To create various metal structures, every owner of a suburban area dreams of having a metal welding machine. The most popular and reliable method is resistance welding, which is also widely in demand in the repair of automotive equipment.
Many are interested in whether there is a technology for making contact welding with your own hands? Yes, at home, many contact connection methods are the most durable and reliable. It is not difficult to make welding machines on your own, and you can use many consumables that have long been considered unnecessary in the household.
Field of contact welding
The name resistance welding indicates that the connection of two parts occurs as a result of exposure to electric current and the application of a sufficiently large compressive force to certain points of the material.
Do-it-yourself resistance welding allowsto interconnect products with a thickness of 0.02 mm to 20 mm. Moreover, the details of the welded material can have different properties and profiles. Most often, products are welded from mild and corrosion-resistant steel or brass and light alloys of non-ferrous metals.
Many methods of this type of connection are used exclusively in industrial production for the construction of aircraft, cars, ships and other complex equipment. Apparatus for resistance welding (including those made with their own hands) in the agricultural sector of the national economy are widely used. And also, no car service and repair station can do without contact-type welding equipment.
At home, do-it-yourself resistance welding is used for the manufacture of various metal frame structures, cabinets, dishes and other household utensils.
Connection Technology
The technological process of contact welding is carried out by heating the junction of two parts when an electric current passes through them. Moreover, the current is applied simultaneously with the use of strong pressure on the surfaces to be welded.
Necessary steps for performing welding work with a contact connection:
- Carrying out preliminary preparatory work on mechanical cleaning of the surface of the materials to be welded.
- Reliable fixation of the workpiece in the welding machine, while paying special attention to the exact alignment of the edges of the welded products.
- Power supplycurrent to the electrode contacts.
- Metal melting process at the connection point.
- Deposit of the junction and power outage.
The main indicators of DIY resistance welding from a welding machine are:
- Time interval for the passage of electric current.
- Nominal value of the compression force of the workpieces to be welded.
Based on these indicators, do-it-yourself resistance welding can be divided into two modes of operation:
- Soft mode is characterized by a long time interval of current strength, as well as relatively smooth heating of the junction. The use of this method can significantly reduce power losses, which significantly reduces the price of self-made resistance spot welding, and also reduces the hardening of the welding zone.
- The hard welding mode is characterized by a short period of current strength with a significant increase in it. The main advantage of this method is the reduction in the total time of the welding process, therefore, a significant increase in the productivity of the work performed.
Advantages of contact welding
Compared to other methods of joining metal surfaces, do-it-yourself resistance welding from a welding machine has a number of significant advantages:
- The process of manufacturing equipment requires minimal expenditure of additional resources, which makes this type of welding economical.
- The junction of twometals, even of a heterogeneous type, is durable, reliable and of high quality. Moreover, the welder does not require high qualifications and extensive work experience, since do-it-yourself resistance welding technology does not involve the use of a large number of precise equipment settings.
- Significant speed of the technological process, and consequently, high productivity are considered one of the most important advantages of the contact connection. So, to complete one joint, it will take only 0.02 seconds, which is much less than other types of welding.
- The environmental safety of the process of contact welding with your own hands is also an important characteristic of it.
Types of resistance welding
The difference in the order of the welding process and the technological features of supplying electric current to the junction determine the division of contact welding into several different types:
- butt welding;
- dot connection;
- seam joining of metals.
Each of these types of welding has its own characteristics and applications.
Butt welding
When butt welding, the contact of products occurs over the entire surface area, so the connection process is carried out using special machines. The machines have devices capable of holding workpieces and applying pressure to parts.
Butt welding is carried out in two ways:
- Resistance at which the metal in the welding zone is heated to a plastic state, after whichsediment of the welding site. This method requires good contact between the two surfaces, so a very important condition for quality work is the pre-treatment of the joined ends of the product.
- Flash welding is the complete melting of the metal at the site of the surface to be joined. If the action of the electric current and the compression force are constant, then a continuous joint is welded. But in the case of a periodic change in pressure on the surfaces to be joined, intermittent melting of the ends occurs, while the current strength is unchanged.
The use of butt welding from a do-it-yourself welding machine at home is very difficult due to the high cost of equipment.
Contact spot welding
This type of connection is most often used at home for welding individual sheet metal parts. Resistance welding technology is based on the action of a heated electrode at the point of contact between two metal surfaces. The ideal application for this type of connection is do-it-yourself resistance welding for batteries.
The quality of the workpiece connection significantly depends on the following parameters:
- size and shape of the electrodes, which has a significant impact on the value of the connection point;
- level of compression applied at the welding point;
- electric current strength;
- surface pre-cleaning quality;
- current exposure time.
Spot welding can be performedboth by one-sided heating, in which the effect on the metal occurs only from one side, and by the two-sided method, in this case, the part is heated from both sides at once.
Before you do resistance welding with your own hands, you need to consider which connection principle is best suited for the quality of the task.
Suture connection
A weld in this type of welding is a series of connection points that overlap each other. As a result of such a technological operation, a sealed and durable weld is formed on the surface of the metals.
Electrodes for seam welding are special disk rollers that, while rotating, provide tight compression of the metal surfaces and heat it at the junction.
Depending on the location of the rotating electrodes, this type of welding can also be one-sided or two-sided.
Of all types of contact welding for use in domestic conditions, the spot type of connection is best suited, since it is not particularly difficult to make contact welding from a microwave oven or use a welding inverter according to the scheme, even for a novice master.
Microwave Spot Welder
Many amateur welders have come up with the idea of using a transformer from an old, unnecessary microwave oven for the manufacture of a welding machine. Therefore, it was developeda simple home-made circuit for resistance welding from a microwave, which you can do at home with your own hands.
For these purposes, you need to disassemble the old apparatus by removing the necessary transformer. All other components of this device will not be needed.
The secondary winding of the transformer is not needed, so it will have to be completely dismantled. To make contact welding from a microwave oven with your own hands, you need to upgrade the secondary winding of the device.
Transformer upgrade
To make a high-quality welding machine, you need to make a small alteration of the transformer. To do this:
- After dismantling the transformer, it is necessary to wind a new secondary winding from a wire with a cross section of at least 16 mm.
- You need to wind two turns to prevent an increase in winding resistance.
- After creating the winding and insulating it, you need to measure the voltage (only 2 V is enough).
When making resistance welding from a microwave oven with your own hands, you must ensure that the current supplied by the device does not exceed 200 A. Otherwise, using a more powerful unit may damage the electrical wiring of the home electrical network.
Of course, if the farm has a factory welding machine, then it is easy to make resistance welding from an inverter with your own hands. Will only have tomake your own special clamps for fixing the electrodes, while the length of the wires connecting the current source and the electrodes should be minimal in order to reduce their resistance and heating during operation.
Making a casing and tongs for homemade welding
Like any other technical device, a homemade resistance welding machine must have a practical case. Very popular for transformer welding is the case from the system unit of a personal computer.
Structurally, the case of the system unit has a fan for cooling the transformer windings, as well as the required number of ventilation holes. You can make a sheet metal welding housing by making an ordinary box that fits the size.
You can make do-it-yourself resistance welding pliers from a steel profile with a cross section of 20 × 20 mm, which is able to provide sufficient strength. A lever 50-60 cm long allows you to create a compression force of the order of 30 kg, which is enough for a home-made device. Welding electrodes are attached to the ends of the arm.
Butt welding for batteries
Rechargeable batteries are widely used in modern household devices. When a power supply malfunctions, it is often necessary to change one or more elements. Replacing batteries by soldering is not possible, as the cells are afraid of overheating. Therefore, it is better for these purposes to make contact welding forDIY 18650 batteries.
The easiest battery repair option at home is to use a car battery. Electrodes can be made from two pieces of copper wire, after stripping them and securing with electrical tape. The ends of the electrodes are located in the same plane at a distance of 2–3 mm from each other. The other ends of the electrodes are connected to the battery terminals using wires with clamps. When connected, the polarity of the battery terminals does not matter.
When connecting do-it-yourself resistance welding for batteries, a short circuit will occur, and the metal at the junction will melt. After cooling, a reliable and durable contact will appear.
Dot connection defects
If the technology of the welding process is violated, some defects may occur at the junction of two parts. Conventionally, they can be divided into external (visible) and internal (invisible) damage.
External defects include:
- metal burn through;
- surface cracks;
- irregular dots;
- darkening the surface of dots;
- dents.
Internal defects are characterized by the following features:
- cracks inside the welding joint;
- incorrect heating of points (bad penetration);
- the appearance of pores and shells.
Visible defects are easy to identify by visual inspectionconnection points. Internal defects are detected using special quality control devices in production.
There are many methods of contact welding. The use of any of them requires compliance with the safety rules for working with electrical equipment, as well as protective equipment necessary when performing operations with elevated temperatures.
