Posted by John Concrane on October 11, 2019 in Business
Applications include attachment of reinforcing braces and stiffeners, functional brackets, hinges and other parts. Often, spot welding is the method of choice for assembly of entire enclosures, cabinets and multipart assemblies. Thickness of the majority of parts joined by spot welding ranges up to 1/8 in. (3 mm) for each member, although parts up to 1/4 in. (6 mm) thick have been successfully spot welded. Based on the experience of stampers and fabricators, certain general recommendations can facilitate spot welding of a sheet metal design, no matter what metalforming process is used to make it. It is always useful to consult with the metalformer in the design stage when questions arise regarding the part design, application of spot welding or, control of spot welding cost for a particular design.
Start off by drilling 7.5mm holes in the front sheet of metal at a spacing of normally 25mm to 40mm (or whatever the original spot weld spacing was). Then clamp this sheet onto the back sheet. 7.5mm is a reasonably good hole size for 0.8 or 1.0mm sheet. Thicker sheet might require a slightly larger hole size. Try a little test piece out like this one before welding a whole sill onto a car and check the weld has penetrated through both sheets.
Copper and its alloys can also be joined by resistance spot welding, although spot welding copper cannot be easily achieved with conventional copper alloy spot welding electrodes, as heat generation in the electrodes and work piece are very similar. The solution to welding copper is to use an electrode made of an alloy with a high electrical resistance and a melting temperature far in excess of the melting point of copper (much greater than 1080°C). Electrode materials typically used for spot welding copper include molybdenum and tungsten. Read more info on Tecna Spot Welder.
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.