subject: Resistance Spot Welding [print this page] Welding is a fabrication or sculptural process that joins materials, usually metals or thermoplastics, by causing coalescence. This is often done by melting the work pieces and adding a filler material to form a pool of molten material (the weld pool) that cools to become a strong joint, with pressure sometimes used in conjunction with heat, or by itself, to produce the weld.
Spot welding is a resistance welding method used to join two to four overlapping metal sheets which are up to 3 mm thick each. In some applications with only two overlapping metal sheets, the sheet thickness can be up to 6 mm.
Resistance spot welding is a type of manufacturing process that uses electrical current to internally fuse two sheets of metal together. The resistance of the metal, to the electrical current, causes heat to build up at the site where the current is applied. When two sheets are clamped together and current is passed through them for a certain amount of time, a weld or spot fastening, can be formed.
The process of resistance spot welding usually involves the use of a machine equipped with copper electrode tips, through which the electrical current passes. As the metal sheets, which are clamped together by the electrode tips and sometimes other positioning devices, receive the current, an interior weld nugget begins to be formed by the melting metal. This is different than arc welding, which forms the weld from the outside of the metal at that spot.
Care must be taken to apply just the right amount of current for the type of metal used in resistance spot welding along with a certain amount of pressure, and for a precise time. The kind of metal that is to be joined, along with its thickness determines the appropriate values of current, pressure, and time. The most commonly used metals steel, nickel alloys, titanium, or aluminium typically vary in size from 0.008 inches (0.2 mm) to 1.25 inches (31.75 mm) in this process.
Resistance spot welding is often utilized in the automobile and aerospace industries. It is also used in orthodontics, in the creation of bands, or braces, that go around teeth. Manufacturers generally like to use this process because it takes very little time to complete. Also, robots can often be used in repetitive welds of this kind, and this can help to eliminate some of the safety hazards that welding can present to people.
