Spot welders are used in almost all plants where it is necessary to join sheets. The advantage of welding machines is the precision of joining (with very good electrical contact), and a very low voltage between the electrodes, which makes the device safe. The presented device is of course not a professional welding machine, but an amateur device to be made in one afternoon, allowing for easy welding of metal. A transformer from a microwave oven with a wound secondary winding was used for the construction. The high-voltage winding was carefully removed with an angle grinder, taking care not to damage the core and the mains winding
Then, 2-3 turns of a copper wire 4AWG with a cross-section of 21mm ^ 2 were wound in the vacated place. Remember to properly protect the sharp edges of the core so that they do not damage the insulation on the wires.
A simple wooden stand and appropriate electrodes remained to be made
When using the welding machine, care should be taken due to the high temperature in the place of welding. Do not overheat the transformer and cables!
Brilliant in its simplicity. What are the electrodes made of? I would add a spring that would not allow the electrodes to be short-circuited accidentally, and a switch that turns the device on only when it is pressed. greetings
Very interesting and brilliant in its simplicity design. in my free time, do something similar because I have to mount a hinge to a metal cabinet are the electrodes maybe from some plug ?? How much power should such a transformer be? roughly yeah ??
In the soldering iron, the transformer has a power of approx. 100VA. The one from the microwave, I think, about 800VA. I also wonder what the smallest transformer power would be enough to make a welding machine. Greetings.
I have a similar device, but from a Rubin transformer (yes TV from behind the eastern border) 300W. It even works well, but the welding takes about 4 seconds, which is quite a long time ... so 300W is a little bit ...
Rather, it is definitely 230V. What would it be otherwise for?
The photos of the transformer show a rather thick flat bar on the primary winding
The visible winding is made of round wire. If you are serious about such a welder, the transformer used must have a central column cross-section above 15cm?. Below this cross-section, at most a toy will be created. A relatively useful welding machine can be made on a core with a cross section of more than 20 cm?.
For 0.5mm low carbon steel sheet: ? working part of the electrode = 4 mm, pressing force = 600 N (1.5 kN), welding current = 2 kA (4 kA), current flow time = 0.2 s (0.04 s). In parentheses, as an example, I have given the parameters of rigid welding, which are mainly used in large-scale production. Source: Welding guide.
I would recommend hobbyists to get acquainted with the method of welding with energy accumulated in capacitors. It is an ideal method for joining thin sheets, wires of various metals and alloys. Tubes were once assembled using this method.
The welding method shown in this thread is not a pure resistance welding method. Rather, it is a game, because the current is turned on by contacting the electrodes with the material and the current is interrupted by opening the electrodes. It looks effective but it is not effective.
As you wrote, first the welded sheets are pressed with electrodes, and in the final phase the voltage is applied to the primary winding of the transformer. The thickness of the sheets to be welded depends on the duration of the current flow and therefore the primary winding is switched on by a timer. Depending on the purpose and construction of the welding machine, the method of pressing itself is carried out in different ways.
so, for example, it would be better to add switching on the primary winding with a foot switch and a triac? Or just a switch on the leg? And something that causes a strong pressure on 2 sheets? additionally, for example, 2 such transformers can be connected in parallel? Additionally, this something is able to weld a sheet to a profile? And the opposite electrode must be on the opposite side, ideally, or if it will be a little next to it or permanently attached somewhere nearby, it will work or not?
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In addition, pressing the electrode with a pneumatic actuator is a good idea? I mean, the higher the contact pressure, the better? I am not going to do any mass production, but the topic interested me
Hmm ... a welding machine, but ... well, the quality of the welds, and this is unmistakable in amateur conditions. For a simple connection of thin plates, it is okay, but hinges, i.e. plates from 0.5 mm, should be connected permanently and probably it is impossible. Here you need pressure and a strong short impulse. In my company, we use welders with powers from 70 kVA to 250 kVA. Practically, the current for point connection of two 0.7 mm sheets at a point of 5 mm is about 60 - 80 kA, heating time from 6-14 periods. Pressure with a pneumatic cylinder of several hundred kilograms (I don't remember exactly). The relationship is such a better weld is formed with a shorter impulse and higher current, and worse if it is the other way around. What is described here is such a toy with little practical usefulness.
It's nice that you shared the information from your plant, but I'm surprised that you want to compare professional equipment to DIY. Maybe you did not read the content carefully, but it is enough to read the title of the topic and everything is clear.
It's not cool I don't want to compare. My main point was that miracles should not be expected. As I wrote for thin plates - some small elements, it may be suitable. The load-bearing elements are unlikely to be welded and due to current limitations, it is better to try the welding by breaking it. The rupture should tear the weld together with the material, the second sheet should have a hole - then the material is welded.