What is spot welding? Pros and cons of this welding method
Spot welding is a type of resistance welding process that is used to join two or more metal sheets together by applying pressure and passing an electric current through the metal at the point of contact. This creates heat that melts the metal and fuses the pieces together.
Spot welding is a fast and efficient method of welding that is widely used in the automotive, electronics, and metal fabrication industries.
One of the main advantages of spot welding is its speed and efficiency. It can weld metal sheets quickly and with minimal distortion. It's also a relatively simple process and requires less skill than other welding methods, making it suitable for automated welding systems.
The Nature Of Spot Welding?
The technology is not particularly complicated and can generally be summarized in a few basic steps:
[caption id="attachment_200" align="aligncenter" width="300"]
What is spot welding?[/caption]
Preparation of the details
The preparation of the processed parts is a very important first step because the stability and durability of the weld depend on it. The sheets to be joined are straightened, cleaned and aligned, and overlapped in the welding area very precisely.
Choice of electrodes
Copper or copper alloy electrodes are most commonly used for this type of welding, as they have a high melting point, retain heat and can resist oxidation.
High voltage current generation
Once the sheets are aligned and overlapped, and after the electrodes are placed on both sides of the workpiece, a high-voltage current is sent (generated) to it. The electrodes are pressed against the sheet metal or sheets of metal with the appropriate pressure.
The heat required to melt the metal is generated by the resistance of the base metal and is limited to the point where the electrodes and the weld zone meet. The time during which the current passes through the workpiece depends on the thickness and type of metal to be welded.
Hold time
After the parts are melted and joined, the current is turned off, but the electrodes remain in direct contact with the metal ( sheet metal ). This is necessary for the weld to cool properly. This last step is very important, as it depends on it whether the weld will be stable or not.
If the dwell time is prolonged, the heat from the weld location can spread to the electrode and heat it, and if the weld material has a high carbon content, the welds can become brittle and crack. If the time is too short and the electrodes are removed before the weld has cooled, this can lead to a weak weld.
[caption id="attachment_201" align="aligncenter" width="300"]
Spot welding[/caption]
What does it take to spot weld?
Appropriate equipment
To join two or more sheets of metal using the spot welding method, you will need the appropriate equipment.
The machines used are of two main types:
Portable devices
These types of machines are small, compact and very suitable for working in small workshops or at home. They do not have a very large capacity for work and they can be used to weld materials with a thickness of up to 2.2 mm, which greatly limits their capabilities.
Stationary machines
Stationary machines are professional and are mainly used in large productions. With them, seams of different thicknesses can be made with great precision, speed and accuracy.
Electrodes
The electrodes used are usually made of a low-resistance alloy (such as copper) and are designed in many different shapes and sizes depending on the required application.
[caption id="attachment_202" align="aligncenter" width="249"]
Spot welding[/caption]
Can you handle spot welding yourself?
This welding is among the oldest methods of joining metals and is well-known and easy to apply even to novice welders. The procedure is well-defined and as long as you have the right equipment and know the basic steps, you can try spot welding thin metals such as stainless steel sheets, sheet metal, nickel, or titanium alloys.
Pros and cons of this welding method
This spot welding owes its popularity to a solid list of advantages:
● No filling is required for the welds, which significantly reduces the cost of funds and time.
● Since it uses heat to melt and fuse the surfaces of the metal parts, the welds are distinguished by enviable stability and hardness.
● This is a very fast process of merging surfaces. According to experts, the average time required for spot welding is 0.01 to 0.63 seconds.
● Welding machines of this type are easy to use and even a novice welder can handle them.
● The aesthetics of the welds do not cause complaints even among the biggest skeptics.
● The cost of the work process is much lower compared to the cost of other welding methods.
● Almost all technological operations can be automated.
Of course, this method also has its drawbacks. But if we have to be completely frank, then its cons are relatively few:
● The relatively low density of the seam compared to the continuous joint that is obtained using a conventional welding method.
● It cannot be applied to all types of metals and thicknesses of the details.
Where is the welding method used?
Car Industry
The ease with which it can be automated and robotic makes it the most common and applied joining process in high-volume production lines for automotive structural elements.
[caption id="attachment_203" align="aligncenter" width="300"]
Spot welding in the car industry[/caption]
Electronics
Spot welding is also widely used in electronics. The manual method is used both in the production of electronic components and in connection and electromagnetic assemblies.
Electronic resistance welding is also applied in the manufacture of complex and delicate electrical components such as switches, cables, tools, in the manufacture of circuit boards, gas sensors, and even solar panels, and many others. Put another way, many electronic components we use today are manufactured using spot welding.
Battery manufacturing
You may be surprised that this welding method is also included in the manufacturing processes of batteries. This process is applied when different metal elements need to be joined and combined to produce strong and powerful batteries. Most manufacturers also prefer spot welding over soldering, as the method controls the heat produced during the process, which prevents the batteries from heating up.
Orthodontics and dentistry
As strange as it sounds, spot welding makes the work of orthodontists easier. This method is used in the fabrication of metal braces, in the fabrication of custom molar braces, and many others.
Mechanical engineering
This welding is also used in mechanical engineering to join different metal structures. Point seams are used in the production of gas boilers, to join pipes, production of small tanks and many others.
Spot welding is also used for the precise execution of seams for joining metal structures with flanges, for welding reinforcement cells, etc., etc.
Conclusion
In conclusion, Spot welding is a widely used welding method that is known for its efficiency, speed and reliability.
The process is simple and suitable for automated welding systems. It also produces a strong and reliable weld with minimal distortion.
However, it has some disadvantages as well, such as being limited to welding metal sheets of similar thickness and composition and can only be used to weld small areas at a time. It also requires that the metal sheets be clean and free of surface contaminants.
When choosing a welding method, it's important to consider the specific needs of the project, the materials being welded, and the available equipment and expertise. Spot welding can be a great option for certain types of welding projects, but may not be suitable for others.