The technique of resistance spot welding is a unique approach to bonding metal workpieces, including rolled sheets, as well as joining various piece parts to metal structures, such as bolts, washers, rivets, and more.

Contact welding is widely utilized in industrial sectors such as automobile, aircraft, and instrument manufacturing, as it provides the ability to create strong and reliable welds without any defects or the risk of surface deformation during or after the welding process.

For DIY projects involving metal products, one can easily perform spot welding using a microwave. This method is well-suited for connecting separate metal parts, such as fences, pipes, car parts, motorcycle parts, and more, into a unified structure without any major difficulties.

When assembling spot welding equipment in a small repair shop, it is crucial to adhere to specific requirements for this type of equipment.

A technique for performing resistance welding is described.

In addition, adherence to safety standards is essential to avoid various negative consequences for the operator’s health, ranging from minor burns on the hands to severe bodily harm. Proper compliance with these standards ensures that the machine will effectively fulfill its intended functions.

The homemade welding device operates on a similar principle to a spot welder. The modified transformer, created from a microwave oven, is connected to a standard 220V power source.

The transformer, redesigned by the operator, decreases the voltage to a safe level of 12V, while simultaneously increasing the current strength to generate enough heat to melt the metal.

The object to be joined together is positioned in between the copper electrodes, which are closed and generate a strong pulse with a duration of 0.01 to 0.1 seconds. This pulse melts the point in the contact area, and upon cooling, a weld can be observed.

If the operator successfully completes the task without any technological violations, the welds will be free from defects such as chips, cracks, or craters.

Afterwards, the electrical charge is once again stored in the capacitor for the next welding cycle. This homemade spot welding configuration, made from a microwave oven, conveys the overall essence of the welding apparatus when working with metal structures.

However, if there is a desire, the craftsman can enhance it by developing various iterations of the design, based on the actual capabilities of the device.

The inclusion of a do-it-yourself spot welding apparatus offers an array of additional possibilities even for novice welders:

• creating connections between parts made from thin sheets of rolled metal;
• working with metals that have low melting points;
• producing aesthetically pleasing, reliable, and highly durable welded seams.

With only some practice, one can achieve high productivity and minimize consumable expenses by using their own homemade equipment for welding.

P O P U L I A R N E:

• What are the steps for replacing the touch panel on your own?

Is the touchscreen on your phone or tablet not functioning properly? One of the most frequent issues with modern touchscreen devices is damage to the touchscreen. It is often referred to as the "touch panel", simply "touch", or "sensor". Don’t worry – you can replace it yourself. The cost of such a panel is relatively inexpensive, much cheaper than purchasing a new phone.

A straightforward and dependable thermostat design for an incubator

• One option is to incorporate a time relay into the device, allowing you to set the precise welding time. This is particularly useful when working on numerous identical parts.
• Another feature that may be worth considering is adding a thermostat. This would allow the device to automatically shut down when the transformer overheats and then restart once it has cooled down, similar to how an iron operates.

P.S. I apologize for the somewhat disjointed nature of this article. Due to the many considerations involved, I had to redesign the device three times over the course of three months. Consequently, I plan to update the article with additional details and photos in the future.

The great thing is that they managed to create a functional spot welding device from a microwave using their own hands, even though it may not seem so at first. They did have to spend around $2,000 on materials, but luckily, they already had all of these materials in their possession.

Here is a photo of their DIY spot welding device made from a microwave:

And here is a video showcasing the process of transforming a microwave into a spot welding machine:

THERMOREGULATOR WITH YOUR OWN HANDS

Incubators are commonly used by backyard bird owners from early spring to mid-summer. They provide a convenient way to incubate any breed of bird at any time, without having to rely on nesting broods.

A thermoregulator is an essential component of any incubator, as the hatching of birds depends on its reliability and accuracy.

This metal detector is simple yet effective. It consists of one microcircuit, a transistor, and several diodes. Despite its simplicity, the metal detector can detect a copper coin (2.5 cm in diameter) approaching the coil from a distance of about 10 cm, and larger non-ferrous metal objects from a distance of over 1 meter!

An out-of-order microwave can be repurposed and transformed into a unique piece of art. The sturdy structure of the microwave’s body makes it an ideal canvas for creative projects. Additionally, its interior can be used as a hidden storage space for items like vegetables and food. Moreover, by adding a hinged cabinet, the old microwave can serve as a functional storage unit. With a little imagination, this seemingly useless appliance can be given a second life as a practical and aesthetically pleasing household item.

Repairing a microwave can often be a more expensive option compared to purchasing a brand new one.

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As a result, you have the option to install it in the microwave and utilize it as an oven, or dismantle it into different components including a transformer that can be repurposed for spot welding, a motor that could be easily transformed into a 220-volt generator, and a fan that can be conveniently employed for a DIY incubator.

Thus, let’s explore the finest homemade microwave on the market that will undoubtedly prove to be valuable in the arsenal of every skilled craftsman.

• Will I require flux? – No, flux is not mandatory.
• Should I employ respirators when I am working? – Respirators are not needed – the process is quick and there are minimal fumes.
• Is it possible for someone to be electrocuted during welding? – You will not be shocked if you avoid contact with the terminals.
• Is it feasible to use this type of welding for connecting batteries? – No, a different type of unit is specifically designed for battery connections.
• Does the factory unit provide better connectivity for the parts? – The strength of the connection is the same.

If you perform spot welding on your own, it will function just as well as factory versions. That is why it is important to thoroughly understand the assembly process and attempt to create a device yourself.

Welding from a microwave with your own hands

After watching fascinating videos on , and being inspired by this particular topic on ChipMaker, I became very eager to try my hand at microwave spot welding.

In order to create a spot welding setup using a microwave transformer, I purchased a 2-meter length of 50 sq.mm copper stranded wire. However, the amount I bought turned out to be more than what I needed. For the electrodes, I utilized soldering iron stingers with a diameter of 13 mm, as I couldn’t find any other suitable copper rods in my city.

Now, let’s get into the process of creating spot welding using a microwave transformer.

How to make a transformer

At first, I severed the transformer to eliminate the additional winding, and I will reiterate:

Please take note that using a microwave transformer can be extremely dangerous! It must not be connected for testing purposes until the secondary winding has been removed, as it possesses a voltage of approximately 2000V and is capable of causing fatal harm to an individual even from a distance!

I stripped the insulation from the copper wire measuring 50 square millimeters, since it is excessively thick and intended for handling 600 volts, whereas the spot welder operates at a much lower voltage of only 2-3 volts.

As the elderly like to jest: Papyrus serves as sufficient insulation.

Let’s start assembling the step-down transformer for the spot welding machine

To begin, carefully position the primary winding where the secondary winding was previously located. If it fits snugly, avoid removing the fiberglass cloth that covers the cores (although in some cases it might be paper). Removing it could potentially damage the insulating varnish. Instead, gently tap on the winding using a rubber mallet (without excessive force) to see if that helps. If not, it suggests that the previous varnish and adhesive have not been fully removed from the core.

Exercise extreme caution while setting up the main coil

Once the main coil has been installed, a suitable option for the secondary coil would be a thick, flexible copper cable. An ideal choice would be a piece of welding cable with thick insulation. These cables can often be found in the "storerooms" of garages, as they were commonly produced in the past. However, it is important to note that modern welding cables tend to have much thinner insulation. In the event that an old cable is not available, a newer one can still be used.

This is an assembled piece of welding cable that I utilized

The primary challenge is in attaching the lugs. To accomplish this, a considerably sized crimper is required, typically only available in manufacturing facilities. In this case, it is advisable to seek assistance from specialists. It is important to note that using a hammer and chisel to attach the lugs should never be done. Firstly, this type of connection will be unreliable, and secondly, loose contact at high currents can generate excessive heat, potentially causing the device to ignite.

The most efficient choice for crimping lugs is the production crimper.

When installing the welding cable, it is essential to consider that the turns (limited to two) must be tightly positioned. This greatly impacts the level of heating experienced by the secondary winding during operation. However, it is typically difficult to space out the cable loosely, as the available area does not permit such an arrangement.

Place two turns of welding cable with caution – these will form the secondary winding

Proceed to the final assembly of the step-down transformer for spot welding.

Now you have to install the platform that was previously removed and secure the resulting transformer in a vise to ensure better contact density between the core metal. The opposite connection can be achieved using the welding technique. However, since I didn’t have access to a welder during the assembly process, I secured the core parts by applying a layer of epoxy glue around the perimeter. This method worked just as effectively.

Having compressed the platform and core using a vise, we proceeded to applying epoxy adhesive on the joints.

Intermediate check of the transformer before starting to assemble the unit

It’s time to examine our findings. To accomplish this, the main winding terminals need to be powered with 220 V, while the secondary winding should be energized using a multimeter, by setting the switch to AC mode. In my situation, I found that the voltage on the secondary winding measures 2,106 V. By performing basic calculations, it can be deduced that with such a significant drop in voltage, the current intensity has risen to approximately 800 A. These values are highly suitable for a garage setting. Consequently, they make for nearly perfect specifications when it comes to a contact welding machine for a garage.

The outcome we desired has been indicated by the multimeter.

The initial trials of the rectifier were fruitful, thus the process of fitting it into the enclosure commenced. Inside the rectifier lies a 200A ammeter, a utility switch and a three-tiered LED voltmeter showcasing the thresholds of 14.2V, 14.6V, and 15V. The LED voltmeter was designed to detect any potential issue with the battery’s charging status once the rectifier was linked. Ultimately, the intention is to substitute this LED indicator with a conventional analog voltmeter.

The enclosure is constructed using sheet metal sourced from a retired computer, and while it may not possess outstanding aesthetics, its functionality, convenience, and dependability are of paramount importance. The construction expenses amount to 600 rubles solely for rectifier diodes, as all other necessary components were readily available. However, if I were to procure all the essential items (transformer, diodes, transformer cable, crocodile clips, switch, enclosure, ammeter), it would be wiser to invest in a pre-assembled starter-charger instead.

Now let’s proceed to the field tests and measurements. The tests were conducted on an ancient tractor equipped with batteries that were a decade old and unable to start the tractor even in warm weather. Initially, we attempted to start the tractor using the rectifier itself. The voltage declined to 5V, the ammeter exceeded its limit, and the tractor shaft showed some movement, albeit without success. Consequently, we tried starting it with the batteries. After connecting the charger, the batteries began charging at a rate of approximately 50 amps, causing us to promptly engage the starter to prevent them from overheating. As a result, the startup was successful and rapid. The rectifier’s ammeter displayed a current draw of 130A, and the voltage did not fall below 10.7V during startup. As you can observe, the rectifier is also suitable for larger vehicles, and it can handle a smaller car with ease.

The total weight of the device, including the wires and clamps, is 10 kg. Technically, the ammeter is not necessary, but it was interesting to measure the charging current. For simplicity, there are no fuses used at the input or output of the rectifier.

If you want, you can use it to create a complete charger that not only initiates but also charges the battery. All you need to do is add a current limiter (for example, according to this scheme) and decrease the transformer current during idle periods so that it is suitable for long-term operation.

In the most extreme cases, the starter runs for a maximum of 20 seconds. Additionally, the rectifier diodes are high-powered, so both the transformer and diodes do not generate excessive heat and the housing has plenty of space. A test after 5 consecutive startup cycles showed that both diodes only become slightly warm. I initially planned to install a thermal fuse on the transformer, but it turned out to be unnecessary.

There is no safeguard against the reverse connection of the cables. It is necessary to carefully consider the actions or include a reverse diode. In general, it is highly recommended to construct similar designs using the MOT transformer due to its excellent power output.

On the flip side, the car battery is charged without any current restrictions, relying solely on voltage. In certain situations, it can briefly exceed 100A.

As previously mentioned, the electrode used for resistance welding may consist of a copper rod or a stinger taken from a high-quality soldering iron if the device’s power is low. The wire from the welding machine is then attached to the electrode through the use of a soldered copper tip.

Installing the lower electrode

The lower electrode is positioned in line with the tip through the use of a securely fastened bolted connection. This connection is crucial to ensure that any increase in resistance at the point of contact does not lead to a loss of power in the spot welder. In order to create this connection, holes of equal diameter are made in both the electrode and the tip.

It is recommended to use copper or its alloys when selecting bolts and nuts to connect the electrodes and tips with wires. These materials have minimal electrical resistance. By using these elements, it becomes much easier to maintain the resistance welding apparatus and it is also possible to create these connections manually if desired.

How to operate a homemade welding machine

Although resistance welding is a relatively simple technological process, it needs to be carefully managed in order to achieve the desired quality of the connection. To accomplish this, it is necessary to equip the DIY microwave apparatus with the appropriate controls. These controls primarily include a switch and a lever, which allow for the proper application of compression force between the electrodes and the parts being joined.

The quality of the resulting connection is directly influenced by the compression force applied, thus it is advisable to make the lever for the welding machine longer.

Ensuring that the microwave contact welding equipment is securely fixed to the work table is of utmost importance. To achieve this, clamps are utilized.

When working with the contact welding machine, it is important to ensure that the electrodes are only energized when they are compressed. If the current is switched on before compressing the electrodes, they may generate sparks upon contact with the parts, resulting in burning and quick failure.

The switch must be installed in the primary circuit, which is also connected to the controls of resistance welding like microwave welding. If you disregard this suggestion and install it in the secondary winding circuit, where a significant current flows, the switch will introduce extra resistance, resulting in the welding of electrodes together.

To create a DIY welding machine using a microwave transformer, it is essential to incorporate a basic homemade cooling system. One option for such a system is to utilize a regular fan. This device would help to cool the transformer, electrodes, and other conductive components. Admittedly, this cooling method may not be exceptionally efficient, so it is still important to take regular breaks in order for all heated elements of the equipment to cool down on their own.

During this stage, the liquid welding core forms, the weld pool expands, and there is plastic deformation and precipitation of the metal parts at the connection point. It is at this stage that the molten metal starts to spurt out of the weld pool. After the current supply to the joint area is halted, the cooling down process begins, which results in the molten metal crystallizing.

Completed welding machine (overhead view)

The described processes result in the creation of a strong cast core in the area where the joint is formed. This joint area contains substantial residual stress, which can be reduced by allowing a period of time to pass before removing the electrodes following the cessation of current supply. It may even be beneficial to apply additional force to the joint area after halting the current supply, as this will further minimize residual stress and promote a forging effect.

A welding machine is a must-have for any car enthusiast or DIY enthusiast. With so many types and models available on the market, it can be overwhelming to decide which one to buy. However, not everyone has the budget to invest in a brand-new welding machine. So, what can you do if you’re short on cash but still want to have a welding machine? Instead of throwing away that broken microwave oven at home, why not repurpose it and turn it into a working welding machine? In today’s discussion, we’ll explore how you can use the transformer from the microwave to create your own DIY welding machine.

In order to create a homemade microwave spotter, it is important to do more than simply gather the required components and assemblies. It is crucial to meticulously assemble all the parts, transforming them from a jumble into a cohesive design. Not only should the final product be aesthetically pleasing, but it should also be functional and user-friendly.

Housing of a homemade spotter

Housing for a homemade spatter can be constructed in a few different ways. One option is to repurpose the case of an old microwave oven, which can provide a sturdy and well-protected enclosure for the power part and electrical circuit of the spatter. However, for those who prefer a more custom approach, it is also possible to build a homemade case specifically for this purpose.

When designing the case, it is important to consider the protection of all circuit elements from mechanical damage and dust. It is also necessary to incorporate a ventilation and cooling system to prevent overheating. Additionally, handles should be included to facilitate transportation.

To construct the case, a thick board made of dielectric material such as getinax, testolite, or aircraft plywood should be used. This board, which should be around ten millimeters thick, will serve as the foundation for mounting all the parts of the device. For optimal balance, it is recommended to place the transformers in the center of the board.

If you plan to have the homemade device mounted on wheels, it is crucial to make holes in the case walls for power cables to pass through.

The electrode holder is typically constructed using the same material as the mounting plate in the housing. Three identical blanks of the desired shape are cut. The middle blank is designated for attaching the power button, cable, and bracket that secures the electrode. Appropriate grooves and notches are made in the blank. Subsequently, the button, bracket, and cables are installed in the designated positions, and all three blanks are folded and fastened using screws.

Drill holes are created for the screws and nuts, with the expectation that the screw and nut heads will be concealed within the handle of the holder. Once assembled, the holder is carefully sanded, and any sharp corners are smoothed. The holder is now ready for use. Experienced craftsmen recommend making the holder from the body of a glue gun.

DIY spot welder electrode clamp

Electrodes

An electrode is typically created by utilizing a copper bar with a circular shape or a bronze tube. This design is particularly advantageous as it allows for current-carrying conductors to be easily drawn inside. The working portion of the electrode is inserted from one end, necessitating the formation of a groove where the washer to be welded can be placed. Prior to this, the tube is flattened.

Spotter, constructed with their own hands, engaging in labor

Reverse hammer

Each master performs the reverse hammer (inopuller) in a way that is convenient for them. One crucial requirement for all designs is a sturdy connection between the power cable and the inopuller tip, which should provide minimal resistance in the conductive connections. The handle can take the form of a pistol, and the motion stem of the impactor should not be excessively long. The impactor should have free motion.

The assembly of the spotter gun includes the incorporation of a hammer for recoil

If the terminals of the devices that need to be connected are not labeled, it is necessary to identify the terminals with the same name among them in order to connect them together. This problem can be solved by connecting the primary and secondary windings of two or more transformers in series. Then, apply voltage to the input of this combined device and connect an alternating voltage voltmeter to the output terminals (terminals connected in series from the secondary windings).

Depending on the direction of the connection, the voltmeter may exhibit different behaviors:

• Show a certain voltage value;
• Show no voltage at all in the circuit.

If there is any voltage detected by the voltmeter, it indicates the presence of crossed connections in the circuitry of both primary and secondary windings. When the windings are improperly connected, the following phenomena occur: the voltage applied to the primary windings of both transformers is halved on each winding; the voltage across the secondary windings increases, with each winding having the same transformation ratio. The resulting voltage registered by the output voltmeter is equal to twice the input voltage.

Find out the outputs of the transformer shown in this diagram

When the voltmeter displays a reading of "0", it indicates that the voltages from each of the secondary windings connected in series are equal in magnitude but have opposite signs, resulting in cancellation. In simpler terms, at least one pair of windings placed together in the circuit have the same outputs. To rectify this situation, the correct arrangement of the circuit components can be achieved by altering the sequence of connection for either the primary or secondary windings, paying attention to the voltmeter indications.