If possible, spot welding of sheet metal components should be restricted to joining flat, coplanar surfaces. Spot welding for assembly of mating parts in multiple planes should be limited to parts smaller than a “bread box” that are easy to handle. With large, heavy parts, another fastening method, welding process or possibly a redesign should be considered unless production quantities support the initial expense of specialized spot welding equipment. Although single- and double-bend electrode tips are available to reach confined weld locations, a small flange dimension may restrict access, and thereby prevent a successful spot weld. Such is the case with C-shaped parts or U-shaped channels with short flanges (Figure 7). For instance, specifying a 1/4 in. (6 mm) diameter weld on a 3/8 in. (10 mm) flange not only violates spacing considerations, but also makes it very difficult for the operator to access the weld location.
If the sheets are the same thickness then the power setting used for plug welding would be the same as you would use for 1.5 times the thickness of one of the sheets. This is the sort of penetration you would expect from a plug weld. The molten pool is just breaking out of the reverse of the back sheet. The heat marks indicate the weld has arced against the back sheet rather than at the side of the hole. If you don’t get these marks then consider a little seam welding just to be sure. There is a special clamp designed for plug welding that makes life really easy. The parts you see in the photograph are attached to a normal mole grip. This clamp came in a set of three random welding clamps all of which are extremely useful.
Materials Appropriate for Spot Welding: Due to its lower thermal conductivity and higher electrical resistance, steel is comparatively easy to spot weld, with low carbon steel being most suited to spot welding. However, high carbon content steels (Carbon equivalence > 0.4wt%) are prone to poor fracture toughness or cracking in the welds as they tend to form hard and brittle microstructures. Galvanised steel (zinc coated) requires slightly higher welding currents to weld than uncoated steels. Also, with zinc alloys, the copper electrodes rapidly degrade the surface and lead to a loss of weld quality. When spot welding zinc coated steels, electrodes must either be frequently exchanged or the electrode tip surface should be ‘dressed’, where a cutter removes contaminated material to expose a clean copper surface and reshapes the electrode. See extra details on Tecna Spot Welder Price.
Electric welding relies on the Joule Effect. This is the thermal result of the electrical resistance, occurring when an electric current passes through a conductive metal – in this case metal sheets for assembly. If that last sentence went over your head, here’s how it works: to weld two or more sheets together without adding a filler metal, they are tightly compressed between two heat-resistant electrodes (i.e. non-melting), generally made of copper, and a high-intensity current is applied to melt the plates together at that point. The result is a small merging of metal which constitutes a welding point. The welding time is very short, between one and two seconds, and the shape of the resulting welding spot depends on your choice of electrodes.
