This device uses an electrical current, to join metal pieces together. Two clamp-able electrodes send an electrical current through the metal pieces. Naturally, the metal between the electrodes heat and fusion occurs. The area that has been “fused” together is referred to as a spot weld.
Spot welding is a process that is most effective for joining thin pieces of metal (ranging for 0.02 to 0.12 inches thick).
One of the benefits of spot welding; is the fact that a lot of energy is delivered to a direct location in milliseconds. This allows the weld to happen quickly, without the possibility of excessively heating the entire metal sheet.
The energy (heat) that is applied to the spot is determined by the resistance between the electrode, and the size and length of the current.
The amount of energy used is directly impacted by the thickness of the material, and the type of electrodes being used in the process. For instance, if too much energy is applied, the piece will melt, creating a hold rather than the intended weld. If not enough energy is used, a poor quality weld is usually created.
The components of a basic spot welder include:
(1) an energy storage unit – such as a capacitor bank
(2) power supply
(3) a switch
The storage unit is helpful, because the welder needs to deliver instantaneous intense power to a workpiece.
The switch releases stored energy into the transformer, and then the transformer increases the current, while decreasing the voltage.
The electrodes are sized and shaped, in order to accommodate the type of application required. They are usually made from a low-resistance alloy, like copper.
Types of spot welders
While there are multiple types of spot welders for sale, These are the two most basic types used today: Hand held and stationary welders. They both have the same components, and the metal is fused in the same manner, but they are designed for purposes that are very different.
Hand-held spot welders
Hand-held versions are great for repairs that are off-site, as this is a portable unit. The drawback of this type of unit is the minimal effects of the cooling system. Electrodes wear out faster, and the speed of spot welding repairs are reduced, due to the excessive heat generated.
Stationary spot welders
Stationary welding machines are used for high production. Water is generally circulated inside the electrodes, to keep the unit cool. Some other features found on a stationary unit are an adjustment for clamping pressure, thickness of metal and welding time.
Applications that use spot welders
Spot welding is commonly found in the aerospace and automobile industries. This is the process of choice for many manufacturers, because the process is completed quickly; and it can be an automated process, which may reduce certain work area safety hazards.
It can also be found in an orthodontist’s office, because this technique is quite effective in re-sizing metal molar bands, and creating braces.
The making of batteries also benefits from this process. Spot welding is a lot cooler than other types of soldering processes.