There are several ways to seamlessly connect metal elements, but capacitor welding occupies a special place among all. 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 that 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 apparatus that has a constant voltage charge. Such a device can be easily moved around the work area.
Of the advantages of the technology, it should be noted:
- high work productivity;
- durability of equipment used;
- ability to connect different metals;
- low heat generation;
- no additional consumables;
- accuracy of connecting elements.
However, there are situations when to applycapacitor welding machine for joining parts is not possible. This is primarily due to the short duration of the power of the process itself and the limitation on the cross section of the combined elements. In addition, the impulse load is capable of creating various interference in the network.
Features and application specifics
The process of joining workpieces 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 heat-affected zone decreases.
It is quite convenient to carry out capacitor welding with your own hands, as the process is economical. The device used can be connected to a conventional electrical network. There are special high power devices for industrial use.
The technology gained particular popularity in workshops designed to repair vehicle bodies. During the work, thin sheets of metal are not burned through and are not subjected 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 observed.
- The pressure of the contact elements on the workpieces directly at the moment of impulse must be sufficient to ensurereliable connection. Opening the electrodes should be done with a slight delay, thereby achieving the best mode of crystallization of metal parts.
- The surface of the workpieces to be joined must be free from contamination so that oxide films and rust do not cause too much resistance when an electric current is applied directly to the part. In the presence of foreign particles, the efficiency of the technology is significantly reduced.
- 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 to be welded.
Technological Techniques
There are three options for influencing blanks:
- Capacitor spot welding is mainly used to connect parts with different thickness ratios. It is successfully used in the field of electronics and instrumentation.
- Roller welding is a certain number of spot joints made in the form of a continuous seam. The electrodes are like spinning 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, which melts the ends. After the parts come into contact, welding is carried out.
As for the classification according to the equipment used, it is possible to divide the technology by the presence of a transformer. In its absence, the design of the main device is simplified, as well asthe main mass of heat is released in the zone of direct contact. The main advantage of transformer welding is the ability to provide a large amount of energy.
DIY capacitor spot welding: a diagram of a simple device
To connect thin sheets up to 0.5 mm or small parts, you can use a simple home-made design. In it, the impulse is fed 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 scheme 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 with a capacity of 1000 - 2000 microfarads. For the manufacture of a transformer, a Sh-40 core with a thickness of 70 mm can be taken. The primary winding of three hundred turns is easy to make from a wire with a cross section of 0.8 mm marked PEV. A thyristor with the designation KU200 or PTL-50 is suitable for control. A secondary winding with ten turns can be made from a copper bar.
More powerful capacitor welding: diagram and description of a homemade device
To increase power performancewill have to change the design of the manufactured device. 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 with a thickness of not more than 1 mm. To control the signal, a contactless starter marked MTT4K is used, designed for an electric current of 80 A.
Usually, thyristors connected in parallel, diodes and a resistor are included in the control unit. The response interval is adjusted using the 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 find the necessary parameters and the number of elements.
| Number of capacitors | Capacity, uF |
| 2 | 470 |
| 2 | 100 |
| 2 | 47 |
The main transformer winding is made of wire with a cross section of 1.5 mm, and the secondary is made of a copper bus.
The work of a home-made device occurs according to the following scheme. When the start button is pressed, the installed relay is activated, which, using thyristor contacts, turns on the transformer of the welding unit. Shutdown occurs immediately after the capacitors are discharged. The impulse action is adjusted using a variable resistor.
Contact deviceblock
The manufactured fixture for capacitor welding should have a convenient welding module that allows you to fix and move the electrodes freely. The simplest design involves manual holding of the contact elements. In a more complex version, the lower electrode is fixed in a stationary position.
To do this, on a suitable base, it is fixed with a length of 10 to 20 mm and a cross section of more than 8 mm. The top of the contact is rounded off. The second electrode is attached to a platform that can move. In any case, adjusting screws must be installed that will apply additional pressure to create additional pressure.
It is mandatory to isolate the base from the movable platform to the contact of the electrodes.
Procedure of work
Before do-it-yourself capacitor spot welding, 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 to achieve high-quality joining of workpieces.
- 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 action on the workpiece stops,electrodes can be moved apart. The finished part is removed. If there is a need, then it is installed at a different point. The gap is directly affected by the thickness of the welded element.
Using 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 mains.
Final part
The described technology for connecting metal elements allows not only welding steel products. With its help, you can join parts made of non-ferrous metals without much difficulty. However, when performing welding work, it is necessary to take into account all the features of the materials used.
