How to spot weld correctly

Spot welding what to cook

Resistance spot welding is one of the most popular welding methods. It allows you to quickly and efficiently join thin metals. In this article we will tell you what spot welding is, what the technology of resistance spot welding is and what defects can result if welding is performed incorrectly.

general information

Spot resistance welding is one of the types of resistance welding. In addition to spot welding, there are also butt, seam and other types of resistance welding, but it is spot welding that is most widespread, so we’ll talk about it in this article. Spot resistance welding is used in many areas: from construction to aircraft manufacturing. For example, when constructing modern airliners, millions of points are located on the hull, forming a strong seam.

The principle of operation is simple: using an electric discharge, the metal is heated at a certain point to its melting point. At the same time, the two parts are pressed against each other with a certain force. Under the influence of temperature and mechanical load, the parts are connected to each other. A very aesthetic and reliable seam is formed.

Multi-spot welding differs from other types of resistance welding in several ways.

First of all, the spot method allows you to significantly reduce welding time (one “point” of the seam is formed in a fraction of a second), while the work uses high values ​​of welding current (more than 1000 amperes), also sets a low voltage (no more than 10 watts), the melting zone small (from a few mm to 1-2 centimeters), a significant mechanical load is used, which can reach up to several hundred kilograms.

In most cases, spot welding is used when thin sheet metal or rod materials need to be overlapped. Spot welding is capable of joining metal with a thickness of 1 millimeter to 3 centimeters, but such indicators are redundant and in practice you will not have to weld parts thicker than 5-7 millimeters. For this reason, spot welding is great for auto body work.

Advantages and disadvantages

The great popularity of do-it-yourself spot welding is due to many advantages. To work, you do not need electrodes, wire, fluxes, and so on. And this saves not only time, but also finances.

Also, the deformation of the metal is insignificant and only in places of “points”; the spot welding machine is very convenient to work with, even a beginner can cope with this task. The seam itself turns out very neat, the workflow is cheaper than analogues, and it can be easily automated.

It is multi-point welding that can perform a huge amount of work, forming up to several hundred weld “points” per minute.

The disadvantages are minor and few. Seams made by spot welding do not have such good tightness as connections made using electrodes, for example. There may also be excess voltage in the area where the “point” is formed; this needs to be monitored.

Welding technology

Resistance spot welding technology consists of three stages, which we will describe in detail. First, the parts are prepared (we will talk about this in more detail later). Then the parts are placed under the tip of the welding machine and are subjected to compression, as a result the surface of the metal is deformed and a small depression is formed - a dot.

Then an electric current is applied, the metal heats up, melts and a so-called liquid core is formed at the “point”. Gradually, the current penetrates through the entire core, and it increases in size. The "spot" becomes part of the weld.

And thanks to the preliminary deformation of the parts, the metal does not spatter during melting and the seam is neat and does not need to be cleaned.

Then the current supply is stopped, the metal cools and crystallizes. The liquid core becomes molten. But there is a nuance: when cooled, the core may decrease slightly in size and residual stress is formed.

It is undesirable and can be dealt with using different methods. We recommend that before completing the welding process, press the parts harder against each other in order to properly heat them and make the seam more uniform.

Otherwise, do-it-yourself spot welding is very simple and does not require highly qualified welders.

Metal preparation

Do-it-yourself spot welding, like any other welding method, requires preliminary preparation of the metal. To do this, you need to clean the areas of the future seam from dirt, corrosion and oxide film (if any).

If this is not done, power will be lost during welding and the degree of wear on the welding machine will increase. To clean the metal, use the sandblasting method, an angle grinder with a wire brush or sandpaper.

You can also etch a small part in a special solution.

Pay special attention to the preparation of aluminum and its alloys. There is a thick oxide film on the surface of this metal, which prevents complete heating and welding of the part. So remove it thoroughly before starting work. This is especially important if particularly important structures are to be welded.

Welding equipment

To do your own spot welding, you will need equipment. You can use a device operating on direct or alternating current, a capacitor-type device, or equipment operating at a low frequency.

All these types differ in the power electrical circuit and the shape of the welding current. Also, each type has its own pros and cons, do not listen to those who tell you about the superiority of this or that equipment.

In our practice, we use a device that runs on alternating current; this is the most common option. You can choose another type of equipment.

Pay attention to modern TIG LORCH welding, it is very technologically advanced.

Source: https://ravon-r2.ru/tochechnaja-svarka-chem-varjat/

How to make spot welding with your own hands: features and principle of operation

If you have a welding machine at hand, you can do not everything, but a lot. And if you decide to do car body repair, then having a large set of tools will come in handy.

In this article we will talk about how to make spot welding with your own hands. This is a device that is useful for repairing car bodies, as well as for other everyday needs. With this tool you can quickly connect several metal elements.

Principle of operation

Before considering how to make mini spot welding with your own hands, you need to know how this device generally works. The demand for such products is extremely high: welding will be indispensable when working with metal - such a connection is much more reliable than a bolted one.

The operation of the welding machine is quite simple - due to the energy of the electric current, metal parts are heated. Thanks to this, a weld is formed. The quality of the final connection depends on the type of material used and its density.

Features of working with welding

When welding, you must pay attention to the following points:

1. Welding should be done with low voltage. Often, voltage up to 10-12 Volts is sufficient for normal operation of the equipment.
2. The process of connecting elements lasts several seconds.
3. The current in the circuit is very high.
4. The smaller the melting area, the higher the welding quality.
5. It is extremely important that the seam can withstand high loads.

If you follow all the rules, the end result will please you - the seam will be not only beautiful, but also durable.

It is worth noting that before you make mini-spot welding with your own hands, you should consider several designs. Making even the simplest is quite difficult. It is extremely important during manufacturing to strictly adhere to the instructions - this directly determines how the device will work in the future.

The simplest designs work by manually changing the pulse duration. In other words, the person working with welding himself regulates the time of the pulse. In more complex designs, a time relay is installed. The duration is preset. The operator only has to press the electrodes to start the process.

Important design qualities

The main element of the welding machine is the transformer. DIYers often use devices from microwave ovens, old TVs, etc. First you need to calculate the current required for the normal operation of the device. Then, leaving the primary winding on the core (note that this is not always possible - we’ll tell you why later), completely get rid of the secondary. It is simply not needed when operating a welding machine.

When winding the secondary winding, thick insulated copper wire is used. The larger its cross-section, the higher the current strength in the circuit will be. Please note that for normal use of the welding machine you need to use not one, but two transformers from the microwave, connected in parallel. This will increase the output current, therefore, it will be possible to work with thicker metal elements.

Before making a spot welding machine with your own hands, it is recommended to study in detail all possible schemes. This will allow you to answer many questions, and first of all the following: what metal do you plan to weld with the machine? Welders are used both for joining sheet metal and wiring cables.

The following points should be taken into account:

1. All equipment must operate from a 220 Volt AC network.
2. The voltage at the transformer output should be up to 12 Volts. Usually 3-7 V is enough.
3. The current during welding reaches 1500 Amps - this is twice as much as the consumption during a short circuit of the car starter.

It is imperative to draw up a detailed schematic diagram on which you indicate all the elements: circuit breakers, thyristors, etc.

In the event that dangerous situations may arise during welding work, it is necessary to provide a switch to turn off the device. It is allowed to use contactless thyristor single-phase switches connected to the power supply circuit of the primary winding of the transformer.

Control circuits

The industry produces MTT4-K systems in which a thyristor switch is installed. It is with its help that the supply voltage is switched. Moreover, the protection unit can operate under voltages of up to 800 Volts and a current of 80 A. The circuit contains the following components:

1. Power unit.
2. Electromagnetic relay.
3. Chain for setting up the device.

In conjunction with such a device, you can use transformers whose power does not exceed 20 watts. Please note that the device is installed in the primary winding power supply circuit. In the secondary, the voltage is not very high; it can be rectified if necessary using semiconductor diodes.

Transformer Features

Today you can find the implementation of various functions of control circuits. In the event that there is a need to turn on the device for a certain period of time, it is enough to set the value correctly. And specify it in the system logic settings. Electrolytic capacitors are used in the manufacture of the device; it is advisable to use devices with a voltage reserve of up to 50-100 Volts.

When manufacturing a transformer, special attention is paid to its windings. Actually, you need to completely get rid of them and leave only the core.

First, wind the primary winding - to do this, use copper wire in varnish insulation. Be sure to reliably separate the primary winding from the secondary - to do this, lay 3-5 layers of varnished fabric. To make the primary winding, you need to use a wire with a thickness of 1.5 mm - only this can withstand high current consumption.

The secondary winding is several turns of thick wire (about 20 mm, maybe even more - depends on the specific case).

Experts recommend making intermediate conclusions when winding the primary winding - this will allow you to get the maximum benefit from the device.

Welding pliers

Before you make spot welding yourself, you need to decide what it will be used for. After all, what kind of pliers are needed directly depends on this:

1. Portable.
2. Stationary.

The latter are easy to use, their insulation is reliable and of high quality, but in order to ensure good clamping force, it is necessary to apply force.

As for portable devices, they are easy to use, and most importantly, they are small in size. To control the force, you simply need to change the length of the pliers extending beyond the body of the device. Copper rods are used to make pliers. Please note that the diameter of the electrode must be the same as the secondary wire of the transformer. The electrode cannot be thicker. To improve the quality of the weld, the ends of the electrodes are sharpened.

Microwave transformers

Now let’s look at a short instruction on how to make spot welding with your own hands from a transformer, which can be found in simple microwave ovens. Of course, it will have to be modernized a little - completely get rid of the windings.

Note that if you use 2, 3 or 4 identical transformers, then it is likely that you will not have to destroy the primary coils. This approach is possible. In fact, if you connect 4 identical windings in parallel, then we can assume (conventionally) that the wire used to wind it is 4 times thicker.

In other words, these four transformers will be able to withstand 4 times the current consumption of one.

By the way, about which microwave to take. Of course, you don't need a new one. It is quite possible that you, your friends or neighbors have one that has fallen into disrepair. Usually in such devices it is not the transformer that breaks down, but the magnetron - a special emitter of microwaves, which, in fact, warms up the food. Also, one of the housings can be adapted for the installation of a transformer and all other devices.

A little about windings

Now let's start creating a transformer. Let's say you decide not to tempt fate and just make a welder out of 2 transformers. A good solution is that you don’t need to calculate the primary winding. And this is the most difficult thing.

It is much easier to calculate the secondary winding data - this can even be done experimentally. To do this, wind several turns (for example, 10) over the primary winding and connect the transformer to the network.

By measuring the voltage at the terminals of the secondary winding, you can calculate how many volts one turn produces.

But this will not be useful to you in the case of making a welding transformer - here you need to use a wire of maximum thickness. And there will be as much as it can fit in the free space. Therefore, the voltage fluctuates up to 12 V. By the way, to increase the current, you can use two transformers connected in parallel. Actually, this is what we plan to do.

Transformer Assembly: Step-by-Step Guide

Before you make spot welding with your own hands from a microwave, you need to correctly calculate all the elements. And first of all, this concerns the transformer. To do this, perform the following manipulations:

1. Using a hacksaw or grinder, saw the core in half - otherwise you won’t be able to disassemble it.
2. Get rid of the windings.
3. Make a frame from dense textolite. The cross-section of the frame must be the same as that of the transformer core. This is the inner ferrule over which you will wind the wire.
4. Wind the primary winding.
5. Install the frame and assemble the core. To connect, use a conductive adhesive. From the outside it is necessary to tighten the core with metal plates.
6. It is recommended to use a wire for the secondary winding that fits tightly into the transformer window. This will allow you to get maximum current. Lay as many turns as possible.

Please note: if you leave the original primary winding, then you do not need to cut the core. Our guide is given only for the most difficult option. Before you quickly make a spot weld with your own hands, make sure that all the necessary materials are on hand.

Final stage

Perhaps now you know how to make spot welding with your own hands. It cannot be used for the battery (charging it) - the voltage is low. But for joining sheet metal it will be just right. Please note that all connections must be made as reliable as possible. All wires must be of the shortest length possible. Moreover, it is important that they are designed to operate with the maximum possible current.

Before you do your own spot welding for a car, you need to think about the design of the pliers. It depends on them how convenient it will be to use the device in the future. And the most important thing is a reliable case. It shouldn't be flimsy - keep that in mind. After all, the welding machine can be subjected to heavy loads.

Source: https://FB.ru/article/456075/kak-sdelat-tochechnuyu-svarku-svoimi-rukami-osobennosti-i-printsip-rabotyi

Do-it-yourself spot welding: diagrams, principle

Spot welding machines are not used as often in everyday life as arc welding machines, but sometimes it is impossible to do without them. Considering that the cost of such equipment starts from $450-$470, the profitability of its purchase is questionable.

Household spot welding machine CBA-1.5AK

The way out of this situation is resistance spot welding with your own hands. But, before we tell you how to make such a device yourself, let's look at what spot welding is and the technology of its operation.

Briefly about spot welding

This type of welding is contact (thermomechanical). Note that this category also includes seam and butt welding, but it is not possible to implement them at home, since complex equipment will be needed for this purpose.

The welding process includes the following steps:

• the parts are combined in the required position;
• they are secured between the electrodes of the device, which press the parts;
• heating is performed, as a result of which, due to plastic deformation, the parts are firmly connected to each other.

A production spot welding machine (such as the one shown in the photo) is capable of performing up to 600 operations within a minute.

Equipment for machine spot welding

Process technology

To heat the parts to the required temperature, a short-term pulse of high-power electric current is applied to them. As a rule, the pulse lasts from 0.01 to 0.1 seconds (the time is selected based on the characteristics of the metal from which the parts are made).

When pulsed, the metal melts and a common liquid core forms between the parts; until it hardens, the welded surfaces must be held under pressure. Due to this, as it cools, the molten core crystallizes. A drawing illustrating the welding process is shown below.

Spot welding process illustration

Designations:

• A – electrodes;
• B – parts to be welded;
• C – welding core.

Pressure on the parts is necessary so that, when pulsed, a sealing belt is formed along the perimeter of the molten metal core, preventing the melt from flowing outside the zone where welding occurs.

To provide better conditions for crystallization of the melt, the pressure on the parts is gradually removed. If it is necessary to “forge” the welding site in order to eliminate inhomogeneities inside the seam, increase the pressure (do this at the final stage).

Please note that to ensure a reliable connection, as well as the quality of the seam, it is first necessary to treat the surfaces of the parts in the places where welding will take place. This is done to remove oxide film or corrosion.

When it is necessary to ensure reliable connection of parts with a thickness of 1 to 1.5 mm, capacitor welding is used. The principle of its operation is as follows:

• the capacitor block is charged with a small electric current;
• the capacitors are discharged through the parts being connected (the pulse strength is sufficient to ensure the required welding mode).

This type of welding is used in those areas of industry where it is necessary to connect miniature and subminiature components (radio engineering, electronics, etc.).

Speaking about spot welding technology, it should be noted that it can be used to connect dissimilar metals together.

Examples of homemade designs

There are many examples on the Internet of creating machines that produce spot welding. Here are some of the most successful designs. Below is a diagram of a simple spot welder.

An example of a device circuit diagram

For implementation we will need the following radio components:

• R - variable resistance with a nominal value of 100 Ohms;
• C – capacitor designed for a voltage of at least 25 V with a capacity of 1000 μF;
• VD1 – thyristor KU202, the letter index can be K, L, M or N, you can also use PTL-50, but in this case the capacitance “C” must be reduced to 1000 μF;
• VD2-VD5 – diodes D232A, foreign analog – S4M;
• VD6-VD9 – D226B diodes, they can be replaced with a foreign analogue 1N4007;
• F – 5 A fuse.

It is necessary to make a digression to tell how to make the TR1 transformer. It is made on the basis of Sh40 iron, with a set thickness of 70 mm. For the primary winding you will need PEV2 wire Ø0.8 mm. The number of turns in the winding is 300.

To make a secondary winding, you will need a Ø4 mm stranded copper wire. It can be replaced with a tire, provided that its cross-section is at least 20 mm2. The number of turns of the secondary winding is 10.

do-it-yourself resistance welding

As for TR2, any of the low-power transformers (from 5 to 10 W) will be suitable for it. In this case, winding II, used to connect the backlight lamp “H”, should have an output voltage within 5-6 V, and winding III – 15 V.

The power of the manufactured device will be relatively low, ranging from 300 to 500 A, maximum pulse time up to 0.1 sec (provided that the ratings “R” and “C” are the same as in the diagram shown). This is quite enough for welding steel wire Ø0.3 mm or sheet metal if its thickness does not exceed 0.2 mm.

Let us present a diagram of a more powerful device, in which the welding electric current of the pulse will be in the range from 1.5 kA to 2 kA.

Circuit diagram of a device with a pulse strength of up to 2 kA

We list the components used in the circuit:

• resistance ratings: R1-1.0 kOhm, R2-4.7 kOhm, R3-1.1 kOhm;
• capacitances in the circuit: C1-1.0 µF, C2-0.25 µF. Moreover, C1 must be designed for a voltage of at least 630 V;
• VD1-VD4 diodes - D226B diodes, replacement with a foreign analogue 1N4007 is allowed, instead of diodes you can install a diode bridge, for example, KTs405A;
• thyristor VD6 - KU202N, it must be placed on a radiator with an area of ​​at least 8 cm2;
• VD6 – D237B;
• F - 10 A fuse;
• K1 is any magnetic starter that has three pairs of working contacts, and the winding is designed for ~220 V, for example, you can install PME071 MVUHLZ AC3.

Now we’ll tell you how to make transformer TR1. The LATR-9 autotransformer, such as shown in the photograph, is used as a basis.

Autotransformer used as a basis

The winding in this autotransformer has 266 turns, it is made with copper wire Ø1.0 mm, we will use it as the primary. We carefully disassemble the structure so as not to damage the winding. We dismantle the shaft and the movable roller contact attached to it.

Next, we need to isolate the contact track; for this purpose, we clean it from dust, degrease it and varnish it. When it dries further, we insulate the entire winding using varnished cloth.

As a secondary winding we use copper wire with a cross-sectional area of ​​at least 80 mm2. It is important that the insulation of this wire is heat resistant. When all conditions are met, we make a winding of three turns.

Setting up the assembled device comes down to calibrating the scale of the variable resistor that regulates the pulse time.

We recommend that before starting welding, you experimentally establish the optimal time for the pulse. If the duration is excessive, the parts will be burned, and if it is less than necessary, the strength of the connection will be unreliable.

As already written above, the device is capable of delivering a welding electric current of up to 2000 A, which allows you to weld steel wire Ø3 mm or sheet steel, the thickness of which does not exceed 1.1 mm.

Source: https://www.asutpp.ru/tochechnaya-svarka-svoimi-rukami.html

Homemade spot welding: how to assemble the device at home (instructions and diagram)

It is not difficult to make homemade spot welding yourself.

Similar mechanisms are produced in several variations:

1. Portable
2. Compact
3. Dimensional

Welding process: manufacturing diagram

When assembling the device yourself, it is necessary to take into account the Joule-Lenz law (Q = I² X R X t), which states: thermal energy is released in conductors in a certain amount in proportion to their resistance, the coefficient of current strength in time and squared.

Experts advise paying due attention to the homemade mechanism, taking into account the large loss of energy in thin wires, and using a high-quality electrical circuit.

Types of contact welding:

In spot welding, the device technology is based on the thermal effect of current. This ensures welding of the part at one or several points.

The size and structural features of the electrode contact surface differ. This affects the strength level of the connections.

We list several existing stages in spot welding technology:

1. The mating components are connected and placed between the electrodes of the device. The components should be positioned tightly against each other. This will ensure the formation of a sealing belt near the molten core, which will prevent hot metal from splashing out during the pulse.
2. The next step is heating the parts. They become thermoplastic, which makes it possible to modify them. It is possible to make high-quality welding at home, the main thing is to follow the key principles of the technology: maintain the speed of movement of the electrodes, a constant pressure value and a tight connection of all parts.

When current passes, a pulse is generated, which heats the welding machine and allows the metal to melt at the points of contact with the electrodes.

Then a common core of liquid consistency 4-12 mm in diameter is formed. After the current is applied to the parts, they will hold securely until the core cools and its further crystallization.

Domestic use of homemade spot welding allows you to ensure mechanical strength of metal seams without high costs, but does not allow you to create hermetic seams.

The state standard regulates safety precautions, work processes and welding equipment.

Welding machine at home

A homemade device can be assembled from scrap materials

There is no need to use a homemade spot welding machine for high power: the device can work with metal wire 0.3 mm in diameter; with steel sheet 0.2 mm thick.

The configuration allows you to weld the thinnest foil components and weld thermocouples.

The electrode is produced from a pistol with light force, which is necessary for pressing small objects.

The technology for producing homemade spot welding is not complicated: the electrode is connected with a flexible cable to the secondary transformer winding, and the most massive part should be connected to the lower end.

Here you will need rectifier bridges; the thyristor is connected to the second part of the bridge. Opening the first part facilitates sufficient voltage from the transformer to the primary winding.

The welding gun is replaced with a gun and the first element is connected to the end of the secondary winding on the transformer. In this case, the second end is securely attached to the device.

Single-phase or three-phase current powers the clamps, which allows them to function. The transformer feeding the clamps supplies a current of several kA.

The thyristor is controlled by pressing a button on the pistol handle. The capacitor is charged when an additional source (rectifier bridges or transformers) is connected to the network.

The thyristor closes, the mechanism turns on and remains open until the capacitor is discharged.

The length of time during which the capacitor can discharge is regulated by a variable resistor. The button is pressed - the next pulse is generated and the capacitor is charged. When you press the button again, the process starts over again.

The duration of the process in a homemade device does not exceed 0.1 second due to the value of the resistor and capacitor, the welding current is 300-500 Amps, while the power is low - 5-10 Watts. These parameters are sufficient for working with small objects.

Homemade spot welding can be created from a steel transformer with a kit thickness of 70mm. For the primary winding, PEV-2 0.8 wire with 300 turns is used, for the secondary winding, a stranded wire of 4 mm in diameter is used.

Production of welding equipment: instructions

The simplest homemade spot welding

According to experts, a three-phase step-down transformer should be chosen as the basis of the equipment.

The secondary windings are removed from the coil, the primary wires and core are left in their original form, the middle wire is wrapped in the same material with 8-10 turns at the output.

To independently produce welding equipment, you need a 25 m cable, a copper pipe 10-12 mm in diameter, a metal disc and a grinder.

It is necessary to ensure that both coils located at the edges are filled by carefully winding the secondary winding using a multi-core three-phase power cable. The flexible wire winds without the need to disassemble the equipment.

The parameters of the wires in the cable are 6-8 mm in diameter. One of them should be thinner, but with good insulation and resistant to current power. For the production of the device 25 m of cable. If necessary, it can be replaced with wires with a smaller cross-section.

It is more efficient to do this work together: one person will do the pulling of the wire, the second will do the laying of the turns. To make a terminal, you need a copper pipe 30-40 mm long and 10-12 mm in diameter.

One part of it is separated, which forms a plate in which a hole up to 10 mm in diameter is made; pre-stripped wires are inserted into the other part. Experts advise crimping the wires with a hammer.

Contact will improve if several notches are made on the outside of the pipe.

New fasteners with M10 threads replace the existing screws and nuts at the top of the transformer, to which the terminals from the secondary winding are then attached.

It is necessary to make 11 holes (no more than 6 mm in diameter) in the textolite board for screws with nuts and washers; and firmly attach it to the surface of the transformer. These components will provide the output of the primary winding.

The electric holder is made from ¾ pipe 25 cm in length. It is necessary to make recesses in the corners, and weld a small piece of metal wire to the holder.

A hole is made on the reverse side and a piece of cable is connected, as with the secondary winding. Then you need to insulate the pipe with a rubber hose.

Electrodes for spot welding

Do-it-yourself spot welding done at home is suitable for a small amount of work. It is recommended to let the device cool down after working with 10-14 electrodes.

The difference between multi-point equipment and its analogues is the work with metal workpieces of a certain shape and size.

Multipoint devices are rare, but are universal for contact pairing of elements. Only experts can re-adjust it.

Contact welding of parts is impossible in the absence of electrodes made of alloys with a high level of thermal conductivity.

Electrodes favor the compression of metals and conduct current to the surface of the elements. The level of heat concentration depends on the tips - thin mechanisms wear out quickly and need constant sharpening.

There are several forms of manufactured tips.

It is possible to extend the life of the tips by following the tips below:

• Electrodes are selected according to the criteria of the metal used in the work;
• Ensure their safety as much as possible;
• For heavy welding, use more massive tips;
• Use a water jacket.

Experts advise not to file the tips due to the appearance of unevenness, which will generally negatively affect the quality of work.

Source: https://prosvarku.info/apparaty/samodelnaya-tochechnaya-svarka

Do-it-yourself spot welding technology

The spot welding process includes several stages. How to weld metal using spot welding? First, the parts to be joined are aligned in the desired position, placed between the electrodes of the welding machine and pressed against each other. After this, they are heated to a state of plasticity and jointly undergo subsequent plastic deformation.

In industrial conditions, when using automatic equipment, the welding frequency can reach up to 600 points per minute. In order to make high-quality spot welding with your own hands at home, it is necessary to maintain a constant speed of movement of both electrodes and ensure the required amount of pressure and full contact of the parts being joined.

Spot welding - diagram

The parts are heated due to the passage of welding current in the form of a short-term pulse with a duration of 0.010.1 seconds, depending on the welding conditions. This pulse ensures the melting of the metal in the area of ​​action of the electrodes and the formation of a common liquid core of both parts, the diameter of which can range from 4 to 12 mm. After the current pulse ceases, the parts are held under pressure for some time so that the molten core cools and crystallizes.

Heating duration

Monolithic connection

The duration of heating or passage of welding current can vary from thousandths to tens of seconds and depends on the welding conditions and the power of the machine.

When welding parts made of steels prone to hardening and possible cracking (for example, carbon steels), it is recommended to increase the heating time to slow down the subsequent cooling of the metal. Welding of parts made of stainless austenitic steels must be performed, on the contrary, with the shortest possible heating time.

This is done to prevent the danger of heating the outer surface of the connection point to the temperature of structural transformations, which could entail a violation of the high anti-corrosion properties of the outer layers of the metal.

Pressure force

The pressure between the electrodes should ensure reliable contact of the parts at the junction. It depends on the type of metal being welded and the thickness of the parts being connected. The pressure after heating is important, since its appropriate value ensures a fine-grained structure of the metal at the welding site, and the strength of the connection point becomes equal to the strength of the base metal.

Electrodes, technical characteristics and features of use

• The quality of welding also depends on the correct choice of the diameter of the copper electrode. The diameter of the connection point must exceed the thickness of the thinnest element of the welded joint by 2 - 3 times.
• By pressing the parts at the moment of passage of the welding pulse, the formation of a special sealing belt near the molten core is ensured, preventing the splashing of molten material from the welding zone. As a result, no additional protection measures are required at the connection point.
• To improve the crystallization of the molten metal, the electrodes must be opened with a slight delay after the welding pulse has passed.
• To obtain a high-quality and reliable weld, the surfaces to be joined must first be prepared, in particular, cleaned of rust.
• The gap between the connection points should provide a reduction in current shunting through adjacent points. For example, for welding two (three) parts with a thickness of 1 to 8 mm each, the distance between the connection points varies accordingly from 15 (20) to 60 (100) mm.

Quality of materials

• Electrodes used for spot welding must provide strength in the operating temperature range, high thermal and electrical conductivity, and ease of machining. These requirements are met by special bronzes containing cobalt or cadmium, cold-rolled electrolytic copper and copper alloys containing chromium, as well as a tungsten-based alloy.
• In terms of electrical and thermal conductivity, copper is significantly superior to bronze and alloys, but 5–7 times worse than them in terms of wear resistance. Therefore, the best alloy for the manufacture of electrodes is considered to be an alloy of the EV type, which is almost pure copper with the addition of 0.7% chromium and 0.4% zinc. In order to reduce wear of the electrodes during operation, it is recommended to use intensive cooling with water.

Application area

At home, do-it-yourself spot welding is most often used when repairing household appliances, various works with aluminum, cables, or repairing small kitchen utensils.
In industry, spot welding is used for welding sheet blanks made of steels of various grades, non-ferrous metals and alloys of various thicknesses, intersecting rods, profile blanks (angles, channels, tees, etc.).

Advantages and disadvantages of spot welding

Like any technological process, electric spot welding has its advantages and disadvantages. The first include, first of all, the mechanical strength of spot welds and high efficiency, as well as the possibility of automating welding work. A significant disadvantage is the inability to ensure the tightness of welding seams.

Using a homemade welding machine

For welding work at home, you can make a spot welding machine assembled by yourself. Homemade welders can have a wide variety of configurations - from small portable ones to quite large ones. At home, desktop versions are usually used, which can be used for welding ferrous and non-ferrous metals.

Base of the device

The main structural part of one of these welding machines is the base transformer. To do this, it is best to use a mass-produced device, for example, OSM-1. The primary winding of the transformer can be left unchanged, but it must contain at least 200 turns. The secondary winding must be replaced with a more powerful one, using wire PEV 2/1.9 or PV Z - 50. Transformer OSM - 1

Adjusting the current value in the device is not necessary. During the welding process, it is necessary to navigate by the duration of heating and control it visually by color. To make electrode holders, you can use a duralumin rod with a diameter of 30 mm.

Electrode design

The lower electrode must be made motionless and isolated from the cheeks and mounting bolts with adhesive tape and washers. To secure the electrodes in the holders, you can use two bolts or brass washers.

Then you can take some springs, say from a folding bed. The holders with electrodes should be moved back to their original position by a spring. The spot welding machine is connected to the network using a circuit breaker rated for a current of at least 20 A.

Device control

The device itself can be controlled by a magnetic starter, which can be turned on by pressing a pedal. The transformer housing and its secondary winding must be grounded. The parts to be connected must be clamped between the electrodes. The current flowing between them heats up the metal, after which the electricity is turned off, the compression force of the electrodes increases and, as a result, a welded joint is formed.

DIY spot welding rollers

1. on the use of the GYSPOT 3502 spot welding machine, designed for removing dents using an inertial hammer, welding rivets, studs, nails, dowels, washers and bolts, removing pits and upsetting surfaces using a carbon electrode:

2. on the use of the double-sided spot welding machine GYSPOT 32D-C for repairing surfaces and connecting the car body:

3. Do-it-yourself capacitor welding with automatic supply of hardware:

Source: https://elsvarkin.ru/texnologiya/texnologiya-tochechnoj-svarki-svoimi-rukami/

Features of spot welding

Spot welding is a type of resistance welding. It differs from other types of welding in that the part is connected not by a long weld, but by one or more welding points. This is the main feature of this type of welding joint. Doing spot welding with your own hands is not at all difficult. Industry, construction and households have been using spot welding since 1877. The main thing is to study the main nuances and aspects of this type.

articles

• Concept of spot welding
• Spot Welding Technology
• Possible defects
• Advantages and disadvantages of the method
• Spot welding machine
• Spot Welding Equipment

Concept of spot welding

Resistance welding is the process of forming a permanent welded joint by heating the metal with an electric current passing through it, coming from the electrodes, and plastic deformation of the joint zone under the action of a compressive force.

This type of connection is made according to the following parameters:

• exposure time – 0.2-2.0 seconds;
• high current during operation - more than a thousand amperes;
• low mains voltage – 2-5V;
• the compressive force of the joint is up to several hundred kilograms;
• minimal melting zone allowing spot welding.

Spot welding in industry is used much more often than other types of contact methods (seam, butt). This popularity is associated with a wide range of applications and very favorable parameters of the process itself.

The strength of the bond depends on many factors. Firstly, the area of ​​the point surface, that is, the point (core) itself. Secondly, the strength of the welding current and the time it affects the parts. Thirdly, the compression forces of the parts being welded. This method is used for products of different strengths and thicknesses, for example, from 0.01 to 20-30 millimeters. As a rule, this method is used when joining parts “overlapping”.

Spot Welding Technology

The technology of this type of resistance welding is as follows: the parts that need to be connected to each other are installed in the required position and secured so that they do not move out during welding.

  Next, on both sides, current is supplied to these parts through electrodes, thereby creating a high temperature at the points of contact between the material and the electrodes - the metal begins to melt. In this case, a welding core is formed (similar to a weld pool in other cases).

Its diameter usually ranges from a few millimeters to 1.5-2 centimeters.

Low quality steel may be able to be joined without melting the core, but the joint will still be considered poor quality. Experts recommend that beginners learn and get better at these kinds of preparations.

Let's look at the step-by-step instructions and all stages of the process of joining parts:

• The preparatory stage, which includes three main aspects:
• preparing parts for fusion. In this case, the edges are sanded for adhesion to remove paint residue or oil stains. After this, they must be fixed (for this, a hand vice or clamps are used) for soldering between the electrodes;
• preparing the workplace in accordance with all norms, rules and safety requirements;
• welder training. Before starting work, be sure to wear a special suit and mask to protect your eyes from sparks that can cause burns.
• A direct welding process in which the metal melts under the influence of high temperatures created by electrodes. To do this, the master fixes the part between the electrodes and supplies a current, due to which energy is generated that melts the metal. When the core appears, the current is removed, and the parts are tightly pressed together, the welding core crystallizes (solidifies) and forms a spot weld.

Due to the simplicity of the process, in order to perform precision welding with your own hands, you do not need to be a highly qualified welder. The main thing is to understand the very essence of welding. Heating is carried out due to the pulse generated by the welding current. It melts the metal (pointwise) and forms the so-called welding core. Then the impulse disappears, and the product remains under pressure for a few more seconds. During this time it has time to harden and hold together.

Important: compression occurs at the moment the pulse is applied in order to avoid splashing.

Possible defects

If you decide to weld at home, then you should familiarize yourself with possible defects and their origin in order to avoid such mistakes. Let's look at the most common defects that can happen during spot welding:

• complete or partial lack of penetration may occur due to poor-quality electrodes, which should be replaced with new ones, low current strength, or excessive compression. This oversight can be examined in two ways: during an external inspection or when using a special device for welding control (radiation or ultrasonic;
• cracks during welding can occur due to high current or poorly cleaned products, which, due to the resulting resistance, violates the temperature regime of welding;
• Breaks at the edges during overlap welding most often occur due to the fact that the craftsman places the weld point too close to the edge of the part. That is, it is necessary to calculate so that the overlap is enough for a high-quality connection;
• internal splash is a defect in which the molten metal “crawls out” beyond the core and creates a gap between the workpieces. The main reason for this error is a long pulse or too much current, causing the core to melt excessively. To avoid this, it is important to install the electrodes evenly and control the current strength. To set up the device, it is recommended to try several points on the rough material;
• external splash is a defect in which the molten mass “climbs” out. It occurs as a result of insufficient compression of parts. That is, there is no forging moment that allows joining the workpieces.
• Indentations from the electrode are left due to the small diameter of the electrode or excessive compression. Due to incorrectly installed conductors, the melting zone may increase, causing defects;
• Burn-through is the most common mistake that novice welders make when doing any type of welding. It happens for several reasons: low compression force of the electrodes, contaminated surface of the workpiece or the tip of the conductor;
• core displacement occurs due to incorrectly installed electrodes in relation to the workpiece;
• External and internal cracks are caused by a strong current and a long pulse, or from untimely forging efforts.

Advantages and disadvantages of the method

We figured out how to do spot welding. Now let's look at the main advantages and disadvantages that characterize this type of connection. The advantages of this method include the following factors:

• in comparison with other types and technologies, this method is considered the most “cultural” and hygienic method;
• there is no need to use additional materials in the process - gases, fluxes, and so on;
• no waste and slag;
• welding without gas does not release harmful substances that harm the health of the worker;
• high level of efficiency;
• the ability to use high-performance multi-point machines, assembly and welding flow machines, units and robotic resistance welding complexes;
• high quality connections in a short period of time.

If you follow the rules and regulations for working with spot welding, then you can get a high-quality connection that is neat and reliable. According to statistics, it is much easier for beginners to learn spot welding than to get the hang of laying out different types of seams.

In addition to the advantages, there are also a number of disadvantages that you need to familiarize yourself with:

• it is very difficult to implement reliable bonding when melting different metals, or rather, almost impossible;
• when a strong impulse is applied, metal splashes;
• the complexity of the design of the welding head and the compression mechanism when welding several points simultaneously;
• complication of the design of electrodes and their operation, especially in multi-point welding.

Spot welding machine

The spot welding machine looks like this and includes the following parts:

• current transformer;
• welding clamp;
• turning on and off relay;
• electrode compression mechanism;
• regulator of current supply strength and duration.

Those devices that are intended for home and household use may not have a power regulator. Then the master himself regulates the compression force of the conductors and the time of exposure to the part, based on his experience and relying on his skills.

During operation, it is very important to monitor the condition of the electrodes. If their diameter increases, then the level of heat at the site of impact on the core decreases. The diameter of the electrode must match the diameter of the weld point. Typically, conductors are made of heat-resistant materials - copper, bronze. But under the influence of high temperature, over time they lose their shape, so it is important to change them in a timely manner.

Spot Welding Equipment

Considering the equipment, the following classification can be made:

• by method of movement - mobile, suspended, stationary;
• according to the method of mechanization - manual and automatic;
• according to the location of the electrodes - parallel and opposite each other.

For production purposes it is necessary to use high-quality equipment. Homemade spot welding, which you can make yourself from any electrical appliance, is also perfect for home use. The video below explains in detail how to build a welding machine yourself.

Source: http://home.nov.ru/osobennosti-tochechnoj-svarki/

The best way to weld a car body

The car body is constantly exposed to the destructive effects of moisture, dirt, and chemicals that are sprinkled on the roads in winter. The problem is aggravated by vibration loads. Therefore, even with careful care, the appearance of cracks and holes eaten by corrosion is inevitable. There is only one way out - welding the car. However, this does not mean that you need to go to a car repair shop. Minor damage can be repaired by welding the car body yourself.

Features of car body welding

For car body repairs, you will need high-quality welding equipment. The work is carried out in a room where it is possible to connect energy-intensive equipment to the electrical network.

A highly qualified performer is required, as welding of thin metal will be required. A universal method for repairing a car body has not yet been invented, therefore, depending on the location and nature of the damage, different technologies are used.

Connections are made by gas, manual, semi-automatic welding.

Wings and sills are most often repaired by spot welding. The lap joint is used to restore the integrity of the load-bearing elements. Butt welding is used when replacing damaged elements.

Which welding method is better to weld a car body?

If you have a simple welding machine, repairs are done manually using ordinary electrodes. However, the applied seams are rough and there is a high probability of burning through thin metal. Therefore, this method is recommended to carry out repairs in places not visible from the outside. For example, under the wings, in the trunk, underbody.

High-quality welding of the car body is performed semi-automatically. With its help, even a beginner can join metal 0.8 mm thick without the risk of burning. If carbon dioxide is replaced with argon, welding of stainless steel and aluminum will be available. Therefore, when thinking about which device to choose, preference should be given to a semi-automatic device.

Preparatory work

Before welding, dirt and dust are removed from the surface and cleaned of corrosion. You can use a gas torch to clean hard-to-reach places. It is impossible to reliably weld rusty metal.

When preparing a semi-automatic machine, you need to make sure that the guide channel corresponds to the diameter of the selected wire. Depending on its size, the required welding tip is installed. There should be no metal splashes in the device nozzle. If they are detected, they are cleaned with sandpaper.

Before repairs using a welding inverter, you must check:

• Is the electrode securely fastened?
• is there any damaged insulation on the cable and holder;
• cable fastening strength;
• proper grounding of the device.

How to weld a car body with a semi-automatic machine

To weld a body with a semi-automatic machine, you need to prepare a wire with a diameter of 1 mm, coated with copper, coarse-grained sandpaper, a pressure-reducing reducer, and a 20-liter carbon dioxide cylinder. The work is performed in the following sequence:

1. The repaired areas, cleaned with sandpaper, are pressed tightly against each other. It is possible to use clamps, bolted connections, and self-tapping screws.
2. On the front panel of the machine, switches set the welding current value and wire feed speed.
3. A reducer is installed on the gas cylinder and connected with a hose to the burner.
4. The nozzle is unscrewed from the burner with pliers, and the tip is removed.
5. A spool of wire is inserted into the apparatus. Its end is inserted 15 - 20 cm into the supply channel.
6. A tip is put on the wire and a nozzle is installed.
7. Switches set the polarity of the current so that the holder is connected to the plus and the burner to the minus. For uncoated wire, the polarity is reversed.
8. After connecting the device to the power supply, the holder with the burner is brought to the place to be repaired. When you press the button on the holder, the supply of wire and carbon dioxide is turned on.
9. To weld a long seam and not overheat the joint, the parts are first tacked in 3 - 4 places. Then, at intervals of 7 - 10 cm, stitches 2 - 4 cm long are applied.
10. After a five-minute break, when the seams have cooled, the gaps between them are boiled.

Source: https://svarkaprosto.ru/tehnologii/chem-varit-kuzov-avtomobilya

Spot welding technology and answers to the question

Spot welding is most common in industrial production due to the high quality of welded points or seams. With its help you can make a lot of welding joints in a short period of time. Most often used in automotive, aircraft and shipbuilding. Often used for assembling agricultural machines and units for them. Collect batteries. It is in the production of batteries that spot welding shows its indispensability.

A little about welding work

With a properly constructed welding process and full compliance with technical standards and requirements, point connections are incredibly strong and of high quality. Thanks to the strong heating of the metal and the pressure that spot welding creates, joints can acquire a strength close to the base metal that the machine is welding.

In this article, we will help you understand resistance welding technology and answer the question of how to make spot welding, tell you about surface preparation, choosing a machine, electrodes and other components. We will describe the welding process step by step and point out possible errors and defects that may occur. We will explain what polarity is and what it can be, and also tell you how to work with thin materials.

Stages of work

Conventionally, spot welding is divided into three steps, after which you get a ready-made homemade contact point that holds two workpieces together. To create subsequent points, the process is repeated in the same order.

Let's get started using the following scheme:

1. Fixing the part in the clamp between the electrodes of the device. A certain specified pressure is immediately applied to the part, which causes deformation due to micro-irregularities.
2. After tight fixation and the necessary compression, an electrical impulse is supplied. Subsequently, the metal heats up to extreme temperatures and begins to melt at the point of contact of the electrodes, and the workpieces are joined. The liquid phase of the metal binds, forming a solid compound that becomes as close as possible to the strength of the material itself.
3. The pulse stops. The welding site is cooled and the final crystallization process occurs. It is necessary to remove increased compression after a certain period of time, since during the cooling process the metal gains a finer-grained structure during compression. It’s even better to increase the compression, so the effect will be even stronger and the connection will be more uniform.

We produce various connections

If it is necessary to create many welding joints, we repeat the entire cycle. If there is a need to make a lot of such points, then you can use a machine in which resistance welding occurs at several specified points at once. This way, you will save time and be more productive.

Defects and errors in resistance welding

Spot welding is a rather complex scheme, in which there are many nuances and features. Very often, beginners encounter the following errors:

• Incorrectly selected power.
• Insufficient or too long period of pressure on the workpiece.
• The electrode is not suitable for the metal being welded.
• The operating diagram of the welding machine itself is not suitable for the conditions of the required welding process.
• The surface for resistance welding is not prepared correctly.

Defects resulting from incorrect resistance welding:

• Insufficient degree of melting, which contributes to incorrect formation of the core of the point.
• Indentation due to contact pressure is too deep.
• The edges of the overlap may tear if the contact weld point is very close.
• A change in the properties of the metal after too much heating. For example, deterioration in battery performance.
• Through burning of metal.
• Formation of internal cracks or voids.

When working with thin metals or when assembling batteries, you should carefully select the power and pressure applied to them. Since with too much power there is a risk of through burning and then such a workpiece becomes unsuitable. If the pressure is too high, dents and various surface defects can form.

When working with aluminum workpieces, you should not overheat them for too long, as this will lead to a change in their anti-corrosion properties and increases the risk of surface deformation.

Welding polarity

Polarity can be straight or reverse. Using straight polarity, a minus is connected to the electrode, and a plus is directed to the workpiece. If you use the reverse, then the plus and minus change places. The process of occurrence of the cathode and anode spots depends on the polarity connection scheme to the device. The anode appears at positive polarities, and the cathode, on the contrary, at minus.

Summarize

Spot welding is a technically complex process that requires careful preparation. You should know all the intricacies of such welding, from the choice of welding machine to the required pressure that is applied to the workpiece. Then your work will be done efficiently and for a long time. Adhering to all the rules, with the help of a contact welding machine you will make all your ideas related to metal and its connection.

Source: http://GeneratorVolt.ru/invertornyjj/tochechnaya-svarka-svoimi-rukami.html

Basic nuances of working with spot welding

04.04.2018

How to determine welding quality

The spot welding method is in great demand in modern industry. Approximately half of all metal structures today are made using this method.

Spot welding is used in almost all industries, mechanical engineering, automotive industry, aircraft manufacturing, construction work, manufacturing of various household items, etc. This is explained by the simplicity and versatility of this method.

However, there are some nuances that need to be taken into account when working with spot welding so that the quality of the products remains at a high level. It is these nuances that we will talk about in this article.

Basic methods for performing SPOT welding

This method is ideal for welding metal sheets or assembling cabinet products. In this case, the thickness of the material that can be processed by this method should be in the range of 0.1-6.0 mm. There is also professional industrial equipment that allows you to work with steel sheets up to 2 cm thick.

There are several most popular spot welding methods that are used in the work. The main difference between them is the supply of electric current to the surface to be welded. You can consider these methods with examples.

Example No1. It is required to connect two metal parts. There are no difficulties, so it is most convenient to use the two-way method. The elements need to be clamped between the electrodes, while applying some force. In this case, electric current is supplied from both sides at once.

Most often, this option is used when connecting small parts of metal structures, if the connection is open or flanged. The advantage of this method is the excellent quality of the weld, which is obtained thanks to the double-sided clamping. The result is a strong connection. The disadvantages include the limited size of parts that can be connected in this way. The problem is that the parameters of the products are limited by the length of the pliers used to clamp the material.

Example No2. The connected elements are part of a closed structure. It will not be possible to supply current from both sides. In this option, you will have to work using the one-sided welding method.

This method can be used when welding parts of any size. The dimensions of the metal structure do not affect the quality of work, however, the depth of the seam is still limited, since the current is supplied only from one side. Professionals use a special copper gasket, which must be installed in the place where the electrodes will be. This spacer helps make the connection stronger.

When welding on one side, you need to pay attention to the thickness of the elements being connected. If one of them is thicker than the other, then electric current is supplied to the thicker part. When welding, the electrodes should not be placed too close to each other, otherwise the metal may spatter.

Advantages of using the one-way method:

• high performance;

• relatively low energy consumption;

• low deformation of the product (the connection is made symmetrically).

The downside is that it is not always possible to clamp the elements with the required force, so the quality of the connection is slightly lower than when using the two-way method.

Welding modes

Spot welding equipment can operate in “hard” and “soft” modes. The hard mode has a high current strength and a short period of operation, while the soft mode has a low current strength and a longer welding time.

Main factors of work:

• The clamping force is needed not only to ensure that the elements contact each other, but also to deform them, which prevents metal from getting into the gap at the joint. The force depends on both the thickness of the elements and the type of metal;

• the thickness and type of metal also affect the required current;

• welding time affects the size of the joint;

• The diameter of the electrodes used determines the size of the connection point.

Before work, it is important to correctly select all these parameters for each specific case. Even a slight deviation will negatively affect the quality of the connection.

As a specific example, consider the connection of low-carbon steel elements. This material is most often used in the manufacture of industrial metal structures and fasteners.

If you plan to weld parts with a total thickness of up to five mm, then a cycle with one electric current pulse and a constant clamping force is optimal. To weld thicker parts, several pulses will be required.

Possible problems during operation

The quality of the resulting joint depends not only on the method used, but also largely on the material from which the welded elements are made.

In enterprises where it is often necessary to work with materials that conduct heat well (copper, aluminum billets), other nuances that affect the quality of the connection must be taken into account. We must not forget that parts made of such metals quickly remove the supplied thermal energy, so to weld them you need to use high-density electric current (up to 300 A/sq.mm).

Another problem is that aluminum particles stick to the electrode during welding. To prevent this, you need to carefully and thoroughly clean the surface of the workpiece before working. Spot welding aluminum alloy products is much easier than welding pure aluminum parts. This is caused by the lower resistance of the material.

In order to qualitatively connect aluminum parts using spot welding, you need to know the exact value of the current strength and operating time. Even small deviations from the established parameters will cause defects, which will certainly affect the quality of work. Poorly welded products differ several times in strength from those made in compliance with all the rules.

How to determine welding quality

If the connection was made correctly, then there should be a crater on one of the elements, and on the other there will be the “core” of the connection itself. If at least one of these signs is not present, then the welding was done poorly. In this case, the work must be done again, increasing the force of pressing the parts against each other or the welding time.

The main indicator of joint quality is the size of the weld core. The optimal diameter of the connection point should be approximately three times the thickness of the smaller part, with an error of 20-80 percent. If the core is less than this indicator, then the connection is not made well enough, there are parts that are poorly welded together. If the diameter is too large, metal has spilled out between the elements.

A high-quality connection is the key to a long service life of the manufactured element. Welding parts when assembling metal structures is one of the most critical stages of work; the strength and reliability of the finished product depends on it.

Source: http://s-awangard.ru/articles/osnovnye_nyuansy_raboty_s_tochechnoy_svarkoy/