Homemade contact devices. How to make a spot welding machine - how to assemble the machine at home with your own hands. Spot welding diagram

The resistance welding machine is not only easy to operate, but also easy to manufacture. The main thing is that it is not necessary to have the skills of this work. Even a beginner can figure out how to make homemade contact welding with his own hands and using available devices. What is a contact connection?

Types of resistance welding:

• point;
• embossed;
• butt and suture.

Design

A resistance spot welding machine made at home can be designed to solve simple problems that arise in everyday life. With its help, it is easy to apply a seam necessary for repairs or manufacturing of products. Resistance spot welding is obtained by heating individual elements with electric current and ensures a reliable connection, and the product being repaired will last for some time.

The device functions directly depending 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 work takes a few seconds.
3. Current strength from 1000 Amperes.
4. Small melting area.
5. The pressure applied to the area of ​​the repaired sample must be strong.

Automatic contact welding, done in a domestic environment, takes into account quality requirements if all parameters are met. To simplify the task, it is recommended to choose alternating current. In this case, the duration of exposure will allow for high-quality seams, while the time period will be increased. Such devices have a relay that provides time control.

It is not difficult to make a resistance welding machine with your own hands. It is quite simple to make. For these purposes, you can use current converters from an old TV as an autotransformer. Resistance welding from a microwave, as well as welding from an inverter or from a LATR will also work well.

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

A control scheme for a technical device is being developed, or you can use an existing one posted on Internet pages, again based on the specified parameters. The resistance welding machine is manufactured in accordance with the types of intended work. In many cases, resistance welding pliers are used.

The connection must be made correctly to ensure direct contact, including the passage of current of one parameter. Particular attention is paid to the transformer for resistance welding and the electrodes for resistance welding mounted on the pliers.

On units with insufficient attention to this criterion, sparking occurs and the final result is not achieved. A good solution would also be to do seam contact welding with your own hands from an inverter or to make a unit with your own hands from a microwave oven, as well as a microwave oven.

A resistance welder can weld all types of materials in accordance with the types of certification. Job openings always require initial training. Arc welding makes connections for more massive structures.

Self-production

Contact butt welding machines must be safe during operation, and you also need to know for what purpose the device will be used. Homemade contact welding is made at home. To do this, it is taken into account that the thickness of the metal should be no more than 1 mm, and the cross-section of the wire electrodes should not be more than 4 mm.

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

The electrical circuits in the drawing combine the following designs:

• switch operating in automatic mode;
• circuits for operating control;
• power unit;
• transformer for resistance welding;
• single-phase thyristor for connecting power to the network.

The winding circuit includes a primary one, which has six outputs for turning on and providing current regulation in the secondary. In this case, the first one connects to the network, and 5 regulate the process parameters.

The starter circuit in the MTT4 drawing includes:

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

The control circuit consists of:

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

Accessories for resistance welding:

1. Current-impervious housing.
2. A transformer on which a wire is wound.
3. Ticks.
4. Electrodes.
5. Electrical circuits.
6. A number of safety devices: gas pressure gauges at the pressure inlet.

Automation of the process is carried out using all components. A resistance welder must have certain skills when making seam or spot joints. Job openings in this specialty can often be found on the Internet.

Blueprints

Transformer manufacturing

Contact welding, the main structural element of which is a transformer, is done by hand. You can remove transformer equipment from any device; the main thing is to 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 core made of thin electrically conductive cardboard. This wire is wrapped in varnished cloth in more than 3 layers.

To make the primary winding, you should use wires insulated with fabric for better impregnation, with a diameter of 1.5 mm. For the secondary, it is better to use a stranded wire 20 mm in diameter in silicon insulation. Calculate the number of turns based on the power of the device. After winding the perchvica, a cotton ribbon is wound, then the secondary is placed on it. Everything is impregnated with varnish.

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

Making pliers

The welding machine for resistance welding is equipped with pliers. Manual pliers for contact joining can be:

• remote;
• stationary.

The second option provides good insulation and perfect contact with the electrodes. To do this, you need to make the remote lever long. It is easier to make handles of the appropriate length on an external structure. The insulation of the moving joint must be reliable; as a rule, washers and bushings made of textolite are used for this.

Resistance welding pliers are manufactured with a specified parameter for the electrode extension in the form of points, which is also important, since the distance from the edge to the place where the parts are joined depends on it. Electrodes are made of copper or beryllium bronze. Welding pliers can also be made from the working part of soldering irons. This is convenient when connecting polyethylene pipes.

A welder on resistance welding machines must be certified, but only if he works in production. Doing spot welding yourself is not a difficult task, just like arc welding. Anyone can do it at home.

Execution of work

Arc welding is not suitable for welding individual points.

Before performing work, it is necessary to sharpen the electrodes for resistance welding, 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 pressing force, a frictional force is created between the electrode and the surface.
3. The maximum gap is set before applying voltage. As current flows, contact resistance is created.
4. Voltage is applied and the electrode moves, gripping the joints, forming a seam.

The connection of aluminum structures is carried out using contact butt welding. Contact welding of aluminum can be seam and spot welding. A 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 according to state standards. The standard is GOST 14098, which quality control workers are guided by and based on laboratory testing.

About the equipment

General mechanical engineering time standards for resistance welding are necessary to complete production tasks within a given period of time. For production needs, equipment is purchased, for example, Tecna resistance welding, which forms joints in the form of points.

PF Contact Welding LLC produces, repairs and retrofits inverter units. The plan of enterprises aimed at producing products in mechanical engineering must be carried out with the availability of modern devices.

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

Do-it-yourself resistance spot welding is needed to repair products made of thin metal, polyethylene, including polyethylene pipes, carried out end-to-end.

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

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

The machine makes single-point connections, and it is also possible to connect polyethylene pipes. MT resistance welding is sufficient for welding reinforcement.

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

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

The Aks 2M machine is used for welding copper and non-ferrous alloys; spot welding of batteries is performed. Do-it-yourself welding for batteries is simple in 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 soldering products. It comes complete with a soldering iron, and nickel is used during operation. Seam work is performed for polyethylene pipes end-to-end on pipelines, and plastic products can also be joined.

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

!

In this homemade product, AKA KASYAN shows the details of manufacturing a resistance welding machine.

Inverter type device. But the device itself is very complicated (in terms of operating mode).

The author had a need to weld nickel plates to lithium batteries.

It was this problem that was the starter of this project.

Many DIYers are familiar with resistance welding devices, which are a bulky transformer in the secondary winding of which several turns of a copper busbar or wire are wound.

They are usually made on the basis of a transformer from a microwave oven.

To obtain high welding currents of several hundred and sometimes thousands of amperes.

An example of a Chinese welding machine. Maximum current 500A. Buy it - a couple hundred bucks.

And here is the author’s welder, with its light weight of 200g, it is capable of briefly creating currents of 200 - 220 amperes.

The inverter mode of operation in this class of devices is a little unusual. This technology is rarely used for resistance welding. In his version, the author uses a pulse circuit that is easy to implement.

That's how it burns!

A bonus is the low-voltage power supply of the device. You can connect this device to DC sources (for example, a regular computer power supply).

When using a 12V battery, you will generally get autonomous and portable welding. Supply voltage range - up to 24 volts.

The appearance of the device at the moment is not very good. He has not yet acquired a body. (I quote the author).
The author assembled it for testing, so we won’t pay attention to its appearance.

Judging by the photographs, it burns right through the blade of the knife. This means that the contact of such welding is beyond doubt.

The push-pull circuit is very popular. An autogenerator, about which the author has many videos, there is no point in explaining the principle of its operation.

This device diagram was created using the service.

Materials and tools:

Two powerful field keys

Pulse transformer from a computer power supply.

Resonant capacitor 1-2uF X 300+ Volts.

The device is turned on using a weak button.

Soldering iron, rosin, solder, textolite.
Copper wires.
Throttle.

The operating frequency of the device depends on the inductance of the primary winding

and the capacitance of the resonant capacitor.

A satisfactory frequency range is from 20 to 50 kHz. Of course, if below 20K then we fall into the audible frequency range.

The greater the capacitance of the capacitor, the higher the current in the primary winding.

The author does not recommend installing capacitors with a capacity higher than two microfarads.
Then the frequency of the device will fall into the audio range.
This will result in a nasty whistling noise from the transformer.
IRFP150 transistors, analogues can also be used, with a current of 40A and a voltage of more than 50V.

The author recommends using keys in the TO247 housing. TO220 is also possible.
We attach a small radiator to the transistors. In the form of a plate.

We must isolate the keys themselves from the radiator.
The throttle is a must. It is wound into two one and a half millimeter wires.

The number of turns ranges from 10 to 30 pieces.

The power pulse transformer was confiscated from a classic ATX 450W computer power supply.

We remove the factory windings. To do this, I recommend heating it with a hair dryer.
So, the rewound primary consists of two loops of four turns each.

It is wound with a bundle of 3 wires with a diameter of 1 mm.

The total squaring of the primary should be 2-4 squares. In principle, you can wind it from stranded wire.

The winding is insulated on top with heat-resistant tape. I would make it with lavsan.

The secondary loop is made from a copper busbar 1.5mm X 22mm

The copper tape is fixed with epoxy.

And solder terminals to the ends of the winding,

In fact, single-core 2 mm copper electrodes are inserted into the terminals

The edges of the electrodes must be sharpened.

In domestic applications, spot welding is used less frequently than arc welding. There are cases when it is difficult to do without it, but if we take into account the price of such devices, the feasibility of purchasing it is called into question. In this case, you can find another way out and look at an example of how to make spot welding with your own hands. For a radio amateur at home, constructing such a device is not difficult. But first you need to understand the features of its work.

How resistance welding works

This is a thermomechanical type of welding. Before starting work, the welded parts are arranged in the desired position. Next, each part of them is fixed between hardware electrodes, under their action the parts are compressed.

The current passing through the electrodes heats the parts, and an alloy is formed at this point. It is the connecting element of two parts. Devices of this type in production have high productivity. They are capable of making 600 weld points in a minute.

But in order for the surfaces to become hot and begin to melt, an electric current of enormous strength is supplied to them. Such an impulse leads to almost instantaneous melting of metals. Its duration depends on the type of metals being fused. Typically the time range is 0.01-0.1 seconds.

In this case, the molten metal surfaces form a welding drop between themselves, which must harden. To do this, the welded parts are kept compressed for some time. The molten drop at this moment forms a kind of crystal lattice.

Pressure plays an important role in this process. It prevents the molten drop from spreading over the area of ​​the parts, thus being held together at one point. The compression force is gradually reduced, then the weld is better set. This work requires clean surfaces of the parts.

Therefore, before work, the intended location of the weld is treated with a special solution. This removes corrosion elements and other oxide films. The result is a high quality seam.

Homemade device designs

Let's look at the structure of a spot welding machine using an example. Let's prepare radioelements and other details:

• Electrical converter;
• Copper cable with a cross-sectional diameter of at least 10 mm;
• Copper type electrodes;
• Breaker;
• Several tips;
• Bolts;
• Frame.

Assembling the device

These are the main design details. Now let's look at a diagram for manufacturing a spot welding machine. There are quite a few of them on the Internet. And each has its own set of radio components. But the main similarity of all the schemes is their simplicity and low power.

Therefore, homemade devices are suitable only for small household work. They will be able to weld thin sheets of iron, or wire strands. For the printed circuit board you will need the following elements:

• Variable resistor – 100 Ohm;
• Capacitor – 1000 mKF, from 25V;
• Thyristor;
• A pair of diodes - D232A;
• Several diodes - D226B;
• Fuse – F (fuse type).

The next stage of assembling a do-it-yourself welding machine is to construct the TR1 transformer. It is based on Sh40 iron, the required plate thickness is 70mm. The design has two windings. A PEV2 conductor with a cross-section of 0.8 mm is used for the primary winding. Next, 300 turns are wound.

The secondary winding is made with a multi-core copper cable with a cross-section of 4 mm. The number of turns does not exceed 10.

For the second transformer TR2, no manual work is required. It can be replaced with any weak converter with a power of 5-10V. Its secondary winding should have no more than 5-6V output. The third winding should output up to 15V.

By completing this assembly, you can get a device with a power of up to 500A. The pulse duration will not exceed - 0.1 sec, but only if the values ​​of the resistance and capacitor coincide with those in the diagram. The power of homemade spot welding will allow you to weld metal sheets with a thickness of no more than 0.2 mm, as well as steel wire with a diameter of 0.3 mm.

Types of homemade spot welding machines differ mainly in power. Some models are capable of delivering current up to 2000A, which allows welding steel sheets up to 1.1mm thick and steel wires up to 3mm in diameter.

DIY spot welding photo

Quite often there is a need to carry out welding work at home. As a rule, these are small volumes performed occasionally. Since factory-made welding machines are very expensive, many craftsmen prefer to make them in various ways from scrap materials. Do-it-yourself contact welding from an inverter is considered a good option for a factory analogue, providing high quality work at a relatively low cost.

The device and principle of operation of resistance welding

The principle of operation of any spot welding machine is to heat metal parts with electric current in certain places, then melt them, mix them together and solidify. As a result, a weld seam is formed in the places where both metals solidify. During operation, both parts are reliably compressed and fixed by electrodes to which electric current is supplied.

Performing resistance welding at home will require powerful power sources, which can lead to overheating and failure of household electrical wiring. In this regard, it is recommended to check the condition of the wiring in advance and replace it if necessary.

When performing spot welding, two workpieces are connected to each other along adjacent edges. This method is very effective for working with small parts, thin metal sheets and rods with a diameter of up to 5 mm.

Surfaces are connected in one of three ways:

• When using the reflow method, all parts to be welded are joined and heated by electric current until they melt. This technology is widely used in working with non-ferrous metals, low-carbon steels, brass and copper workpieces. In other areas, this method is used extremely rarely due to high temperature requirements and the absence of impurities at the joints. Homemade resistance welding from a welding machine works in exactly the same way.
• Continuous welding of workpieces using the reflow method is performed using welding tongs. The connection of parts occurs at the moment the current is turned on. After the edges of the mounted parts have melted, they are upset and the current supply is stopped. Thin-walled pipelines and workpieces with different structures are welded using this method. The main disadvantage of this method is the likelihood of metal leaking out of the weld and the appearance of carbon monoxide.
• The third method is intermittent melting, which ensures alternately tight or loose contact between the workpieces. The welding line is closed in the joint area with clamping pliers until their temperature rises to 950 degrees. This method is used if the power of the welding device is initially insufficient to perform continuous reflow.

Preparing parts and assembling spot welding

The standard design of a resistance welding machine consists of a power section, a circuit breaker and a protective device. In turn, the power part includes a welding transformer and a thyristor starter, with the help of which the primary winding is connected. The entire inverter is not needed for a homemade welding machine; you only need to take the main parts from it. This is a transformer with a power supply, a control system and a switch.

When making spot welding, first of all, you need to remove the secondary winding from the transformer, since it is not used at all during operation. The main thing when removing the winding is to keep the primary winding intact. Instead of the removed secondary winding, another one is placed, made of thick copper wire, with a cross-section of approximately 2-3 cm. Then it is wrapped in insulating paper and varnished for additional insulation and fixation.

The direction of each winding is then checked using a conventional voltmeter. There should be no short circuits in the newly created circuit. After this, the current strength is determined. This procedure is mandatory for all such devices with two or more windings. The current value should not be more than 2 kiloamperes. If the set level is exceeded, it must be reduced.

When preparing the transformer coil and winding the secondary winding, it is recommended to follow the mandatory rules. To calculate the number of turns, you can use the formula N = 50/S, in which N is the number of turns, and S is the core area (cm2). An online inductor calculator will help speed up calculations. Since the design uses parts from the inverter, the parameters of the primary coil are first determined, the necessary calculations are made, and only then the secondary winding can be manufactured.

Pay attention to the grounding of both windings. This is due to the high power of the current received, which can be fatal if it comes into contact with live parts. Along with careful insulation, tight laying of the turns is of great importance. Otherwise, interturn short circuits may occur and the wires will burn out as a result of overheating. It is also necessary to take care of cooling the transformer. It may be necessary to install an additional cooling system, which includes radiators blown by fans.

Additional elements of the welding machine

The next step after manufacturing the transformer will be the manufacture of contact clamps. The quality of their manufacture largely determines how resistance welding from an inverter will work. The design of the pliers is selected depending on the specifics of future welding work. The gripping device is manufactured in accordance with the drive system and the dimensions of the parts to be connected.

The most important part of the pliers is the contact tips. You can use copper tips from a soldering iron or purchase ready-made products. It should also be taken into account that they should not melt during operation, so a refractory metal should be used for their manufacture. Typically rods with a diameter of about 15 mm are used. The diameter of the connected cable is always less than the diameter of the lugs.

The wires are connected to the electrodes using ordinary copper lugs. Direct connection is carried out by bolts or soldering, which significantly reduces the likelihood of oxidation at the contact points. Soldering is most often used in low-power devices, eliminating incorrect connections that cause current disturbances at the output of the device.

The main advantage of bolted connections is the ability to quickly replace failed parts without additional soldering work. All bolts and nuts must be copper. If it is intended to apply connecting seams over a long distance, in this case the tips are equipped with special rollers.

After manufacturing the pliers, the time comes to solve an equally difficult task - ensuring the necessary pressure of the electrodes at the point of welding the parts. The main difficulty lies in the fact that it is impossible to create high and uniform pressure manually. If other options are not considered, then it is best to initially refuse to make spot welding from an inverter, because the efficiency of such a device will be extremely low.

In industry, this problem is successfully solved by using amplifiers based on pneumatic or hydraulic systems. It is almost impossible to make such devices at home. For homemade spot welding, the best option is a compressed air system driven by a conventional pneumatic compressor. The most optimal maximum indicator required for normal operation will be a force at the ends of the electrodes of 100 kg or more. The pressure changes using a separate regulator, which can also be built into the overall control system.

At the final stage of assembling resistance welding from the inverter, all that remains is to mount the entire system. For installation, it is recommended to use ready-made elements, which greatly simplifies assembly and improves performance characteristics. All the missing parts are in the inverter, from which the transformer was already taken.

The capacity of the capacitors installed in the inverter may not be sufficient for normal operation. Therefore, if necessary, they are replaced with other parts that are most suitable in their parameters. Next, stepwise current adjustment is performed, the accuracy of which is affected by the technical characteristics of the secondary winding. By making such adjustments, it is possible to create equipment capable of operating in different modes.

Welding capabilities in body repair

The need for welding work during body repair is beyond doubt. And so that this process does not take time, and also allows you to fix many problems yourself, it is important to select the appropriate equipment.

Body repair is unthinkable without resistance welding

Welding process during body repair

The vast majority of work when repairing a car body can be performed by resistance welding. This type, being quite specific, is used mainly due to its simplicity, lack of consumables and high level of performance.

More about resistance welding

According to the technical definition, this type of welding is a process during which a permanent connection is formed. Such a connection is a consequence of heating the metal through a passing electric current, as well as plastic deformation of the connection zone itself (the latter occurs as a result of compression).

There are several ways to do resistance welding yourself, including spot welding. This scheme involves connecting parts in separate sections, which are called points.

To obtain a welded point, the parts to be welded (preliminarily thoroughly cleaned) are overlapped, compressed with a certain force, after which a current pulse is passed through the place of their contact. At the contact boundary of the parts being welded, the machine forms a melt point called the core of the point. When the flow of current is completed, this core will crystallize and form a very strong connection.

Drilling before joining parts

There are a number of factors that can influence quality, i.e. point strength and size:

• We are talking about such a parameter as compression force;
• The value of the welding current that the machine produces also plays a certain role;
• The duration of the current pulse is also important;
• Finally, the diameter of the contact surface of the electrodes matters.

Appliances used

Do-it-yourself contact welding during body work is carried out using appropriate welding machines. The scheme of their use assumes the following: the machine (device in other words) heats up, and as a result of heat generation, direct welding occurs in those places where the parts are connected.

It turns out that any device is based on the principle of heating the welding site with current while simultaneously applying pressure.

A stationary machine can be used, as well as a suspended or mobile machine (for manual work). Each such device, in turn, is divided into certain varieties, taking into account the welding method.

The design of each device assumes the presence of a number of parts: electrical, mechanical, hydraulic system, pneumatic system (or water cooling system).

A resistance welding machine can easily be constructed with your own hands, which is what we propose to talk about in more detail.

Factory seam sample

Self-assembly of the device

The resistance welding apparatus consists of two units:

• Remote welding gun;
• Power unit.

The manual assembly procedure is well demonstrated in numerous videos. The process of making a gun begins with the creation of an adapter and electrodes. To do this, take a textolite sheet and cut out overlays from it (the dimensions are determined according to your own hand). Then you need to drill channels in the lamp holder for the wires. These wires will lead to the backlight.

The microswitch is attached to the finished overlays using screws and two holders. Spacer strips can be bent from a strip of plexiglass, taking into account their location on the overlays. We should not forget about the placement of the welding cable passing through the handle.

The end of such a cable is soldered, then inserted into the adapter hole and secured with a screw. It is recommended to dull the sharp edges of the linings. It is important to wrap the handle with insulating tape. The finished version, again, is perfectly seen in the video.

As for the power supply, it is assembled from a relay on a welding transformer and a thyristor. The electrode is connected to one terminal of the low-voltage winding using a welding cable. During manual welding, the second terminal must be reliably connected to the largest part to be welded.

The primary winding of the transformer is connected to the network via a diode bridge and a thyristor included in its diagonal. In this case, an auxiliary transformer is also needed to control the thyristors and the backlight.

That is, homemade resistance welding is quite possible. After assembly is completed, the welding machine must be tested. The finished device (the video shows what it looks like) will allow you to perform many jobs.

Thus, when assembling the corresponding resistance welding machine with your own hands, you need to stock up on the above elements for the gun, as well as for the transformer. Since it is the transformer that influences the final size of the device, it is recommended to start the assembly process with it.

How to do spot welding with your own hands and what you need to know

Preface

Do-it-yourself spot welding can be done in just a few hours. This is not a high-tech mechanism that should only be assembled at the factory, and you will soon see this! Now we will assemble a device whose technical characteristics will not be inferior to those of the purchased product!

Assembling the transformer

The most important part, the heart of any electrical device of this type, is the transformer, with the help of which we will receive the necessary voltage. The transformation coefficient must be very high, so we immediately turn our attention to powerful and voluminous microwave ovens - this is where you can get the necessary element. The power should be about 1 kW - this is an ideal option, but if this is not available, 700-800 W will do. In a microwave oven, a step-up transformer produces up to 4 kW to power the magnetron. Exactly what we need. We consider step-by-step instructions for making the necessary transformer.

Step 1: Remove the transformer from the microwave.

You shouldn’t immediately disassemble it with a hammer - we will need it entirely. We unscrew the base, remove all the fasteners, and take it out.

Step 2 We knock down the secondary winding.

We only need the primary one (this is the one inside, the wire on it is much thicker and there is less of it). You can do this with a chisel, hammer, hacksaw, even drill out the corners with an electric drill - anything, as long as the result is what you need. Your task: do not damage the primary winding and magnetic circuit, and you can do with everything else as you wish, even for scrap metal.

Step 3 We wind the secondary winding.

We need to get a current of about 1000 A as a result, so we go to the market and buy a wire with a diameter of 1 cm. It is expensive, but we cannot do without it. If you want to save money, buy it in a bunch, and not one whole piece - this does not affect the progress of the matter.

Step 4 Make 2-3 turns.

We make 2-3 turns of the secondary winding, at the output we get about 2V. The more you put into the window, the greater the voltage will be, although after 3 turns there is no room left in the window. If you need a powerful device, then you can disassemble 1 more microwave or find an additional transformer and connect 2 together. It will be possible to work with metal up to 5 mm thick.

Step 5 Check the direction of the windings.

Using a voltmeter, we check the direction of the windings, as well as the presence of short circuits. If none can be traced, you can move on to further work.

Step 6Check the current strength.

When connecting 2 or more transformer windings, it is necessary to check the current strength at the output. If it is more than 2000 A, reduce it. This will lead to drops in network voltage and you simply won’t be able to fend off your neighbors who will run around complaining about you.

Making electrodes

Everything here is simpler than steamed turnips. We buy electrodes from scrap metal or the market; copper rods with a diameter of 1.5 cm or more are suitable for this. The main thing to remember is that the diameter of the electrode should not be less than the diameter of the wire and that’s it. If your welding is weak, then you can destroy 2 soldering irons and take the tips from them - ideal and durable electrodes that will last a long time!

The wire that connects to the electrode must be of a minimum length to reduce current loss. For the connection, a copper tip or hole is used, which can be made with an electric drill and an 8-mm drill bit. Tighten the bolted connection and the rod will not run away anywhere. You can solder the tip to the wire to avoid oxidation that will occur when you first start the device. Unsoldered contacts can create additional resistance, which is very noticeable at low power of the device.

The only advantage of bolted connections is that the electrodes can be removed quickly, otherwise they will have to be completely re-soldered. This is often done during intensive use, so it makes sense to fasten it this way. It’s easier to buy copper bolts and nuts - the result will be much better. Homemade resistance welding will be “fun”; you can remove the electrode in a minute, instead of soldering them for half a day.

Process control and "infrastructure"

This includes the lever and switches. You simply cannot do without good compression force, especially when welding thick sheets of metal. That is why you need to take care of high-quality leverage. On a production scale, the force can reach 50-100 and even 1000 kg, but 30 kg will be enough for us, so we make the lever moderately long so that doing resistance welding with your own hands is convenient.

It is best to pull the beginning of the lever arm out from the table so that the emphasis is on it and not on the machine (suitable for stationary welding devices). The length of the handle should be about 60 centimeters with a fastening ¾ from the bottom, so that the arm on the clamp is equal to at least 1:10. Then, when applying 2 kg on the handle, you will be pushing up to 20 kg on the metal leaning against the work surface.

As for the switch, everything is simple: we put it on the primary winding, since there will be a very large current on the secondary winding, the resistance of the switch will interfere with the operation of the device. You can place the lever on the handle - original and very practical. You will be able to turn on the device only after metal contact, which will reduce energy costs and protect against sparks.

Homemade spot welding is already ready and now it’s enough just to test it in operation to check the correctness of the assembly. It is suitable for welding metal up to 2-3 millimeters thick when using a 1 kW transformer and up to 5 mm when connecting two or more in series!

Due to the fact that welding contact for a time that is much less than fusion by fusion, it provides greater productivity and less flexibility of operation, since

Contact welding. Types of resistance welding.

Since the process is easy to automate and easier to integrate with flow conveyors, this method is better used for mass production and mass production.

This method has been used in the automotive and aerospace industries.

Since joints obtained by resistance welding have very high strength and quality, and do not depend on the quality of welding, this method is used in other industries.

With the thickness of the weld seam, connect from hundreds to tens of millimeters, as well as tens of mm.

Also welding of oil and gas pipelines.

For robots, systems with an increased supply voltage frequency are used, which makes it possible to reduce the size of the transformer.

Classification of welding methods

In accordance with GOST 158-78-77 “Resistance welded and welded joints” there are 3 main types:

— spot welding;
— seam welding;
— Direct welding.

However, the series of these methods reaches 300 names.

Spot welding(Kt) - a method in which parts are welded at separate points with two electrodes and a welding pressure is applied to them, transferring the welding current.

pulse welding time

Relieve the pressure, cool the part and get a casting of the core.

The design of a welded joint (a shaped core of a certain size) is determined by two important physical phenomena:

1. Welding metals with welding current
Q = J^2cRtu
second

Heat transfer from the welding zone λ-thermal conductivity

Sv In the range of electrodes, heat is released during the passage of current and heat, transferred to the mass of work and the action of the electrode.

because

E. Thomson decided to use a copper electrode and λcu >> If the shape of the cast core is lens-shaped, it is favorable for the welded joint.

If Jcb and Tcc are increased, a molten core begins to develop.

The use of cast electrodes and the increased heat transfer in them compared to the mass of work determine the development of the melting process in the casting core precisely in the mass of work, and not in the electrode.

In this regard, the probability of failure is reduced by melting at the core, i.e.

Burns are complex, which determines the effectiveness of spot welding.

Relief Welding - This may be associated with one of the types of site welding.

A spot weld joint is created by local heating of the work with electric current and plastic deformation in the joint area due to compressive force.

Q (R) - due to increased stability;
— Q (λ) — metals actively redirect heat.

The connection is created due to two effects:

QI^2R
—Qλ

Protective welding contact(Cylinder)

Rm - The seam seal overlaps the welded parts in the flow line of the cylinders (electrodes), pushing the parts from the side that feed the JSV flow and the moving parts at the VSV welding speed - even through those rollers.

It is used in cases where welded joints must be sealed with welding contacts.

Sealed Sewing - For welding containers, gas cylinders, tanks, cavities, etc.

J = I / S - current density
Jš - current

The process is carried out by removing heat and heat.

Seam welding is divided into three processes:

- continuously

With this method, where the thread is constantly continuous, a continuous weld is obtained without the distinctive casting of the core that overlaps.

The disadvantage is the increased heating of the electrode and the need for frequent flow.

— Individual impulses (interruption)

— Q = f (λ) (tcb + tn)

Changing the amplitude of the current JSV, the duration of its generation - Jc, the duration of the rupture - tn and the welding speed - USV can regulate the amount of overlap LN of cast cores, which is usually sufficient up to 25%, but should not be performed ln>50%.

Thanks to the better impact of the electrode, their resistance is significantly improved.

When welding heat-resistant steels with low thermal conductivity and high resistance to deformation at high t (thermal resistance), the welding forces increase, i.e.

welding stage.

Step welding— the welding current is interrupted, the electrodes stop when the welding current passes.

It provides more reliable contact in the current range when the electrodes stop and the welding pulse passes.

After turning off the current, welding forces in the contact area avoid hot cracks.

Contact - welding

There are several types of welding contacts (Ks).

Consider the method weld resistance, while the parts are first pressed against the electrodes using jaws (prismatic electrodes) to ensure electrical contact and not slip through the electrodes.

It is then compressed by the welding force P, the welding current is turned on, and the parts in the joint are heated by this current Ic.

Then place the rosette 1.5-2 times less than the heating, then turn on the current, and the parts are exposed to P precipitation.

At the moment when the smallest deformable resistor is used, the sediment force is applied and the current is switched off, and the metal layers, heated to high ductility, are compressed from the intersection to the periphery.

At the same time, residual oxide films and honeycomb (metal on the edge of the bonding zone) are removed from the joint.

Thus, small parts with a diameter of up to 20-40 mm are welded, and the connection is formed in the solid phase without melting the metal. The heated plastic metal is forced into the hail, and the solid heated particles of the working material come into contact.

The disadvantage is the need for careful preparation of the weld ends and the need to connect large capacities to the large plant capacity.

Another way - flash welding.

It is technologically different from resistance welding, so the voltage in the primary winding of the transformer (and in the secondary) is guaranteed until the ends of the break-up contact.

As the parts approach contact, individual microscopes enter the contact surface in much fewer numbers than if the parts had been pressed in advance.

The keels are destroyed and the contact surface increases. At the first contact, the welding current arises and occurs on several microspheres, so the current density in the contact of an individual microspace is so high that the metal heats up in milliseconds and then boils. In this case, explosive destruction of the liquid contact bridges occurs.

New microstate contacts are in contact with metal vapor, i.e.

The increased metal vapor pressure in the joint protects the welding area, which heats up to TPL when interacting with the atmosphere.

When melting, the ends work in such a state that a thin layer of liquid metal appears on the surface, which ensures uniform heating over the entire area of ​​the joint; the force of the sediment is applied to it. The liquid layer is compressed from the ends to the edge of the joint - in hail and under high pressure, the compressed parts of the part come into contact,

TV. I'm next to the liquid layer is not much lower than the tpl, and was very ductile, and then partially and the solid metal is compressed into the hail, and under pressure a strong welded joint is formed with the least amount of errors. degradation products and oxide films were extruded into hail.

Fused welding provides a better connection because the metal on the surface of the ends where contamination can occur is removed when the liquid bridges explode during the reflux process.

The liquid layer and part of the ductile metal are compressed into a hail, and completely clean (young) surfaces come into contact.

This does not require careful processing of the weld ends, as is the case with resistance welding.

In addition, if welding parts with different cross-sections form a special edge section, the initial contact surface is reduced, the fusion process is more efficient and the process continues, the parts are heated and have a normal shape.

Shield welding with intermediate payment or preheating

When front welding large parts: rails, pipes, main pipelines - to facilitate the initial phase of the reflow process, the process used includes the first stocks to slowly reduce the occurrence of contact and the formation of liquid and metal vapor.

The parts are then heated, and the heat generated in the fusion zone spreads to the work mass and is heated.

The contact between the switches is then recreated until the ends are heated, so that the further process is continuous, without interruption.

Turn to lightweight welding(WITH)

This may be due to the types of spot welding.

It is used for welding parts that occupy a large spatial position.

Usually the Scheme 1 process does not work because the contact with all parts of our work cannot be the same due to the difference in device quality, deformation conditions, contact location from the current guide device.

This fusion welding process occurs by forming a solid-phase joint by extruding a liquid phase to the periphery.

To ensure the same conditions for contacting and deforming a large number of parts are necessary to ensure reliable contact with each electrode and parts in the first welding force (or previous pressing force) that compresses all the rods.

This should provide slight deformation of the parts in contact.

The forces are then removed to the welding force value. Because the same conditions for contact with all parts are not guaranteed, but it is better to first provide a heat pump pulse in which the parts are heated in contact and by the welding force.

Then you can still JOP, then turn on the welding current.

Forging force is used to reduce the base and we obtain a multi-point connection with high quality.

At the starting point, the current flows along the points, the area is small and the current is high, they begin to melt and then become deformed during welding.

We kill cores and small tracks without any supports or fins.

When welding once, several welded joints are obtained. However, if the parts have a protective coating that must remain on the surface after welding, only weld welding should be used, since the large surface area between the electrode and the part has a low current density and the coating will remain.

Physicochemical conditions for the formation of compounds
Weld design in resistance welding.

Welding metals with welding current
Heating and melting of metals at the point of contact, releasing energy when passing through an electric current. Spot welding current
Replacement of current in contact welding at several points.

Contact zone welding and seam welding
Factors influencing the design of a quality weld.

Welding on the floor
Spot contacts in resistance welding. Seam welding
Merge in a seam of successive dots.

Relief welding
Welding with contact in prepared relief. Control circuits for switching welding devices
Electrical circuits for providing welding current and voltage on contact machines. Contactor machine contactors
On and off devices. Welding or secondary circuit of contact machines
Current-carrying elements for high currents and compressive forces.

Transformers for resistance welding machines
Characteristics of transformers for resistance welding. Pneumatic equipment for contact machines
Pressure relief devices.
Also on topic:

Special methods

Resistance welding modes are a set of parameters that are set by the welder before starting work. The parameters of these welding modes depend on the metal product that is planned to be welded, the experience of the welder, and other things. The selected welding modes directly affect the quality of the resulting joint: incorrectly selected parameters can lead to a poor-quality weld, which may subsequently crack.

The main parameters for resistance welding will be:

• Electric current strength.
• Increased compression for welded parts.
• Duration of current flow.

We will talk about different welding modes, and specifically the contact welding method, further.

Welding modes and their influence on the weldability of metals.

Welding modes are divided into two main types:

Both types differ in the duration of current exposure to the part being welded.

The hard mode of welding a metal product involves a short-term exposure to current on the parts, while soft welding modes, on the contrary, involve a long-term exposure.

The choice of one type or another depends, first of all, on the metal that needs to be welded: its thickness, thermal conductivity, etc. matter.

Thus, severe welding modes are usually used for metals that have greater thickness, but at the same time lower thermal conductivity. For example, the welding conditions for low-carbon steel will be much tougher than for aluminum alloys

The form of metal melting and the location of the melt zone largely depends on the processes of heat release and heat removal that occur in the electrode and the part being welded.

The duration of exposure to current affects heat generation and heat removal, and, accordingly, the welded joint itself.

When welding is carried out in a soft mode, the shape and location of the cast zone will depend directly on the electrode and the materials being welded. Thus, in the soft welding mode, the cast core is at the same distance from the surfaces of the part, this contributes to the fact that the irregularities formed during the welding process are shifted into a part that has a greater thickness.

Note that under soft welding conditions (in which the heating time of the metal product is much longer), the heat-affected zone will also be wider than during hard welding.

During rigid welding, this core will be located quite symmetrically in relation to both parts being welded.

During welding, it is necessary to take into account that the heat dissipation into the electrodes during hard welding is minimal, this is what makes it possible to obtain a greater height of the cast zone in this welding mode (in other words, hard welding modes of parts having the same thickness give a greater depth of penetration).

The quality of the resulting welded joints made under different welding modes is assessed according to the following parameters:

• The seam should not have significant softening in the metal joining area.
• The formation of rather fragile structures in the joint zone, which may subsequently collapse, is unacceptable.

  This especially applies to the transition zone of the seam.

• The joint area must be uniform and tight, the cast and transition zones must not have any visible disruption of their complexity.
• The connection must be strong enough.
• Welding work should not reduce the corrosion resistance of the metal product.
• Deformations of parts are allowed within normal limits.

Note that when performing resistance welding, compliance with these conditions depends on the capabilities of your welding equipment, the product itself that will be welded, and the experience of the welder.

Keep in mind that metals that have good weldability allow welders to use a variety of parameters to set the weld, which in turn leads to better joints.

Contact welding methods and joint formation.

All methods and modes of resistance welding are based on heating parts using heat, which is released when an electric current flows through them.

The amount of heat released mainly depends on the strength of the current, the time it flows through the metal, and also on the resistance of the metal itself in the welding zone.

If two or more parts compressed together are welded, then electric current is supplied to them through conventional electrodes.

Spot welding device

In this case, the voltage can be small, from 3 V, but the current can reach tens of thousands of amperes. The heat that is necessary for welding is released mainly in the parts, in the area of ​​​​contact of the parts with each other and their contact with the electrodes. In this case, the electrical resistance of metals is of significant importance in resistance welding modes.

Thus, we conclude that the choice of welding mode depends directly on the properties of the selected materials.

Resistance welding modes depend on the thermal conductivity and thickness of the parts.

Note that in harsh modes the amount of heat released is many times greater, so they are used only for metals with low thermal conductivity, for example steel.

According to physical characteristics, contact welding belongs to the thermomechanical class. This means that it is carried out using thermal energy and pressure. Heat is released from special sources when an electric current passes at the point of contact of the parts being connected. The metal is heated to a plastic state and at the same time it is joined under significant compression.

This type of welding is used to join ferrous, non-ferrous and dissimilar metals.

3. Resistance welding methods

Depending on the contact welding method, metal up to 20 mm thick can be welded. Resistance welding is used in many areas of industry - aircraft, aircraft, shipbuilding, mechanical engineering, energy industry, agriculture, construction.

Resistance welding methods

The main welding methods are:

• point;
• suture;
• butt.

Spot welding is used to overlap parts made of profile, sheet and strip metal.

Parts made of both homogeneous and dissimilar metals, as well as having different thicknesses, are connected. Depending on the equipment used, welding can be carried out at one point or at several points simultaneously.

The spot welding process consists of the following steps:

• cleaning parts;
• alignment and placement of parts between the electrodes of the welding machine;
• heating to a state of plasticity;
• compressing the electrodes with the necessary force.

Cleaning of parts is carried out immediately before welding by mechanical or chemical means.

Rust, oxides and other contaminants are removed.
To combine parts, special devices called jigs are used.

Heating of parts at the welding site is carried out by applying a short-term pulse (0.1 ÷ 3 seconds), which ensures melting of the metal.

The current power can reach 100,000A, and the voltage can reach 10 V. A liquid core is formed. After the pulse is removed, the parts are compressed to form a point (crystallization and cooling occurs). The core diameter, depending on the equipment used and welding technology, ranges from 4 to 12 mm.

Spot welding can occur in 2 modes:

They differ in the density of welding and the passage time of the electric current.

In the soft mode, heating is carried out gradually (0.5 ÷ 3 sec.) with a moderate current intensity (does not exceed 100 A/mm2), and in the hard mode, the welding time usually occurs in the range of 0.01 - 1.5 sec., and the current density is 120 ÷ 300 A/sec. The compressive force of the electrodes ranges from 3 to 8 kN/mm2.

In seam welding, or also called roller welding, the parts are also connected by points that may or may not overlap each other.

The welding process takes place on special machines with disc rollers-electrodes. During the welding process, they rotate, while tightly compressing the parts being welded. The equipment may have one or two electrode rollers. This type of welding is used to make containers for various purposes (barrels, pipes, gas tanks, etc.), where the products are subject to tightness requirements.

Seam welding can be performed in 3 ways:

• stepping;
• intermittent;
• continuous.

Step welding is used to weld clad metals, aluminum and its alloys up to 3 mm thick.

The parts are welded at a certain pitch, and a large welding current is switched on when the rollers stop.

Intermittent seam welding is performed to join metals up to 3 mm thick under the following conditions:

• continuous supply of parts to the welding zone;
• short-term interruption of the current as it passes through the workpieces.

During the welding process, points overlap as a result of the correct selection of the rotation speed of the electrode rollers and the pulse frequency of the welding current.

Thanks to this welding method, the parts and rollers do not overheat, which allows you to obtain a high-quality sealed seam.

Continuous seam welding differs from intermittent welding only in that with the continuous supply of parts to the welding zone, a continuous flow of current occurs. This type of welding is used for parts made of low-carbon steels up to 1 mm thick, and also parts of non-critical structures are made using this method.

The quality of the weld is low, because During the welding process, overheating of the welded parts and electrode rollers occurs.

For resistance seam welding, electrodes Ø 40 ÷ 200 mm made of pure copper (grade M1), bronze (cadmium, beryllium and other types) and their alloys are used.

Contact butt welding, depending on the method of its execution, is used for butt-joining parts made of a wide variety of materials and their combinations, with an area of ​​up to 1000 cm2.

In this way, rods of any shape (round, rectangular), profiles, rails, corners, wheel rims, etc. are welded. To carry out butt welding, a large number of machines and resistance welding devices (spotters) have been developed, varying in power and design.

The essence of welding is that parts, during the heating process, are connected along the entire plane of their contact.

Welding can be performed in 2 ways:

• reflow;
• resistance.

Flash welding is widely used because... does not require preliminary preparation of the product for welding. It comes in two types - with preheating of parts before welding and without it (continuous fusion welding).

To carry out resistance butt welding, a wide range of machines are produced that have special clamps in which parts are secured before welding.

The clamps are installed as follows - one on a fixed plate, and the second on a movable one. When the parts come together until they touch, a current is switched on, which melts the metal to a plastic state, then compression occurs under the influence of force, the magnitude of which depends on the thickness of the product and the metal.

This ensures a strong connection between the parts.

Flash welding with preheating is carried out for metals that can be hardened during the welding process. This heating promotes uniform heating of the metal and its slow cooling, which has a positive effect on welding.

Welding pliers

Welding tongs are suspended type devices.

Used in industry and small repair shops, as well as service centers. The thickness of metal parts welded using such devices does not exceed 4 mm.

The pliers are connected to the welding transformer using flexible wires, which allows work to be carried out in the required place. And allows you to weld large-sized products.

Various manufacturers produce a wide range of welding guns.

Some of them allow you to remotely select welding programs, change the welding position during operation, auto-repeat welding, monitor the condition of the electrodes, and even issue a message about the need to replace the electrodes or the need to clean them.

Making resistance welding yourself

A country house always requires special care from the owner. There are many more of them than in the apartment. Repairing and rebuilding a house, constructing decorative bridges and gazebos, constructing foundations and ceilings, all this work requires the ability to work not only with wood, but also with metal. Appropriate tools and equipment are needed for such work.

Skill and experience, the ability to work and come up with interesting projects sometimes comes down to only one thing: not all the work can be done by the owner himself. And this very often stops interesting creative ideas.

As a rule, this happens when it comes to welding. It is believed that it is impossible to weld metal structures without a specialist with a special apparatus. Yes, of course, not every welder can make a neat weld.

Of course, welding of bridge structures and building floors should be performed by professionals. But even an amateur can make a garden gate or a frame for a decorative composition from metal rods. If he has a special device.

It turns out that making such a homemade welding unit is quite simple and craftsmen came up with the design a long time ago.

Do-it-yourself resistance welding can be done quite quickly if a person has basic knowledge and skills in electrical engineering.

To manufacture the unit, you will need the following materials and accessories:

• power transformer;
• switch;
• timer;
• copper rod with a diameter of 1.5 cm;
• copper wire with a diameter of one centimeter.

If you do not have any skills in radio engineering, it is best to purchase a time timer at a specialized store.

Manufacturing a transformer for resistance welding

The most important part of the apparatus intended for resistance welding is the transformer. This unit allows you to obtain the required voltage for welding work.

The transformation ratio must be high; for this reason, for the manufacture of this element of the welding machine, it is best to use devices that are included with microwave ovens. The power of this component of the unit must be at least one kilowatt. In microwave ovens, as a rule, a unit with a power of up to 4 kW is used.

The transformer is removed from the microwave, and the secondary winding is removed from it.

To manufacture a welding transformer, only the primary winding of the unit is required. When removing the wire, all disassembly operations should be carried out very carefully.

Types and characteristics of resistance welding

This is required so as not to damage the copper wire of the primary winding and the magnetic circuit during the manufacturing process.

After the preparatory stage, the secondary winding is manufactured. At the output of the unit, you need to obtain a current of 1000 A. For this purpose, a copper wire with a diameter of 1 cm is used. When manufactured from such a copper wire, 2-3 turns are obtained in the device. The voltage at the output of the power device is about 2 volts.

The use of such a transformer in a welding machine for resistance welding allows you to work with metal up to 5 mm thick. After winding the copper wire, the direction of the windings is checked; in addition, at this stage of manufacturing, the presence of short circuits in the transformer is checked. In the absence of the latter, proceed to the further manufacturing process. When using two or more transformers in the design of a welding device, the output current is checked - it should not be more than 2000 A.

If this value is exceeded, the current strength should be reduced, since high current strength provokes significant changes in the household electrical network during operation of the device. After winding the copper wire and checking the parameters of the transformer, it is ready for use.

Manufacturing of electrodes for resistance welding machines

Electrodes are made from thick copper rods, the diameter of which is 1.5 cm.

When making electrodes, you must strictly adhere to the rule that the thickness of the electrode must be no less than the wire used in the secondary winding of the device.

If you use a low-power transformer, you can use tips from a pair of soldering irons as welding electrodes. Soldering iron tips have one undoubted advantage - they are durable and, thanks to this, will last for a long time.

The wires connected to the electrodes must have a minimum length, this is required in order to reduce current losses. To connect the wire to the electrode, a copper tip or a hole in the electrode made with a drill is used.

The wire is attached to the electrode using a bolted connection. For better contact, it is best to solder the wire to the tip; this will prevent the oxidation process and current losses during the oxidation process.

The advantage of a bolted connection is the ability to quickly remove the electrodes. When making a connection by soldering, if it is necessary to replace the electrodes, the joints will need to be re-soldered, which takes a lot of time.

Welding process control and welding machine infrastructure

Do-it-yourself resistance welding requires equipment with a control lever and switches.

The quality of welding of metal products is ensured not only by the current strength, but also by the compression force. For this purpose, the device is equipped with a lever. Compression force plays a particularly important role when welding thick sheets of metal.

When welding at home, the compression force must be at least 30 kg, for this reason the lever must be made of the appropriate length. This will ensure ease of use of the welding machine and high quality welding of parts. The length of the lever handle to ensure the compression ratio should be 60 cm.

The lever is attached 3/4 from the bottom. Therefore, the arm to clamp ratio is 1:10. With this design of the lever, if a pressure of one kilogram is applied to the lever, a pressure of ten kilograms is applied to the metal.

The switch is installed on the primary winding of the transformer, since a large current circulates in the secondary winding of the device, and the resistance of the switch in the circuit to the secondary winding will lead to loss of current.

For ease of operation, the switch is located on the handle of the lever, this allows the supply of electrical energy to the device only after the metal has made contact with the electrodes of the device. This placement of the switch allows for significant energy savings due to the absence of idle operation of the device.

When working with thin metal, it is best to install a timer in the control circuit of the welding device.

The timer allows you to regulate the operating time of the unit; to cool the device and its components, you can use a cooler from an old desktop computer.

After completing assembly of the device, it should be tested.

RESISTANCE WELDING METHODS

There are butt, spot and seam welding.

Butt welding

Contact butt welding is a resistance welding method in which workpieces are welded over the entire contact area.

The resistance butt welding diagram is shown in Fig.1. Weldable workpieces 1 secured in the clamps of the jointing machine. Clamp 3 installed on a fixed plate 2 , clamp 4 - on a movable plate 5 . Welding transformer 6 connected to the plates by flexible busbars and powered from an alternating current network through a switching device. Using a pressure mechanism, the movable plate 5 moves, the welded workpieces 1 are compressed under the influence of force R.

There are resistance butt welding and flash welding.

Resistance welding — butt welding with heating of the joint to a plastic state and subsequent upsetting. Reflow welding called butt welding with heating of the joint until melting and subsequent upsetting.

The parameters of the resistance butt welding mode are the current density j(A/mm2), specific compression force of the ends of the workpieces p (Mpa), current flow time t(c) and installation length L(mm).

Installation length L is the distance from the end of the workpiece to the inner edge of the electrode of the butt machine, measured before the start of welding.

For the correct formation of a welded joint and high mechanical properties of the joint, it is necessary that the process proceed in a certain sequence. Joint graphical representation of current change I and pressure R when welding is called a cycle or cyclogram of a contact machine .

Resistance butt welding.

The resistance butt welding cycle is shown in Fig. 2.

When resistance welding, the cleanly machined ends of the workpieces being welded are brought into contact and compressed with force R.

Then turn on the welding current I. After heating the metal in the contact zone to a plastic state, increase the force (upsetting the workpieces) and simultaneously turn off the current. In this case, plastic deformation of the metal occurs at the joint and the formation of a joint in the solid state.

When resistance welding, it is difficult to ensure uniform heating of the workpieces over the cross section and sufficiently complete removal of oxide films. Therefore, resistance welding is used to a limited extent.

This method welds identical workpieces of simple shape (circle, square, rectangle with a small aspect ratio) of small cross-section (up to 250 mm2) from low-carbon and low-alloy structural steels and non-ferrous metals and alloys.

Flash butt welding Unlike resistance butt welding, it does not require preliminary preparation of the ends of the workpieces.

Flash butt welding has two varieties: continuous and intermittent flash.

With continuous reflow the workpieces are brought together with the welding current turned on and very little force. At the beginning, the contact of the workpieces occurs over separate small areas through which a high-density current passes, causing melting of the workpieces as a result of the continuous formation and destruction of contacts - jumpers between their ends.

As a result of melting, a layer of liquid metal is formed at the end. Then the upset is carried out and the current is turned off. During precipitation, the liquid metal, along with impurities and oxide films, is squeezed out of the joint, forming a burr.

The compound is formed in a solid state. The continuous reflow welding cycle is shown in Fig.3.

With intermittent reflow the clamped workpieces are brought together under current, brought into brief contact and again separated by a short distance.

By repeating the approach and separation one after another, the entire section is melted. Then the current is turned off and the workpieces are upset.

Flash butt welding can be used to weld workpieces with different sections, both simple and complex shapes, from homogeneous or dissimilar metals. Continuous fusion welding is used to connect workpieces with a cross-section of up to 1000 mm2, and intermittent fusion welding - up to 10,000 mm2.

The most typical products welded by butt welding are elements of tubular structures, wheels, rings, rails, reinforced concrete reinforcement, etc.

SELF-TEST QUESTIONS

7. What is called butt welding?

8. What is the sequence of technological operations during welding

resistance and reflow?

What is the difference between resistance butt welding and flash butt welding?

10. What is the difference between continuous flash butt welding and intermittent flash butt welding?

In what cases is it advisable to use resistance butt welding? And when is reflow (continuous or intermittent)?

Resistance spot welding

Spot welding is a type of resistance welding in which workpieces are joined at separate points.

Before welding, the surfaces of the workpieces are thoroughly cleaned of dirt, oil and oxide films (with an emery wheel, a wire brush or etching).

In spot welding (Fig. 4), overlapped workpieces are compressed by electrodes connected to a welding transformer, when turned on, the workpieces at the point of contact are heated by electric current until a molten zone (the core of the point) appears.

Then the current is turned off, and the compression forces are kept constant for some time so that the crystallization of the molten metal of the point occurs under pressure. This prevents the formation of shrinkage defects - cracks, looseness, etc. In some cases, to improve the structure of the weld point, the compression force before turning off the current is increased (forging the point).

Spot welding, depending on the number of simultaneously welded points, can be one-, two-, or multi-point.

According to the method of supplying current, spot welding can be double-sided ( Fig.4a) and one-sided ( Fig.4b)

In double-sided welding, the current is supplied to the upper and lower workpieces; in single-sided welding, the current is supplied to one of them.

To increase the current density in the connection zone with one-sided current supply, the workpieces are placed on a current-carrying copper pad. Single-sided welding is used when access to one of the workpieces is difficult, as well as when it is necessary to increase the productivity of the process, since in this case two points can be welded simultaneously.

One of the spot welding cycles, the cycle with forging, is presented in pic 5.

The entire welding cycle consists of four periods: compression of the workpieces to be welded by electrodes, turning on the current and heating the contact point to a melting temperature with the formation of a cast core point; turning off the current and increasing the compression force (forging the point); removing force from the electrodes.

The spot welding mode can be soft or hard.

The soft mode is characterized by a relatively low current density (j=80...160A/mm2) and a long flow time (T=0.5...3s) at a relatively low specific pressure (p=15...40MPa). The hard mode is characterized by high current density (j=160...350A/mm2), high specific pressure (p=40...150MPa) and short current flow time (t=0.001...0.1s). Soft modes are used mainly when welding carbon and low-alloy steels, hard modes - corrosion-resistant steels, aluminum and copper alloys.

Spot welding can be used to weld sheet blanks of the same or different thickness, intersecting rods, sheet blanks with rods or profile blanks (angles, channels, etc.) made of low-carbon, carbon, low-alloy and corrosion-resistant steels, aluminum and copper alloys.

The thickness of the metals being welded is 0.5-6 mm, and in some cases can reach 30 mm.

Multi-spot resistance welding - a type of resistance welding, when several points are welded in one cycle.

Multi-spot welding is performed according to the principle of single-sided spot welding. Multi-point machines can have from one pair to 100 pairs of electrodes; accordingly, 2 to 200 points can be welded simultaneously. Multi-spot welding is used mainly in mass production;

A type of spot welding is relief welding ,

Relief welding

Relief welding is a method of contact spot welding in which the location of the points is determined by pre-prepared protrusions (reliefs) in the workpiece 2 .

When projection welding ( Fig.6) blanks 2 And 4 clamped between flat electrodes 5 And 1 (contact plates). The connection occurs at points 3 (defined by protrusions), which are obtained by stamping in one of the blanks.

When the current is turned on, the upper electrode compresses the workpieces and presses them until the protrusions are completely destroyed. Thus, in one stroke the machine makes as many welding points as there are protrusions between the electrodes; This method is highly productive.

The disadvantage is the significant power consumption.

SELF-TEST QUESTIONS

What is spot welding?

13. What is the sequence of technological operations for spot welding?

14. What is the difference between double-sided spot welding and single-sided spot welding?

15. In what modes is spot welding performed?

What is the difference between soft mode and hard mode?

17. For welding what products is spot welding used?

18. What is called multi-spot welding?

19. What is called projection welding?

Resistance seam welding

Seam welding - a type of resistance welding in which a weld is formed by placing a sequential series of overlapping points, which determines its density and tightness.

For seam welding, current supply i force transmission R to blanks 1 and their movement is carried out through rotating disk electrodes - rollers 2 (Fig.7).

Before welding, workpieces with surfaces cleaned of dirt, oil and oxide films are assembled in an overlap. Level welding, as well as spot welding, can be performed with double-sided ( Fig.7a) and one-sided ( Fig.76) supplying current.

On Fig.8 the most common cyclograms of seam welding with continuous current are presented (A) and with intermittent (b) with continuous rotation of the rollers.

The sequence of operations is the same as for spot welding.

The first cycle is intended for welding short seams and metals and alloys that are not prone to grain growth and do not undergo noticeable structural transformations when the heat-affected zone is overheated (low-carbon and low-alloy steels); the second cycle is for welding long seams and metals and alloys for which overheating of the heat-affected zone is dangerous (stainless steels, aluminum alloys).

The main parameters of the seam welding mode are: current density j in A/mm2" specific pressure R in MPa and welding speed vsv m /h.

Seam welding is widely used in mass production to produce various containers, reservoirs, automobile fuel tanks, etc.

from low-carbon, alloyed structural steels, as well as non-ferrous metals and alloys. The thickness of the welded sheets is 0.3...3 mm.

SELF-TEST QUESTIONS

20. What is called seam welding?

21. What is the sequence of technological operations during seam welding?

Description of the process of self-assembly of spot welding

In what cases is intermittent seam welding used, and when is continuous seam welding used?

23.For what structures is it advisable to use seam welding?

EXERCISE

For one of the options, develop a technological process for assembling and spot welding a low-carbon steel beam ( Fig.9).

Dot pitch t=3dt. Large-scale production.

1. Specify the preparation of workpieces for welding. Based on the thickness of the workpieces to be welded, select the type of machine and indicate its technical data.

Calculate the electrode contact surface area. Based on current density valuesj (A/mm2) and pressure R(MPa) determine the welding currentJ (A) and effort R(MN) applied on the electrodes. Determine the welding time of the productt (With).

2. Draw and describe the spot welding cycle.

Many people do not want to depend on circumstances. If you suddenly need welding, you want to solve the problem in your workshop. A do-it-yourself resistance welding machine is a solution in the right direction.

To perform resistance welding with your own hands, you need to purchase or make a special machine yourself.

Of course, if you need to weld large metal structures, then it is difficult for resistance welding to compete with other types. At the same time, at home there is a great need for welding small parts. Such problems become easily solvable if you make your own resistance welding machine.

Resistance Welding Basics

In general, resistance welding is welding using electric current, when it passes through the contact zone of the metals being welded under the influence of compressive pressure. The principle of contact welding is based on the fact that when an electric current is applied, an arc appears at the point of contact of two metals, which melts them. The duration of exposure to welding current is very short (0.01-0.1 s). The main parameters of any resistance welding are: the strength of the welding current, the time of application of the current and the amount of compression of the metals in the contact zone. There are the following main ones: spot, relief, seam and butt welding.

Fundamentals of apparatus design

To carry out resistance welding, it is necessary to assemble a resistance welding machine. When manufacturing the apparatus and accessories, several basic rules must be taken into account. Typically, spot or butt welding machines are used for domestic purposes. Then you should think about what type of device it will be - stationary or portable, which determines its weight and dimensions. It is necessary to decide on the basic parameters of the device:

1. Type of welding current (alternating, direct) and its strength.
2. Voltage in the welding zone.
3. Welding pulse duration.
4. Number and type of electrodes.
5. Simplicity of the device.

Any resistance welding machine contains an electrical and mechanical part. The electrical part includes a welding current source, a control system for basic parameters and a contact block. The mechanical part must provide fastening of the workpieces to be welded, as well as the application of a compressive load.

Welding power source

The main element of the resistance spot welding machine is the welding current source, i.e. short current pulse. The most common current sources use energy storage and capacitor discharge. One of the simple circuits of such a source is based on the supply of direct current from the secondary winding of a transformer, onto the primary winding of which a capacitor is discharged (in Fig. 1 there is a diagram of the power source).

Figure 1. Power supply diagram.

The primary winding of the output transformer T2 is connected to the input electrical network so that one branch of the circuit passes through the diagonal of the rectifier bridge (diodes V5-V8). In this case, control is carried out through thyristor V9 connected to the “Impulse” start button by connecting it to the second diagonal of the bridge. Energy is stored in capacitor C1, located in the thyristor V9 circuit and connected to the diagonal of the bridge. The discharge of the capacitor through this circuit enters the primary winding of the output transformer T2. Capacitor C1 is charged from an auxiliary circuit, which is connected when the main circuit is turned off.

This welding pulse source works as follows. Capacitor C1 is charged while the output transformer T2 is turned off. When you press the “Impulse” start button, charging of the capacitor stops and it is discharged into an adjustable resistor R1 connected to the primary winding of transformer T2. The discharge parameters are controlled by thyristor V9. The duration of the welding pulse is regulated using a variable resistor R1, into which the discharge occurs. When the button is turned off, the capacitor charging process resumes.

Recommended parts for the circuit: capacitor C1 with a capacity of 1000 μF for operating voltage up to 25 V; thyristor PTL-50 or KU202, input transformer T1 with a power of 10 W for a voltage in the windings of 220/15 V. It is better to make the output transformer T2 with your own hands: the primary winding is PEV-2 wire with a diameter of 0.8 mm, 300 turns; secondary winding – copper busbar 20-25 mm², 10 turns. Output parameters of the device: current up to 500 A, pulse duration up to 0.1 s.

Increasing the power of the current source

Figure 2. Diagram of a high-power source: 1. schematic diagram; 2. winding of transformer T2; 3. starter connection diagram.

To increase the power of the welding pulse, you can make some changes to the device. The current is supplied through a contactless magnetic starter type MTT4K (operating current up to 80 A). 2 thyristors (Fig. 2), 2 KTs402 diodes and resistors R1-R2 are introduced into the control circuit. The response time is controlled by the RES time relay. A battery of capacitors C1-C6 of 6 pieces is recommended as energy storage devices (in Fig. 2 there is a diagram of a high-power source: 1) circuit diagram; 2) winding of transformer T2; 3) starter connection diagram).

It is recommended to install the following parts: electrolytic capacitors C1-C6 with a capacity of 47 μF, 100 μF and 470 μF (two of each type) for an operating voltage of 50 V; time relay RES42 or RES43 for a voltage of 20 V. Transformer T2 has a primary winding made of wire with a diameter of 1.5 mm, a secondary winding made of a copper bus with a cross-section of 60 mm² (number of turns - 4-7). The welding current of such a device is up to 1500 A.

Making an output transformer

One of the most important elements of equipment is the output welding transformer. Its production should begin with the selection of a type-setting core. A standard core with a total cross-section of at least 60 cm² should be used. The tie-down elements are made using an angle or strip and secured with bolts with a diameter of 8 mm. The primary winding is wound manually with PET or PETV wire onto one side of the core. The turns are spaced evenly along the length of the core. The ends of the winding are brought out onto the panel and secured in the connecting block. The secondary winding is made on the second side of the core from a copper busbar. The copper busbar is pre-insulated with fluoroplastic tape or fabric insulating tape. At the ends of the bus, brought out, holes are drilled for bolting the cable. An insulating layer is placed on top of both windings.

Contact block design

The simplest contact block device involves supplying current directly to the parts being welded. This method is used in butt welding. Alligator clips are used to ensure contact.

A more complex system involves direct connection of current only to the most massive part. The second contact is provided by a movable top electrode, which is fed into the welding zone manually. A welding gun can be recommended as such a contact. It is made from two identical textolite plates, cut in the shape of a pistol. Nuts are installed in the front part for screwing the copper electrode into them, and a start button is located in the central part. A cable is inserted into the device from above, which is connected to the electrode, and a wire from the circuit of the primary winding of the transformer, which is connected to the start button.

The plates are fastened together so as to securely fix the electrode mount.

Assembling the device

Figure 3. When assembling the welding machine, the input cable from the electrical network is attached to the contact block, which is located on the electrical plate.

The welding current source is placed in a metal housing. The electrical plateau is assembled on a PCB and fixed inside the source body, usually vertically. The output transformer is mounted on the base of the housing. A welding cable is bolted from above to the busbar of the secondary winding of the transformer, the second end of which is connected to the electrode in the contact gun. The input cable from the electrical network is attached to the contact block located on the electrical plate (Fig. 3).

Tools and auxiliaries that are necessary when making a resistance welding machine with your own hands:

• Bulgarian;
• electric drill;
• hacksaw for metal;
• file;
• chisel;
• hammer;
• pliers;
• screwdriver;
• vice;
• calipers;
• scissors;
• tap;
• die.

Making a resistance welding machine is not difficult. You can choose a very simple design, or you can make universal equipment.