a conventional circuit breaker can be tightly welded.

In the case of a lever clamping mechanism, the switch should be mounted on the lever, then with one hand you can press on the lever and turn on the current. The second hand will remain free to hold the parts to be welded.

Exploitation. Turning the welding current on and off is only necessary with compressed electrodes, otherwise intense sparking occurs, leading to the burning of the electrodes.

It is advisable to use forced cooling of the device using a fan. In the absence of the latter, it is necessary to constantly monitor the temperature of the transformer, conductors, electrodes and take breaks to prevent them from overheating.

The quality of welding depends on the experience gained, which boils down to maintaining the required duration of the current pulse based on visual observation (by color) of the weld point. More details about spot welding can be found in the article Contact spot welding.

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