It is difficult to overestimate the importance and necessity of a device for performing spot welding at home. In this way you can connect fence rods, make a cage for a pet, or attach a holder to a ladle. welding equipment industrial production It has high price. A good solution is to make spot welding from a microwave with your own hands.
Necessary equipment for spot welding
To perform welding work, equipment is required that can convert electric current in the network with a frequency of 50 Hz into high frequency. In this case, the voltage of 220 V is reduced to a safe 12 V, and the current rises to a value sufficient to melt the metal.
The spot welding process occurs according to the following scheme:
- Accumulation of charge in a capacitor.
- Metal plates are placed between two copper electrodes.
- During the circuit, a powerful impulse is generated and the metal at the point of contact melts.
- Cooling down.
To create a welding point device The following parts and devices will be required:
- transformer;
- terminals, button;
- copper rods - 2 pcs.;
- set of capacitors;
- automatic 20 A;
- relay REK74;
- two LEDs and a diode bridge;
- fan (suitable from a computer).
Sequence of work with a transformer
The most important and required part in the manufacture of a device for spot welding from a microwave, it is a transformer. Before you pull it out, you will need to disconnect all the fasteners and unscrew the base. The secondary winding is not required for the manufacture of the welding machine; it must be removed. This is done using a hammer and chisel, a hacksaw, or a grinder. Work is carried out with care, trying not to damage the primary winding.
For a new secondary winding, you can use a cable with a cross-section of 50 mm 2, which approximately corresponds to a diameter of 1 cm. The main thing is that it is new, without defects or damage. Choose convenient option: stranded in common insulation, or several wires assembled together.
The secondary winding is wound around the core in 2-3 turns so that its middle part falls on the core. Exceeding the length will result in an undesirable increase in resistance. The main difficulty in creating a secondary winding is the lack of space. To make work easier, you can remove the factory coating on the cables and use homemade rag insulation; when assembling, cover the outside of the cable with grease or grease.
Power of a converted transformer for spot welding from microwave oven designed to produce a welding current of 800 A, which is sufficient for welding metal with a thickness of 3 mm or rods with a diameter of 3 mm. For greater thickness, use two transformers connected in series. Such a device will be able to deliver current up to 2000 A.
Manufacturing of electrodes
The spot welding process occurs when the electrodes are short-circuited. The following are used as electrodes:
- tip from a professional soldering iron;
- copper rods with a diameter of 10–20 mm.
Before work, the electrodes are sharpened into a cone shape. You can use special tungsten rods.
During welding work, the electrodes become dull and wear out. With constant use of welding point apparatus they will need to be changed and sharpened. Therefore, the electrodes are attached and centered using bolts. To eliminate voltage losses at contact points, all other parts are made monolithic or connected by welding. For subsequent fastening of the secondary winding, a terminal is soldered to the ends of the cable.
Features of manufacturing the working part of the welding machine
The working part of the device consists of a lever on which copper electrodes are attached. The fixed lower base must be very stable because it bears heavy loads. It is made from a durable bracket, timber or profile.
The movable upper lever must be unlocked in the non-operating position to provide access to the product. For girth use a rubber band or a rigid spring. Electrodes are attached to the levers, trying to achieve precise alignment.
A pulse button is installed on the top part; it is connected to the primary winding of the transformer, where the current value is lower. When making the device, you can use the button installed on the microwave door. Cables are connected to the electrodes. To prevent future breakage and damage, they are secured to a bracket.
Levers are chosen to be half a meter long - such dimensions make it easy to install parts and do not require much effort during operation. For ease of operation of the lever, a handle is attached to its upper part. You can use an old soldering iron blank. To ensure stability, during the welding process the lower arm of the machine is clamped on the table using a clamp.
Manufacturing of the working case
For homemade spot welding machines, choose the simplest case, consisting of a base, side walls and a top cover. Connect the parts using:
- Corners.
- Self-tapping screws.
Holes are made in the side parts, through which the power cable. A special tape is attached to the top cover for easy transportation.
The spot welding machine does not have a front part. Working pliers are placed in the resulting hole. A fan from the computer provides ventilation during the welding process; it is attached to the back of the machine. There are no ventilation holes. To control the welding time, you can install a special relay. Experienced welders focus on the color of the point at the welding site.
There is often a need to use a welding machine in your home. Purchasing a finished unit will significantly affect family budget. You can find a way out of the situation by doing it yourself welding machine from an old microwave.
The financial costs are minimal, and the possibilities are quite sufficient to solve household problems. The main thing is that the microwave oven transformer is in working condition. It is this microwave unit that can provide stable supply electricity for welding metal parts.
An unnecessary microwave oven can easily be found among friends, neighbors, or among your own old trash. Our people are accustomed to storing used equipment just in case, in order to build something out of it with their own hands.
A small microwave oven is enough. In most cases, a power of 800-650 W is sufficient. If the microwave power value is higher, the capabilities of the welding machine will increase.
The transformer has two different windings. One is primary, has large quantity turns, used when connecting to a centralized electricity supply network.
The other winding, the secondary winding, has fewer turns. To make a welding machine with your own hands, it is not needed. The craftsman’s task is to carefully remove it from the microwave transformer.
In order not to damage the primary winding, which is located very close to the secondary, you can lay and fix a metal plate or ruler between them.
After this, the unnecessary part can be cut off with a hacksaw without fear of damaging the turns of the primary winding. You can very carefully cut off everything unnecessary with a chisel. Carefully check the strength of your hands so as not to damage the microwave blocks that need to be saved for the welding machine.
The procedure should be repeated on the other side, carefully removing the filament winding. After cutting, you need to pull out all the wires of the secondary winding from the transformer body until complete liberation both niches. It makes cleaning the microwave transformer easier by drilling out all the excess with a drill.
Sometimes the windings are located very close to each other. You can carefully remove them only by disassembling the core and then re-gluing it with your own hands.
New winding
In the resulting niches, a new secondary winding is made from enameled or copper wire large diameter. Minimum size The cross section should be 1 cm.
The wires may not be solid, but multi-core. Important indicator for a microwave welding machine, this is the total diameter of the wires. They need to be laid tightly, leaving no gaps.
The exact cross-sectional size and the required number of turns can be calculated using special tables or using online calculators, focusing on the dimensions of the core and required power at the exit. Some craftsmen select experimentally. The ends of the winding should be well secured with lugs.
The transformer removed from the microwave is ready for use in a new capacity. It will be able to supply a current whose strength reaches 1000 A, which is quite enough for a home unit. main part For contact welding Made with my own hands from an old microwave.
If you need a more powerful welding machine, you will have to remake two transformers. The connection of two transforming blocks is carried out in series.
It is important to connect windings of the same name, otherwise a short circuit will occur. The correct operation is checked by markings or using a voltmeter. When both microwave transformers are connected, the current strength should be checked.
It should not exceed 2000 A. Large values will cause an overload of the home electrical network, and the welding machine will either not work at all or will burn through the metal.
Case manufacturing
There are several options for manufacturing a housing for a welding machine. Some craftsmen make the body out of wood. However, it is most convenient to use welding from a transformer from a microwave if you place the device in a case from the computer system unit. Finding an old “system unit” is not difficult. They also accumulate in many homes when replacing outdated equipment with new models.
The legs are screwed onto the body fragment with ventilation holes at the bottom. You can take support legs from an unnecessary VCR, player, or any other equipment.
A window should be cut out in the side of the welding machine body and covered with a dielectric plate made of any heat-resistant insulating material. Due to the fact that the terminals on the plate will heat up, the plate should not melt.
Using a computer case is convenient for several reasons:
- it has an on and off button;
- on the case there is a ready-made socket for connecting to the network, to which all that remains is to connect the converted transformer from the microwave;
- ventilation cells provide effective cooling of the contents of the case. The fan can also be taken from an old PC;
- The design has a decent appearance.
It makes sense to install an LED indication on the thermal insulation plate. This will help you easily notice the condition of the welding machine.
Selecting Electrodes
For the right choice for resistance welding electrodes, it is useful to look at GOSTs, which stipulate all the required parameters. Straight-shaped electrodes provide convenient access to the site of the future seam. The diameter of the copper rods cannot be less than the diameter of the working wires.
It is better to make the connection by soldering. This will reduce the likelihood of oxidation during operation. Due to the fact that electrodes are inevitably consumed during welding, they need to be sharpened in a timely manner.
In ideal condition, the electrode ends should have the shape of a sharpened pencil. The result of working on a microwave machine after gaining some experience will be indistinguishable from factory resistance welding.
Important Options
For getting good seam the process must be skillfully managed. The welding machine switching system can be used from an old system unit.
For ease of operation you will need good levers optimal length, which will help hold the part and press it. It is not difficult to mount the lever mechanism yourself using screws.
If it is placed on the lever itself, the master will have the opportunity for additional manipulations, freeing up his second hand when working with the welding machine.
For home welding, not very high clamping forces are sufficient. For thick sheet steel, a homemade welding machine is not suitable for many reasons. In particular, the capabilities of microwave transformers are not enough for this.
If you need to weld at several points, a lever with a length of about 60 cm is sufficient. This will save physical activity masters The pressure on the working point will be 10 times greater than the force applied by the welder.
To ensure a static position of the microwave oven, you need to firmly fix it on the work surface using clamps.
Good welding occurs when the electrodes come into contact with the work piece for a strictly defined time, which can be determined visually with experience. If you don’t have to rely on experience, it makes sense to mount a special relay.
During the entire operating period, a welding machine made from a microwave should be well cooled by one or more fans. In addition, it is always useful to take breaks during work, allowing the equipment to cool down and the technician to rest.
You can use an old microwave to make various gadgets for your garage. One of these is microwave spot welding, which makes it possible to connect metal elements and structures made of sheet steel, up to 5 mm thick.
And if you have an unnecessary microwave lying around at home with a working power transformer, then it can be adapted for these purposes. It is the transformer that will act as the main working element of the welding machine.
This article from a construction magazine will talk in detail about the production of spot welding, which will definitely come in handy for work in the garage.
The main element of the welding machine is a power transformer, which has a high transformation ratio. The microwave transformer, which is used to power the magnetron, meets precisely these conditions. Its power can be 700-800 W, and even more than 1 kW.
You should know that low-power transformers from microwaves are suitable for making spot welding for working with metal, the thickness of which will be no more than 1 mm. If you need to make your spot welder more powerful, it is recommended to connect two transformers from the microwave together.
Also, in addition to the transformer, to make spot welding from a microwave you will also need some materials.
First of all, this is:
- A profile pipe or other rolled metal for making a handle with a base (wooden blocks can also be used);
- A spring through which the handle will be thrown upward;
- A canopy to make the handle of the welding machine movable;
- Copper busbar, for the manufacture of electrode holders;
- Copper rods will be used as electrodes for spot welding from the microwave;
- Piece copper cable in insulation with a diameter of at least 1 cm. If the cable does not fit into the transformer, then the insulation will have to be removed, after which it is necessary to wrap the cable with several layers of ordinary electrical tape.
After all of the above materials have been found, you can safely begin making a welding machine for spot welding with your own hands.
First of all, you need to remake the microwave transformer so that the output of the secondary winding would have a voltage of approximately 2 V. For these purposes, the factory secondary winding is completely removed from the microwave transformer and a new one is wound with a thick copper cable.
In total, you will need to make 2-3 turns of the secondary winding on the power transformer being converted. You can remove the old secondary winding from the transformer using a hammer and chisel, but you must act extremely carefully so as not to damage the primary winding. She is needed safe and sound for normal operation spot welding machine.
When the transformer has been rebuilt, you can begin making other parts of the welding machine. You can use two pieces to make controls profile pipe, 60 cm long, which are connected by a canopy. You can go the other way and make a base with two supports, between which the spot welding control lever will be located.
In general, the controls can be made from anything, even from wooden blocks, if spot welding from a microwave is used for some small work. Clamps for electrodes deserve special attention, which would be best made from a copper bus bar, then drilling holes in them for bolts.
It is the bolts that will subsequently hold the electrodes for spot welding, for which it is recommended to use a copper rod (the larger its diameter, the better). To ensure that the welding machine is turned on only when the handle is pressed, a switch should be placed between it and the base. It should be connected only through the primary winding of the transformer to avoid heavy loads.
Microwave spot welding will be an excellent tool in the hands of a craftsman. Such a homemade welding machine can be used to make other homemade products and metal crafts, of which there are a lot of ideas on the Internet.
Today let's take a closer look at how to make a spot welding machine with your own hands from a high-voltage transformer or MOT (Microwave Oven Transformer - microwave oven transformer)from an old, unusable microwave. Of course, provided that the high-voltage transformer is working (at least its primary winding), and something else is faulty: magnetron, cable, control board, etc.
For a master, there is a need for spot welding. This spot welding produces a current of up to 800 Amps, which is quite enough for welding sheet metal up to 1.5mm.
So we need old microwave and the larger it is, the better. Larger microwaves have a higher power transformer. If you don’t have an unnecessary microwave, you can often buy old microwaves cheaply on forums and free bulletin boards, or you can look for them near trash containers or ask at TV repair shops.
Attention! Before disassembling, the microwave must be turned off from the power supply. Next, we disassemble the microwave oven. There are several components inside a microwave oven that are dangerous even when turned off and can cause serious electric shock - these are capacitors (see photo) that can hold a charge for some time. Therefore, we discharge the capacitors by shorting their terminals together with a screwdriver. The high voltage transformer is located below.
Of the insides of the microwave, we are primarily interested in the high-voltage transformer.
The transformer consists of a core and two windings: primary and secondary. The primary winding is wound with thicker wire and contains much fewer turns.
The transformer core is held together using two thin welds, as seen in the photo.
How to make a transformer for welding?
There are two options for removing the winding:
- Disassemble the transformer core.
- Cut off the winding with a chisel.
Method 1.
You will need a hacksaw or grinder to cut this seam, as well as a hammer and chisel to get to the transformer windings.
Be careful when removing the primary winding from the transformer, as we will need it later.
Try not to bend or scratch it.
The secondary winding can be wound very tightly and is difficult to remove, so if you don’t need it, you can cut it and pull it out in pieces, it will be much easier.
Now, after all the manipulations, you should have in your hands an intact and undamaged primary winding of the transformer and its core, divided into two parts (without glue and paper that held its windings inside).
The next step is to wind the secondary winding of the transformer. To do this, you need to take a copper (required!) cable of approximately the same cross-section as the slots in the transformer core (about 7 mm) and wind two turns.
I then bonded the transformer core to its base using a regular 2-piece epoxy resin and carefully pressing it in a vice, left it to stick together.
Once the epoxy has dried, the transformer should look something like this.
Method 2.
It’s also not easy, but the transformer hardware will remain intact, which is important. To do this, you need to remove the winding using a chisel, chisel, hacksaw, etc.
We also remove shunts.
Next, we wind a new winding onto the transformer. It is made from stranded wire with a cross-section of at least 100 mm 2 (or a diameter of more than 1 cm). It will be enough to make 2-3 turns. If the wire has too thick insulation, you can remove it and replace it with fabric insulating tape. If two transformers are used at once, then the secondary winding for them is made common, but it is very important to correctly connect the leads from their primary windings.
The voltage at the output of the transformer turned out to be a little more than 2 volts, but the current strength was about 800 Amperes! This is sufficient current to ensure a strong connection when welding metals.
DIY welding body
Now all that remains is to make a housing for the spot welding machine. You can make it out of metal.
You can make the body out of wood. You can make it based on what you have on hand.
The photo below shows the process of making the case.
Once I had all the body pieces cut out, I carefully rounded the edges using a router bit. You will need to make a notch on the upper arm so that the arm can easily rise up without resting on the body.
On the back panel I cut two holes, one for the switch, the second for the power wire.
I then attached the switch to the back panel and inserted the power cable into the hole. The thickening on the cable prevents it from falling out.
I attached the transformer to wooden base using ordinary self-tapping screws. I put a terminal on one of them, which I connected to ground.
I then 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 cable;
- Door handle;
- Switch;
- Copper holders for contact electrodes (2 pcs) (they can be bought in stores selling welding equipment);
- Thick single-core copper wire for making contact electrodes (about 5 mm);
- Wood screws, nails;
After the painted body has dried (I gave it about 2 days), we proceed to final assembly devices.
Electrodes for spot welding
The electrodes of equipment for spot welding perform several functions simultaneously: compression of the sheets being joined, supply of current to the welding zone, and subsequent heat removal. Important parameters when choosing an electrode, it is its shape, dimensions, etc. It is these parameters that directly determine how high-quality the welded joint will be. The geometric shape of the electrodes can be straight or curly, 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 possible diameters of these elements (10, 13, 16, 20, 25, 32, 40 mm).
Homemade electrodes. To make them, cut two pieces of thick copper wire, each about 2.5 cm long. Clamp them into the holders. The electrodes in the holders are tightened using a regular screwdriver. The denser the better.
The electrical part could be considered complete, but for greater safety and convenience, I decided to add another button (microphone), which will be located on the upper lever under small angle. Microswitches can also be taken from the microwave. This way, spot welding will only work when the rear panel switch is on and the mic is pressed (in other words, two switches are in series).
You can use a timer to set the welding time. For example:
Note: Remember to carefully insulate all connections!
I screwed the sides with self-tapping screws (6 pieces per side).
I secured the levers in the following way - experimentally (by eye) I installed them one on top of the other, drilled two holes in the side walls (for the lower and upper levers) and inserted an ordinary nail into the hole, the end of which I then bent. The result was a cheap and reliable axle.
I installed contact electrodes at the ends of the levers. For convenience, the top wire goes in one direction, the bottom in the other.
After the contact electrodes burn out, they can be easily removed and replaced with new ones.
To ensure that the upper arm was always raised, I used a regular rubber band.
If, after assembly, the axes of the electrodes do not align correctly with each other, this can be easily corrected by bending them a little.
Homemade spot welding tests
To use, place thin sheets of metal between the electrodes, then press the button (micric) for 3-4 seconds. Powerful impulse electric current heats them to the melting temperature, and the pressure of the electrodes further strengthens the welded joint.
Now you can remove your finger from the button and wait until weld won't cool down.
The DIY spot welder works so well that after welding these washers together, I could not separate them (I was only able to do this using 2 pairs of pliers).
The device has been in use for 5 years now, and by the way it works well, although the CA is not used very often. The transformer from which the welding machine is made was torn out of a rather strong microwave oven, as was the fan that was installed to cool the windings. The secondary winding has been removed from the transformer without affecting the network winding (). The next step to take is winding the new secondary winding with a thick cable (under 10 mm in diameter).
Both the transformer and the fan are screwed to the plywood. A board with two holes is attached in front of the transformer, through which both ends of the secondary winding are inserted. Plywood is also a kind of screen that stops cold air from the welding site. Next to the transformer, as can be seen in the photographs, a timer is used to adjust the power-off time.
The transformer is turned on using a foot pedal - then the operator will have both hands free to work with the electrodes and the part. The electrodes are made of an 8 mm copper rod, which is threaded. The cable clamp is made from cut copper tube.
Welding machine in action
The fan starts working from the very moment the plug is inserted into the socket, since the transformer becomes very hot during operation. Next, we install two electrodes opposite each other, press the pedal, switching the voltage on the timer, which gives it some more time to supply the trans. Here this switch is used only for unintentional long pressing of the pedal or unwanted blocking of the button.
Select the cross-section of the secondary winding, or more precisely the number of coil turns, experimentally. When powered by 220 V, it does not blow out fuses (even 10 A) and does not cause the light to blink at startup.
Naturally, the welding voltage is low and the electrodes can be taken bare hand, but it is better to wear protective gloves, since the electrodes heat up from long-term operation.
The power of the welding machine depends on the transformer - a microwave oven usually has 800-1200 watts, so the larger the transformer, the better. When welding, a large current is created - 1-2 kA or more at a voltage of 1-8 V. The higher the current, the better connection, because the welding time is very short, and when it comes to long-term welding with low power, it will result in a blackened area.