Spot Welding Machine

The spot welding machine is an indispensable tool in many technological processes, ensuring reliable connection of parts. The quality of the result is influenced by factors such as the magnitude of the current, the type of material, the area of the joint and the dimensions of the electrodes.

Description

Spot welding is used both in industrial and domestic conditions. It is optimally suited for working with bent profiles, steel and non-ferrous metal products. This technique provides high strength of the seam and economy. In addition, it is possible to use kitchen equipment and various tools for repairs.

The process is based on the combination of individual elements and their fixation. After that by means of an electric current heating of details is made. Particular attention is paid to the relative location of the elements at the desired point, which is maintained throughout the entire work process. The parts become one as a result of the melting of the material that has occurred under the influence of the heat pulse.

Types

The mechanical device for spot welding has manual control and requires setting the current value before each use. The main advantage is a simple design and the ability to manufacture at home. They have become most widespread and have found application in many industries.

Automatic tools allow you to get connections with the minimum amount of reject. At the same time, the work does not require special skills and labor costs are reduced.

In the industry, pneumatic and hydraulic devices are actively used.

The inventory for spot welding is quite high in cost, but it has become widespread due to the possibility of connecting to the household network, an extensive set of functions and compact dimensions.

Despite the fact that portable units are somewhat inferior to stationary ones, they provide a qualitative weld at a minimal cost for the purchase of equipment. In this case, it is possible to work with a metal up to 6-7 mm thick.

Essential elements

Welding machine spot welding can be done at home. The most popular devices were devices with an unregulated current value. Such a device is controlled by an electric pulse, the duration of which is changed by means of a special relay or switch.

One of the main elements is a transformer, which provides the necessary level of current. For this purpose, it is possible to use a microwave oven coil that has suitable characteristics and is characterized by availability. This homemade spot welding machine is suitable for working with metal parts 1-2 mm thick. If possible, for greater efficiency, it is worth choosing transformers from powerful microwave ovens. It should be noted that in household appliances of this type the magnetron operates at 4000 V. Therefore, the transformer wires have a large thickness, and the number of turns on the secondary winding is much less than on the primary winding.

Winding

Secondary winding wires in the transformer are removed using a hacksaw or a chisel, in some cases it is necessary to resort to drill. It is not recommended to knock out the winding so as not to damage the cables. In the presence of shunts, they must also be removed, since they contribute to current limitation.

A new secondary winding is produced after the extraction of the necessary parts. With the help of a copper cable with a cross-section of at least 100 mm², optimum voltage levels can be achieved. In some cases it is necessary to remove the external insulation, which does not allow making a suitable winding. It can be replaced with fabric insulating tape, while cables with a shorter length are used to reduce the resistance.

For domestic needs, as a rule, three turns are enough, with increasing their number, the current of the device rises. Also, additional power can be obtained by installing several transformers.

What you need to know

The spot welding machine , assembled with its own hands from the microwave , requires the use of electrodes in secondary circuits. In the case of using two transformers with the same power, they must be connected with cables of 10 mm thickness, the ends of which are connected to the electrode. Care must be taken when connecting the primary and secondary windings to prevent short circuits.

With an insufficient window size of the magnetron, which makes it difficult to add cable turns, and simultaneous use of high-power transformers, a series connection of the secondary windings is recommended. The direction of winding must be consistent, if this rule is not observed, the probability of obtaining an antiphase and, as a consequence, of zero output voltage is high.

Voltage

On transformers, the terminals of the same name are indicated by a symbol or a letter. In the absence of any identification marks, it is recommended to use a voltmeter for verification. It is necessary to energize the primary windings by connecting the device to secondary windings. In the case of connecting windings with unlike terminals, the voltmeter will indicate the voltage. This is due to the fact that the primary winding gives the voltage to the secondary, where it is converted and doubled.

When connecting a pair of windings with the same terminal, the voltage on the secondary windings will be opposite and the voltmeter will show a zero value.

In order to make the spot welding machine more powerful, you can use several transformers, while taking into account the network performance. The total voltage of the devices must not exceed the set value. Optimum option will be the current strength in the range of 1000-2000 A.

Electrodes

Electrodes are best made from copper rods having a sufficient thickness, and the diameter must correspond to the parameters of the wire. Over time, the electrodes change their shape and become unsuitable for work, so they need to be systematically pumped. It is recommended to reduce the number of connections and the length of the cable going from the transformer to the electrode, to increase the power. The best option is to connect the electrodes to the tips made of copper, and fixed at the ends of the wires. To prevent oxidation of copper at points of contact, it is necessary to solder the parts, and this will simplify further cleaning. It is worth noting that you can use crimping to reduce losses.

Control

The spot welding machine for batteries is often equipped with a screw clamp, providing additional force during operation. The device is controlled by a lever or switch. Of particular importance is the qualitative fixing of the electrodes, which is necessary for normal functioning. In operation, the apparatus with the possibility of stationary fixing and sufficient mass will be more convenient. The switch must be reliable and long.

Connection of the switch button is made only to the primary winding, in this case the integrity of the contacts will be preserved and additional resistance will be prevented.

On devices with the lever principle of control, the switch is mounted on the clamp, thus it becomes possible to control the welding process with one hand.

Switched on and off point-wise manual welding machines only with compressed electrodes. It is recommended to install forced ventilation, which will allow to work without regular interruptions and monitoring of the level of heating of current leads and electrodes.

Getting a quality connection is possible only if you know all the subtleties of the process, in particular, you need to be able to determine the stages of readiness for external characteristics and shade of the material, have experience with the current pulse. The speed of moving the electrodes must be at the same level throughout the entire welding process.

Security

Of particular importance is compliance with safety standards during operation, since a faulty spot welding machine can harm health and spoil processed products. It is also necessary to adhere to the following requirements:

• Use a special mask to protect the face and eyes from metal sprays and sparks;
• Insulation of connecting and electrical cables;
• Absence of flammable materials and liquids near the place of welding;
• Application of mittens and gloves for protection from burns;
• Regular airing of the room, ensuring the purification of air from harmful gases;
• Availability of fire fighting equipment;
• Protection of wooden surfaces (floor covering, table) from sparks.

Process Features

Do not forget about the preparatory work necessary to obtain a quality welded seam. The elements used are previously cleaned from dust and dirt with brushes and special compounds. Spot welding from the welding machine with their own hands always includes several basic stages, including the following:

• Placing the elements to be connected in the required position;
• Clamping of parts between electrodes;
• Heating to the appearance of plasticity, which allows to deform the metal.

It is worth noting that during operation, there may be a point of failure, which arises due to the absence of a molten core or its small size. Tracking this defect is difficult, but it can lead to the following consequences:

• Formation of dents and shells;
• Melting surfaces of elements;
• Cutting through the material
• Porous structure of the welded core.