A good welding machine makes all metal work much easier. It allows you to connect and cut various iron parts, which differ in their thickness and steel density.
Modern technologies offer a huge selection of models that differ in power and size. Reliable designs have a fairly high cost. Budget options usually have a short service life.
Our material provides detailed instructions on how to make a welding machine with your own hands. Before starting the work process, it is recommended to familiarize yourself with the type of welding equipment.
Types of welding machine
The devices of this technology come in several types. Each mechanism has some features that are reflected in the work performed.
Modern welding machines are divided into:
- DC models;
- with alternating current
- three-phase
- vector
The AC model is considered the simplest mechanism that you can easily make yourself.
A simple welding machine allows you to perform complex work with iron and thin steel. To assemble such a structure, you must have a certain set of materials.
These include:
- wire for winding;
- core made of transformer steel. It is necessary for winding the welder.
All these parts can be purchased in specialized stores. Detailed consultation with specialists helps you make the right choice.
AC design
Experienced welders call this design a step-down transformer.
How to make a welding machine with your own hands?
The first thing you need to do is to correctly manufacture the main core. For this model, it is recommended to choose a rod type of part.
To make it you will need plates made of transformer steel. Their thickness is 0.56 mm. Before you begin assembling the core, you must observe its dimensions.
How to correctly calculate the parameters of a part?
Everything is quite simple. The dimensions of the central hole (window) must accommodate the entire winding of the transformer. The photo of the welding machine shows a detailed diagram of the assembly of the mechanism.
The next step is to assemble the core. To do this, take thin transformer plates, which are connected to each other to the required thickness of the part.
Next, we wind a step-down transformer consisting of turns of thin wire. To do this, make 210 turns of thin wire. On the other side, a winding of 160 turns is made. The third and fourth primary windings should contain 190 turns. After this, a thick platinum is attached to the surface.
The ends of the wound wire are secured with a bolt. I mark its surface with the number 1. The following ends of the wire are secured in a similar way with the corresponding markings applied.
Pay attention!
The finished structure should contain 4 bolts with different numbers of turns.
In the finished design, the winding ratio will be 60% to 40%. This result ensures normal operation of the device and good quality of welding fastening.
You can control the supply of electrical energy by switching wires to the required amount of winding. It is not recommended to overheat the welding mechanism during operation.
DC apparatus
These models allow you to perform complex work on thick steel sheets and cast iron. The main advantage of this mechanism is its simple assembly, which does not take much time.
The welding invector is a secondary winding design with an additional rectifier.
Pay attention!
It will be made of diodes. In turn, they must withstand an electric current of 210 A. For this, elements marked D 160-162 are suitable. Such models are quite often used for work on an industrial scale.
The main welding injector is made from a printed circuit board. This semi-automatic welding machine can withstand power surges during long-term operation.
Repairing a welding machine will not be difficult. Here it is enough to replace the damaged area of the mechanism. In the event of a serious breakdown, it is necessary to re-install the primary and secondary windings.
Photo of a do-it-yourself welding machine
Pay attention!
From the article you will learn what they are like. Making them with your own hands is quite simple if you have basic knowledge of electrical engineering and the necessary tools. Both a ready-made transformer and a home-made one can be used as the basis for an automatic welding machine.
Of course, such designs consume a lot of power, therefore, there will be a strong voltage drop in the network. This may affect the functioning of household electrical appliances. It is for this reason that designs based on semiconductor elements are much more effective. To put it simply, these are devices.
The simplest welding machine
So, the first step is to consider the simplest designs that anyone can repeat. Of course, these are devices that are based on transformers. The design discussed below allows operation from 220 and 380 Volts. The maximum diameter of the electrode used in welding is 4 millimeters. The thickness of the metal elements being welded ranges from 1 to 20 millimeters. You will now learn about this in full. Moreover, you can move from simple to complex.
Despite such excellent characteristics, the welding machine is manufactured from readily available materials. For assembly you will need a step-down transformer operating on three-phase voltage. Moreover, its power should be about 2 kilowatts. It is also worth noting that you will not need all the windings. Therefore, if one of them fails, there will be no problems with further design.
Transformer conversion
The bottom line is that you only need to make changes to the secondary winding. To make the task easier, the article below shows a diagram of the welding machine; connecting it to the network is also described.
So, you don’t need to touch the primary winding; it has all the characteristics necessary to operate from a 220 Volt alternating current network. There is no need to disassemble the core; it is enough to directly disassemble the secondary winding on it and wind a new one in its place.
The transformer you must select has several windings. Three primary, the same number of secondary. But there are also middle windings. There are also three of them. It is instead of the middle one that you need to wind the same wire that was used to make the primary one. Moreover, it is necessary to make taps from every thirtieth turn. Each winding should have about 300 turns in total. By properly winding the wire, you can increase the power of the welding machine.
A secondary winding is wound on both outer coils. It is difficult to indicate the exact number of turns, since the more there are, the better. The wire used has a cross-section of 6-8 square millimeters. A thin wire is wound along with it at the same time. As a power cable, you need to use multi-core in reliable insulation. This is exactly how they are made with their own hands.
If we analyze all the structures made using this technology, it turns out that the approximate amount of wire is about 25 meters. If there is no wire with a large cross-section, you can use a cable with an area of 3-4 square millimeters. But in this case it must be folded in half when winding.
Transformer connection
The design is of a simple welding machine. A semi-automatic machine can be made on its basis if you make another winding to power the electric drive for supplying electrodes. Please note that the output of the transformer will be very high current. Therefore, all switching connectors must be made as durable as possible.
To make terminals to connect to the secondary winding terminals, you will need copper tubing. It should have a diameter of 10 millimeters and a length of 3-4 cm. It needs to be riveted at one end. The result should be a plate in which you need to make a hole. Its diameter should be about one centimeter. Wires are inserted from the other end. Regardless of whether the welding machine is DC or AC, the switching is made as rigid and reliable as possible.
It is advisable to clean them perfectly, if necessary, treat them with acid and neutralize it. To improve contact, the second edge of the tube should be slightly flattened with a hammer. It is best to attach the leads of the primary winding to a textolite board. Its thickness should be about three millimeters, more is possible. It is rigidly attached to the transformer. In addition, 10 holes need to be made in this board, each with a diameter of about 6 millimeters. Look at the diagram of the welding machine, how it is connected to the 220 and 380 Volt network.
They need to be installed with screws, nuts and washers. The terminals of all primary windings are connected to them. In the event that welding is required to operate from a 220-volt household network, the outer windings of the transformer are connected in parallel. The middle winding is connected in series with them. Welding will work ideally with a power supply of 380 Volts.
To connect the primary windings to the power supply network, you need to use a different circuit. Both outer windings are connected in series. Only after this the middle winding is switched on in series with them. The reason for this lies in the following: the middle winding is additional; with its help, the voltage and current in the secondary circuit are reduced. Thanks to this, welding machines made with their own hands using the above technology operate in normal mode.
Manufacturing of the electrode holder
Of course, an integral part of any welding machine is the electrode holder. There is no need to buy ready-made if you can make it from scrap materials. You need a three-quarter pipe, its total length should be about 25 centimeters. It is necessary to make small notches at both ends, approximately 1/2 of the diameter. The welding machine will work normally with such a holder. There is a separate requirement for plastic structural elements - they must be located as far as possible from the transformer and holder.
They need to be done three to four centimeters from the edge. Then take a piece of steel wire, the diameter of which is 6 millimeters, and weld it to the pipe opposite the larger recess. On the other side, you need to drill a hole, attach a wire to it that will connect to the secondary winding.
Network connection
It is worth noting that you need to connect the welding machine according to all the rules. First, you need to use a switch, with which you can easily disconnect the device from the network. Please note that welding machines made by yourself should not be inferior in safety to analogues produced by industry. Secondly, the cross-section of the wires for connecting to the network must be at least one and a half square millimeters. The current consumption of the primary winding is a maximum of 25 amperes. In this case, the current can be changed in the range of 60..120 amperes. Please note that this design is relatively simple, so it is only suitable for domestic use.
Spot welding machine
A spot welding machine will also be useful. The designs of such devices are no less simple than the previous ones. True, the output current is very large. But it is possible to carry out contact welding of metals up to three millimeters thick. Most designs do not have output current adjustment. But you can do this if you wish. True, the whole homemade product becomes more complicated. There is no need to regulate the output current, since the welding process can be controlled visually. Of course, inverter welding machines will be much more efficient. But point ones can do things that no other design can do.
For manufacturing you will need a transformer with a power of about 1 kilowatt. The primary winding remains unchanged. Only the secondary one will need to be redone. And if you use a transformer from a household microwave, then you need to knock out the secondary winding and instead wind several turns of large-section wire. If possible, it is better to use a copper busbar. The output should be about five volts, but this will be enough for the device to fully operate.
Electrode holder design
Here it is slightly different from the one discussed above. For manufacturing you will need small duralumin blanks. Rods with a diameter of 3 centimeters are suitable. The bottom one must be motionless, completely isolated from contacts. Textolite washers and varnished fabric can be used as insulating material. Any, even the simplest spot welding machine needs a reliable electrode holder, so pay maximum attention to its design.
The electrodes are made of copper, their diameter is 10-12 millimeters. They are firmly fixed in the holder using rectangular brass inserts. The initial position of the electrode holder is that its halves are separated. Springs can be used to add elasticity. Ideal for old folding beds.
Resistance welding work
It is necessary to connect such welding to the electrical network using a circuit breaker. It must have a current rating of 20 amps. Please note that at the entrance (where your counter is located) the machine must be either the same in parameters or larger. To turn on the transformer, a simple magnetic starter is used. The operation of a contact-type welding machine is somewhat different from that discussed above. And you will now recognize these features.
To turn on the magnetic starter, you need to provide a special pedal, which you will press with your foot to generate current in the secondary circuit. Please note that resistance welding is turned on and off only if the electrodes are completely brought together. If you neglect this rule, a lot of sparks will appear, and as a result, this will lead to burning of the electrodes and their failure. Try to pay attention to the temperature of the welding machine as often as possible. Take short breaks from time to time. Do not allow the unit to overheat.
Inverter welding machine
It is the most modern, but more difficult to design. It also uses high-power semiconductor transistors. Perhaps these are the most expensive and scarce parts. First of all, the power supply is made. It is pulsed, so it is necessary to make a special transformer. And now in more detail about what such a welding machine consists of. See below for the characteristics of its components.
Of course, the transformer used in the inverter is much smaller in size than those discussed above. You will also need to make a throttle. So, you should get a ferrite core, a frame for making a transformer, copper busbars, special brackets to fix the two halves of the ferrite core, and electrical tape. The latter must be selected based on the data of its thermal resistance. Follow these tips when making inverter welders.
Winding the transformer
The transformer is wound over the entire width of the frame. Only under this condition will it be able to withstand any voltage drops. For winding, either a copper busbar or wires collected in a bundle are used. Please note that aluminum wire cannot be used! It cannot handle the high electrical current density found in the inverter. Such a welding machine for a summer house can help you out, and its weight is extremely light. The coils are wound as tightly as possible. The secondary winding is two wires with a thickness of about two millimeters, twisted together.
They should be isolated from each other as much as possible. If you have large supplies of old TVs, you can use them in the design. 5 pieces are required, and you need to make one common magnetic circuit out of them. In order for the device to work with maximum efficiency, you need to pay attention to every detail. In particular, the thickness of the transformer output winding wire affects its uninterrupted operation.
Inverter design
To make a welding machine 200, it is necessary to pay maximum attention to all the details. In particular, power transistors must be mounted on a radiator. Moreover, the use of thermal paste is encouraged to transfer heat from the transistor to the heatsink. And it is recommended to change it from time to time, as it tends to dry out. In this case, heat transfer deteriorates, and there is a possibility that the semiconductors will fail. In addition, forced cooling needs to be done. Exhaust coolers are used for this purpose. Diodes used to rectify alternating current must be mounted on an aluminum plate. Its thickness should be 6 millimeters.
The terminals are connected using bare wire. Its cross-section should be 4 millimeters. Please ensure that there is a maximum distance between the connection wires. They should not touch each other, no matter what impact the body of the welding machine experiences. The choke must be secured to the base of the welding machine using a metal plate.
Moreover, the latter must completely repeat the shape of the throttle itself. To reduce vibration, it is necessary to install a rubber seal between the body and the throttle. The power wires inside the device are routed in different directions. Otherwise, there is a possibility that a short circuit will occur. It is necessary to install the fan in such a way that it blows air across all radiators at the same time. Otherwise, if you cannot use one fan, you will have to install several.
But it is better to fully calculate in advance the installation location of all system elements. Please note that the secondary winding must be cooled as efficiently as possible. As you can see, not only radiators need effective airflow. On this basis, you can make an argon welding machine at no cost. But its design will require the use of other materials.
Conclusion
Now you know how to make several types of welding machines. If you have skills in designing radio-electronic equipment, then it is, of course, better to choose an inverter welding machine. You will spend time, but at the end you will get an excellent device that is not inferior even to expensive Japanese analogues. Moreover, its production will cost mere pennies.
But if there is a need to make a welding machine, as they say, in a hurry, then it will be easier to connect two transformers from microwave ovens with modified secondary windings. Subsequently, the entire unit can be improved by adding an electric drive to supply electrodes. You can also install a cylinder filled with carbon dioxide to weld metals in its environment.
No work with iron can be done without a welding machine. It allows you to cut and connect metal parts of any size and thickness. A good solution is to do the welding yourself, because good models are expensive, and cheap ones are of poor quality. To implement the idea of making your own welder, you need to acquire special equipment that will allow you to hone the quality skills of a specialist in real conditions.
Types and characteristics of the tool
After all the necessary conditions of the preparatory stage have been successfully met, the opportunity opens up to make a model of the welding device with your own hands. Today there are many schematic diagrams that can be used to make a device. They follow one of the following approaches:
- Direct or alternating current.
- Pulse or inverter.
- Automatic or semi-automatic.
It is worth paying attention to the device, which belongs to the transformer type. An important characteristic of this device is its operation on alternating current, allowing it to be used in domestic conditions. AC devices are capable of ensuring the standard quality of seams in welded joints. A unit of this type can easily find its use in everyday life. when servicing real estate located in the private sector.
In order to assemble such a device, you must have:
- About 20 meters of cable or large-section wire.
- A metal base of high magnetic permeability that will be used as the core of the transformer.
The optimal core configuration has a U-shaped core base. In theory, a core of any other configuration could easily be suitable, for example, a round shape taken from a stator that has become unusable for an electric motor. But in practice, winding a winding on such a base is much more difficult.
The cross-sectional area for a core belonging to a home-made household welding machine is 50 cm 2. This will be enough to use rods from 3 to 4 mm in diameter in the installation. Using a larger cross-section will only lead to an increase in the mass of the structure, and the efficiency of the device will not become higher.
Manufacturing instructions
For the primary winding, it is necessary to use copper wire with high heat resistance, since when performing welding work it will be exposed to high temperatures. The wire used must be selected according to fiberglass or cotton insulation, intended for stationary use in high temperature zones.
For the winding of the transformer, it is not allowed to use wire with PVC insulation, which will immediately become unusable when heated. In some cases, the insulation for the transformer winding is made independently.
To perform this procedure, you need to take a piece of cotton fabric or fiberglass, cut it into strips about 2 cm wide, wrap them around the prepared wire and impregnate the bandage with any varnish that has electrical properties. Such insulation in terms of thermal characteristics is not inferior to any factory analogue.
The coils are wound according to a certain principle. First, half of the primary winding is wound, followed by half of the secondary. Then proceed to the second coil using the same technique. To improve the quality of the insulating coating, fragments of strips of cardboard, fiberglass or pressed paper are inserted between the layers of windings.
Equipment setup
Next you need to configure. It is performed by connecting the equipment to the network and taking voltage readings from the secondary winding. The voltage on it should be from 60 to 65 volts.
Precise adjustment of the parameters is carried out by reducing or increasing the length of the winding. To obtain a high-quality result, the voltage on the secondary winding should be adjusted to the specified parameters.
A VRP cable or a ShRPS wire, which will be used to connect to the network, is connected to the primary winding of the finished welding transformer. One of the terminals of the secondary winding is fed to the terminal to which ground will subsequently be connected, and the second is fed to the terminal connected to the cable. The last procedure is completed and the new welding machine is ready for use.
Production of small-sized units
An autotransformer from a Soviet-style TV is easily suitable for making a small welding machine. It can easily be used to produce a voltaic arc. In order for everything to work out correctly, graphite electrodes are connected between the terminals of the autotransformer. This simple design allows you to perform several simple welding jobs, such as:
- Making or repairing thermocouples.
- Heating high-carbon steel products to maximum temperature.
- Hardening of tool steel.
A homemade welding machine, created on the basis of an autotransformer, has a significant drawback. It must be used with additional precautions. Without galvanic isolation from the electrical network, it is a rather dangerous device.
The optimal parameters of an autotransformer suitable for creating a welding machine are considered to be an output voltage ranging from 40 to 50 volts and low power from 200 to 300 watts. This device is capable of delivering from 10 to 12 amperes of operating current, which will be sufficient for welding wires, thermocouples and other elements.
You can use pencil leads as electrodes for a DIY mini welding machine. The terminals found on various electrical appliances can serve as holders for improvised electrodes.
To carry out welding work, the holder is connected to one of the terminals of the secondary winding, and the part to be welded to the other. The handle for the holder is best made from a fiberglass washer or other heat-resistant material. It should be noted that the arc of such a device acts for a fairly short time, preventing the used autotransformer from overheating.
Figure 1. Diagram of a bridge rectifier for a welding machine.
Welding machines come in direct and alternating current.
S.A. direct current are used for low current welding of thin sheet metal (roofing steel, automotive, etc.). The DC welding arc is more stable; direct and reverse polarity welding is possible. You can weld on direct current using electrode wire without coating and electrodes designed for welding on both direct current and alternating current. To make the arc burning stable at low currents, it is desirable to have an increased open-circuit voltage Uxx of the welding winding (up to 70 - 75 V). To rectify alternating current, the simplest “bridge” rectifiers on powerful diodes with cooling radiators are used (Fig. 1).
To smooth out voltage ripples, one of the outputs of S.A. And they are connected to the electrode holder through inductor L1, which is a coil of 10 - 15 turns of a copper bus with a cross section of S = 35 mm 2, wound on any core, for example, from. To rectify and smoothly regulate the welding current, more complex circuits are used using powerful controlled thyristors. One of the possible circuits based on thyristors of type T161 (T160) is given in the article by A. Chernov “It will charge and weld” (Model Designer, 1994, No. 9). The advantages of DC regulators are their versatility. The range of their voltage changes is 0.1-0.9 Uxx, which allows them to be used not only for smooth adjustment of welding current, but also for charging batteries, powering electric heating elements and other purposes.
Figure 2. Diagram of the falling external characteristic of the welding machine.
Rice. 1. Bridge rectifier for welding machine. Connection shown S.A. for welding thin sheet metal with “reverse” polarity - “+” on the electrode, “-” on the part being welded U2: - output alternating voltage of the welding machine
AC welding machines are used when welding with electrodes whose diameter is more than 1.6 - 2 mm, and the thickness of the welded products is more than 1.5 mm. In this case, the welding current is significant (tens of amperes) and the arc burns quite steadily. Electrodes designed for welding with alternating current only are used. For normal operation of the welding machine it is necessary:
- Provide output voltage for reliable arc ignition. For amateur S.A. Uxx = 60 - 65v. A higher open circuit output voltage is not recommended, which is mainly due to ensuring operational safety (Uxxindustrial welding machines - up to 70 - 75 V).
- Provide the welding voltage Usv necessary for stable arc burning. Depending on the diameter of the electrode - Usv = 18 - 24 V.
- Provide rated welding current Iw = (30 - 40) de, where Iw is the value of the welding current, A; 30 - 40 - coefficient depending on the type and diameter of the electrode; dе - electrode diameter, mm.
- Limit the short circuit current Isk, the value of which should not exceed the rated welding current by more than 30 - 35%.
Stable arc burning is possible if the welding machine has a falling external characteristic, which determines the relationship between the current strength and voltage in the welding circuit (Fig. 2).
S.A. shows that for rough (stepwise) overlap of the range of welding currents, switching of both primary and secondary windings is necessary (which is structurally more difficult due to the large current flowing in it). In addition, to smoothly change the welding current within the selected range, mechanical devices for moving the windings are used. When the welding winding is removed relative to the network winding, the magnetic leakage fluxes increase, which leads to a decrease in the welding current.
Figure 3. Diagram of a rod-type magnetic circuit.
When designing an amateur SA, one should not strive to completely cover the range of welding currents. It is advisable at the first stage to assemble a welding machine for working with electrodes with a diameter of 2 - 4 mm, and at the second stage, if it is necessary to work at low welding currents, supplement it with a separate rectifier device with smooth control of the welding current. Amateur welding machines must satisfy a number of requirements, the main of which are the following: relative compactness and low weight; sufficient operating time (at least 5 - 7 electrodes dе = 3 - 4 mm) from a 220V network.
The weight and dimensions of the device can be reduced by reducing its power, and the operating time can be increased by using steel with high magnetic permeability and heat-resistant insulation of the winding wires. These requirements are easy to fulfill if you know the basics of designing welding machines and adhering to the proposed technology for their manufacture.
Rice. 2. Falling external characteristic of the welding machine: 1 - family of characteristics for different welding ranges; Isv2, Isvz, Isv4 - ranges of welding currents for electrodes with a diameter of 2, 3 and 4 mm, respectively; Uxx - CA open circuit voltage. Is - short circuit current; Ucv - welding voltage range (18 - 24 V).
Rice. 3. Rod-type magnetic circuit: a - L-shaped plates; b - U-shaped plates; c - plates made of transformer steel strips; S = axb - cross-sectional area of the core (core), cm 2 s, d - window dimensions, cm.
So, choosing the type of core. For the manufacture of welding machines, rod-type magnetic cores are mainly used, since their design is more technologically advanced. The core is made from electrical steel plates of any configuration with a thickness of 0.35-0.55 mm, tightened with pins insulated from the core (Fig. 3). When selecting a core, it is necessary to take into account the dimensions of the “window” to fit the windings of the welding machine, and the cross-sectional area of the core (core) S =axb, cm 2. As practice shows, you should not choose the minimum values of S = 25 - 35 cm, since the welding machine will not have the required power reserve and it will be difficult to obtain high-quality welding. And overheating of the welding machine after short-term operation is also inevitable.
Figure 4. Diagram of a toroidal magnetic circuit.
The cross section of the core should be S = 45 - 55 cm 2. The welding machine will be somewhat heavier, but it will not let you down! Amateur welding machines on toroidal-type cores are becoming increasingly widespread, which have higher electrical characteristics, approximately 4 to 5 times higher than those of a rod type, and electrical losses are low. The labor costs for their manufacture are more significant and are associated primarily with the placement of the windings on the torus and the complexity of the winding itself.
However, with the right approach they give good results. The cores are made from transformer strip iron, rolled into a torus-shaped roll. An example is a core from a 9 A “Latr” autotransformer. To increase the internal diameter of the torus (“window”), a piece of steel tape is unwinded from the inside and wound onto the outside of the core. But, as practice shows, Latra alone is not enough to produce high-quality SA. (small section S). Even after working with 1 - 2 electrodes with a diameter of 3 mm, it overheats. It is possible to use two similar cores according to the scheme described in B. Sokolov’s article “Welding Baby” (Sam, 1993, No. 1), or to produce one core by rewinding two (Fig. 4).
Rice. 4. Toroidal magnetic core: 1.2 - autotransformer core before and after rewinding; 3 design S.A. based on two toroidal cores; W1 1 W1 2 - network windings connected in parallel; W 2 - welding winding; S = axb - cross-sectional area of the core, cm 2, s, d - internal and external diameters of the torus, cm; 4 - electrical diagram S.A. based on two joined toroidal cores.
Amateur SAs made on the basis of stators of high-power asynchronous three-phase electric motors (more than 10 kW) deserve special attention. The choice of core is determined by the cross-sectional area of the stator S. Stamped stator plates do not fully correspond to the parameters of electrical transformer steel, therefore it is not advisable to reduce the cross-section S to less than 40 - 45 cm.
Figure 5. Scheme of fastening the terminals of the CA windings.
The stator is freed from the housing, the stator windings are removed from the internal slots, the groove bridges are cut off with a chisel, the inner surface is protected with a file or an abrasive wheel, the sharp edges of the core are rounded and wrapped tightly, covering it with cotton insulating tape. The core is ready for winding windings.
Selection of windings. For primary (network) windings, it is better to use a special copper winding wire in cold steel. (fiberglass) insulation. Wires in rubber or rubber-fabric insulation also have satisfactory heat resistance. Wires in polyvinyl chloride (PVC) insulation are unsuitable for work at elevated temperatures (and this is already included in the design of amateur SA) due to its possible melting, leakage from the windings and their short circuit. Therefore, the polyvinyl chloride insulation from the wires must either be removed and the wires wrapped along the entire length of the cotton wool. insulating tape, or do not remove it, but wrap the wire over the insulation. Another proven winding method is also possible. But more on that below.
When selecting the cross-section of the winding wires, taking into account the specifics of the work of S.A. (periodic) we allow a current density of 5 A/mm 2. With a welding current of 130 - 160 A (electrode dе = 4 mm), the power of the secondary winding will be P 2 = Isw x 160x24 = 3.5 - 4 kW, the power of the primary winding, taking into account losses, will be about 5 - 5.5 kW, and therefore the maximum current of the primary winding can reach 25 A. Therefore, the cross-section of the wire of the primary winding S 1 must be at least 5 - 6 mm. In practice, it is advisable to use a wire with a cross section of 6 - 7 mm 2. Either it is a rectangular busbar or a copper winding wire with a diameter (without insulation) of 2.6 - 3 mm. (Calculation using the well-known formula S = piR 2, where S is the area of the circle, mm 2 pi = 3.1428; R is the radius of the circle, mm.) If the cross-section of one wire is insufficient, winding in two is possible. When using aluminum wire, its cross-section must be increased by 1.6 - 1.7 times. Is it possible to reduce the cross-section of the network winding wire? Yes, you can. But at the same time S.A. will lose the required power reserve, will heat up faster, and the recommended core cross-section S = 45 - 55 cm in this case will be unreasonably large. The number of turns of the primary winding W 1 is determined from the following ratio: W 1 = [(30 - 50):S] x U 1 where 30-50 is a constant coefficient; S - core cross-section, cm 2, W 1 = 240 turns with bends from 165, 190 and 215 turns, i.e. every 25 turns.
Figure 6. Diagram of methods for winding CA windings on a rod-type core.
A larger number of network winding taps, as practice shows, is impractical. And here's why. By reducing the number of turns of the primary winding, both the power SA and Uxx increase, which leads to an increase in arc voltage and a deterioration in welding quality. Consequently, it is impossible to cover the range of welding currents without deteriorating the quality of welding by simply changing the number of turns of the primary winding. To do this, it is necessary to provide for switching the turns of the secondary (welding) winding W 2.
The secondary winding W 2 must contain 65 - 70 turns of an insulated copper bus with a cross-section of at least 25 mm (preferably a cross-section of 35 mm). A flexible stranded wire (for example, a welding wire) and a three-phase stranded power cable are also quite suitable. The main thing is that the cross-section of the power winding should not be less than required, and the insulation should be heat-resistant and reliable. If the wire cross-section is insufficient, winding in two or even three wires is possible. When using aluminum wire, its cross-section must be increased by 1.6 - 1.7 times.
Rice. 5. Fastening the terminals of the CA windings: 1 - CA housing; 2 - washers; 3 - terminal bolt; 4 - nut; 5 - copper tip with wire.
The difficulty of purchasing switches for high currents, and practice shows that it is easiest to insert the welding winding leads through copper lugs under terminal bolts with a diameter of 8 - 10 mm (Fig. 5). Copper lugs are made from copper tubes of suitable diameter 25 - 30 mm long and attached to the wires by crimping and preferably soldering. Let us especially focus on the order of winding the windings. General rules:
- Winding should be done along an insulated core and always in the same direction (for example, clockwise).
- Each layer of the winding is insulated with a layer of cotton wool. insulation (fiberglass, electrical cardboard, tracing paper), preferably impregnated with bakelite varnish.
- The winding terminals are tinned, marked, and secured with cotton wool. braid, additionally put cotton on the terminals of the network winding. cambric.
- In case of doubt about the quality of insulation, winding can be carried out using a cotton cord, as if in two wires (the author used cotton thread for fishing). After winding one layer, winding with cotton. the thread is fixed with glue, varnish, etc. and after drying, wind the next row.
Figure 7. Diagram of methods for winding CA windings on a toroidal core.
Let's consider the order of arrangement of windings on a rod-type magnetic core. The network winding can be positioned in two main ways. The first method allows you to obtain a more “hard” welding mode. The network winding in this case consists of two identical windings W 1 W 2, located on different sides of the core, connected in series and having the same wire cross-section. To adjust the output current, taps are made on each of the windings, which are closed in pairs (Fig. 6a, c).
The second method involves winding the primary (network) winding on one side of the core (Fig. 6 c, d). In this case, the SA has a steeply falling characteristic, welds “softly”, the arc length has less influence on the value of the welding current, and therefore on the quality of welding. After winding the primary winding of the CA, it is necessary to check for the presence of short-circuited turns and the correctness of the selected number of turns. The welding transformer is connected to the network through a fuse (4 - 6A) and preferably an AC ammeter. If the fuse burns out or gets very hot, then this is a clear sign of a short-circuited turn. Consequently, the primary winding will have to be rewound, paying special attention to the quality of the insulation.
Rice. 6. Methods for winding CA windings on a rod-type core: a - network winding on both sides of the core; b - the corresponding secondary (welding) winding, connected in counter-parallel; c - network winding on one side of the core; g - the corresponding secondary winding, connected in series.
If the welding machine makes a loud noise and the current consumption exceeds 2 - 3 A, then this means that the number of primary windings is underestimated and it is necessary to wind up a certain number of turns. A working CA consumes no-load current of no more than 1 - 1.5 A, does not heat up and does not buzz much. The secondary winding CA is always wound on both sides of the core. For the first winding method, the secondary winding also consists of two identical halves, connected to increase the stability of arc burning (Fig. 6) in counter-parallel, and the wire cross-section can be taken slightly smaller - 15 - 20 mm 2.
Figure 8. Connection diagram for measuring instruments.
For the second winding method, the main welding winding W 2 1 is wound on the side of the core free from windings and makes up 60 - 65% of the total number of turns of the secondary winding. It serves mainly to ignite the arc, and during welding, due to a sharp increase in the magnetic dissipation flux, the voltage on it drops by 80 - 90%. An additional welding winding W 2 2 is wound on top of the primary one. Being a power source, it maintains the welding voltage and, consequently, the welding current within the required limits. The voltage across it drops in welding mode by 20 - 25% relative to the no-load voltage. After manufacturing the SA, it is necessary to set it up and check the quality of welding with electrodes of different diameters. The setup process is as follows. To measure welding current and voltage, you need to purchase two electrical measuring instruments - an AC ammeter for 180-200 A and an AC voltmeter for 70-80 V.
Rice. 7. Methods for winding CA windings on a toroidal core: 1.2 - uniform and sectional winding of windings, respectively: a - network b - power.
Their connection diagram is shown in Fig. 8. When welding with different electrodes, take the values of the welding current - Iw and welding voltage Uw, which must be within the required limits. If the welding current is small, which happens most often (the electrode sticks, the arc is unstable), then in this case, either by switching the primary and secondary windings, the required values are set, or the number of turns of the secondary winding is redistributed (without increasing them) towards increasing the number of turns wound on top network winding. After welding, you can make a break or saw the edges of the welded products, and the quality of the weld will immediately become clear: the depth of penetration and the thickness of the deposited layer of metal. It is useful to create a table based on the measurement results.
Figure 9. Diagram of welding voltage and current meters and design of a current transformer.
Based on the data in the table, optimal welding modes are selected for electrodes of different diameters, remembering that when welding with electrodes, for example, with a diameter of 3 mm, electrodes with a diameter of 2 mm can be cut, because The cutting current is 30-25% higher than the welding current. The difficulty of purchasing the measuring instruments recommended above forced the author to resort to making a measuring circuit (Fig. 9) based on the most common 1-10 mA DC milliammeter. It consists of voltage and current meters assembled using a bridge circuit.
Rice. 9. Schematic diagram of welding voltage and current meters and design of a current transformer.
The voltage meter is connected to the output (welding) winding SA. The setting is carried out using any tester that controls the welding output voltage. Using a variable resistance R.3, the arrow of the device is set to the final scale division at the maximum value of Uxx. The voltage meter scale is quite linear. For greater accuracy, you can remove two or three control points and calibrate the measuring device to measure voltages.
Setting up a current meter is more difficult because it is connected to a homemade current transformer. The latter is a toroidal core with two windings. The dimensions of the core (external diameter 35-40 mm) are not of fundamental importance, the main thing is that the windings fit. Core material - transformer steel, permalloy or ferrite. The secondary winding consists of 600 - 700 turns of insulated copper wire of the PEL, PEV brand, preferably PELSHO, with a diameter of 0.2 - 0.25 mm and is connected to a current meter. The primary winding is a power wire running inside the ring and connected to the terminal bolt (Fig. 9). Setting up the current meter is as follows. To the power (welding) winding S.A. connect a calibrated resistance made of thick nichrome wire for 1 - 2 seconds (it gets very hot) and measure the voltage at the SA output. The current flowing in the welding winding is determined. For example, when connecting Rн = 0.2 ohm Uout = 30V.
Mark a point on the instrument scale. Three to four measurements with different RH are enough to calibrate the current meter. After calibration, the instruments are installed on the CA body, using generally accepted recommendations. When welding under different conditions (high or low current network, long or short supply cable, its cross-section, etc.), the SA is adjusted by switching the windings. to the optimal welding mode, and then the switch can be set to the neutral position. A few words about resistance spot welding. Towards the design of S.A. This type has a number of specific requirements:
- The power delivered at the time of welding should be maximum, but not more than 5-5.5 kW. In this case, the current consumed from the network will not exceed 25 A.
- The welding mode must be “hard”, and therefore, the winding of the windings S.A. should be carried out according to the first option.
- The currents flowing in the welding winding reach values of 1500-2000 A and higher. Therefore, the welding voltage should be no more than 2-2.5V, and the no-load voltage should be 6-10V.
- The cross-section of the primary winding wires is at least 6-7 mm, and the cross-section of the secondary winding is at least 200 mm. This cross-section of wires is achieved by winding 4-6 windings and then connecting them in parallel.
- It is not practical to make additional taps from the primary and secondary windings.
- The number of turns of the primary winding can be taken as the minimum calculated due to the short duration of the operation of the SA.
- It is not recommended to take a cross-section of the core (core) less than 45-50 cm.
- Welding tips and underwater cables to them must be copper and pass appropriate currents (diameter of tips 12-14 mm).
A special class of amateur S.A. represent devices manufactured on the basis of industrial lighting and other transformers (2-3 phase) with an output voltage of 36V and a power of at least 2.5-3 kW. But before undertaking the alteration, it is necessary to measure the cross-section of the core, which should be at least 25 cm, and the diameters of the primary and secondary windings. It will immediately become clear to you what you can expect from remaking this transformer.
And finally, some technological tips.
The welding machine must be connected to the network using a wire with a cross-section of 6-7 mm through an automatic machine with a current of 25-50 A, for example AP-50. The diameter of the electrode, depending on the thickness of the metal being welded, can be selected based on the following relationship: da= (1-1.5)L, where L is the thickness of the metal being welded, mm.
The arc length is selected depending on the diameter of the electrode and is on average 0.5-1.1 d3. It is recommended to weld with a short arc of 2-3 mm, the voltage of which is 18-24 V. Increasing the length of the arc leads to a violation of the stability of its combustion, increased losses due to waste and spatter, and a decrease in the depth of penetration of the base metal. The longer the arc, the higher the welding voltage. The welding speed is selected by the welder depending on the grade and thickness of the metal.
When welding with straight polarity, the plus (anode) is connected to the part and the minus (cathode) to the electrode. If it is necessary for less heat to be generated on the parts, for example, when welding thin-sheet structures, reverse polarity welding is used (Fig. 1). In this case, the minus (cathode) is connected to the part being welded, and the plus (anode) is connected to the electrode. This not only ensures less heating of the part being welded, but also accelerates the process of melting the electrode metal due to the higher temperature of the anode zone and greater heat input.
Welding wires are connected to the SA through copper lugs under the terminal bolts on the outside of the welding machine body. Poor contact connections reduce the power characteristics of the SA, deteriorate the quality of welding and can cause overheating and even fire of the wires. If the welding wires are short (4-6 m), their cross-section should be at least 25 mm. When performing welding work, it is necessary to comply with fire and electrical safety rules when working with electrical appliances.
Welding work should be carried out in a special mask with protective glass grade C5 (for currents up to 150-160 A) and gloves. Perform all switching of the SA only after disconnecting the welding machine from the network.
According to experts, making a welding machine with your own hands is not difficult.
However, to make it, you need to clearly understand why, for what work it will be used.
A homemade device is completed and assembled from available components and parts. A plasma mechanism can also be considered as an option for craftsmen.
Practice shows that with precise selection of components, the device will serve for a long time and reliably.
It is important that the electrical circuit is as simple as possible. Sometimes they even use a microwave transformer.
The device must operate from a household AC voltage of 220 V.
If you choose 380 V as the operating voltage, the circuit and design of the device will become noticeably more complicated.
Block diagram of the welding machine
For welding work, devices operating on alternating and direct current are used.
The circuit of any device includes a transformer (it is possible to use a transformer from a microwave oven), a rectifier, a choke, a holder, and an electrode. It is in this sequence that electric current flows through a closed circuit.
The circuit is completed when an electric arc occurs between the electrode and the metal workpieces to be connected.
In order for the quality of the welded joint to be high, it is necessary to ensure stable combustion of this arc.
And to set the required combustion mode, a current regulator is used.
DC machines are used for welding elements made of thin sheet metal. With this welding method, you can use any electrodes and electrode wire without ceramic coating.
The electrode holder is connected to the rectifier through a choke. This is done in order to smooth out voltage ripples.
The choke is a coil of copper wires that is wound on any core. The rectifier, in turn, is connected to the secondary winding of the transformer.
The transformer is connected to the household electrical network. The connection sequence is simple and clear.
AC voltage conversion is done using a step-down transformer.
According to Ohm's law, the voltage that is induced on the secondary winding of the transformer decreases, and the current increases from 4 amperes to 40 or more.
This is approximately the amount required for welding. In principle, this device can be called the simplest welding machine.
And use wires to attach the electrode holder to it. But it is impossible to use the holder for practical purposes, since the circuit does not contain other necessary elements.
And most importantly, it does not have a current regulator. As well as a rectifier and other elements.
The transformer is considered the main element of the welding machine. You can buy it or adapt one that is already in use.
Many craftsmen use a transformer from a microwave oven that has expired. Due to its dimensions and weight, a micropulse element always takes up a lot of space in the structure.
If we consider the welding unit as a whole, we can distinguish three main blocks that it includes:
- power unit;
- rectifier unit;
- inverter block.
A homemade inverter device can be configured in such a way that it has minimal dimensions and weight.
Such devices, designed for use in the home, are sold in stores today.
The advantages of an inverter device over traditional units are obvious. First of all, it should be noted that the device is compact, easy to use, and reliable.
Only one component in the parameters of this device is of concern - its high cost.
The most general calculations confirm that making such a device with your own hands is easier and more profitable.
The main elements can almost always be found among electrical machines and devices that end up in storage rooms. Or in a landfill.
The simplest current regulator can be made from a piece of heating coil, which is used in household electric stoves. The choke is made from a piece of copper wire.
Radio amateurs have come up with the simplest pulse welding method. It is used to attach wires to a metal board.
No complicated devices - just a choke and a couple of wires. A current regulator is also not needed. Instead, a fuse-link is connected to the circuit.
One electrode is connected to the board through an inductor.
The second one is a crocodile clip. The plug with wires is plugged into a household outlet.
The clamp with the wire is sharply applied to the board in the place where it needs to be welded. A welding arc occurs and at this moment the fuses located in the electrical panel may blow out.
This does not happen because the fuse link burns out faster. And the wire remains securely welded to the board.
Product contents
The homemade one is assembled in order to perform small jobs around the household.
All elements, electronic devices, wires and metal structures must be assembled in a specific place. Where the product will be assembled.
The choke can be used from the fluorescent lamp fittings. You need to stock up more wires, preferably copper, of different sections.
If it was not possible to find a ready-made throttle, then you need to make it yourself.
To do this, you will need a steel magnetic core from an old starter and several meters of copper wires with a cross-section of 0.9 square.
power unit
The main element of the power supply in the inverter is the transformer.
It can be converted from a laboratory autotransformer or used to remake a transformer from a microwave oven that has already served its useful life.
It is very important not to damage the primary winding when removing the transformer from the microwave oven.
The secondary winding is removed and rebuilt. The number of turns and diameter of copper wires is calculated depending on the pre-selected power of the welding machine.
The spot welding method is well implemented by a device made on a transformer from a microwave oven.
The rectifier is used to convert AC voltage to DC voltage. The main elements of this device are diodes.
It is switched into certain circuits, most often bridge circuits. An alternating current is supplied to the input of such a circuit, and a direct current is removed from the output terminals.
Diodes are selected with such power to withstand the initially specified loads. To cool them, special radiators made of aluminum alloys are used.
When marking the installation board, it is advisable to provide space for a choke, which is designed to smooth out pulses. The rectifier is assembled on a separate board, made of getinax or textolite.
Inverter block
The inverter converts the direct current coming from the rectifier into alternating current, which has a high oscillation frequency.
The conversion is performed using electronic circuits using thyristors or high-power transistors.
If a voltage of 220 volts with a frequency of 50 Hz is supplied to the input terminals of the transformer, then a direct current of up to 150 Amperes and a voltage of 40 volts is fixed at the output terminals of the inverter.
These current parameters allow welding of metal parts from various alloys.
The electronic regulator allows you to select the mode appropriate for a specific operation.
Practice shows that a homemade welding machine, in terms of its characteristics, is not inferior to factory products.
Some time ago, mini welding inverters appeared in the retail chain. It took manufacturing companies years to achieve this miniaturization.
While craftsmen have long been able to make a plasma welding machine made by themselves.
They were pushed to this step by local conditions - cramped conditions in the workshop and the significant weight of factory inverters. A plasma device is an excellent way out of this situation.
And the fact that instead of copper wires the secondary winding of the transformer is made of copper tin has also been known for a long time.
Assembly sequence of the welding machine
When placing elements on a metal or textolite base, you need to follow a certain order. The rectifier must be located next to the transformer.
The choke is on the same board as the rectifier. The current regulator should be located on the control panel. The body of the device can be made of sheet steel or aluminum.
Or adapt a chassis from an old oscilloscope or even a computer system unit. It is very important not to “sculpt” the elements as close to one another as possible.
It is necessary to make holes in the walls to install cooling fans and constant air flow.
The board with thyristors and other elements is placed as far as possible from the transformer, which gets very hot during operation. Exactly the same as the rectifier.