The principle of spot welder from 220V
Take a look at the picture at the ready to use machine.
A very large amount of current needs to be applied to the metal to melt it. The voltage is not important. 3 volts or even less is enough. It is not desirable to make various experiments with the indicators. Have long tested homemade welding machines, made from a transformer of the microwave oven. They have been repeatedly tested and are therefore quite reliable.
The power of the transformer must be chosen according to the thickness of the workpieces. For example:
The primary winding must be chosen based on the capacity of the unit. It is very difficult to make a transformer yourself, so it is desirable to use a ready-made one that fits in the microwave oven. This unit has its own peculiarities:
- The radiating element will require a high voltage of several thousand volts. But the level of amperage will not play a role;
- The power on the windings will be the same. If one wants to increase the number of turns on the secondary winding, the voltage will also increase, but the amperage will decrease;
- The transforming elements in the microwave oven have a power of 3000 volts or slightly less. To make a spot weld, it is enough.
The necessary components are bought in radio shops. Or you can use the insides of an old microwave oven to make one. The result is a current output of 1kA. This is enough to melt the metal at the contact points. This will result in a good connection of several parts. A 3kW transformer is used for this purpose.
Schematic diagram of a home-made device
The main element of the welding machine is the transformer, which is taken out of the unnecessary microwave oven. The household appliance must be serviceable. When you make a device for welding thick metal sheets in a circuit include 2 transformers, connected by a winding. To avoid mistakes, before assembling, we make a drawing, on which all elements of the construction are transferred. You can use ready-made circuits that allow you to easily assemble a welding machine from a microwave with your own hands.
How I made a welder from 4 microwaves
Post, I think, for the masters of amateur, a simple welder from affordable components will be to everyone’s taste.
So, we are going to do with microwave transformers, we need 4 of them
We saw off all the excess with an angle grinder, and. This is a small secondary winding, the one that is shorted to the body
Now we wind the 8 turns of thick copper wire in the holes in each of the transformers, easily and without straining.and in no case do not cut the wire but let it all through.
Next, we fix these comrades on some plank and connect the power to the primary windings in parallel.
That is, we take the wire from the same microwave and connect one contact to each, for example, the right contact on the windings of the transformer, and the second to each left.
Basically everything is ready, you can plug it in and check the voltage.
Voltage should be 26 to 32 volts. it is enough for welding.
but if you get 14-15 volts. it happens. This can be fixed by swapping the pins on the last transformer in the circuit.
Then we screw the controls, the holder and the clamp to the ends of the thick wire and weld. You can also put a microwave fan on the blower.
Weld carefully, observing all safety rules.
I’m not very good at it, but I’m just learning.
To create it took 12 meters of soft copper wire single core, copper core diameter of 4.5 mm and a braid of 6 mm
4 identical transformers from microwaves
and a meter of simple 1mm wire to connect everything. and terminals.
Anyone interested, you can check out the creation video in detail
It remains to know where to get 4 transformers at once. Buy 3 more microwaves? Chet in my opinion, it is easier to buy a welder in Leroy.
This stuff eats up to 4 kilowatts and a regular socket, especially in old houses can’t handle it. We have a limit of about 3.5 kW.
I thought at first it was an extra finger.
now you teach people how to assemble welding machines!!
Creosan was made from one microwave in my memory. Everything worked fine.
Why do you need four irons?? Because there were.?
We check the voltage with a voltmeter is clear, and the current with a current meter?
35 volts? And what are you going to use it for, ears to buttons??
Contact welding from a microwave how to make?
I’ve been seeing a lot of lithium-ion batteries in different devices lately. Sometimes it even came to assembling batteries and I connected the cells by soldering. However, I wanted to take a better route and use a contact welding machine for this.
Buy ready-made welding torch, even on Aliexpress, I was stifled by greed, as the need for welding batteries I have very rarely, and the device is expensive. So I decided to build such a machine by myself and enjoy the process.
There are many methods of assembling a contact welder with your own hands. You can use a car battery, you can use a transformer from an old microwave oven. There are different ways to control the welding current and pulse width. In the simplest case, you can simply connect two thick wires to a car battery, make electrodes out of copper wire, connect it all together and weld manually, measuring the time “by eye”. You can make control based on Arduino or a specialized time controller, relay from a motorcycle, etc.д.
Well, I decided to make a welding machine based on a transformer from a microwave oven (microwave). It is in any case will be smaller and lighter than the car battery. And the controller, which doses both current and pulse width, I bought on Aliexpress, because it is inexpensive, and it is a finished product, which does not need to assemble itself.
An old 750 watt microwave transformer I bought on Avito for 600.
And also at the market I bought 1 meter of multicore power cable with a cross section of 25 squares for 125. precisely, I took 2 meters (with reserve), but one is enough.
On Aliexpress I bought: a controller with triac for 40 amps (no more needed for welding 18650 batteries), a 9 volt AC transformer to power the controller, a foot pedal for easy operation, as well as the most expensive. is the wire with connectors (you could save on this detail by making electrodes from a thick copper wire and connecting them, for example, through the terminal block to the power wires) electrodes (copper needles). In general, from what I bought on Ali need only the controller and AC transformer for 9 volts, the rest is optional.
Cables with connectors and handles with collet clamps:
The first thing to do is to get rid of the secondary winding of the transformer. It’s at the top and wound with a thin wire. Just saw off the coil with a hacksaw.
After that, the rest of the wires can easily be drilled out with a thick drill bit.
And then. you can knock out the wire with a file and a hammer. It’s not hard at all.
If your transformer has these additional bags of metal plates, they also need to be removed.
Now you need to take a thick cable and put it in the place of the former secondary winding, making two turns. So from a step-up transformer we get a step-down transformer. The output voltage is now only about 2 volts, but the current has increased many times over, in the tens or perhaps even hundreds of amps. This voltage is safe for a human and it’s ok if you touch the electrodes with your hand.
The cable ends are clamped in the terminals and insulated with heat shrink.
Now you need to assemble the rest of the electrics according to the diagram.
The foot pedal comes with a 10 cm piece of wire, so I replaced it with a long one, so the pedal can be put on the floor.
Connected the supply wires with a terminal strip. You could have soldered.
I connected the wires to the transformer via removable terminals, so that it could be easily disconnected.
Well, I simply soldered two wires to the controller, although it would be better to screw on the screws and round terminals, but I do not have them on hand, unfortunately.
Anyway, the circuit is ready and you can plug it in. Please note that we used an AC transformer to power the controller, not a DC transformer.
When turned on, the digital indicator and the various LEDs light up.
The left knob is used to set the pulse duration (1 to 50, each one equal to 20 milliseconds). The right knob sets the power, ranging from 30 to 99%.
When the pedal is pressed, the circuit turns on for a set number of milliseconds.
To weld the strip to the battery, you need to press the electrodes firmly against the surface. The surfaces of both battery and tape should be absolutely clean, without dirt, glue, oxide, etc.п. Otherwise the tape won’t weld.
I had no experience in resistance welding, so I had to choose all parameters experimentally, practicing on a useless battery. Properly welded tape holds up well and comes off when force is applied, leaving a small piece on the radiator. The pulse width and current intensity depend on the transformer power, the thickness of the nickel strip, and maybe other conditions too.
At me more or less correct welding began to turn out with parameters 35/70. But I think I would have been better off with a more powerful transformer, the pulse width would have been shorter and there would have been less overheating. But I still have to experiment.
In general, the self-assembly of the contact welding machine is not difficult at all. For me the most painful thing is to make a case for it, which I will do in the future. Or maybe I’ll just mount all the components on a piece of plywood. The main thing is that the welder works :).
Note: This article and the images in it are subject to copyright. Reproduction in part or in full on other resources without permission is prohibited.
What I got in the end
The power of my microwave spot welder during welding is about 4150 watts, current consumption after 2 sec. welding about 18 A, the secondary voltage was about 2.5 V, the approximate current in the secondary winding of 1650 A.
The machine welds 3 mm wire very fast, even melts it if you overdo it. Welds sheet steel in 2 pieces of 1.5 mm is great and also welds: 2 pieces of 1mm, 3 pieces of 1mm, haven’t tried more yet, I think it can weld steel up to 2mm (2 pieces of 2mm).
The secondary winding warms up after about 7-10 points.
Homemade arc welder, made from a microwave: detailed photos of making, also a video.
A simple welder can be made from two transformers from old microwave ovens, the whole process of making a welder is shown in these pictures.
We disassemble the two microwave ovens that are in disrepair and take out a couple of transformers. These transformers are step-up transformers, to operate a magnetron, such a transformer gives out 2.5 kV.
We will not disassemble the core of these transformers, we just saw and drill out the secondary high-voltage winding. Usually this winding comes from the top and the 220V primary from the bottom.
Use a metal saw to cut the secondary winding on both sides of both transformers, working carefully so as not to damage the primary winding.
The rest of the winding is drilled out and knocked out with a hammer.
In the picture, the transformer on the left, above the winding, has a current shunt that separates the windings. To increase the power it also needs to be knocked out.
Then we need a stranded wire in plastic insulation, six squares, about 12 meters long. You can get more stranded wire.
Wind about 17-18 turns on each transformer, the height of 6 rows and a thickness of 3 layers. It needs to be wound very tightly, the wire shouldn’t wiggle.
The windings (those that are wound) connected in series.
Now connect the 220V high-voltage windings (those that were already on the transformers) in parallel. I used automotive lugs, insulated with heat shrink tubing.
I plugged it in and measured the voltage on the secondary winding I wound, it was about 31-32 volts.
I used self-tapping screws to attach the transducers to the board.
When welding I will use 2.5 mm electrodes and weld metal 2 mm thick.
To summarize: welding with this homemade welding machine can be, but not for a long time, transformers begin to heat up, and so after each electrode should give time to cool down.
I’m satisfied with the result, for home use it is quite useful, considering the fact that I got the materials for free.
In addition, you can watch the author’s video, which shows how to make a welding machine with their own hands out of the microwave.
Microwave spot welding with my own hands
Homemade spot welding made from a transformer from a microwave: scheme, photo and description of making a welding machine at home.
Greetings! I want to show a homemade spot welding, made by Vadim Orekhov. Further from the words of the author.
For the basis of self-made, was taken an old and broken microwave oven, from which was safely extracted the transformer and the fan.
From the transformer was removed the secondary winding, and instead it was wound three turns of welding wire cross section of 16 mm2.
Later purchased at a flea market, 16mm copper rod. from which the turner turned out at my request future electrodes. The electrode drawing is attached
Well, while the turner is creating, I am improving the transformer and all components that serve it. Included in the circuit was a circuit breaker, a fan to blow the transformer, a magnetic starter, a microswitch to control the starter and a pair of lights to indicate the presence of the network and the transformer. For the especially curious, wanting to know how it is connected, I attach the circuit diagram.
In my scheme, used in the micro switch is operating on 220V, this is fraught with current losses, to avoid such cases, it is necessary to introduce a low-voltage relay to the circuit, which I will certainly do in the following refinements
This is how I arranged the nodes inside the unit.
The lid of the case, was made from the same microwave, the ribs of air intake (those at the side) are native, and the holes on the back wall are made in the form of tube grids calculated in the program COMPASS 3D. printed and transferred to metal, drilled and deburred.
Well, with pliers will have to work more to ensure that the clamp the desired force, I think to make the eccentric, because the lever system will take up a lot of space.
In operation: the metal thickness less than 0.8mm. welds well, but that would cope with a metal thicker, I think you need to finalize pliers and possibly make a sharper angle on the electrodes. I think the above information is enough for the same samodelchiki, like me, who will want to repeat this design.
Spot welding with their own hands from the microwave!
Earlier we wrote: what can be made from an old microwave oven. Today, let’s look in detail how to make a machine for spot welding with his own hands from a high-voltage transformer or MOT (Microwave Oven Transformer) from an old no good microwave. Provided, of course, that the HV transformer is intact (at least its primary winding) and something else is faulty: magnetron, loop, control board, etc.д.
For the craftsman there is a need for spot welding. This spot welding gives a current of up to 800 amps, which is enough to weld sheet metal up to 1.5mm.
So we need an old microwave oven and the bigger it is the better. Larger microwave ovens have a higher wattage transformer. If you don’t have an unwanted microwave, old microwaves are often available for cheap on forums and free bulletin boards, or you can look for them near dumpsters or ask at telemarketers.
Attention! Before starting to disassemble the microwave oven must be turned off from the mains. Next we disassemble the microwave oven. Inside the microwave oven there are some parts which are dangerous even when turned off and can cause serious electric shock, these are capacitors (see Pic. photo) that can hold a charge for some time. So we discharge the capacitors by shorting the leads with a screwdriver. The HV transformer is on the bottom.
Among microwave oven internals we are primarily interested in the high-voltage transformer.
The transformer consists of core and two windings: primary and secondary. The primary winding is wound with thicker wire and has far fewer turns.
The core of the transformer is bonded together with two thin welds, as you can see in the photo.
How to make a transformer for welding?
You’ll need a hacksaw or angle grinder to cut this weld and a hammer and chisel to get to the windings of the transformer.
Be careful when taking the primary out of the transformer as we will need it again.
Try not to bend or scratch it.
The secondary winding might be wound too tightly and be hard to get out, so if you don’t need it you can cut it and pull it out piece by piece to make it easier.
Now, after all the manipulation, you should have in your hands a whole and undamaged transformer primary and its core, divided into two parts (without glue and paper, which held its windings inside).
The next step is to wind the secondary of the transformer. To do this, you need to take a copper (must be!) cable of about the same cross section as the slots in the transformer core (about 7 mm) and wind two coils.
Then I fastened the core of the transformer to its base using regular 2-component epoxy and gently pressed it in a vise and left it to glue.
After the epoxy dries, the transformer should look like this.
Also not easy, but the transformer iron will be intact, which is important. To do this you need to remove the winding, using a chisel, a chisel, a metal saw, etc.д.
Next, wind the new winding on the transformer. It is made of a stranded wire of at least 100 mm2 (or more than 1 cm in diameter). It will be enough to make 2-3 turns. If the wire has too thick insulation, it is allowed to remove it and replace it with fabric insulation tape. If two transformers are used at once, the secondary winding for them is made common, but it is very important to connect the leads from their primary windings correctly.
The output voltage of the transformer was a little over 2 volts but the current was about 800 amps! That’s enough current to make a solid connection when welding metals.
Welding enclosure with my own hands
Now all that is left is to make the case for the spot fusion machine. You can make it out of metal.
You can make it out of wood. You can make it based on what you have on hand.
The photo below shows how to make the case.
After I cut out all the parts of the enclosure I carefully rounded off the edges with a router. You will need to make a notch in the top lever so that the lever can move up easily without catching on the housing.
I cut two holes in the back panel, one for the switch and one for the power cord.
Then I attached a switch to the back panel and plugged the power cable into the hole. The thickening on the cable prevents it from falling out.
I fastened the transformer on a wooden base with ordinary self-tapping screws. On one of them I put a terminal, which I connected to the ground.
Then I sanded, primed and painted all the parts. I chose two colors. black for the body and yellow for the moving parts (levers).
Also, when making spot welding with my own hands, I used:
- Power cord;
- Door handle;
- Copper holders for the electrodes (2 pcs) (you can buy them at welding equipment stores);
- Thick solid copper wire for making contact electrodes (about 5 mm);
- Self-tapping wood screws, nails;
DIY Arc Welding Machine Using 2 Microwave Transformers 50 / 100 amps
After the painted housing dried (I gave it about 2 days), we proceed to the final assembly of the device.
Spot welding electrodes
The electrodes of the spot welding equipment perform several functions simultaneously: compression of the connected sheets, current supply to the welding area, the subsequent heat removal. Important parameters when choosing an electrode are its shape, size, etc. It is from these parameters directly depends on how good the quality of the welded joint will be. The geometric shape of the electrodes can be straight or shaped, but preference is given to straight models, as they provide better access to the welding area.
When choosing electrodes for a microwave welding machine, you can simply refer to the corresponding GOST (14111-90), which already specifies all the possible diameters of these elements (10, 13, 16, 20, 25, 32, 40 mm).
Home-made electrodes. To make them, cut two pieces of thick copper wire, about 2.5 cm long each. Clamp them into holders. The electrodes in the holders are tightened with an ordinary screwdriver. The tighter the better.
The electrical part could be considered complete at this point, but for greater safety and convenience, I decided to add another button (micro switch), which will be located on the top lever at a slight angle. The microswitches can also be taken from a microwave. This way the spot welding will work only when the switch on the back panel is on, and the micro switch is pressed (in other words the two switches are installed in series).
You can use a timer to set the timing of the welding. For example:
Note: Remember to carefully insulate all connections! I screwed the sides with self-tapping screws (6 pcs.). each side).
I attached the levers in the following way. by experience (by eye) I mounted them one on top of the other, drilled two holes in the side walls (for the lower and upper lever) and inserted a standard nail into the hole, the end of which I then bent. It’s a cheap and sturdy axle.
I installed the contact electrodes on the ends of the arms. For convenience, the upper wire goes to one side, the lower to the other.
Once the contact electrodes have burned out, they can easily be removed and replaced with new ones.
In order to keep the top lever always up, I used an ordinary rubber band.
If, after assembly, the axes of the electrodes don’t fit together accurately. this is easily corrected by bending them a bit.
Testing a homemade spot weld
To use, put a thin sheet of metal between the electrodes, then press the button (click) for 3-4 seconds. A powerful pulse of electric current heats them to the melting point, and the pressure of the electrodes further strengthens the welded joint.
Now you can take your finger off the button and wait for the weld to cool down.
The device for spot welding with his own hands worked so well that after welding these washers to each other, I could not separate them (I managed to do it only using two pairs of pliers).
Do not short the electrodes together!
Welding galvanized metals produces zinc oxide fumes, which are harmful. That is why it is desirable to carry out welding works in a well-ventilated room.
Microwave spot welding/spotter.
Spot welding is quite popular in industry. It allows you to quickly and strongly heat a local area of the metal. It can be used to weld individual metal rods in a mesh or two sheets of metal. It is also useful to unscrew rusted nuts and bolts, you only need to heat them with this unit.
The principle of spot welding is quite simple. The parts to be welded are placed between two electrodes, which exert a compressive force and a high current, from 500A and above, flows through them. The result is that the metal is heated to a temperature where it becomes malleable and thus an inseparable connection is formed after the welded workpieces have cooled.
In industry, rather serious devices are used that have water-cooled working electrodes and pneumatic clamps. Such devices allow you to weld a large number of points in a fairly short time. But for home use a simpler machine is enough.
Spot welding and safety.
This kind of welding is quite safe, even though high currents are used to heat the metal. But in addition to the high current on the electrodes creates a voltage of only 1 to 3 volts. Recall Ohm’s law for a circuit.
Substituting in the formula the voltage of 2 V and resistance of 1000 Ohm (human resistance), we get the current that will pass through a person. 0.002A. Currents up to 0 are considered safe.1A and voltages up to 42V.
Microwave spot welding assembly.
In order to make a welding machine, we need a transformer. We take it from an old microwave oven that doesn’t work. It doesn’t even have to be the whole transformer, just half of it. We only need its operating primary winding. The secondary winding is unnecessary and must be removed.
Important! Do not plug the transformer into the mains in any case! It is a step-up transformer and generates a very high voltage on the secondary, about 2,000 volts.
It is very easy to distinguish the secondary of the transformer from the primary. The primary winding is wound with a larger wire cross section than the secondary and the primary has fewer turns of wire.
Remove the secondary coil. This can be done in several ways. It can be cut with an angle grinder or metal saw. Since the copper wire is quite soft, it can be cut with a chisel or chisel. When removing the secondary winding it is very important not to snag the primary winding. If you damage it, you have to throw it away or scrap it.
After removing the protruding parts of the secondary winding you need to knock the rest of the winding out of the middle of the transformer.
If you can’t dislodge the secondary winding then bore it out with an electric drill and then remove the rest.
After removing the windings you have to remove the shunts. They are a set of metal plates wrapped in paper. In the picture below they are circled in red.
The purpose of shunts is to close the primary winding by magnetic flux, and reduce the flux through the secondary winding. Simply put, shunts reduce the secondary current and therefore reduce the power of our welder. Therefore, it is imperative that they be removed.
Now it is time to do cables. It is obligatory that the wire has copper cores. The length of the wire is approximately 1.5м. The best wire for a welding machine is 50 mm 2, which is about 8 mm in diameter without insulation. This wire will be heated by the current flowing through it as the welder operates. And the smaller the wire, the faster it will heat up. That’s why it is better to use as thick a wire as possible.
If the wire is hard to screw on the transformer, you can remove the insulation from it, wrap it with cotton insulation tape and put a heat shrink tube on top. That way the cable with the new insulation will be a little smaller in diameter. The tape must be cotton. It does not melt when heated, unlike conventional duct tape.
In the same way you can make a wire of the desired diameter from several wires of smaller cross section, preliminarily stripping them of insulation and twisting them into one core.
It remains to put on the wire special crimp terminals. They can be crimped simply by flattening them with a hammer or in a vise.
Now wind the wire around the transformer. You need to make two full turns as shown in the photo below.
The power part of the spot welder is ready. Now make the contact pincers with the copper electrodes. They can be of most diverse construction. You can make them out of different materials. Looking at variations in spot-welding tongs below.