Do-it-yourself spot welding: how to make a home-made apparatus for contact welding. Homemade spot welding Simple timer for spot welding

Once I was puzzled by the creation of spot welding with my own hands to connect 18650 batteries. First, a 555 timer was assembled, then on a pic16f628a microcontroller. A self-made firmware was written for him, control of the encoder with pressing, from 0.01 sec to 10 sec and up to 10 pulses. But this spot welding machine was sold a long time ago and I needed to weld 18650 batteries with something. To do this, this timer was ordered on aliexpress for $ 11.14 or about 700 Russian rubles.
Arrived a little less than a month.
Let's see what he is.

What is contact welding?
We take a large trance so that the traffic jams in the apartment do not knock out (from the microwave, for example). We cut off the secondary, the primary remains at 220. We choose a shunt. Instead of thousands of turns of the old secondary, we stuff 2-5 turns of thick wire. For welding batteries, 3-5 turns with a section of 35 mm are possible. For thicker plates and wire 2 turns with a section of 70-120mm. We finish thick wires. We attach electrodes to the ends of the wire, depending on the task. And if you apply 220 volts to the primary trance, then a current will flow in the secondary in the region of 1000A, which heats up the place of contact of the electrodes with the metal. If it is thick iron or wire, then the shutter speed is usually long, a few seconds, and you can simply apply 220 volts to the trance through an automatic machine or any other manual method. If you cook round lithium batteries, then there are thin plates of 0.1-0.3 mm and very short shutter speeds are needed, while they must be the same for repeatability of results. Burning batteries is unacceptable, depressurization of a can - a can to be thrown away. Here, to replace an automaton or a button, in order to accurately set a short shutter speed, this timer is used.
For those who have little idea what it is and what it is eaten with, you can read:

Packed well, a cardboard box and inside a board under several layers of polyethylene foam. If you play football with a box, then nothing will be damaged.
Inside board with good quality.

Controller microcircuit from STMicroelectronics STM8S003F3, Schmitt trigger 74hc14d, optocoupler moc3021 and pc817, triac BTA41600B, stabilizer lm317k diodes and other piping.

Power triac it is desirable to fasten to the radiator through thermal paste. You can screw it directly onto the contact welding body, but then this must be done through an insulator. Mica gasket and insulator on the fastening screw. The board is divided into two parts by a white strip - the part that is closer to the triac is under a dangerous voltage of 220 volts. The Chinese characters near this band are just talking about it. Most of the resistance welding board is low voltage and safe.

Deciphering the inscriptions near the LEDs in order from the knobs of the regulators:
- State. Lights up when powered.
- Status. Flashes normally and lights up when DC voltage is connected. When powered by constant voltage, the board will not work.
- Pedal. Goes out when the pedal is pressed.
- Trigger. It shines while the triac is open and welding is in progress.

The remote display of the timer for spot welding contains several LED seven-segment indicators, a TM1650 seven-segment LED driver, and a harness to it.

For contact welding, in addition to this timer board, you need:

- Supply transformer for alternating voltage 9-12v. From a constant payment does not work. Does not see network pulses. The second LED from the left should blink, it does not blink from a constant. A large transformer power is not needed, only logic is powered from it. Cell phone charger won't work. The same seller has a ready-made suitable trans. You need to choose the 220v version, it costs less than $ 6 or 370 rubles.
- Pedal or button. Something that will close the contacts on the board. Normally open.
The finished pedal from the seller costs about the same.
- Contact welding transformer. The power part is. Well, if you are interested in such a board, then you probably know what it is. This is a transformer with a primary winding for 220V and a secondary winding for low voltage (1-6V) and high current (100-1000A). This current cooks.
This timer switches the primary, that is, it gives voltage to the primary winding of the welding power transformer. Similarly, instead of this timer, you can simply put a switch - when the switch is turned on, welding will cook while the switch is on. But for welding 18650 batteries, a very short pulse (0.01-0.1 sec) is needed, otherwise the metal of the battery is burned through. You also need the constancy of the results, that is, all exposures of spot welding must be strictly the same. Such conditions - exposures in fractions of a second and repeatability of exposures - cannot be realized manually, so I bought this spot welding timer.
The same seller has a pedal and a trance, a power transformer for spot welding can be taken from a microwave oven or a larger one. The transformer is heavy, it is expensive to order from China. You can look for a non-working microwave or an old one at a flea market for little money. Or ask at home appliance repair shops.

Timer operation:

We connect the power transformer (change 9-12V) and the pedal to the corresponding terminal blocks, the wires going to the microwave power transformer are soldered. There are two knobs on the board - the left one for adjusting the welding time delay, the right one for adjusting the current. On the remote display you can see the numbers, similarly showing on the left - the time delay and on the right - the current. The welding time delay is adjustable from 1 to 50, 1 is one network period, that is, 0.02 seconds. That is, the timer can set shutter speeds up to 50 * 0.02 = 1 second. The welding current is adjustable from 30 to 99.

When the pedal is pressed, the microcontroller monitors the voltage in the 220 volt network, at the peak or bottom of the sinusoid it gives a signal to the triac. While the thyristor is open, current flows through the primary of the welding transformer and welding is in progress. The board works as an electronic switch, a key.
With a time value of 1 on the display and a current value of 99, the timer turns on the triac for 20 ms, for one network period. If you need less, then you can reduce the current with the right regulator and the controller will open the triac not to a full sinusoid, but only to a part of it.

I took oscillograms from the secondary winding of the welding transformer at different current values and shutter speeds, they can be seen in the photo below:

my oscilloscope is not of super quality, amateur, so I give a photo from Ali's reviews - how it should look on the oscilloscope screen:

The point of adjusting the current is that if the transformer is too powerful for welding 18650 batteries and other similar ones, and the time delay of 0.02 seconds is too long and burns through the plate or batteries, then you can still lower the current - the pulse will become weaker and the batteries will not burn through.
I tried to weld a nickel plate at a shutter speed of 1 and currents from 30 (rightmost) to 99 (to the left), the result is clearly visible. This can be seen in the photo below.
Plate 8 mm wide, 0.15 mm thick.

The last two welding tests I tried to do at a slow shutter speed and low current. With a shutter speed of 10 and 30 and a current of 30, the plate heats up, even changes color, but does not weld. For welding thin nickel plates, a short high current pulse is better than a long low current pulse.

The last points on the left, one of them is through, were made just at shutter speeds of 10 and 30 and a low welding current value of 30.
All this can be clearly seen in the video version of the review below:

In general, I liked the resistance welding board, there are 50 time settings from 0.02 sec to 1 sec, and at the same time another 70 current gradations. The board controller monitors the mains periods and starts the timer at the maximum or minimum period of the sine wave, which guarantees the same welding results and excellent welding repeatability of 18650 batteries.
I recommend this timer for creating do-it-yourself spot welding from a microwave oven.
If you need a more powerful welder, a spotter for welding cars, then the seller has the same timer with a more powerful 100A triac, it will be cheaper than buying a 100A triac and a board separately. I plan to buy +103 Add to favorites Liked the review +101 +161

A spot welding device can be useful when assembling products from a thin steel sheet from 0.1 to 4 mm, for working with metal at a service station when straightening dents, welding small parts in a garage. Industrial designs of devices are not cheap, but you can assemble a resistance spot welding device with your own hands practically from improvised means. The only thing you have to tinker with is finding an electrical transformer. In this review, we will talk about the device and the principle of operation of the device, the schemes for assembling the device, and also offer several ideas for creating a home-made tool.

Read in the article:

Contact spot welding - what is it and where is it used

Spot welding is a type of thermomechanical welding. The process of working on it includes the following steps:

Align parts in desired position.
They are pressed between the electrodes of the apparatus, the latter act as a clamping mechanism.
At the docking point of the clamps, a discharge is applied, heating occurs, deforming under the influence of current, and they are firmly connected to each other.

Masters are also attracted by the fact that devices of such a plan can be assembled literally from trash, and the welding process is as neat and automated as possible. Very often, such devices can be found at service stations. Do-it-yourself spot welding for welding a car allows you to even out dents without the need to dismantle body elements, as well as repair hard-to-reach structures.

DIY spot welding for car welding:

Some industrial designs are capable of performing up to 600 operations per minute. The tool is used for riveting metal structures up to 4 mm. This type of soldering is used when welding fittings, flat and corner meshes, as well as frames. In this way, it is convenient to connect intersecting rods or rods with flat elements: a sheet, a strip, a channel and other structures.

Spot welding can solve a number of complex problems:

Provides point and careful connection of products without overheating of the excess surface.
Able to connect metals of different configurations: ferrous and non-ferrous.
Perfectly fastens profiles on bends, as well as intersecting metal workpieces, especially in hard-to-reach places.
Welding points are characterized by high strength and resistance to further deformation.

The principle of operation and the device of spot welding machines

After the metal plates to be welded are clamped by electrodes, a short-term pulse of electric current of high strength is applied to them. The pulse time is selected depending on the characteristics of the two metals being welded. Typically, the discharge lasts from 0.01 to 0.1 fractions of a second.

When the pulse passes through the metal, the parts melt and a common liquid core forms between them, and until it hardens, the surfaces to be welded must be kept under pressure.

The pressure on the parts is removed gradually, if it is necessary to forge the sheets to a deeper thickness relative to each other at the final stage, the pressure increases, this will achieve maximum uniformity of the metals at the welding site.

Important! To improve the quality of welding, it is important to pre-treat the surfaces of parts to remove oxide film or corrosion.

Types of contact welding

Spot welding is one of the most popular types of resistance welding at home. However, there are two more types of welding in this category, which are used most often in factories and in specialized metalworking shops.

Seam contact welding. The principle of operation of seam contact welding does not differ from spot welding. The tongs we are used to are replaced by special copper rollers. Welding in this case occurs pointwise, but at a certain distance, and the welding seam resembles a path from separate welded sections.
Seam contact welding is used for welding seams, both on circles and on elongated large-sized sheets.
Butt contact welding. This type of welding is characterized by a larger area of one-stage welding. An alternating pulse electric current is applied to the workpieces to be welded, which are in contact at the joints. Thus, during the pulse, heating occurs over the entire area of contact, it is also called the cross-sectional area. This process is completely mechanized, so it is not suitable for self-assembly at home.
Scheme of a butt welding machine
Capacitor welding. Capacitor welding works on the same principle. It is used in those areas of industry where miniature parts with a thickness of 0.5 to 1.5 mm are fused. This type of welding is used in the field of electronics and instrumentation. The advantage is that it leaves virtually no marks and does not burn through the metal.
Homemade capacitor welding machine

Do-it-yourself resistance welding from a microwave

Many craftsmen are wondering how to make a welding machine out of a microwave. In fact, the most difficult thing in this process is to disassemble and prepare the transformer.

Options for a homemade microwave spot welding machine:

What tools are needed for the job

For work, we need the following tools and components:

The transformer that we dismantle from the microwave. Depending on the power of the tool, two or three can be used.
Thick copper wire.
Electrodes (copper or copper-plated), which we will use in the future instead of clamps.
Lever for manual clamping.
Base for welding machine.
Cables and winding materials.
A set of screwdrivers and a grinder for opening the transformer.

Important! For domestic use, electrolytic copper and its mixtures with the EV marking are suitable.

How to prepare for operation the power part of the installation - transformer

The transformer is the heart of the device. The easiest way to get it is to take it out of an old, but still working, microwave. The minimum output power of the device must be 1 kW. Such power will be sufficient to weld sheets up to 1 mm in contact method.

For us, it is not the transformer itself that is of value, but its magnetic circuit and primary winding. The secondary winding must be carefully dismantled.

Extraction from the microwave and the creation of a resistance welding transformer

In order to remake it to our needs, it is necessary to carefully open the housing along the weld seam with a grinder and get to the magnetic circuit.

Next, we begin the procedure of winding the secondary winding. Most often, a stranded wire with a cross section of at least 100 mm 2 is used for these purposes. It is enough to make 2-3 turns, since the voltage in this type of welding is not high. It is important that the insulation of this wire is heat resistant.

Combining transformers to obtain a device of greater power

However, there are times when the power of one transformer is not enough and you have to connect several devices in series. In this case, the wire is wound in turn through each coil, and the number of turns on each of them must be the same, otherwise you risk getting zero voltage due to the resulting antiphase.

Important! The more powerful the transformer, the stronger the voltage surge in the mains can be when the device is turned on test

Determining the correctness of serially connected pins

For convenience, identical wire leads are usually marked. But if this is not the case, then they can be determined by connecting the primary windings of two transformers in series. Next, check the voltage with a voltmeter.

If the voltmeter shows readings that are equal in value, but opposite in sign, then it is necessary to change the sequence of connecting the secondary windings of the transformer. With the correct assembly of transformers in a circuit, the device gives a double reading of the voltage received from the two secondary windings.

How and from what to make electrodes for resistance welding

Spot welding electrodes come in a variety of shapes and configurations. The smaller the workpiece, the sharper the tip of the electrode.

The shape of the electrodes can be straight, curved, with a flat tip or sharp. But most often in practice, electrodes with cone-shaped tips are used. In order to prevent the device from oxidizing, the electrodes are connected to the working wires by soldering. However, they can still wear out during work, so they need to be sharpened (by analogy with a pencil).

The electrode performs several functions at once:

Clamps workpieces.
Carries out a current discharge.
Dissipates excess heat.

For the correct manufacture of electrodes, we turn to GOST (14111-90), which already specifies all possible diameters of these elements (10, 13, 16, 20, 25, 32, 40 mm). These are acceptable and working indicators, which are not recommended to deviate from.

Important! The electrode diameter must be greater than or equal to the working wire diameter.

What does the resistance spot welding control circuit consist of and how does it work?

In a welding machine, a very important parameter is the time of exposure to the metal. The following elements are used to adjust this indicator:

Electrolytic capacitors C1-C6, with a charge voltage of at least 50 volts. The capacitance of the capacitors is: for C1 and C2 - 47 microfarads, C3 and C4 - 100 microfarads, C5 and C6 - 470 microfarads.
P2K switches with independent fixation.
Buttons (on the KH1 diagram) and resistors (R1 and R2). The contacts of the KN1 button must be: one is normally closed, the other is normally open.

To install the switch, you must select the primary winding, or rather, its circuit. The fact is that the secondary winding circuit has too much current, which can cause additional resistance and welding of the contacts.

It is also necessary to create a sufficient compression force, which is provided by the lever. The longer the handle, the stronger the pressure between the electrodes. Do not forget that it is necessary to turn on the equipment with the contacts brought together, otherwise sparking and burning will occur.

Advice! The clamping lever can be equipped with a durable rubber ring. It will ease the load force, and the elastic band will fix it.

Make sure that the resistance welding equipment from the microwave is securely fixed on the table, as force can cause it to fall and fail. For a home-made welding machine made by hand from a microwave oven, it is necessary to provide a cooling system. A PC fan can be used for this purpose.

Article

Resistance spot welding has a number of advantages - this is the ability of the seams to withstand significant mechanical loads, the low cost of equipment, the ability to create an automated process, etc.

A welding machine of this type is relatively easy to assemble, which is also its advantage and makes it possible to make the machine yourself. The only drawback of this type of welding is the inability to create a sealed weld.

How to make a transformer for spot welding

The main component of the welding machine is the transformer. Ensuring an increased indicator of welding current is achieved by a large transformation ratio. The transformer must have a power of at least 1 kW. For this purpose, transformers from microwave ovens with sufficient power are excellent.

It is easy to find such a transformer, and a welding machine of this type can be used to weld 1 mm steel sheets. For the manufacture of an apparatus with greater power, several transformer installations can be used.

The transformer contains the primary winding and the magnetic circuit, which you will need. The secondary winding should be cut with a hacksaw or any other tool. In this case, it is very important to prevent damage to the magnetic circuit and the primary winding. If the transformer has current limiting shunts, they must be removed.

Having removed all unnecessary (in this case) elements, a secondary winding (new) should be created. In order to provide a large current, a copper thick wire is required, the diameter of which should be at least 1 cm. Three turns will be enough, make sure that the output is approximately 2 V.

More powerful do-it-yourself welding will turn out if you connect two (or more) transformers together. The main thing at the same time is to take into account the capabilities of your network, otherwise, including spot welding, you will have to deal with various troubles when lights flash, fuses work, etc.

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Do-it-yourself spot welding assembly and electrode manufacturing

Electrodes are a very important element in welding, so they should be made taking into account all recommendations. For the manufacture of these elements, you will need copper rods. It is better to choose rods of large diameter (at least the thickness of the wire). If your plans include making a welding machine that has a low power, you can use tips that contain powerful soldering irons.

Depending on how often resistance spot welding is used, over time the shape of the electrodes is lost. After some time of use, they can be sharpened, and if necessary, replaced with new ones.

It is desirable that the wire that goes from the electrodes to the transformer be of a minimum length and with a minimum number of connections. The fact is that at the junction, power is partially lost. Copper tips should be put on the ends of the wire and the wire and electrodes should be connected through them.

Each tip should be soldered to the wire. Such measures are necessary for the reason that during welding, copper contacts can gradually oxidize. This explains the significant loss of power and failure of the do-it-yourself welding machine. Soldering the wire and the tip is a rather difficult task, due to the large diameter. For this purpose, you can use tin-plated solder tips, which can be purchased at any specialized store.

The reason for the additional resistance that spot welding can cause may be in the non-soldered connections of the tips to each of the electrodes. However, this drawback cannot be corrected, because the electrodes must be periodically removed for sharpening or for the purpose of complete replacement. But here it is worth noting that these connections are quite easy to clean from oxide, unlike stranded wires that are crimped with a ferrule.

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Spot welding and how to manage it

Spot welding is controlled by a switch and a lever. In order to ensure proper contact of the parts that are being welded, it is necessary to provide sufficient compressive force between the electrodes.

If it is necessary to weld thick sheets of iron, it is required to use more powerful contact spot welding (with a greater compression force between the electrodes). It is desirable that the lever is not short, while it must be strong enough. The welding machine must have a massive base, make sure in advance that it can be fixed to the table.

For a large clamping force, which do-it-yourself resistance spot welding should have, both the lever described above and the lever-screw clamp in the form of a screw tie located between the base and the lever itself can be used. If desired, you can use other methods, but they may require special equipment.

If you decide to use a lever clamping mechanism, it is better to choose a lever for mounting the switch. In this case, during operation, switching on the current and operating the lever can be performed with one hand. Thus, holding the parts to be welded will be as convenient as possible.

is a very useful skill.

If any inverter models are available for sale, a person planning to weld at home has a choice - to purchase a ready-made device or make it yourself.

In this article, we will look at what it is, show a training video on contact welding, give step-by-step instructions on how to independently carry out contact welding and how you can make a home-made contact welding machine with your own hands from a microwave and used car batteries.

Owners of private houses, motorists and not only need welding.

At home or in a small workshop, using a welding inverter to connect metal parts is quite possible.

The principle of its operation is that with the help of an electric current, the metal is heated, melted and solidified, forming a weld.

To fix and prevent shifting, the parts to be welded are compressed by means of electrodes through which an electric current is supplied.

To work at home, powerful power sources will be required, which affects the overheating of household wiring.

Before carrying out work, you should check the quality of the wiring and, if possible, replace it with a new one.

In resistance spot welding, two workpieces are joined along the surface of adjacent edges.

This technology is suitable for thin sheets, small parts and metal rods up to 5 mm thick.

Three types of surface connection are used: with the help of resistance, intermittent reflow or continuous reflow.

For resistance welding, prepared workpieces or sheets are fixed and heated by welding current until melting.

The method is applicable to the following metals:

low carbon steel;
non-ferrous metal;
compounds of copper with brass and steel.

Due to stringent requirements for temperature conditions and the absence of impurities at the joints, this method is rarely used.

With continuous melting of the workpiece, pliers or other clamps of the part are used, they are connected with the current turned on, after melting the edges of the parts to be joined, precipitation is carried out and the current is turned off.

This method is most suitable for pipes with thin walls. It is possible to connect workpieces of different structure.

The main plus is the high speed of work, a serious minus is the leakage and waste of metal along the weld.

Intermittent melting occurs when alternately dense and loose contact of the workpieces during the switched on current.

Clamping pliers ensure the closing of the welding line at the point of contact of the workpieces until they reach a temperature of 900-950 degrees Celsius.

This method is used if the initial power of the device is not enough to ensure continuous reflow.

Thus, resistance welding consists of the following steps:

Preparation of surfaces for joining (cleaning, leveling the contour).
Aligning the edges and fixing the workpieces under the welding machine.
Supply of electric current.
Heating and melting under its action of the edges of parts.
Draft and power off.

The methods of resistance welding discussed above differ in the fixation of workpieces and the supply of current; in general, the welding process is similar.

For home resistance welding, you can design a home-made apparatus.

Its main working units are a welding clamp and a voltage supply unit on capacitors, to the low-voltage winding of which an electrode is connected.

The second wing of the clamp serves as a support or is connected (depending on the attachment of the apparatus) to a workpiece that has a larger size.

Video instruction for resistance spot welding is presented above.

microwave welding machine

A device for spot welding can be made independently using a microwave transformer.

In the manufacture of such a welding device, you need to weigh what will be cheaper - to buy an inverter or do it yourself using a transformer from an unnecessary microwave oven.

The transformer is the most expensive part of our future home-made device. All other consumables - wires, a casing and a base on which the mount will be made, will be in almost any workshop.

We need a transformer power of at least 1 kW. With the help of a welding machine using such a transformer, it is realistic to do spot welding of sheets up to 1 mm.

Doubling the power of the transformer will allow you to work with sheets up to 1.8 mm thick. The transformer of a modern microwave oven can be up to 3 kW.

If necessary, two or three transformers can be used. This circuit will increase the power of the supplied current.

It is required to remove the transformer from the metal casing and get rid of shunts for current limiting and secondary winding.

The microwave oven uses high voltage, so there are fewer loops on the primary of the transformer than on the secondary.

This results in a potential difference. Our task is to change the secondary winding, adapting it to the purposes of resistance welding.

Thoroughly clean the transformer from remnants of secondary wiring and shunts, if necessary, use a metal brush or a long narrow object (for example, a screwdriver).

Only the primary winding will remain intact, we will do the secondary again.

Given the high voltage, we take stranded electrical wiring with a cross section of at least one square.

If a circuit of two or more transformers is used, then the conclusions of all secondary windings from them are reduced to one.

When a single transformer is used, the housing for it can be adapted from the same microwave oven, reducing the width and length.

For a transformer system, the casing can be made of iron sheet, provided with an insulating layer. The secondary winding is formed by 2-4 turns of wire.

However, the thick layer of insulation in which the wire is packed will not allow it to be bent around the coil.

Therefore, we take the wire out of the insulation and we can use ordinary flexible electrical tape as an insulating coating.

With two or three loops of wire, we will achieve a voltage of 2 watts.

To supply current to the welding site, we create a lever mechanism, one lever of which is rigidly fixed on the main surface (for the convenience of resistance welding, a transformer in the casing can also be fixed on the same surface with the help of clamps).

The second lever, when lowered, will squeeze the parts. We introduce the switch into the primary winding circuit and install it on the upper lever.

This will allow you to simultaneously compress the part and start the current. In this case, pliers are not used, and the tips themselves are pre-soldered with wires to prevent oxidation.

When spot welding, we will use copper rods with a thickness greater than the diameter of the wire. In the process of work, they need to be sharpened and, if necessary, changed.

In the course of work, the part is clamped with the help of levers between two electrodes and a current is started.

Battery welder

When welding with an electric welding machine, household electrical networks suffer a significant overload.

Prolonged contact welding can lead to melting of electrical wiring or failure of household appliances. The welding machine can be powered from an autonomous power supply.

In this capacity, a portable station (a generator running on gasoline or diesel) can act, which is very expensive, or you can make a power source yourself.

You will need several car batteries, used ones are quite acceptable. Ideally, if they are of the same capacity.

Then the current strength will be calculated as 1/10 of the battery capacity. If devices of different capacities are assembled, then the smallest capacity will be needed for the calculation.

Let's make a chain of series-connected batteries, fastening the corresponding "pluses" and "minuses" with wires and wire cutters, or, even better, lighter wires.

You can also use any pliers. From the free "minus" we bring the wire to the electrode, which we clamp in tongs, and from the free "plus" to the working plate, it is recommended to put a rheostat in the circuit.

The resulting car battery spot welding machine is ready and can be used away from a power source.

You can make a homemade device for charging to it. This option can be successfully used by experienced welders and is not recommended for learning welding skills.

As shown in the article, homemade spot welding is quite affordable. We considered the options and technology of resistance welding.

The information provided will help you get the basic skills of contact welding and ensure the creation of a welding inverter for spot welding on your own from improvised means.