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.
The welding heat is generated by the electric current, which is transferred to the workpiece through copper alloy electrodes. Copper is used for the electrodes as it has a high thermal conductivity and low electrical resistance compared to most other metals, ensuring that the heat is generated preferentially in the work pieces rather than the electrodes. The amount of heat depends on the thermal conductivity and electrical resistance of the metal as well as the amount of time the current is applied. Other materials commonly spot welded include stainless steels (in particular austenitic and ferritic grades), nickel alloys and titanium. Read extra details at Tecna Spot Welder Arms.
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.