Home-made welding machine from a microwave

Spot welding machine from an ordinary microwave

When performing various repair work, it is sometimes necessary to securely fasten thin metal sheets or their fragments. The ideal in this case is the use of electric contact spot welding.

In contrast to devices designed for manual arc welding, which have long been customary attributes of domestic workshops, devices for resistance spot welding are much rarer.

How to assemble from a transformer 6 nuances

In any microwave ovens install a magnetron. It needs a significant voltage. The transformer has fewer turns in the primary winding and many more in the secondary. It is there that the voltage will be 2,000 volts. If there is a doubler, the value will increase several times. It is this property that must be used.

The transformer must be removed very carefully. To avoid damaging anything, it is not desirable to use various rough tools. First it is necessary to get rid of the housing, as well as to remove all fasteners. Take out the transformer from the fixing point. From this device will be used magnet wire, and the primary winding, which has a strong wire and a small number of turns.

Secondary winding

Look at the picture of the secondary winding. It is not necessary to use it for welding assembly, so it is desirable to get rid of it. Use a chisel and hammer for this. It is important to carry out all work very carefully, so that the desired winding is not spoiled. When working, a person may find a shunt device used in various microwave ovens. It is also necessary to get rid of them.

Magnet wire on the weld

Look at the picture of the magnet wire attached to the weld. If there is a microwire in the microwave that is not glued, and welded, then the removal of this part will have to be done with a metal hacksaw or chisel. The winding will be tightly seated in the magnetic core, so a lot of effort is required. In this case, you will have to use rougher methods in order to remove the construction by any improvised means. But it is worth bearing in mind that the operation is carried out very carefully.

After performing all of the above operations, we come to the creation of the secondary winding using a solid wire, with a diameter of 100 mm square or slightly larger. This corresponds to one centimeter. A bundle of wires is also used to provide the necessary diameter.

The winding created a transformer will be able to create a current force equal to 1kA. That’s what you need for spot welding.

If there is a need to make the machine more powerful, a single transformer will not be enough. For this purpose it is necessary to combine several elements from different microwave oven. Two or three coils are needed.

If the insulation is very thick, it will need to be removed and replaced with thinner, preferably fabric. If several transformers are used, the secondary winding is made according to the common connection diagram. But then you need to properly connect the outputs.

Manufacturing technique

Before you begin making the spotter, you need to make a drawing, prepare all the details. In addition to the transformer you converted yourself, you will need:

  • D32A and D226B diode bridges;
  • thyristor PTL50;
  • A 1000Mcf capacitor;
  • 100 Ohm resistor;
  • fuse;
  • power button.

All components and parts must be conveniently placed in the housing and isolated from each other.

Self-made starts with the winding of the transformer. After that, the other parts are connected to the circuit in turn.


It is optimal to use a disassembled microwave body. After removing the disk and the rotation mechanism, the bottom should be reinforced with plywood or dielectric sheet.

On the back, at the point of wire outlet, bolts are inserted into the holes and tightened with nuts. Wires plus and minus are fastened to them. On the inside, the mount should be fixed. On the outside of the cable terminals must be freely removable and locked with nuts.

The holes provided in the microwave housing are used for the current and voltage regulators of the spotter.

Holes are drilled in the upper part of the housing, and a handle is installed for easy movement of the machine. If the spotter turns out to be very heavy, they attach wheels to it or mount it on a crosspiece from a computer chair.

Spotter control diagram.

Holder, electrodes

The mechanics who are engaged in repairing car bodies by a spotter recommend to make a holder from an old glue gun. The cable is wound up behind. In the front part, remove the spout and install the sleeve, firmly connected to the housing and the long tube. Button is replaced by a switch.

In the absence of suitable broken equipment, the body of the handle is sawed out of plywood. The inside surface is covered with insulation. A hole is made in the handle for the starter, so that the button can be pressed without taking away the hand.

The electrode in the form of a plate with a sharp end is made of copper. It is small in length and is secured to the rod with a nut and bolt and washers.

The electrode can be made from a copper tube. It is connected to the cable with a union nut or soldered. The working end is flattened. The point of contact with the body metal should be minimal.


A reverse hammer with which the dent is gradually smoothed out. the inopuller. It is a long hollow rod with a handle. At the end of it a fixture is attached to hold the electrode. The other end of the inopuller is attached to the pistol holder. A wire carrying current is passed inside.

Make sure the cable is well connected to the electrode, keep the current loss to a minimum. The handle should be comfortable, well insulated from all conductive parts.

What you can use from the microwave for a new design

You need to take the microwave oven apart. It’s not hard: the housing is easy to remove, revealing all the complicated electronics. Don’t throw anything away. You only need a few parts today, but the rest can be used for other purposes

Another microwave part you’ll need is a wire to connect it to your microwave. It makes no sense to look for another. This one is already grounded and made pretty well. Also, it connects perfectly to the transformer. But remember: don’t touch a transformer connected like this with your hands, you can get a very powerful discharge, which can cause irreparable harm to your body

So you only need two parts from the microwave: an electrical cord with a plug and a transformer.

How to make a welding machine from a microwave

In your home it is often necessary to use a welder. Buying a ready-made unit will have a noticeable impact on the family budget. The way out can be found by making your own hands a welding machine from an old microwave.

Financial costs are minimal, and the capabilities are quite sufficient for solving household problems. The main thing is that the transformer of the microwave oven is in working order. It is this microwave unit will be able to provide a stable supply of electricity for welding metal parts.

Preparing the core for reassembly

Before proceeding to reassemble, it is necessary to thoroughly clean the core of the old varnish and glue. The neater this work is done, the easier it will be to get the primary winding into place. In addition, the old varnish can damage it during reassembly.

Core cleaned and prepared for reassembly

How I made a welder from 4 microwaves

Post, I think, for the masters of selfmade, a simple welder from available components will be to everyone’s taste.

So, we will do from the transformers from microwaves, they need 4

Saw off all the extra with an angle grinder, and the extra. is the small secondary winding, the one that’s shorted to the frame

Now, easily and without straining wind a thick copper wire in the resulting holes 8 turns on each of the transformers.and in any case do not cut the wire, but let it all through.

Further we fix these comrades on some plank and connect the power supply in parallel to the primary windings.

That is, we take the wire from the same microwave and connect one contact to each, for example, the right terminal on the winding of the transformer, and the second to each left.

Basically everything is ready, you can plug them into the socket and check the voltage.

The voltage should be 26 to 32 volts. This is enough for welding.

home-made, welding, machine, microwave

But if you get 14-15 volts. it happens. This can be fixed by swapping the pins on the last transformer in the circuit.

Next, screw the controls, the holder and the clamp to the ends of the thick wire and weld. You can also put a fan from the microwave.

We weld carefully, respecting all safety rules.

I have not really succeeded, 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 just 1mm wire to connect everything. and terminals.

Who is interested, you can watch the detailed video of the creation of check out

I just need to know where to get 4 transformers at once. Buy 3 more microwave ovens? I think it’s easier to buy a welder from Leroy.

This stuff burns up to 4 kilowatts and a regular socket, especially in older homes can not stand. We have a limit of about 3.5 kW.

I first thought that the extra finger.

Now you’re gonna teach people how to build welding machines!!

Creosan was made from one microwave in my memory. Everything worked fine.

Why do we need four iron?? Because it was?

We’ll check the voltage with a voltmeter, but the current with a current meter?

35 volts? And what are you going to weld them, ears to buttons??

Contact welding from a microwave

Simple and practical home-made contact welding from a microwave, a description of the home-made, as well as photos.

A contact welding machine was needed. On occasion got a faulty microwave oven 800 W, with a working power transformer.

Removed from the transformer, the secondary high-voltage winding, with a chisel. Wound 2 coils of KG-35 in place. From 10 mm fiberglass. Cut 4 strips 250 x 40 mm and a base of 400 x 125 mm. Three 40s 110mm angles, for mounting the leads.

The no-load voltage of the secondary winding was a little over 1 volt. The test, gave a disappointing result: the parts welded disgusting.

Then I found a microwave transformer for 1350 W. From a piece of welding cable KG-50 the rubber insulation was removed and replaced with a double layer of heat shrink. On the secondary I wound three coils.

No-load voltage on the secondary was 2.85 V.

Tests with a more powerful transformer gave a positive result: easily welded a rod 4 mm, plates of 1.5 mm is generally easy.

Here’s a microwave spot welding the nut on the bolt M12 heated easily.

Microwave contact welding without AC power adjustment is not comparable to the production unit, but within the scope of a household need will do the job just as well.

The basic element of the device is a transformer. Finding and purchasing a factory product is not necessary if you have a used high wattage microwave.

The principle assembly diagram in both cases is the same. Visual criterion for selecting a microwave for disassembly. dimensions. The transformer capacity is rigidly linked to the volume.

The transformer ratio in this case will ensure that the input voltage is increased sufficiently:

Negligible no-load voltage consumption: in the range of 3 V, has no effect on penetration depth and quality. High-speed connection of parts under pressure to eliminate the gap thermoelectric method belongs to the economical and safe.

Dismantling the magnetron transformer without damage is half the battle. The integrity of the primary winding must be checked, which will be the operating element. The secondary winding is step-up, made of a wire with a smaller cross section, the number of turns is increased.

Disassembling the transformer

A donor transformer for a 0.8-1kW microwave welding transformer removed from its place of installation with a screwdriver is valuable for the magnetic core and the primary winding. Dismantling of the secondary winding is simplified, if the magnetic core is divided into 2 parts by the weld.

  • in most cases, the primary winding will open, which due to the tight fit will be difficult to remove and reinstall;
  • Cutting the joint and restoring the integrity of the core are precise operations, it is better to do without simplification, if you are not sure.

Safely release the window without separating the casing involves the following operations:

  • Clamp the transformer in a vice or clamp it to the workbench.
  • Put wooden spacers or corrugated cardboard between the windings.
  • The outer cleanliness of the secondary winding is cut off with a sharp chisel. Recommendations on sawing with a hacksaw are less successful. you will have to break wires that have lost their lacquer impregnation layer.
  • Current-limiting shunts are removed as unnecessary.
  • Tightly clogged wires in the windows are drilled out in several stages with a drill without touching the drill bit the walls of the case.
  • Remains are removed with pliers and a pry bar without undue force.

The final steps are aimed at the final cleaning of passages for the introduction of a conductor with a large cross-section. Use only hand-held mechanical tools to avoid scratching the insulator surfaces.

Selection of cable for the secondary

Material selection is based on the experience of DIYers, calculations are not needed. The measurement of the windows will give you an idea of the cross-sectional area needed for the conductor. It is enough to make 1.5-3 turns for the output current to reach the value of about 1000 A.

Multicore cable is preferable to a bundle of individual conductors. A soft conductor with a high synthetic film insulation and a 1.2 mm thick top layer is preferred to a hosiery wire that is difficult to pull and takes up a lot of space with a 2.2 mm thick protective layer.

You will need to buy 2 m copper soft cable with a total cross section of not less than 10 mm type KG 1×35 (70 mm 2 is a guideline). What are the nameplate characteristics of a step-down winding conductor that are important when selecting:

  • long-term operation at voltages up to 1000 V;
  • 300A continuous load;
  • Transferring of short duration pulses up to 1200 A

Adding a new winding

Restricting window space will require trimmings. Slip relief is provided by applying 2 layers of duct tape to the inner surfaces of the core. Additional padding on corners. Paraffin waxed stripes on the conductor will increase slip.

Of textolite, if the original insulation inside the core is not preserved, will benefit. Do not forget to put on the glue!

The length of the cable takes into account the meterage of the leads, and additional elongation for easy pulling when pulling and laying in place. Section size will compensate for the reduced number of turns.

DIY Arc Welding Machine Using 2 Microwave Transformers 50 / 100 amps

Maximum number of windings not exceeding 3. Accurate laying and pulling calculations will ensure equal lead lengths. The first coil is fixed with counter wooden wedges. Further friction will prevent slip and shear. By tensioning it, the slack is eliminated. Struggle to shorten the wire is to increase current by reducing the resistance of the conductor.

Manipulation with the change of the ratio of turns at the initial transformer power of 0.8 kW changes the voltage and current values by a factor of tens of times. The control indicators of the coil assembly are put into the frame:

At this stage we take care of the installation of the protective cover and the grounding.

The desire to double, triple the power is carried out by the inclusion of additional assembly units. A variant with simplification provides a series connection of secondary windings. Correctness of the connection is checked by probing the circuit to avoid a short circuit.

Spot welding with your own hands from a microwave with two transformers is subject to simple addition rules: the amperage at the output when connected in series is summed up. The pulse welding current is also added, but the resistance losses of the electric circuit are minus.

The following conditions are required when connecting transformers:

  • the number of turns of the secondary windings are equalized;
  • To avoid a phase failure with a voltage drop to zero, the direction of the turns must be coordinated.

The second method of connecting the power into a single unit is shown in the photo below. Follow the same rules of serial connection, but with one wire. The labor involved in pulling and laying is higher.

transformers with currents in excess of 2000 A are intended for industrial mains connection. The domestic circuit is not designed for such loads.

Determining the correct serial connection of transformers

The leads of rewound interlocked spot wires from a microwave may not be factory marked. The test of the correct connection is carried out by the template method:

  • Primary and secondary winding pairs are connected in series.
  • Voltage is applied to the collective input, a voltmeter of alternating voltage is installed on the output.
  • Excess of the mains value indicates a faulty assembly. twinned opposite leads: there is a reverse process, the secondary windings increase, the voltage drop in the primary windings.
  • No voltage. one of the paired connections is made correctly, the other. the same name terminals; the order of connection should be changed.
  • Parallel connection will result in a doubling of power at a voltage equal to the mains voltage.
  • Correct connection will give the output a sum of the calculated 3-6V.


Selection of electrode material is limited to copper and alloys. Commercial network offers industrial products made of bronze, brass in all kinds of configurations. They are designed for intensive use, quick replacement. Holders will have to be sought or ordered for the seats.

Self-made from rods, adaptation of soldering iron stings are subject to the requirements of expediency:

  • Compliance of the size of the cross-sectional area of the step-down wire.
  • The shape of the tip is designed so that the weld core area increases relative to the contact surface by up to a factor of 3.
  • The size of the force affects the way of fastening, forming of the head: metal lever of pincer type develops a pressure of more than 100 kg.
  • Electrode orientation is related to the type of activity: overlap welding is done with counter electrodes, accumulators. with electrodes arranged in parallel.
  • Minimization of diameter of the electrode end allows to reduce the pressing force with good quality of connection.
Required welding depth Electrode sizes
electrode body Ø Ø descending cone R sphere
0,5-0,8 12 (16) 4 20 (35)
1-1,2 14 (18) 5 30 (50)
1,5 16 (20) 6 50 (75)
2 20 (25) 8 70 (100)
3 24 (32) 12 100 (150)

For the do-it-yourselfer it makes sense to choose the threaded connection. A hard fit at home is difficult to achieve. A bolt-nut with milled flats for a key is the best solution in this case.

An alternative to this type of connection is a counterpart with a screw pair fixing the tip to the electrode. This variant saves at least 2 joints. The size of the hole exceeds the screw diameter by no more than 0.5 mm. The laboriousness of manufacturing is compensated by the reliability of the screed.

The electrode ends are tapered. The contact points are not sharpened, they form a spherical surface. The ball profile is less amenable to burning by discharge sparks caused by insufficient compression. The cleanliness and integrity of the working areas are restored by circular file movements.

When planning the active operation of the microwave spot welding device as a production equipment for car repair, other type of business, ordering of duplicate pairs of electrodes is justified. Expendable red copper electrodes have a short lifespan.


The most important point of following the instructions for making, operating microwave spot welding is and will be to reduce the length of the conductors and the tightness of the connections. These factors are a constant source of power loss.

If the length of current-carrying components is reduced at the manufacturing stage, the number of connections is reduced to a minimum, the remaining disassembled contacts and long-term connections, which are not sufficiently prepared, are source of permanent losses.

What is good for linear circuits misfires in a microwave welder with your own hands. Let’s turn the crimping of the copper ferrule on the wire from the point of resistance growth into a monolith-like monolith in two additional steps, making the ferrule and the conductor one piece:

Fusion of the electrode with the inventory tip is carried out with a threaded pair of copper alloy. Washers made of the same metal. Completeness of the electrode and lug holes in relation to the bolt is minimal.

tends to stretch when subjected to prolonged stress. Loosen the tightening torque at the end of the job.

The lower support electrode is fixed to the base of the unit. If the base is metal, the dielectric gasket is compulsory. The upper moving electrode is supported on a lever which provides clearance-free contact by means of physical force.

The alignment of the electrodes is an issue. Lever axle and bushing are made without play to avoid divergence of centers, otherwise there will be no melting of the workpieces. In a simplified design, the sleeve is adjusted to the size of the tie bolt.

Control and monitoring devices

The microwave welder has one control device. an LED to warn you that the welder is energized. Safety is a primary concern. It is controlled by a power lever and an intermittent switch button.

home-made, welding, machine, microwave

The length of the lever arm determines the applied force. For a powerful unit, a rectangular cross-sectional tube is used. The ratio of the axis-electrode distance to the lever length is a measure of the multiplicity of pressure increase.

Return mechanism to home position. spring or rubber. The support platform is strengthened in this case. Measures are taken to prevent overturning: the construction is fastened to the workbench with clamps, self-tapping screws.

Micro switch mounted on the handlebar to free the other hand. The circuit breaker is connected only to the primary winding circuit. As soon as enough pressure is applied, the finger touches the switch. current is generated.

The user visually assesses the result of penetration, the reference point is the change of color of the contact point. The release of a pushbutton interrupts the power supply. Short activation times do not rule out overheating of the unit.

Transformer, conductors work in extreme conditions. Cooling breaks or forced ventilation are a necessity.

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