A simple and cheap spot welder

As for the functionality in the workshop, I recommend that I made a very similar device, but with the use of a thicker wire on the secondary and the pot handle it was possible to weld without any problems.
The microwave Trafo is perfect for amateur workshops.

tygrysek467 wrote:

As for the functionality in the workshop, I recommend that I made a very similar device, but with the use of a thicker wire on the secondary and the pot handle it was possible to weld without any problems.
The microwave Trafo is perfect for amateur workshops.

Congratulations. However, for the welding machine to be a truly functional device, the transformer core should have a cross-section of at least 25 cm square. The secondary winding should be made not with a wire, but with several layers of copper tape slightly smaller than the length of the transformer column. In a correctly calculated transformer, the voltage on the secondary winding is 3-4V, and this is sufficient for the correct operation of the welding machine. The whole problem lies in the correct cross-section of the secondary winding. To obtain a current of 2-3kA, the winding cross-section must be quite large. The current distribution per mm square can be taken much higher than in a transformer designed for continuous operation, but it is not worth exceeding the current density above 10A / mm square. If you count straight, to obtain a current of 2-3000A, the cross-section of the secondary winding should be 200-300mm square. Obtaining such a cross-section when winding with a round conductor is rather impossible. The electrodes can be purchased original (suitable alloy), but they are quite expensive. In a friendly factory that makes a car tinsmith, we can obtain electrodes that are no longer useful for them, and in our case we will restore them to a second youth and they will serve us for a long time.

I like this patent, but why was the magnetic shunt left in the match?
In a microwave oven it has a justified application, while in a welding machine it limits the already thin possibilities.

greetings..........

It is worth congratulating the author on the performance, he showed that thin sheets can be welded. Not everyone needs to weld sheets with a thickness greater than 1mm.
I had a welding machine that could handle 1mm sheets, it was a market import from across the eastern border. I have added a timer for it on ucy121. The system measured the welding time precisely enough, but I had to give it up. At the moment of tightening and disconnecting the 230V circuit with the contactor, such a large self-induction force arose that the contactor, after opening for up to a second, held the arc. I am writing this as a cautionary tale for using disconnect drivers.
The only way in simple solutions is to work in an idle state and practice in the pressing force and pressing time,
Greetings, Marek

I have a question for the author, I need to weld sheet metal with a thickness of about 0.2 mm (battery terminals), can it be done with this welding machine?

The battery welder must have a specific design, i.e. both electrodes side by side. Something like below.
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Quote:

The system measured the welding time precisely enough, but I had to give it up. At the moment of tightening and disconnecting the 230V circuit with the contactor, such a large self-induction force arose that the contactor, after opening for up to a second, held the arc. I am writing this as a precaution against the use of disconnect drivers.

So why didn't you use the triac ??

Kamis47 wrote:

So why didn't you use the triac ??

Because in 1977-79 I could see the triac in Radiotechnik with a question mark,
Marek

This is sorry. I was born in an age where when you need something, you only need to have enough money ...

A question for you about a microwave transformer or in every microwave oven, no matter what company, is the same power?
MEGABIT I have a question, where does this copper holder for the migomat tips come from?

austin00 wrote:

A question for you about a microwave transformer or in every microwave oven, no matter what company, is the same power?

Not. Depends on the microwave oven model. Most often 750-850W. the bigger one is 900-1000W. But once upon a time I saw an old powerful Sharp that had 1200W of microwave output power.

I am at the stage of building a welder and here it is a bit of a dilemma, because the veins do not fit in all, so I split the veins in half and part of the veins (the protruding one I hit towards the bolt ... Will it lose the ampere amperage through this solution or is it suitable for nickel-plated plates?

I know aesthetically this is not the top of my dreams, but at the moment I do not have access to the eyelets.
Everything will be in heat shrink.

yetihehe wrote:

In this machine, the electrodes are from MIG.

What electrodes? As already, this contact tip is a professional name.

Alya wrote:

Aa, that is, such a transformer from a welding machine will be suitable?

karol3 wrote:

It all depends on which welder. While the primary winding can be used in most cases, unfortunately the secondary winding cannot.

The secondary winding can always be wound up, as long as there is room, the circus can start with columnar 3-phase cores, which are usually wound with copper flat bars of square or rectangular cross-section, insulated with dialectric material impregnation, stove, resin or mixed varnishes.

morph13 wrote:

The same solution (trafo) is used in a transformer soldering iron.
I wonder if such a luck can be adapted for this purpose.

Mercy. Definitely not, because spot welding requires currents in kA. And the times of current flow are counted in ms and not rarely in us. Also, for example, the welding machine must reach the maximum current during welding in order to heat up the point-pressed sheets in a given time to the temperature of the molten plasticized metal (called the welding nucleus). The time of current flow and its value depend on the physical properties of a given material, and these in turn depend on the thickness and size of the weld that we want to obtain.

Hello. I have recently made a welder for welding battery cells. Trafo from the microwave. On the secondary, three coils of the line with the maximum cross-section possible. It is necessary to remove this jumper between the windings because it lowers the power. As for the time control of switching on the trafo, I had a problem with triacs because they got a breakdown and they were on 800V. I used the R15 relay. I made the electrodes from 10mm2 Copper wire. Batteries are welded, I have not tested on thicker sheets.

kuraś wrote:

I had a problem with triacs because they got puncture and they were on 800V.

And were the extinguishing circuits? As it was not, and by the way, the triacs should be at 1200V, they would not beat me even without the extinguishing circuits. But each transformer has different parameters, so we won't do much with divination. You have to choose the extinguishers and that's about it. The relay is also not the best way to control such a luck, because dirt, burning the contacts will cause the power of the transformer to be reduced. Linear contactors look better in this situation, but they are expensive.

I made a ready-made schematic on a PCB purchased on alledrogo. There was, of course, a throttle circuit in the triac circuit. The relay for my occasional use is enough for years, that's why I finally put it in. Greetings.

What was the LC or RC or RLC extinguishing system?

Where can you buy such electrode holders in Poland? or what is it called in Polish? because in English you can find it under the name "copper lugs solderless"

flubber.trip wrote:

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. Regards

The welding electrodes are usually made of special copper alloys, mainly CuCr1Zr (eg Wirbalit HF / N) or CuCo2Be (eg Wirbalit B). I recommend that you visit the website of a company that sells the material in the form of semi-finished products (round bars, flat bars, etc.) or ready-made electrodes:

https://www.gjg-system.pl/elektrody-do-zgrzewarki-punktowej/