Understanding Resistance Spot Welding Machine

Posted on May 6, 2021

Resistance Spot Welding Machine

The resistance spot welding machine is designed for joining multiple sheet metal together through the electro-thermal process, utilizing the special electrodes, stable electric current, and proper amount of pressure.

What Is a Resistance Spot Welding Machine Used for?

The resistance spot welding machine is designed for joining multiple sheet metal together through the electro-thermal process, utilizing the special electrodes, stable electric current, and proper amount of pressure. Also called the spot welder, the resistance spot welding machine is one of the most classic and commonly used electric resistance welding machines in the modern metalworking environment. 

The electric resistance welding process refers to the permanent metal fabrication operations, which fuse two or more materials, including various metals, heavy gauge material, or plastics together to form unique profiles. The interface of the sheet metals will be melted due to the generated heat in the resistance spot welding machine as the electric currents consistently transfer to the “spot”, the weld joint. 

The resistance spot welding machine is greatly suitable for a large range of industrial production lines as well as assembly lines. For example, in medical equipment manufacturing, railway industry, electronics, aerospace and automotive industry, and so on. With the evolvement and employment of robotic technology and other automation techniques, more and more smart resistance spot welding machines are rapidly becoming demanding for high-volume industrial production applications.

Resistance Spot Welding Process

Spot welding processes utilize unique electrodes that are made from copper-based alloys to transfer the current and heat, which act on the weld joint, in order to fuse the sheet metals. The alloy is used because copper has exceptionally high heat conductivity, so the generated heat from electric resistance tends to work on the weld joint instead of the conductive tools. 

Also, copper has lower electrical resistance. Using the copper electrodes to deliver the electrical currents through the metal parts, the high heat will melt the metals while the energy is concentrated to a very small welding spot. As a great density of current is applied to the weld spot at a predetermined period of weld time, the base materials will be effectively melted in the resistance spot welding machine.

In the resistance spot welding machine, an appropriate amount of force is also required to be applied to the weld spot in order to join the sheet metals. Once the electric current that creates the resistance and high heat to the weld spot is turned off, there is still the electrode pressure that keeps working on the weld spot until the molten sheet metals are permanently fused and solidified eventually. The electrodes and other conductive accessories will then be cooled down by water after the cycle is completed in a resistance spot welding machine.

:: Read more: Resistance Spot Welding Machine for Buyers

What Is Required During Resistance Spot Welding?

The weld current (i) and the weld time (t) of the resistance spot welding machine are essential factors affecting the efficiency to bring the material to welding temperature, typically 1400°C. When it comes to the weld current in a resistance spot welding machine, the typical weld current used in normal metal workshops ranges from 3000 to 5000 A. 

The weld time is typically about 10 milliseconds. The short weld time allows the spot welder to fuse the sheet metals without excessive heating of other areas on the surfaces. In modern resistance spot welding machines, the weld current and also weld time can be predetermined by the users while the electric resistance is determined depending on the types of the raw materials. 

The changes of the weld current are often critical and dramatic to the whole welding cycle. In the resistance spot machine or applications that use a lower weld current, the corresponding weld time should be increased, however, it might end up overheating the welding equipment and tools and the weld transformer. In general, the thickness of the sheet metals being welded in the resistance spot welding machine is ranged from 0.5 to 3mm. If the energy transmitted to the weld spot is not sufficient to fully melt the material, the spot welder will produce a poor weld. 

On the other hand, as the currents adjust higher, the weld time should be reduced, preventing excessive heat from creating a hole on the surfaces of the sheet metals. The risk of expulsion is also higher when using a higher weld current in a resistance spot welder. Expulsion is the condition where the molten metal squirts from the multiple steel layers, for instance, when handling automotive parts with the galvanized coatings.

The efficiency of different spot welders depends on the power supply, the magnitude as well as the resistance among the electrodes. Selecting a resistance spot welding machine that has the capability to effectively regulate the weld current and provides an easier setting for users to manipulate is important for welding equipment buyers, especially for today’s vehicle manufacturers.

Applications of Resistance Spot Welding Machine

Resistance spot welding machines are typically utilized to weld sheet metals and wire meshes. When identifying if the metals are suitable for resistance spot welding, two factors of the material to weld that are essential include thermal conductivity and electrical conductivity. 

For instance, aluminum alloy that has great heat conductivity requires a larger weld current to complete the welding process. Also, the material needs much more powerful weld transformers that are more costly, making aluminum alloys and other materials have similar features less suitable for joining by the welding method. 

On the other hand, steel parts, like stainless steel sheets or plates, which have sufficiently lower thermal conductivity and higher electrical resistance, are better suitable to be fused by resistance spot welding machines. Exceptionally, low carbon steel is the most ideal welding metal.

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