Knowledgeable designers recognize such cost-saving and quality-improvement methods and specify them in the manufacturing process. The consistency attainable with such methods surpasses that of sophisticated jigs and fixtures but the greatest value is the cost efficiency. Additionally, these techniques can be used for fillet welding applications, and mechanical assemblies. A refinement of resistance spot welding is resistance projection welding (RPW). It makes use of projections previously formed on the workpiece to reduce the power required to make a resistance weld. Consequently, multiple welds can be made more easily at the same time, and thicker sections can be joined more readily than in RSW. Other advantages include reduced shunting effects, closer weld-to-weld spacing and welding of workpieces with smaller flanges.

One alternative to plug welding is “MIG spot welding”. It is similar to plug welding, although a hole is not drilled in the front sheet of metal. Instead the power of the MIG is relied upon to fully melt the top sheet and penetrate into the back sheet. This technique would require less preparation work than plug welding, but the two sheets need to be in tight contact and high amps used to complete the weld or else the weld could be very weak. Plug welding is a much more suitable technique for all but the most experienced welders.

Although aluminium has a thermal conductivity and electrical resistance close to that of copper, the melting point for aluminium is lower, which means welding is possible. However, due to its low resistance, very high levels of current need to be used when welding aluminium (in the order of two to three times higher than for steel of equivalent thickness). In addition, aluminium degrades the surface of copper electrodes within a very small number of welds, meaning that stable high quality welding is very hard to achieve. For this reason, only specialist applications of aluminium spot welding are currently found in industry. Various new technology developments are emerging to help enable stable high quality spot welding in aluminium. Read extra info at Tecna Spot Welder Arms.

What type of sheets can be welded? Rust-free, non-painted sheets of the same or different metals can be welded provided they are compatible alloys with a very similar melting point. Metals such as stainless steel, aluminium, steel alloys and galvanized steels can be spot welded, subject to operating adjustments (current, welding time, intensity of compression). Note that the coating on galvanized metals tends to clog the electrodes – which must be cleaned regularly!