Spot Welding Tips
Spot welding may be defined as a process in which the contacting metal surfaces are joined by heat generated from resistance to electric current flow. Or still more simplistically, spot welding is one of a group of resistance welding processes that involve the joining of two or more metal parts together in a localized area by the application of heat and pressure. Work-pieces are held together under pressure exerted by electrodes. Typically the process uses two copper alloy electrodes to concentrate welding current into a small spot and to simultaneously clamp the sheets together.
The amount of energy is chosen to match the sheet's material properties, its thickness, and type of electrodes. It is to be noted that applying too little energy will not melt the metal or mean a poor weld. Applying too much energy will overmelt metal and make a hole rather than a weld. Electrodes used in spot welding can vary greatly with different applications:
- Radius style electrodes are used for high heat applications
- Electrodes with a truncated tip are for high pressure,
- Eccentric electrodes for welding corners
- Offset eccentric tips for reaching into corners and small spaces,
- Offset truncated for reaching into the workpiece itself.
Projection welding is a modification of spot welding and is frequently used to join crossed wires and bars. Experts say that spot welding is one of the oldest welding processes and spot welding can be used on very thin foils but is rarely used on metals above 6mm thickness. High quality welds can also be made in stainless steels, nickel alloys, aluminum alloys and titanium for aerospace applications. Spot welding indeed offers a number of advantages over other welding techniques, such as high speed, ease of automation and energy efficiency.
It should be borene in mind that spot welding can be extremely perilous as large amounts of current and heat are involved. The welder must make sure to clamp the electrodes tightly, protect the eyes from the intense light that emanates and protect the hands because the workpiece can get very hot during welding. The other safety hazards are - the risk of crushing fingers or hands, the likely burn problems and possible eye injury from splash metal.
Automatic spot welding entails specific demands on resistance welding equipment. Often, equipment must be specially designed and appropriate welding procedures developed to meet robot welding requirements. Welding robots are of course available in various sizes, rated by payload capacity and reach. A spot welding gun applies needed pressure and current to the sheets to be welded. There are different types of welding guns available, to be used for different applications.
There are some critical areas of spot welding where further researches are called for. The automotive industry is greatly interested in high strength and ultra-high strength steels, coated steels and aluminum alloys that can have welding problems. Although the problems are understood, further improvements in welding and electrode lives are still causing concern. There are also limitations in the ability of spot welding to join sheet to tube, which need to be addressed.