Good design practices attempt to limit spot welding on appearance or cosmetic surfaces. While textured paints can be used to hide small electrode marks on finished surfaces, grinding, or filling and grinding, is often required and can double the cost of the welding operation. Often, structural elements such as stiffeners are required to reinforce large cosmetic surfaces. For these applications, designers should select material which is thinner than the material from which the appearance part is fabricated. This assures that weld shrinkage will occur on the noncosmetic part which helps to control the cost of filling and abrasive finishing.
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.
How Does Spot Welding Work? A form of resistance welding, spot welding is one of the oldest welding processes whereby two or more sheets of metal are welded together without the use of any filler material. The process involves applying pressure and heat to the weld area using shaped alloy copper electrodes which convey an electrical current through the weld pieces. The material melts, fusing the parts together at which point the current is turned off, pressure from the electrodes is maintained and the molten “nugget” solidifies to form the joint. Read extra info at Spot Welder.
Spot welding machines represent a significant long-term investment that can decline in value. Their high performance has led to widespread use in automotive manufacturing; their use can be automated by combining them with extremely fast, precise robots. Radiators can be welded by the same process except using rollers to obtain a continuous, watertight weld. Industrially made furniture and other functional metal objects such as lampshade frames are also spot-welded. The process gives an impressive quality of weld without deforming the components it is used on.