How is contact resistance spot welding done?

Resistance spot welding has a number of advantages - the ability of seams to withstand considerable mechanical loads, low cost of equipment, the ability to create an automated process, etc.

Spot Welding Scheme

Spot welding scheme.

The welding machine of this type is relatively easy to assemble, which is also its advantage and makes it possible to make the machine with your own hands. The only disadvantage of this type of welding is the inability to create a sealed welding seam.

How to make a spot welding transformer

The main component of the welding machine is a transformer. Ensuring an increased rate of welding current is achieved by a large transformation ratio. The transformer must have a capacity of at least 1 kW. For this purpose, perfect transformers from microwave ovens with sufficient power.

It is easy to find such a transformer, and a welding machine of this type can be used for welding 1 mm steel sheets. For the manufacture of apparatus with greater power, you can apply multiple transformer units.

Diagram of the spot welder

Diagram of apparatus for spot welding.

In the transformer are the primary winding and magnetic core, which you will need. The secondary winding should be cut with a hacksaw or any other tool. It is very important to prevent damage to the magnetic circuit and the primary winding. In the event that there are shunts in the transformer to limit the current, they must be removed.

After removing all unnecessary (in this case) elements, you should create a secondary winding (new). In order to provide a large current, it is required to use thick copper wire, the diameter of which should be not less than 1 cm. Three turns will be quite enough to achieve an output of approximately 2 V.

More powerful welding with your own hands will turn out if you connect two (or more) transformers to each other. The main thing is to take into account the possibilities of your network, otherwise, including spot welding, you will have to face various troubles, when the lights flash, fuses and so on.

Back to table of contents

Assembling spot welding with your own hands and making electrodes

Electrodes are a very important element in welding, so they should be manufactured with all the recommendations taken into account. For the manufacture of these items you need copper rods. It is better to choose rods of large diameter (at least with the thickness of the wire). If your plans include making a welding machine that has a small capacity, you can use the tips that contain powerful soldering irons.

Depending on how often resistance welding is used, over time the shape of the electrodes is lost. After a while, they can be sharpened and replaced with new ones if necessary.

Scheme homemade welding machine spot welding

Scheme homemade welding machine spot welding.

It is desirable that the wire that goes from the electrodes to the transformer, has a minimum length and with a minimum number of connections. The fact is that at the junction the power is partially lost. On tips of a wire it is necessary to put on tips from copper and already through them to connect a wire and electrodes.

Each tip should be soldered to the wire. Such measures are necessary for the reason that when welding copper contacts can gradually oxidize. This explains the significant loss of power and the failure of a self-made welding machine. Soldering the wire and the tip is a rather difficult task, which is explained by the large diameter. For this purpose, you can use tinned soldering tips, which can be purchased at any specialty store.

The reason for the additional resistance that spot welding is capable of causing may be in the solder joints of the tips with each of the electrodes. However, this deficiency cannot be corrected, because the electrodes should be periodically removed for sharpening or for the purpose of complete replacement. But here it is worth noting that these compounds are quite easy to clean from the oxide, in contrast to stranded wires that are crimped tip.

Back to table of contents

Spot welding and how to manage it

Spot welding is controlled by a switch and a lever. In order to ensure proper contact of parts that are subjected to welding, it is necessary to provide sufficient compression force between the electrodes.

If necessary, weld thick sheets of iron is required to apply a more powerful contact spot welding (with greater force of compression between the electrodes). It is desirable that the lever was not short, while it must be strong enough. The welding machine must have a massive base; make sure in advance that it can be fixed to the table.

Spot welding and spot welding machines

Schemes of spot resistance welding and machines for spot resistance welding.

For a large clamping force, which should be carried out by contact spot welding, made by hand, both the lever described above and the lever-screw clamp in the form of a screw tie located between the base and the lever itself can be used. If you wish, you can use other methods, but they may require special equipment.

To install the switch, select the primary winding, more precisely, its circuit. The fact is that the secondary circuit is characterized by too much current, which can cause additional resistance and welding of the contacts.

If you decide to use a lever presser mechanism, it is better to choose a lever for fastening the switch. In this case, during operation, the current can be switched on and the lever can be operated with one hand. Thus, it will be most convenient to hold the parts to be welded.

Back to table of contents

On the operation of homemade resistance spot welding

Block diagram of the installation of resistance spot welding

Block diagram of the installation of resistance spot welding.

In order for a self-made welding machine to serve you for quite a long time, it is very important to use it correctly. When turning the welding current on and off, the electrodes should be compressed. Failure to comply with this condition can lead to intense sparking, which can cause burning of the electrodes.

It is recommended to cool the welding machine by using a fan for this. Otherwise, you will have to keep under constant control the temperature of such elements of resistance spot welding, such as transformer, conductors, as well as electrodes. And to prevent overheating of the welding machine, it is necessary to work with periodic interruptions.

Use a home-made welding machine should be based on its capabilities, otherwise the spot seams may turn out to be of poor quality or not at all.

Back to table of contents

Recommendations for making a welding machine do it yourself

Assembling resistance spot welding at home has a number of nuances that must be followed. Some seemingly minor flaws can cause rapid failure of the welding machine.

Examples of the use of electric arc spot welding

Examples of the use of electric arc spot welding.

In order to make (described) contact spot welding with your own hands, you may need the following materials and tools:

  • transformer;
  • copper rods (rods);
  • lever arm;
  • switch;
  • copper thick wire;
  • tinned tips for soldering;
  • hacksaw (for metal);
  • Bulgarian;
  • drill;
  • drill;
  • screwdriver;
  • insulating tape.

Today, there are a large number of amateur designs for spot welding machines. Various components can be used for the assembly of spot welding, for example, TC270 power transformers, which are embedded in old (color) lamp TVs.

To create structures of this type at least six transformers are used. Already known designs with microprocessor control. At the same time, any homemade dotted device remains unchanged: the creation of a short-term pulse of welding current, as well as ensuring sufficient clamping force in the area for welding.

Add a comment