The machine for spot welding is an indispensable tool in many technological processes, providing a reliable connection of parts. The quality of the result is influenced by such factors as the magnitude of the current, the type of material, the area of the connection and the size of the electrodes.
Spot welding is used both in industrial and domestic conditions. It is optimally suited for working with bent profiles, steel products and non-ferrous metals. This technique provides high weld strength and economy. In addition, it is possible to use in the repair of kitchen equipment and various tools.
The process is based on the combination of individual elements and their fixation. Then with the help of electric current the parts are heated. Particular attention is paid to the relative arrangement of elements at the required point, which is maintained during the entire work process. Details become one as a result of melting of the material that has arisen under the influence of a thermal pulse.
The mechanical spot welding machine has manual control and requires setting a current value before each use. The main advantage is the simple design and the ability to manufacture at home. They gained the greatest distribution and found application in many industries.
Automatic tools allow you to receive connections with a minimum amount of marriage. At the same time, special skills are not required for work and labor costs are reduced.
Pneumatic and hydraulic devices are actively used in industry.
The spot welding machine is quite expensive, but it has become widespread due to the ability to connect to a 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 high-quality seam at the minimum cost for the purchase of equipment. In this case, you can work with metal up to 6-7 mm thick.
Spot welding machine can be made at home. The most popular devices with unregulated current. Such a device is controlled by an electric pulse, the duration of which is changed using a special relay or switch.
One of the main elements is a transformer, which provides the necessary level of current. For this purpose, you can use the coil from the microwave, which has the appropriate characteristics and is affordable. Such a home-made 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 microwaves. It is worth noting that in household appliances of this type, the magnetron operates at a voltage of 4000 V. Therefore, the transformer wires are thicker, and the number of turns on the secondary winding is significantly less than on the primary.
The wires of the secondary winding in the transformer are removed using a hacksaw or chisel, in some cases you have to resort to drilling. It is not recommended to knock out the winding so as not to damage the cables. If there are shunts, they must also be removed, as they contribute to current limitation.
A new secondary winding is made after extracting the necessary parts. Using a copper cable with a cross section of at least 100 mm², optimum voltage values can be achieved. In some cases, removal of external insulation is required, which does not allow a suitable winding to be made. It can be replaced with fabric tape, while shorter cables are used to reduce resistance.
For domestic needs, as a rule, three turns are sufficient, with an increase in their number, the current value of the device increases. Additional power can also be obtained by installing several transformers.
What you need to know
A do-it-yourself spot welding machine assembled from a microwave requires the use of electrodes in secondary circuits. If two transformers with the same power are used, they must be connected with 10 mm thick cables, the ends of which are connected to the electrode. Care must be taken when connecting the primary and secondary windings to prevent short circuits.
If the magnetron window is insufficient, which makes it difficult to add cable turns, and at the same time use transformers with high power, a series connection of the secondary windings is recommended. The winding direction must be consistent, if this rule is not observed, the probability of obtaining an antiphase and, as a result, zero output voltage is high.
On transformers, leads of the same name are indicated by a symbol or letter. In the absence of any identification marks, it is recommended to use a voltmeter for verification. It is necessary to apply voltage to the primary windings by connecting the device to the secondary. In the case of connecting the windings with opposite terminals, the voltmeter will show the voltage. This is due to the fact that the primary winding gives voltage to the secondary, where it is converted and doubled.
When a pair of windings is connected 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 it is worth considering the network performance. The total voltage of the devices must not exceed the set value. The best option is the current strength in the range of 1000-2000 A.
The electrodes are best made from copper rods having a sufficient thickness, and the diameter should correspond to the parameters of the wire. Over time, the electrodes change their shape and become unsuitable for work, so they must 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 power. The best option is to connect the electrodes to ferrules made of copper and fixed at the ends of the wires. To prevent oxidation of copper at the points of contact, it is necessary to solder the parts, this will also simplify further cleaning. It is worth noting that crimping can be used to reduce losses.
The spot welding machine for batteries is often equipped with a screw clamp, which provides additional force during operation. The device is controlled using a lever or switch. Of particular importance is the high-quality fixing of the electrodes, which is necessary for normal functioning. In operation, a device with the possibility of stationary fixing and sufficient mass will be more convenient. The switch must be reliable and long.
The switch button is connected 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 a lever control principle, the switch is mounted on the clip, thus, it becomes possible to control the welding process with one hand.
Manual spot welding devices are turned on and off only with compressed electrodes. It is recommended to install forced ventilation, which will allow you to work without regular interruptions and monitor the level of heating of conductors and electrodes.
Obtaining a high-quality connection is possible only with knowledge of all the subtleties of the process, in particular, it is necessary to be able to determine the stages of readiness by the external characteristics and shade of the material, and have experience working with the current pulse. The speed of movement of the electrodes should be at the same level throughout the welding process.
Of particular importance is the observance of safety standards during operation, since a faulty spot welding machine can be harmful to health and ruin the workpiece. It is also necessary to adhere to the following requirements:
- the use of a special mask to protect the face and eyes from splashes of metal and sparks;
- insulation of connecting and electric cables;
- lack of flammable materials and liquids near the place of welding;
- the use of mittens and gloves to protect against burns;
- regular ventilation of the room, ensuring the purification of air from harmful gases;
- availability of fire extinguishing agents;
- protection of wooden surfaces (flooring, table) from sparks.
Do not forget about the preparatory work necessary to obtain a high-quality weld. The elements used are pre-cleaned of dust and dirt with brushes and special compositions. Do-it-yourself spot welding from a welding machine always includes several basic steps, which include the following:
- placement of the connected elements in the required position;
- pressing parts between electrodes;
- heating until plasticity, allowing the metal to deform.
It is worth noting that during operation, a lack of fusion point may occur due to the absence of a molten core or its small size. Tracking this defect can be difficult, but it can lead to the following consequences:
- dents and shells;
- melting of surfaces of elements;
- through burning material
- porous structure of the welded core.