A form of alternating magnetic force welding, the spot welding technique is also called as alternating current welding and is one of the older welding techniques through which two or more pieces of metal are welded together using only the application of heat and pressure. This type of welding method involves the application of heat and pressure to the welding region with metal electrodes that convey an electrical charge through the weld workpiece. The working of a spot welder is similar to that of a typical arc welding machine. However, in the case of spot welding, the welder places the workpiece in between the two pieces of metal while an electric arc is generated. The workpiece, which is not in contact with any metal, acts as a conductor and discharges the electrical charge to the workpiece through conductors that are connected to both ends of the piece of metal.
Because of this type of welding, it does not provide a protective service against corrosion and rusting. Furthermore, the welding process also generates a lot of heat and produces smoke, so safety precautions need to be observed when working with welded materials. This type of welding also has a shorter life span than the continuous-load method of welding. This is because the welder continuously exposes his work to elevated temperatures and stresses. Therefore, he needs to make adjustments in the workmanship of his shop for each type of welding operations.
The weld time is also affected by the electrode. Higher the voltage, higher is the requirement for the current and vice versa. In some cases, low voltage can reduce the weld current to a great extent. So, it is necessary to choose the appropriate electrode for your weld machine before starting the procedure. Moreover, the electrode has a direct effect on the weld time and is often adjusted while purchasing a new unit or replacing an old unit with the spot welding machine.
A continuous-load welder operates at lower amperage and provides better weld quality than the intermittent-load welders and continuous-load welders. The difference between them is that the intermittent-load machine often overloads the weld point, which creates excessive heat and the sheet metals are not protected. On the other hand, continuous-load spot welders protect the sheet metals from overheating and protect the weld point from corrosion.
The weld point of the machine can be protected by fitting it with a six-mm half threaded steel rod. If it is not available, the smaller steel shunt piece can be used. The welders are equipped with a variety of features like a taper and variable speed drive, heat shielding, and primer feeders. They are usually called as full swing or continuous feed welders. Their primary use is to weld aluminum and other metal sheet materials to produce tubes, pipe, or sheets. They can also weld two pieces of metal together that are thinner than the other, which results to stronger joints.
The welders come with a weld control switch that controls the amount of current produced. The weld rate, temperature and amperage can be regulated using the weld control switch. Some models of welders have a reversible on-off switch, which allows the operator to switch to ‘on’ when all the pieces are completed and then to ‘off’ to allow a cooling off period. The welded metal sheet is placed on a tester plate to test for weld uniformity.