How a spot welder works
To heat the metal to the melting point, you need a large current, hundreds of amperes. The magnitude of the voltage does not matter, so to save the wire and the safety of work is usually used 2-3 volts.
You can learn about the principles of spot welding from this
Experimenting with the strength of the current makes no sense. All the described variants have been repeatedly tested and no time can be wasted on calculations. The power of the transformer is selected based on the thickness of the metal to be welded.
The primary winding of the welding machine is calculated according to the total power of the device. Because making the transformer yourself is a troublesome and costly task, you can use an off-the-shelf design.
Optimal option. a power transformer from an old microwave oven. The electrical circuit works according to the following principle:
- The magnetron (the emitting element of the oven), requires a voltage of several thousand volts, and the current strength does not matter;
- The power on the primary and secondary of the transformer is the same, so if you increase the number of turns on the secondary, the voltage increases in the same proportion, at the cost of losses in current strength;
- Microwave transformers are rated up to 3 kW. This value is quite sufficient for making a spot-welding machine.
The required parts can be purchased at a flea market, in appliance repair service centers, or simply by buying a faulty microwave oven by advertisement for a symbolic price.
The secondary windings usually burn out (because of the thinner wire), so the chances of buying a transformer with a functioning primary are quite high.
The current strength of up to 1000 amperes (at 3 kW and a secondary voltage of 2 volts) allows you to easily melt the metal at the point of contact, thereby ensuring a reliable spot welding.
A simple example of domestic welding machine assembled at home from improvised means
Choice of electrodes
Electrodes of spot welding equipment perform several functions simultaneously: compression of joined sheets, current supply to the welding area, the subsequent removal of heat. Important parameters when choosing an electrode are its shape, size, etc. Exactly on these parameters directly depends on how high quality the welded joint will be made. The geometric shape of the electrodes can be straight or shaped, but straight models are preferred because they provide better access to the welding area.
How To Make Spot Welder Using old Microwave Transformer
When choosing the electrodes for the welding machine from the microwave, you can simply refer to the corresponding GOST (14111-90), which already stipulates all the possible diameters of these elements (10, 13, 16, 20, 25, 32, 40 mm).
A variant of electrodes for homemade resistance welding
The diameter of the copper bars to be used as electrodes should be greater than or equal to that of the working wires. To avoid active oxidation of the electrodes in the process, they are connected to the work leads by soldering. The electrodes of the contact welding device (including those made from a microwave) wear out actively during operation, so they must be sharpened regularly, giving them the shape of a sharpened pencil with a file.
Scheme of manufacture
Before you start assembling a welding machine from a microwave with your own hands, you need to understand the principle of the transformer, which will help to weld metal. The transformer consists of two windings (primary and secondary), they are enclosed in a case. “core”, which is typed from sheets of special steel. The primary winding is supplied with electric current, which, passing through the core, enters the secondary winding. This in turn increases or decreases the current. Hence their classification into step-down and step-up transformers. In this circuit, the second version will be used, that is, the voltage will decrease and the current will increase. With this effect the welding of materials will take place.
Depending on how thick the parts to be welded, you need to select the transformer and the cross section of the cable for the new winding.
First you need to disassemble the microwave oven to get the transformer, which will later be used in the work. It consists of two windings of copper wire, which can be varnished or wrapped in special paper. It can also be in a plastic or metal cover that protects it from the external environment.
Remove the secondary winding from the transformer body, usually this is the upper element. To remove the winding, the branches that protrude beyond the transformer body should be cut with an angle grinder or hacksaw. The remains of the winding, which are hidden inside the case, must be drilled out with a drill (electric screwdriver): first with a drill of small diameter and then with a drill of increasing diameter. Small protruding parts can be removed with a screwdriver and hammer and simply knocked out of the case.
It is very important not to damage the primary winding!
After the winding has been completely removed, the place of installation must be cleaned of any residual varnish or paper. After a thorough cleaning, the new winding can be fastened.
Then we take the cable of the desired cross-section. You can use a 6-square multi-core copper cable, but you have to make about 15 windings. Or take a cable with a larger cross-section, but with fewer turns. It depends on the cable used. The winding should be tightly wound (no gaps) and not “chatter” in the transformer body. After the wire has taken its new place, the transformer should be secured to a platform of planks for better stability of the microwave welder. This can be done with another board or corners.
The circuit for connecting the primary winding is very simple. From the winding come out two contacts (they are also terminals), to them we connect the power wire. You can also connect the connector, which already has a power wire, which will increase its mobility and improve transport.
The diagram shows the power wire, the instantaneous disconnect button, which can be mounted on the body of the welder, and the primary winding itself. It is also possible to introduce into this circuit:
- current regulator, with which you can regulate the voltage coming to the primary winding;
- a timer, which will additionally switch on the machine for a certain period of time, thus reducing electricity consumption and additionally protecting the transformer itself from overheating.
To the platform with a transformer bolt the lower stationary arm, on which is installed one of the copper electrodes connected to the secondary winding.
Most often, such electrodes of different shapes and sizes can be purchased in the store, they are certified and comply with GOST (14111-90), have a diameter of 10 to 40 mm. You can also make them yourself using a piece of copper wire section of 4 square meters and the holder for the wire. After placing the stationary lever and the electrode on it set the movable arm with a second electrode, which will serve as an electricity supply to each other and press the two welded parts for better contact. It can be attached to the platform by a movable element in the form of an axle and a spring. It can also be independent of the welding machine. for more convenient welding parts. All wires on the arms need to be additionally insulated for your own safety, because the current that goes through this wire has a large charge. standard insulation can not withstand the heat, its properties will decrease over time.
Surround the transformer on all sides with planks, thereby forming the housing of the microwave welder, on which the momentary power-off button is installed.
In the resulting recesses make a new secondary winding of enameled or copper wire of large diameter. The minimum cross-section size should be 1 cm.
The wires can not be solid, but multicore. An important indicator for a microwave welder is the total diameter of the wires. They must be stacked tightly, leaving no gaps.
The exact size of the cross section and the required number of turns can be calculated by special tables or with on-line calculators, focusing on the size of the core and the required power output. Some craftsmen select the wire for the welding machine by experience. On the ends of the winding, the tips should be well fixed.
The transformer, taken from the microwave, to be used in a new capacity is ready. It will be able to supply current, the strength of which reaches 1000 A, which is quite enough for a home unit. The main part for contact welding is made by our own hands from an old microwave oven.
If you need a more powerful welding machine, you will have to redo the two transformers. Connect the two transformer units in series.
It is important to connect the same windings, otherwise a short circuit will occur. Correct operation should be checked against the markings or with a voltmeter. When both microwave transformers are connected, you should check the current strength.
It should not exceed 2000 A. Higher values will cause overloading of the domestic power supply and the welder will either not work at all or will burn through the metal.
How to make a device for spot welding from a microwave with your own hands
Contact type welding today is often used not only in industrial, but also in garage conditions. It is successfully used for a variety of works that are associated with metal alloys. Equipment of commercial type, designed for such operations, is quite expensive. But the device can also be made independently, using an unnecessary microwave oven.
Homemade Stick Welder. From Microwave Parts!
The transformer from an old microwave oven will form the basis of the homemade device.
It would power a magnetron and provide up to 4 kilowatts thanks to the high transformation ratio. In large ovens it produces 700-800 watts. The unit created on it will be able to join thin metal.
- Transformer (if you need a unit of higher power, you will need two).
- Platform for installation.
- Copper wire with a large cross section.
- A long lever.
- Screw clamp.
- Cable and insulation material.
- Chisel or hacksaw.
How to make a microwave spot weld
Microwave spot welding with your own hands
Surely those who are fond of welding have seen how a spot welder works more than once. With its help, you can do a lot of useful things for the house, as well as easily work with thin metal.
, and more. However, if you have an old microwave, you can make such a device at home. All that is required of it is a transformer, which is subject to small remodeling.
Consider in this article of the site mmasvarka.ru. How you can make microwave spot welding with your own hands.
Homemade spot welding from a microwave
Such spot welding with their own hands from the microwave will be the most accessible technology, not only in terms of knowledge, but also in terms of cost.
The most simple design for self-made has a welding machine, based on the principle of contact or spot welding. over, such spot welding with their own hands out of the microwave will be the most accessible technology, not only in terms of the required knowledge baggage, but also the value of costs to achieve the goal.
Making the controls
In order to make the spot welding was easy and convenient to operate it is necessary to make a device case, with which you can easily perform welding of metals.
The first thing to do is to fix the transformer. For this purpose, you can use a thick plywood sheet, in which a drill makes holes for mounting the transformer. Control of the spot welding process can be carried out as a remote unit, when the transformer is separate from the housing, and from it on the wires voltage is fed to the pincer contacts. Such a device makes it possible to perform welding work in hard-to-reach places and on large objects.
A significant disadvantage of the remote unit is the need to use a fairly long cable, when passing through which the electric current will be significantly reduced due to the heating of the conductor at the time of welding metal. Also to the disadvantages of the external device includes the inability to use the pliers with a long lever, so the contact force will be insignificant, which cannot but affect the quality of welding.
You can make the tongs yourself if you have an inverter welder. To make the pincers you will need to find 2 large washers with a thickness of at least 8 mm and a diameter of 50 mm. If you don’t have the right parts, you can make them yourself on a lathe. If you make the washers yourself, you have to make a hole with a diameter of 20 mm in the middle of each of them.
The next step of making the pliers yourself is to cut the insulation from a thick ebonite rod.
The rod should preferably be chosen so that its diameter matches the outside diameter of the metal washers. The middle insulation is made as follows.
- A piece of 30 mm length is cut from the ebonite rod.
- Ebonite washer is securely fixed in the drilling machine and a through hole with a diameter of 8 mm is made exactly in the middle.
- On a lathe, the material on both sides of the ebonite washer is removed to a diameter of 20 mm. The material should be removed to a distance equal to the thickness of the metal washer.
This produces a solid insulator that prevents short-circuits between the pliers’ levers.
In the next step of making homemade pliers to the metal washers are welded, on one side of the handle about 40 cm long, on the other side the contact part of the device, to which the power cable and the electrode clamp will be attached. The handles and the contact part of the device can be made from a metal bar, which must be straight on the operator’s side and L-shaped on the contact part. The bending of the tongs on the side of the working part is necessary to ensure that contact is made only at the point where the parts are welded together. After the welding work is finished, the metal washers, to which the handles and the contact parts have been welded, are deburred with a file or emery so that after the assembly of the pliers the parts can slide freely on the ebonite insulator.
The assembly of homemade pliers is done as follows:
- A metal washer is put on the bolt with a length of 50 mm and a diameter of 8 mm, then a washer from any insulating material with an outer diameter of at least 30 mm.
- One half of the pincer is being fitted.
- Install the separating ebonite insulator.
- The second half of the clamping pincer is being fitted.
- An insulating washer is put on, then a metal washer, then an M8 nut is screwed on.
In addition to the significant loss of power on the conductor, it is not always possible to bring the contacts together with the necessary force when using the pincers. This defect is especially noticeable on resistance welding of metal parts with a thickness of 0.5 mm or more. To ensure sufficient force contact welding with their own hands from an old microwave is made in the form of a stationary machine.
DIY Arc Welding Machine Using 2 Microwave Transformers 50 / 100 amps
All the main parts of this type of resistance welding are made according to the principle described above, but with the only difference that the movement of the working part is carried out only in the vertical plane, and the contacts, thanks to the longer lever, are closed under much greater force.
In the stationary device, only the upper lever is movable, which, like in the case of pliers, has to be isolated from the main body with an ebonite insert.
The use of a single lever greatly simplifies the control of the welding machine, and also allows to make a mechanism that automatically turns on the device when moving the lever down.
It is also necessary to equip the lever with a spring, which will return the upper contact immediately after the cessation of pressure.
There is no need to equip the stationary design with scissor-type levers, so it is enough to make one movable upper lever, which will be installed to connect the wire from the transformer and the electrode fixation mechanism.
The lower part is made as a fixed platform with an upward extending element, on which the power cable and the lower working electrode are also fixed.
Spot welding with a homemade device
The advantage of a stationary device is that this device can easily weld metal with a thickness up to 1 mm. Higher output is achieved because the transformer is mounted
on the same platform as the operating part. This arrangement allows to minimize electric current losses by using a shorter cable between the secondary winding and the electrodes.