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Posted on Dec 23, 2020
Through heating and applying pressure on the welding spot, portable spot welding machines can fuse multiple metal sheets permanently. The term “spot” in this welding method refers to the welding point where the pressure applied and the heat conveyed. Spot welding, which is also widely known as resistance spot welding, is a type of electric resistance welding.
A portable spot welding machine, also called portable resistance spot welder or portable spot welder, is used for permanently fusing two or more metal sheets together. What is welding? There are a large variety of welding processes today, and many of these welding methods can join and connect similar or dissimilar raw materials including metals and thermoplastics together under high pressure and high temperature. In typical welding processes, the materials will be melted first, the welded sheets will later be cooled down. Some welding methods for metals can also be performed at room temperature, removing the melting process of the raw materials during metal fabrication. These cold working methods include but not limited to friction welding, soldering, brazing. General energy sources of the metal welding process are electrical, electron beams, electric arcs, chemicals, lasers, ultrasounds, and frictions.
Through heating and applying pressure on the welding spot, portable spot welding machines can fuse multiple metal sheets permanently. The term “spot” in this welding method refers to the welding point where the pressure applied and the heat conveyed. Spot welding, which is also widely known as resistance spot welding, is a type of electric resistance welding. In a portable spot welding machine, the heat is generated on the resistive raw materials through the movements of the contacting electrodes which travel on the metal surfaces. At the same time, the set pressure will also be applied to the welding spot.
Resistance spot welding is a conventional yet popular metal fabrication process, it is preferred to be applied in the automotive manufacturing industry for over a century. Portable spot welding machines can be easily found in production lines of automotive and aerospace parts, in the rail industry, metal furniture production, electronic and medical industries, and so on. Taking little space, incorporating robots and automatic controllers, making portable spot welders a great choice for high volume production.
In a portable spot welder, without inserting any filler materials, the metal sheets can be easily joined together. Portable spot welding machines, in general, use electrodes that are made from copper electrodes to convey the electric currents toward the surfaces of the resistive metals in the welding area. The heat generated on the small welding spot where the energy is transferred and concentrated. As a result, the metal melts. The portable spot welding machine can apply a large amount of the electric current to the welding spot, which can efficiently melt the raw materials to perform the weld. As the currents sent by the controller are turned off, the pressure of copper electrodes still remains on the spots, completing the permanent fabrication of metal sheets after the metals are cooled down and solidified.
Typically, the material from which the electrodes are made is copper, which has great heat conductivity and lower electrical resistance. Thanks to the feature of copper, generated heat tends to work on the surfaces of metals rather than the electrodes. Not only the electric current, the magnitude, the resistance between electrodes but also the characteristics and thickness of the base materials can define the efficiency of the portable spot welders. The available thickness of the metal sheets ranges from 0.5 to 3mm.
In portable spot welding machines, if applying less than enough energy toward the base materials, the quality of the weld joints will reduce. However, if transferring the energy and generating too much heat, the heat might create holes in the welding spot. A portable spot welder is responsible for regulating the energy that is transferred to prevent these conditions from happening during metal welding production. Another benefit of portable spot welders lies in the short process time where a large volume of energy can perform the tasks, which is about 10 milliseconds. The feature permits the portable spot welding machine to complete metal fusing without excessive heating in other areas on the raw materials.
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Portable spot welders are widely used in the high-volume production of welded metal sheets and welded wire meshes. Thicker base materials are more challenging to join together because the heat can affect the surrounding metal considerably. The thermal conductivity and electrical conductivity of the metals are essential that determine if the materials are appropriate for resistance spot welding.
Typically, since steels have lower thermal conductivity and also greater electrical resistances, they are relatively suitable for resistance spot welding by portable spot welding machines. Low carbon steels are much more ideal for welding over than high carbon content steels. High carbon steel which is used in welding might lead to hard and brittle structures, increasing the risks of cracking or poor fracture toughness. Stainless steel is also popular spot-welded material as well as nickel alloys and titanium.
Aluminum has similar thermal conductivity and electrical resistance to copper. Although the welding is possible because the melting point of aluminum is low, very high levels of electric currents are required when joining aluminum, which is about two times higher than the currents for welding steel.
Copper welding cannot be simply completed with typical copper electrodes in portable spot welding machines because the generation of heat is similar between the materials and the electrodes. The solution to this condition is to change the electrodes to ones that have a far higher melting point and also electrical resistances.
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