The spot welding machine 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 connection area and the size of the electrodes.
Description
Spot welding is used in both industrial and domestic environments. It is optimally suited for working with curved profiles, steel and non-ferrous metals. This technique provides high seam strength and cost-effectiveness. In addition, it can be used in the repair of kitchen equipment and various tools.
The process is based on the combination of individual elements and their fixation. After that, with the help of electric current, the parts are heated. Particular attention is paid to the relative position of the elements at the required point, which is maintained throughout the entire workflow. Parts become one as a result of the melting of the material that has arisen underthermal pulse.
Types
The mechanical spot welder is manually operated and requires the current to be set before each use. The main advantage is the simple design and the ability to manufacture at home. They have become the most widespread and have found application in many industries.
Automatic tools allow you to get connections with a minimum amount of rejects. At the same time, special skills are not required for work and labor costs are reduced.
Pneumatic and hydraulic devices are widely used in industry.
The inventory spot welder is quite expensive, but it has become widespread due to its ability to connect to a household network, an extensive set of functions and a compact size.
Despite the fact that portable units are somewhat inferior to stationary ones, they provide a high-quality seam at minimal cost for the purchase of equipment. At the same time, you can work with metal up to 6-7 mm thick.
Basic elements
Spot welding machine can be made at home. The most popular devices with unregulated current. Such a device is controlled by an electrical impulse, the duration of which is changed using a special relay or switch.
One of the main elements is a transformer that providesrequired current level. For this purpose, you can use a coil from a microwave oven, which has suitable characteristics and is affordable. Such a home-made spot welding machine is suitable for working with metal parts with a thickness of 1-2 mm. 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 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.
Wrapping
The wires of the secondary winding in the transformer are removed with a hacksaw or chisel, in some cases it is necessary to resort to drilling. It is not recommended to knock out the winding so as not to damage the cables. If shunts are present, they must also be removed as they help limit current.
A new secondary winding is made after removing the necessary parts. With a copper cable with a cross section of at least 100 mm², you can achieve optimal voltage values. In some cases, it is necessary to remove the outer insulation, which does not allow making a suitable winding. It can be replaced with fabric tape, using shorter cable lengths to reduce resistance.
For domestic needs, as a rule, three turns are enough, with an increase in their number, the current of the device increases. Also, additional power can be obtained by installing several transformers.
What you need to know
A spot welding machine, assembled from a microwave oven with your own hands, 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 10 mm thick, the ends of which are connected to the electrode. Care must be taken when connecting the primary and secondary windings to prevent a short circuit.
When the size of the magnetron window is insufficient, which makes it difficult to add cable turns, and at the same time using transformers with high power, series connection of the secondary windings is recommended. The winding direction must be consistent, if this rule is not observed, there is a high probability of obtaining antiphase and, as a result, zero output voltage.
Voltage
On transformers, 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 to check. 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 leads, 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 connecting a pair of windings with the same output, 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 canuse several transformers, while taking into account the performance of the network. The total voltage of the devices must not exceed the specified value. The best option would be a current strength in the range of 1000-2000 A.
Electrodes
Electrodes are best made from copper rods of sufficient thickness, while the diameter must match the parameters of the wire. Over time, the electrodes change their shape and become unsuitable for work, so they need to be pumped up systematically. It is recommended to reduce the number of connections and the length of the cable from the transformer to the electrode in order to increase the power. The best option would be to connect the electrodes to tips made of copper and fixed at the ends of the wires. To prevent oxidation of copper at the points of contact, you need to solder the parts, and this will also simplify further cleaning. It is worth noting that crimping can be used to reduce losses.
Management
The battery spot welder is often equipped with a screw clamp to provide additional force during operation. The device is controlled by 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 weight 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 clamp, so it becomes possible to control the welding process with one hand.
Manual spot welding machines turn on and off only when the electrodes are compressed. It is recommended to install forced ventilation, which will allow you to work without regular breaks and monitoring the heating level 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, to have experience with a current pulse. The speed of movement of the electrodes must be at the same level during the entire welding process.
Safety
Observing safety regulations during work is of particular importance, as a defective spot welding machine can be harmful to he alth and spoil the workpieces. You must also adhere to the following requirements:
- using a special mask to protect the face and eyes from metal splashes and sparks;
- insulation of connecting and electrical cables;
- no flammable materials and liquids near the welding site;
- use of mittens and gloves to protect againstburns;
- regular ventilation of the room, which cleans the air from harmful gases;
- availability of funds to extinguish the fire;
- protection of wooden surfaces (flooring, table) from sparks.
Process Features
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 the help of brushes and special compounds. Do-it-yourself spot welding from a welding machine always includes several main steps, which include the following:
- placement of connected elements in the required position;
- pressing parts between electrodes;
- heating until plasticity appears, allowing the metal to deform.
It is worth noting that during operation, a point of lack of fusion may appear, which occurs due to the absence of a cast core or its small size. Tracking this defect can be difficult, and it can lead to the following consequences:
- dents and shells;
- melting element surfaces;
- Pierce through material
- porous structure of the welded core.
