Spot welding is a welding process in which metal surfaces in contact are joined by heat generated from resistance to the flow of electric current. The work piece is made by welding both surfaces under extreme pressure exerted by the electrodes. The process generally uses two copper-alloy electrodes that concentrate the welding current in a small spot and then the sheets are clamped together simultaneously. Forcing large intensities of current through the designated spot will end up melting the metal and form a weld. The best advantage of spot welding is that lots of energy can be concentrated on the spot in a short period. That permits welding to take place without excessive heating of the remaining part of the sheet.
The heat or energy delivered on the spot is determined by resistance between electrodes and amplitude, time period of the current. Applying very little energy will not melt the metal and will subsequently make a very poor weld. Applying large quantities of energy will end up melting too much of the metal, and make a hole instead of making a weld.
The equipment that is generally used in the process of spot welding normally consists of components like electrodes and tool holders. The tool holders serve as a mechanism that clamps the electrodes firmly in their place such that they do not shift or move during the welding process, as unsteady electrodes can end up ruining the welding process and create an untidy, weak, and irregular weld. The whole apparatus as a hole are known as spot welders.
Spot welders also support additional water hoses that can be used to cool down the electrodes during and after the welding process. Tool holding methods also include paddle type, regular offset, and light duty. The electrodes are generally made of low resistance alloys like copper and tin, and are available in different designs in several dissimilar shapes, sizes depending on application that is required. The different types of spot welders are portable spot welder, battery spot welder, mini spot welder, homemade spot welder, etc.
The two materials that are welded together are called work pieces and must necessarily conduct electricity. Width of the work pieces are restricted by throat length of the spot welder and ranges usually between 5 to 50 inches. Work piece thickness is generally between 0.008 inches and 1.25 inches.
After current is removed from work piece, cooling operation is carried out via coolant holes in the electrodes. Both brine solution and water can be used as a coolant in the spot welding mechanism.