home Exterior decoration Scheme and description of contact capacitor welding for batteries. Scheme and principle of operation of homemade capacitor welding Do-it-yourself capacitor contact welding for batteries

Scheme and description of contact capacitor welding for batteries. Scheme and principle of operation of homemade capacitor welding Do-it-yourself capacitor contact welding for batteries

This type of welding refers to the spot method. It is convenient when you need to weld small parts to each other, or one small one. Capacitor welding is mainly used to work with non-ferrous metals.

As soon as it became possible to carry out precision welding at home, the method began to gain popularity among inexperienced welders. This situation has added relevance to the issue today. What is this process and how to do welding for home use yourself? We will try to examine this question in detail today.

The first difference that catches your eye is the welding speed and its environmental friendliness. A standard capacitor welder operates at high voltage. This allows you to save energy and get a high-quality and even seam. Its main application is in microwelding or, if necessary, welding large sections. This happens according to this principle:

Capacitors collect the required amount of energy;
The charge turns into heat, which is used for welding.

As mentioned earlier, this type of welding is environmentally friendly. The devices do not require liquid for cooling due to the absence of heat emissions. This advantage allows you to add time to the life of the capacitor device.

Operating principle of capacitor welding

During the spot welding process, the parts are clamped by two electrodes, which receive a short-term current. Then an arc forms between the electrodes, which heats the metal, melting it. The welding pulse comes into operation within 0.1 sec., it provides a common melt core for both parts of the workpieces being welded. When the impulse is removed, the parts continue to compress under the pressure of the load. The result is a common weld.

There are secondary windings, from which the current flows to the electrodes, and the primary winding receives the pulse that was formed during the capacitor charge. In a capacitor, charge accumulation occurs in the interval between the arrival of a pulse at two electrodes. Particularly good results come when it comes to or copper. There is a limitation on the thickness of the workpieces; it should not exceed 1.5 mm. This may be a minus, but this scheme works great when welding dissimilar materials.

Types of spot welding

There are two main types of do-it-yourself capacitor welding:

Transformer. At which the capacitor discharges the energy charge onto the winding of the transformer equipment. In this case, the workpieces are located in the welding field, which is connected to the secondary winding.
Transformerless.

Advantages

Like all other types, self-condenser welding has a number of positive features:

With stable operation, it is possible to save energy;
Reliability and practicality. The speed of operation allows spot welding to be possible with air cooling;
Speed of work;
The welding current is very dense;
Accuracy. Taking into account the dose of energy consumed, a reliable seam of compact thickness is formed in the contact field. This method is widely used for fine welding of non-ferrous metals;
Economical. Power consumption is 20 kVA maximum. This occurs through power take-off due to voltage stabilization in the network.

DIY unit assembly diagram

The primary winding is passed through a diode bridge (rectifier) and then connected to a voltage source. The thyristor sends a signal to the bridge diagonal. The thyristor is controlled by a special button to start. The capacitor is connected to the thyristor, or more precisely to its network, to the diode bridge, then it is connected to the winding (primary). To charge the capacitor, an auxiliary circuit with a diode bridge and a transformer is turned on.

A capacitor is used as a pulse source; its capacity should be 1000-2000 µF. To design the system, a transformer is made from a Sh40 type core, the required size is 7 cm. To make the primary winding, you need a wire with a diameter of 8 mm, which is wound 300 times. The secondary winding involves the use of a copper bus with 10 windings. Almost any capacitors are used for the input, the only requirement is a power of 10 V, a voltage of 15.

When the work requires connecting workpieces up to 0.5 cm, it is worth applying some adjustments to the design diagram. For more convenient signal control, use the MTT4K series trigger; it includes parallel thyristors, diodes and a resistor. An additional relay will allow you to adjust the working time.

This homemade capacitor welding works using the following sequence of actions:

Press the start button, it will start the temporary relay;
The transformer is turned on using thyristors, then the relay is turned off;
A resistor is used to determine the pulse duration.

How does the welding process take place?

After the capacitor welding has been assembled with our own hands, we are ready to begin work. First, you should prepare the parts by cleaning them from rust and other dirt. Before placing the workpieces between the electrodes, they are connected in the position in which they need to be welded. Then the device starts. Now you can squeeze the electrodes and wait 1-2 minutes. The charge that accumulates in the high-capacity capacitor will pass through the welded fasteners and the surface of the material. As a result, it melts. Once these steps have been completed, you can proceed to the next steps and weld the remaining parts of the metal.

Before welding work at home, it is worth preparing materials such as sandpaper, grinder, knife, screwdriver, any clamp or pliers.

Conclusion

Capacitor welding is very widely used both at home and in industrial areas; as we see, it is very convenient and easy to use, plus it has a large number of advantages. With the help of the information provided, you will be able to take your knowledge to a new level and successfully apply spot welding in practice.

The technology has been known since the 30s of the last century, however, it has not lost its relevance to this day. This method is intended for fastening small parts together, and the most popular materials for such procedures are aluminum and copper. Due to its simplicity and the ability to use the device in private production, this type has gained popularity among novice welders, and it is easy to make it yourself.

Distinctive features

Standard welding involves the use of complex equipment that uses special electrodes. They are applied to the surface being processed, which creates ignition of the winding, leading to melting of the rolled metal. Next, the molten metal flows into the bath, where, after solidification, it holds the elements together. Only an experienced person can handle such a thing, and the gas and ultraviolet radiation released will have a negative effect on the body. It should be noted that this system cannot weld small components.

Capacitor welding does not harm the environment, and after manipulation there are practically no traces of external influences left on the plane. This approach will also save electricity, and the process requires minimal personal protective equipment. The device does not require cooling, and everything will take a minimum of time. A special feature is the high precision and accuracy of the connection. The equipment is compact, and its scope of application is micro-welding and electric welding of large sections.

Operating principle

Objects are tightly held together by two conductors, to which a short-term discharge of electricity is applied. This reaction creates an arc, which melts the steel with its heat. After the impulse, compression continues under load, making a common seam for a pair of objects. If we look at the event in more detail, it goes like this:

storage capacitors collect the necessary energy, which enters through the primary circuit;
when the electrode comes into contact with the material being processed, an intense burst of particles occurs, promoting heating and melting of rolled metal;
then everything happens again and in the same sequence.

The activity can be carried out with a limited number of rolled products, and with a thickness of no more than 0.15 cm.

Important! In this manner it is possible to weld thin wire to a solid steel surface, but the chemical compositions of the alloys can differ significantly.
It should be noted that the result of the connection is obtained with very positive properties, and you do not have to buy consumable components for the unit. During use, a load may appear that creates interference in the electrical network. Despite this, the capacitor fastening approach is widespread in both large-scale industry and private use.
Varieties
The riveting of both sections occurs due to the strong electrical influence that accumulates in the two-terminal networks, and the process itself is divided into three categories:
contact implies tight pressing of both workpieces and contact of the electrodes to the required place. As a result of touching, electricity is supplied to a small area of the object, the temperature of which promotes melting and future attachment. Regarding the voltage, it is equal to 15 kA, and lasts for 0.3 seconds;
impact technology is also designed to connect both elements, however, the supply of electricity is carried out using a short-term impact. The operation time is reduced to 1.5 m/s, which reduces the melting area;
point technique. In this situation, you will need two copper contacts that touch the object on two sides. The current intensity reaches 10 kA, and the products are bonded at the point of contact.

This way you can repair cables, restore household electrical appliances, rework small automotive components, and more. And the main advantage is that it does not require purchasing expensive equipment. Anyone can do an analogue of such an installation at home.
Requirements for capacitor welding
To produce a high-quality design, it is recommended to take into account some rules:
a good supply of short-term flow is created, with an activity period of no more than one millisecond;
rapid accumulation of new energy for the next action is ensured (in the shortest possible time);
the conductors are able to hold the sheets tightly, but they must quickly detach to reduce the temperature;
the rods are selected from copper, and their thickness must be three times greater than the thinnest part of the sheet;
Before processing, the object is thoroughly cleaned of rust, dirt and grease.

Do-it-yourself capacitor welding will be good only if you have 2 power units. Among other things, it is necessary to provide for adjusting the flow rate for different types of work, and take care of high-quality safety equipment.
A simple scheme for spot welding
Here it is relevant to consider a simplified model that transmits an impulse through an electromagnetic device. During work, you must connect the first wire directly to the part, and the secondary wire to the transmitter. Pressing the components is possible using a crocodile. The circuit diagram of the device is as follows: the primary transformer coil is connected to the network (one end of it is routed through a diode bridge). The other side of the same bridge receives a signal from the thyristor.
After startup, the charge will accumulate in the transistors (they are located in the chain of the semiconductor device and connected to the transformer bridge). Electric current will be taken from this link in the future.
The sequence occurs in the following manner: first, the two-terminal circuits are charged from the mains. After start-up, charging is turned off and the current passes to the electromagnetic device, bypassing the resistor. The duration can be controlled using a special regulator.
The transformer is one of the key components of the module. It can be formed like a core with dimensions of 40 by 70 (length and width). The primary layer is made of 0.08 cm cable and is wrapped 300 times. The secondary one is made with a wire tire with a size of 2 cm, and 10 turns are made to it. You can take any transformer, however, its power must be 10 W and voltage 15 V.
Device with increased power
Here it is necessary to remake the unit using a different method, but this will make it possible to weld thicker sheets and wire. This is also a homemade design, but capacitor welding will turn out no worse. To create it you will need: an MTT4K starter with a current of 8 A and a return voltage of 800 V. Thyristors, a pair of diodes and one resistor are connected to the control module.
All reactions proceed as in the previous case, but here you need to pay attention to the choice of capacitors. They are available in 3 pairs with the following power:
1st 47uF;
2nd 100uF;
3rd 470uF.

In this case, the voltage must be at least 50 V. You will also need a reed relay with a voltage of 20 V. As for the winding, you will need a 1.5 mm wire and a busbar with 60 mm 2. The electric current in the cooking zone will reach 1500 A.
Of course, such equipment will not be able to weld pipes or fittings, but for small jobs it will be an excellent assistant.
Contact block
The device is responsible for fastening and moving the rods. In most situations, installation involves fixing the sample manually. A better quality one fixes the lower one and makes the upper rod movable (the finished block resembles a bench vice). A copper rod of small length and with a circumference of 0.8 cm is fixed here. It should move freely in a vertical plane. The lower one remains motionless. A screw type regulator is also installed on the top part, thanks to which additional pressure can be created. In this case, the upper platform and the base of the power unit must be well insulated from each other. In some models, you can attach a flashlight on top, this will provide additional convenience for work.
Preparation of products. High-quality riveting will be possible with perfectly clean surfaces. They should be free of dirt, corrosion, foreign mixtures, etc.
Connecting parts. Here the alloys are placed in the required manner, installed between two contacts and compressed by them. After pressing the start button, the welding procedure begins, and upon completion the electrodes are disconnected.
Repeat. The second point is repeated until the entire area is securely welded.

The welder will also need auxiliary construction tools: chisel, hammer, compass, knife, emery board, etc. They carry out preparation, alignment and marking of metal. Despite the simplicity of the entire process, the employee is obliged to strictly adhere to safety precautions. Failure to do so may result in electric shock or fire.

Aluminum electrolytic capacitors are one of the main elements that ensure stable operation of high-frequency inverters of welding machines. Reliable, high-quality capacitors for this type of application are produced by companies.

The first devices using the electric arc welding method used adjustable alternating current transformers. Transformer welding machines are the most popular and are still used today. They are reliable, easy to maintain, but have a number of disadvantages: heavy weight, high content of non-ferrous metals in the transformer windings, low degree of automation of the welding process. It is possible to overcome these disadvantages by moving to higher current frequencies and reducing the size of the output transformer. The idea of reducing the size of the transformer by moving from a power supply frequency of 50 Hz to a higher one was born back in the 40s of the 20th century. Then this was done using electromagnetic transducers-vibrators. In 1950, vacuum tubes - thyratrons - began to be used for these purposes. However, it was undesirable to use them in welding technology due to low efficiency and low reliability. The widespread introduction of semiconductor devices in the early 60s led to the active development of welding inverters, first on a thyristor basis, and then on a transistor one. Insulated gate bipolar transistors (IGBTs) developed at the beginning of the 21st century gave new impetus to the development of inverter devices. They can operate at ultrasonic frequencies, which can significantly reduce the size of the transformer and the weight of the device as a whole.

A simplified block diagram of the inverter can be represented as three blocks (Figure 1). At the input there is a transformerless rectifier with a parallel-connected capacitance, which allows you to increase the DC voltage to 300 V. The inverter unit converts DC into high-frequency alternating current. The conversion frequency reaches tens of kilohertz. The unit includes a high-frequency pulse transformer in which the voltage is reduced. This block can be manufactured in two versions - using single-cycle or push-pull pulses. In both cases, the transistor unit operates in a key mode with the ability to adjust the on-time, which allows you to regulate the load current. The output rectifier unit converts the alternating current after the inverter into direct welding current.

The principle of operation of the welding inverter is the gradual conversion of the mains voltage. First, the AC mains voltage is increased and rectified in the preliminary rectification unit. A constant voltage powers a high-frequency generator using IGBT transistors in the inverter unit. The high-frequency alternating voltage is converted to a lower one using a transformer and supplied to the output rectifier unit. From the output of the rectifier, current can already be supplied to the welding electrode. The electrode current is regulated by circuitry by controlling the depth of negative feedback. With the development of microprocessor technology, the production of inverter semi-automatic machines began, capable of independently selecting the operating mode and performing such functions as “anti-sticking”, high-frequency arc excitation, arc retention and others.

Aluminum electrolytic capacitors in welding inverters

The main components of welding inverters are semiconductor components, a step-down transformer and capacitors. Today, the quality of semiconductor components is so high that if they are used correctly, no problems arise. Due to the fact that the device operates at high frequencies and fairly high currents, special attention should be paid to the stability of the device - the quality of the welding work directly depends on it. The most critical components in this context are electrolytic capacitors, the quality of which greatly affects the reliability of the device and the level of interference introduced into the electrical network.

The most common are aluminum electrolytic capacitors. They are best suited for use in the primary network IP source. Electrolytic capacitors have high capacitance, high rated voltage, small dimensions, and are capable of operating at audio frequencies. Such characteristics are among the undoubted advantages of aluminum electrolytes.

All aluminum electrolytic capacitors are composed of sequential layers of aluminum foil (the anode of the capacitor), a paper spacer, another layer of aluminum foil (the cathode of the capacitor) and another layer of paper. All this is rolled up and placed in an airtight container. Conductors are brought out from the anode and cathode layers for inclusion in the circuit. Also, the aluminum layers are additionally etched in order to increase their surface area and, accordingly, the capacitance of the capacitor. At the same time, the capacity of high-voltage capacitors increases by about 20 times, and low-voltage ones by 100. In addition, this entire structure is treated with chemicals to achieve the required parameters.

Electrolytic capacitors have a rather complex structure, which makes them difficult to manufacture and operate. The characteristics of capacitors can vary greatly under different operating modes and operating climatic conditions. With increasing frequency and temperature, the capacitance of the capacitor and ESR decreases. As the temperature decreases, the capacitance also drops, and the ESR can increase up to 100 times, which, in turn, reduces the maximum permissible ripple current of the capacitor. The reliability of pulse and input network filter capacitors, first of all, depends on their maximum permissible ripple current. Flowing ripple currents can heat up the capacitor, which causes its early failure.

In inverters, the main purposes of electrolytic capacitors are to increase the voltage in the input rectifier and smooth out possible ripples.

Significant problems in the operation of inverters are created by large currents through transistors, high requirements for the shape of control pulses, which implies the use of powerful drivers to control power switches, high requirements for the installation of power circuits, and large pulse currents. All this largely depends on the quality factor of the input filter capacitors, so for inverter welding machines you need to carefully select the parameters of electrolytic capacitors. Thus, in the preliminary rectification unit of a welding inverter, the most critical element is the filtering electrolytic capacitor installed after the diode bridge. It is recommended to install the capacitor in close proximity to the IGBT and diodes, which eliminates the influence of the inductance of the wires connecting the device to the power source on the operation of the inverter. Also, installing capacitors near consumers reduces the internal resistance to alternating current of the power supply, which prevents excitation of the amplifier stages.

Typically, the filter capacitor in full-wave converters is chosen so that the ripple of the rectified voltage does not exceed 5...10 V. It should also be taken into account that the voltage on the filter capacitors will be 1.41 times greater than at the output of the diode bridge. Thus, if after the diode bridge we get 220 V pulsating voltage, then the capacitors will already have 310 V DC voltage. Typically, the operating voltage in the network is limited to 250 V, therefore, the voltage at the filter output will be 350 V. In rare cases, the mains voltage can rise even higher, so capacitors should be selected for an operating voltage of at least 400 V. Capacitors can have additional heating due to high operating currents. The recommended upper temperature range is at least 85...105°C. Input capacitors for smoothing out rectified voltage ripples are selected with a capacity of 470...2500 µF, depending on the power of the device. With a constant gap in the resonant choke, increasing the capacitance of the input capacitor proportionally increases the power supplied to the arc.

There are capacitors on sale, for example, of 1500 and 2200 µF, but, as a rule, instead of one, a bank of capacitors is used - several components of the same capacity connected in parallel. Thanks to parallel connection, internal resistance and inductance are reduced, which improves voltage filtering. Also, at the beginning of the charge, a very large charging current flows through the capacitors, close to the short circuit current. Parallel connection allows you to reduce the current flowing through each capacitor individually, which increases the service life.

Choice of electrolytes from Hitachi, Samwha, Yageo

On the electronics market today you can find a large number of suitable capacitors from well-known and little-known manufacturers. When choosing equipment, one should not forget that with similar parameters, capacitors differ greatly in quality and reliability. The most well-proven products are from such world-famous manufacturers of high-quality aluminum capacitors as, and. Companies are actively developing new technologies for the production of capacitors, so their products have better characteristics compared to competitors' products.

Aluminum electrolytic capacitors are available in several form factors:

for mounting on a printed circuit board;
with reinforced snap-in pins (Snap-In);
with bolted terminals (Screw Terminal).

Tables 1, 2 and 3 present the series of the above manufacturers that are most optimal for use in the pre-rectification unit, and their appearance is shown in Figures 2, 3 and 4, respectively. The given series have a maximum service life (within the family of a particular manufacturer) and an extended temperature range.

Table 1. Electrolytic capacitors manufactured by Yageo

Table 2. Electrolytic capacitors manufactured by Samwha

Table 3. Electrolytic capacitors manufactured by Hitachi

Name	Capacity, µF	Voltage, V	Ripple current, A	Dimensions, mm	Form factor	Service life, h/°C
	470…2100	400, 420, 450, 500	2,75…9,58	30×40, 35×35…40×110	Snap-In	6000/85
	470…1500	400, 420, 450, 500	2,17…4,32	35×45, 40×41…40×101	Snap-In	6000/105
	470…1000	400, 420, 450, 500	1,92…3,48	35×40, 30×50…35×80	Snap-In	12000/105
	1000…12000	400, 450	4,5…29,7	51×75…90×236	Screw Terminal	12000/105
GXR	2700…11000	400, 450	8,3…34,2	64×100…90×178	Screw Terminal	12000/105

As can be seen from Tables 1, 2 and 3, the product range is quite wide, and the user has the opportunity to assemble a capacitor bank, the parameters of which will fully meet the requirements of the future welding inverter. The most reliable are Hitachi capacitors with a guaranteed service life of up to 12,000 hours, while competitors have this parameter up to 10,000 hours in Samwha JY series capacitors and up to 5,000 hours in Yageo LC, NF, NH series capacitors. True, this parameter does not indicate a guaranteed failure of the capacitor after the specified line. Here we mean only the time of use at maximum load and temperature. When used in a smaller temperature range, the service life will increase accordingly. After the specified period, it is also possible to reduce the capacity by 10% and increase losses by 10...13% when operating at maximum temperature.

There are many technologies for welding various materials, and among them is capacitor welding. The technology has been known since the 30s of the last century and is of a variety. The joining of metals occurs during melting in places of short circuit of electric current due to the applied discharge energy of charged high-capacity capacitors. The process takes 1-3 milliseconds.

The basis of the device is a capacitor or a block of capacitors, which are charged by a constant voltage power source. After reaching the required energy level during the charging process, the capacitor electrodes are connected to the welding points. The current flowing during the discharge between the parts being welded causes the surfaces to heat to such an extent that the metal melts and high-quality metal is formed.

Despite a number of advantages, capacitor welding has a number of limitations that do not allow its use everywhere. Among them:

pros	Minuses
high process speed in automated production, up to 600 points per minute	short-term power of the welding process
accuracy of parts connection and repeatability of processes on the line	restrictions on the cross-sectional dimensions of welded parts
does not transmit infrared and ultraviolet radiation	pulsed load creates network interference and high short-term loads
equipment durability
welding different metals
low heat generation, no need for coolant
lack of consumables such as electrodes or welding wire

Despite some disadvantages, the method of joining metals is widely used in industry and in everyday life.

Types of capacitor welding machines

There are two types of capacitor welding machines - with a discharge of energy storage devices directly on the surfaces being welded and with a discharge from the secondary winding of a transformer. The first, transformerless method, is more often used in shock-capacitor welding. The second method, transformer, is used to create a high-quality seam.

Impact-capacitor equipment welds parts when one of the electrodes hits the part. During an impact, the surface parts are pressed tightly against each other. A capacitor discharge occurs, forming a microarc that heats the surfaces to the melting point of metals. The parts are firmly connected.

In the transformer welding method, after charging, the capacitor is connected to the primary winding of the step-down transformer. A potential appears on the secondary winding that is several times smaller than the amplitude of the incoming pulse. During the discharge, the parts are welded, the capacitor is charged again and again transfers energy to the primary winding of the transformer. This allows long bursts of up to 5 discharges per second to be produced, which creates strong and precise welds.

Application specifics

Capacitor welding is an economical process, so it is convenient to use at home with a low-power single-phase network. The industry produces household welders with a power of 100-400 watts, which are intended for home use or in small private workshops.

Capacitor welding has gained particular popularity in car body repair shops. Unlike arc welding, capacitor welding does not burn through or deform the thin walls of sheets of body parts. There is no need for additional straightening.

Capacitor welding is also used in radio electronics for welding products that cannot be soldered using conventional fluxes or fail due to overheating.

Capacitor welding machines are used by jewelers to make or repair jewelry.

In industry, point connection is used for:

welding bolts, hooks, nuts, studs and other hardware to surfaces;
connections between different metals, including non-ferrous ones;
welding of watch parts, photo and film equipment;
manufacturing of optical and lighting devices;
electronic equipment assemblies
and etc.

Capacitor welding is used to join microscopic parts that cannot be welded using the arc method.

DIY capacitor apparatus

You can make a capacitor-type welding machine yourself and use it at home. For this you will need

220 volt transformer with a power of 5-20 W with an output voltage of 5V;
four rectifier diodes with a forward current of at least 300 mA (for example, D226b);
thyristor PTL-50, modern replacement T142-80-16, KU 202 or similar;
electrolytic capacitor 1000.0 x25 V;
variable resistor 100 Ohm;
a transformer with a power of at least 1000 W (suitable for microwave ovens);
electrodes or welding gun (different designs are described on the Internet many times);
copper wire with a cross-section of at least 35 mm2. - 1 meter.
switches, fuses, housing at your discretion.

If the installation is carried out according to the diagram without errors and the parts are in good working order, then there will be no problems with the operation of the device.

There is only one problem - the output transformer. If you really decide to use a microwave transformer, and it can be bought cheaply on used parts markets, then be prepared that it will need to be rebuilt.

It is necessary to remove the magnetic shunts and the secondary winding and wind 2-5 turns of the secondary winding with a thick copper wire onto the free space. During the setup process, the number of turns may have to be changed. It is considered optimal that the output voltage should fluctuate between 2-7 volts, but this value also depends on the duration of the welding pulse and the thickness of the materials being welded. There is no need to be afraid to experiment, choosing different modes with a variable resistor and changing the number of turns. But don't try to get the machine to do what a conventional arc process can do. You won’t be able to cook water pipes and fittings; this device is for other purposes.

Devices for the transformerless type are not much more complicated, but they are more cumbersome. You will need a set of capacitors with a total capacity of about 100,000 microfarads. This is a decent weight and size battery. It can be replaced with a compact ionistor, but the device is not cheap. In addition, electrolytic capacitors do not last long. Therefore, portable and household capacitor spot welding machines are usually manufactured using a transformer circuit.

Modern devices are manufactured using slightly different technologies. The frequency and power of the discharge are regulated by PIC controllers; it is possible to automate processes and control via a computer or monitor interface. But the physical processes of welding have not changed. Having once assembled the simplest unit, you can subsequently add elements of computer control, production automation and control to it.

If this topic is close to you and you are ready to complement it or challenge it, share your opinion, tell us, post descriptions of your solutions in the comments block.

Spot welding principle
Requirements for capacitor welding
Simple design for spot welding
Device with increased power
Contact block designs
Carrying out capacitor spot welding

Often there is a need for spot welding when you do not need to connect pipes or profiles, but simply need to attach a small but important part. Do-it-yourself capacitor welding will help you accomplish this.

Contact welding is a fairly popular type of joining metals, especially non-ferrous ones. Many people strive to be able to do it at home. Do-it-yourself capacitor welding is quite affordable and easy to do.

Types of capacitor welding

Capacitor welding is a type of welding in which the melting of metal occurs due to the stored electrical energy in capacitors. According to the method of implementation, capacitor welding can be divided into contact, impact and spot welding.

Resistance welding implies that the capacitor is discharged onto two metal workpieces previously pressed against each other. An arc appears at the point of contact, which melts and connects the workpieces in a small area of their contact. The welding current in the arc zone reaches 15 kA with an exposure time of up to 3 ms. In impact welding, contact between metal workpieces to which a discharge is applied occurs in the form of a short-term impact. The arc duration does not exceed 1.5 ms, which further reduces the welding area.

In spot welding, a discharge is applied to two copper electrodes, which at points touch the surface of the metals on both sides. An arc is formed between the electrodes for 0.01-0.1 s, depending on the adjustment. The welding current can reach 10 kA. Welding of metals occurs almost at a point.

Capacitor welding scheme.

Based on the type of discharge generated, capacitor welding is divided into transformerless and transformer welding. In the first type, the discharge from the capacitors arrives directly at the metal surface. Such welding can be carried out by high-voltage discharge (voltage up to 1 kV) with a current of up to 100 A for 0.005 s or low-voltage discharge (voltage up to 60 V) with a current of 1-2 kA for up to 0.6 s.

The transformer type of capacitor welding is that the discharge from the capacitor is produced on the winding of the transformer, and from its secondary winding it enters the welding zone. This type of welding expands the possibilities for adjusting the process. The discharge voltage reaches 1 kV, while in the secondary winding a welding current of up to 6 kA is achieved, which is supplied for up to 0.001 s.

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The most common type of capacitor welding in domestic conditions is transformer spot welding. The basic principle of spot welding is that the workpieces to be welded, combined in the required position, are clamped between two electrodes, which are supplied with a short-term high-magnitude welding current. The electric arc formed between the electrodes melts the metal of the workpieces in a zone with a diameter of 4-12 mm, which leads to their connection.

The action of the welding pulse is provided for 0.01-0.1 s, which ensures the formation of a melt core common to both metals being welded. After the current pulse is removed, the compressive load continues to act on the workpieces, which ensures the formation of a common weld. Limitation of the metal melting zone is achieved by the fact that at the moment the pulse is applied, the metals are in contact with each other, providing heat removal.

The welding current (pulse) is supplied to the electrodes from the secondary winding, where a high current is provided at low voltage. A pulse is applied to the primary winding, which occurs when a capacitor (or bank of capacitors) is discharged. In the capacitor itself, the charge accumulates in the period between the application of pulses to the electrodes, i.e. The capacitor is charged while the electrodes are moved to another point for welding.

The scope of application of such welding is wide depending on the type of material. Particularly good results are obtained when welding non-ferrous metals, including copper and aluminum. There is a significant limitation on the thickness of the sheets being welded - up to 1.5 mm. But spot welding has shown itself to be excellent in the case of attaching thin strips of wire to any massive structure. In this case, the materials being connected can be dissimilar.

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In order for do-it-yourself capacitor spot welding to be carried out efficiently, certain conditions must be met. It must be possible to supply a short-term pulse for up to 0.1 s and then accumulate energy from the network for a new pulse in a very short time.

The pressure exerted by the electrodes on the parts to be welded at the moment the welding pulse is applied should ensure reliable contact between them. The opening of the electrodes must be delayed so that the melt cools under pressure, which improves the crystallization of the metal in the weld.

Copper electrodes are the most common electrodes for spot welding. The diameter of the point at the point of contact should exceed the thickness of the thinnest workpiece being welded by 2-3 times.

The surface of the workpieces to be welded must be thoroughly cleaned before welding so that oxide films and rust do not create high resistance to current.

Do-it-yourself capacitor spot welding can only be done if you assemble a device that has at least two blocks: a welding pulse source and a welding unit. In addition, it is necessary to provide the ability to regulate the welding mode and protection.

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When welding thin sheets (up to 0.5 mm) or when welding thin elements to any parts, you can use a simplified design of the welding machine. In it, the welding pulse is supplied through a transformer. In this case, one end of the secondary winding is connected directly to a massive part, to which a thin part is welded, and the second end - to the electrode. In other words, the device provides for the use of only one (upper) electrode. Pressing it onto a thin part is done manually. To attach and hold the electrode, you can, for example, use standard clamp terminals for a car battery (alligator clip).

When making a simple source of welding current (pulse), you can use the following circuit. The primary winding of the transformer powering the welding unit is connected to the electrical network, with one end through one of the diagonals of the diode bridge rectifier. The other diagonal of this bridge is supplied with a signal from a thyristor, which is controlled using the start button.

The welding pulse is accumulated in a capacitor, which is located in the thyristor circuit and connected to the diagonal of the bridge with output to the primary winding of the transformer. The capacitor is charged from an auxiliary circuit, including an input transformer and a rectifier diode bridge.

The source operates in the following order. While the welding transformer is disconnected, the capacitor is charging from the auxiliary network. When you press the start button (turning on the welding transformer), the capacitor is disconnected from the auxiliary network and discharged onto the primary winding of the transformer through a resistor. The capacitor discharges through the control thyristor. The discharge duration time is changed using a control resistor. When the button is turned off, the discharge circuit is broken, and the auxiliary circuit is turned on, and the capacitor charging cycle begins.

The pulse source is a capacitor with a capacity of 1000 μF or 2000 μF for voltages up to 25 V. An important element of the circuit is a transformer. It can be made on the basis of a Ш 40 core with a thickness of 70 mm. The primary winding is made of PEV-2 wire with a diameter of 0.8 mm. The number of turns is 300. The secondary winding has 10 turns and is made of a copper busbar with a cross-section of 20 mm². For control, you can use a PTL-50 or KU202 thyristor. Any 10 W transformer with a secondary voltage of 15 V can be used as an input transformer. When using the recommended source, a current pulse of up to 500 A with a duration of up to 0.1 s can be provided.

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Seam welding diagram.

To increase the power of the welding current source, a design change should be recommended that allows welding sheets up to 1 mm thick or wire up to 5 mm thick. The signal is controlled using an MTT4K contactless starter with a current of 80 A and a reverse voltage of up to 800 V. The control module includes two parallel-connected thyristors, two diodes and a resistor. The response time is adjusted using a time relay connected to the input transformer circuit.

Energy storage occurs in electrolytic capacitors assembled into a battery by parallel connection. Capacitors, usually in the amount of 6 pieces, are selected as follows: two capacitors with a capacity of 47 μF, two with a capacity of 100 μF, two with a capacity of 470 μF, for an operating voltage of at least 50 V. As a time relay, you can use a reed relay RES42, RES43 on voltage up to 20 V.

Relief welding diagram.

The primary winding of the welding transformer is made of wire with a diameter of 1.5 mm, and the secondary winding is made of a copper busbar or wire with a cross-section of at least 60 sq. mm. The number of turns in the secondary winding is 4-7. At the same time, a current in the welding zone of up to 1500 A is provided.

The device works as follows. When the start button is pressed, a relay is activated, which turns on the welding transformer through the control contacts of the thyristors. After the capacitors are discharged, the relay turns off. Precise regulation of the pulse duration is carried out by a variable resistor.

Due to the increase in power, the welding unit should be made more reliable. It uses two copper electrodes. Quite often, welding pliers are used as electrodes, which provide a pressure of up to 20 kg/cm². The diameter of the contact pads is selected to the minimum.

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The welding block is a contact block, i.e. a device that allows you to attach and move electrodes. The simplest design involves manually holding and squeezing the electrodes. A more reliable system is one that includes a stationary bottom electrode and a movable top electrode. In this case, a short-length copper rod (10-20 mm) with a diameter of at least 8 mm is fixed to any base. The upper cut of the electrode is rounded. The upper electrode, made of the same rod, is fixed on a platform that can move freely upward or recline. Adjustment screws must be provided to allow additional pressure to be created after the top electrode contacts the workpiece surface. The base of the block and the upper platform must be reliably isolated from each other until the electrodes come into contact.

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The entire process of do-it-yourself capacitor spot welding can be divided into several stages. First, the surface of the workpieces to be welded is prepared. Then the workpieces are combined in the required order, placed in the space between the electrodes and compressed by them. The welding impulse is sent using the start button. 1-2 minutes after the impulse stops, the electrodes are moved apart. The welded part is removed and installed at another point.

The gap between welding points depends on the thickness of the workpiece and usually ranges from 15-60 mm.

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The welding process is repeated.

To do spot welding with your own hands, you will need the following additional tool:

vice;
hacksaw;
Bulgarian;
emery wheel;
file;
pliers;
screwdriver;
wrenches;
sandpaper;
tester;
hammer;
chisel;
calipers.

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Do-it-yourself capacitor welding will help you connect thin sheets of any metal or weld small ones to any metal structure. This spot welding is quite simple and affordable.

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Scheme and description of capacitor welding

There are several ways to seamlessly join metal elements, but among all of them, capacitor welding occupies a special place. The technology has become popular since about the 30s of the last century. Docking is carried out by supplying electric current to the desired location. A short circuit is created, which allows the metal to melt.

Advantages and disadvantages of technology

The most interesting thing is that capacitor welding can be used not only in industrial conditions, but also in everyday life. It involves the use of a small-sized device that has a constant voltage charge. Such a device can easily move around the work area.

Among the advantages of the technology, it should be noted:

high work productivity;
durability of the equipment used;
the ability to connect various metals;
low level of heat generation;
lack of additional consumables;
accuracy of connection of elements.

However, there are situations when it is impossible to use a capacitor welding machine to join parts. This is primarily due to the short duration of the power of the process itself and the limitation on the cross-section of combined elements. In addition, pulsed load can create various interferences in the network.

Features and specifics of application

The process of joining workpieces itself involves contact welding, for which a certain amount of energy is consumed in special capacitors. Its release occurs almost instantly (within 1 - 3 ms), due to which the thermal impact zone is reduced.

It is quite convenient to carry out capacitor welding with your own hands, since the process is economical. The device used can be connected to a regular electrical network. There are special high-power devices for industrial use.

The technology has gained particular popularity in workshops designed to repair vehicle bodies. During the work, thin sheets of metal are not burned through and are not subject to deformation. There is no need for additional straightening.

Basic process requirements

In order for capacitor welding to be performed at a high quality level, certain conditions must be adhered to.

The pressure of the contact elements on the workpiece immediately at the moment of the impulse must be sufficient to ensure a reliable connection. The opening of the electrodes should be done with a slight delay, thereby achieving a better crystallization of metal parts.
The surface of the workpieces to be joined must be free of contaminants so that oxide films and rust do not cause too much resistance when electric current is applied directly to the part. The presence of foreign particles significantly reduces the efficiency of the technology.
Copper rods are required as electrodes. The diameter of the point in the contact zone must be at least 2-3 times the thickness of the element being welded.

Technological techniques

There are three options for influencing workpieces:

Capacitor spot welding is mainly used to join parts with different thickness ratios. It is successfully used in the field of electronics and instrument making.
Roller welding is a certain number of spot connections made in the form of a continuous seam. The electrodes resemble rotating coils.
Impact capacitor welding allows you to create butt joints of elements with a small cross-section. Before the collision of the workpieces, an arc discharge is formed, melting the ends. After the parts come into contact, welding is carried out.

As for the classification according to the equipment used, the technology can be divided according to the presence of a transformer. In its absence, the design of the main device is simplified, and the bulk of the heat is released in the direct contact zone. The main advantage of transformer welding is the ability to provide a large amount of energy.

Do-it-yourself capacitor spot welding: diagram of a simple device

To connect thin sheets up to 0.5 mm or small parts, you can use a simple design made at home. In it, the impulse is supplied through a transformer. One of the ends of the secondary winding is connected to the array of the main part, and the other to the electrode.

In the manufacture of such a device, a circuit can be used in which the primary winding is connected to the electrical network. One of its ends is output through the diagonal of the converter in the form of a diode bridge. On the other hand, a signal is supplied directly from the thyristor, which is controlled by the start button.

The pulse in this case is generated using a capacitor having a capacity of 1000 - 2000 μF. To manufacture a transformer, a Sh-40 core with a thickness of 70 mm can be used. The primary winding of three hundred turns can be easily made from wire with a cross-section of 0.8 mm marked PEV. A thyristor with the designation KU200 or PTL-50 is suitable for control. The secondary winding with ten turns can be made of a copper busbar.

More powerful capacitor welding: diagram and description of a homemade device

To increase power indicators, the design of the manufactured device will have to be changed. With the right approach, it will be possible to connect wires with a cross-section of up to 5 mm, as well as thin sheets no more than 1 mm thick. To control the signal, a contactless starter marked MTT4K, designed for an electric current of 80 A, is used.

Typically, the control unit includes thyristors connected in parallel, diodes and a resistor. The response interval is adjusted using a relay located in the main circuit of the input transformer.

Energy is heated in electrolytic capacitors, combined into a single battery through a parallel connection. In the table you can see the required parameters and the number of elements.

The main transformer winding is made of wire with a cross-section of 1.5 mm, and the secondary winding is made of a copper busbar.

The homemade device operates according to the following scheme. When you press the start button, the installed relay is activated, which, using thyristor contacts, turns on the transformer of the welding unit. The shutdown occurs immediately after the capacitors are discharged. The pulse effect is adjusted using a variable resistor.

Contact block device

The manufactured device for capacitor welding must have a convenient welding module that provides the ability to fix and freely move the electrodes. The simplest design involves manually holding the contact elements. In a more complex version, the lower electrode is fixed in a stationary position.

To do this, it is fixed on a suitable base with a length of 10 to 20 mm and a cross-section of more than 8 mm. The upper part of the contact is rounded. The second electrode is attached to a platform that can move. In any case, adjustment screws must be installed, with the help of which additional pressure will be applied to create additional pressure.

It is imperative to isolate the base from the moving platform to the contact of the electrodes.

Work order

Before doing capacitor spot welding with your own hands, you need to familiarize yourself with the main steps.

At the initial stage, the elements to be connected are prepared properly. Contaminants in the form of dust particles, rust and other substances are removed from their surface. The presence of foreign inclusions will not allow achieving high-quality joining of the workpieces.
The parts are connected to each other in the required position. They should be located between two electrodes. After squeezing, an impulse is applied to the contact elements by pressing the start button.
When the electrical influence on the workpiece stops, the electrodes can be moved apart. The finished part is removed. If there is a need, then it is installed at a different point. The size of the gap is directly affected by the thickness of the welded element.

Application of ready-made devices

Work can be carried out using special equipment. This kit usually includes:

apparatus for creating an impulse;
device for welding and clamping fasteners;
return cable equipped with two clamps;
collet set;
instructions for use;
wires for connecting to the electrical network.

Final part

The described technology for connecting metal elements allows not only to weld steel products. With its help, you can easily join parts made of non-ferrous metals. However, when performing welding work, it is necessary to take into account all the features of the materials used.

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Do-it-yourself capacitor welding

This type of welding refers to the spot method. It is convenient when you need to weld small parts to each other, or one small one. Capacitor welding is mainly used to work with non-ferrous metals.

How does the capacitor method differ from other types?

Capacitors collect the required amount of energy;
The charge turns into heat, which is used for welding.

Operating principle of capacitor welding

There are secondary windings, from which the current flows to the electrodes, and the primary winding receives the pulse that was formed during the capacitor charge. In a capacitor, charge accumulation occurs in the interval between the arrival of a pulse at two electrodes. Particularly good results come when it comes to welding aluminum or copper. There is a limitation on the thickness of the workpieces; it should not exceed 1.5 mm. This may be a minus, but this scheme works great when welding dissimilar materials.