What is Projection Welding? – Working, Advantages, Disadvantages and Applications

Projection welding is the resistance welding process which joins the metal pieces together by using the heat generated by an electric current. In this welding process, different projections are formed on the workpieces for effective welding, which is why the name "projection welding."

Projection welding does not use electrodes for concentration of heat, instead the projection on the workpiece is used for this purpose. Actually, projection welding is a modified version of spot welding. It consists of forming slight projections on one of metal.

Working of Projection Welding

The schematic diagram of projection welding is shown in the figure.

• The set up used for projection welding consists of two copper electrodes.

• The metal pieces to be welded are kept between these two electrodes as shown in the above figure.

• After that, the projections are accurately formed in precise locations on the metal workpieces by using a special set of dies.

• Once the projections are formed, the raised portions on one workpiece are pressed into contact with another workpiece.

• At the same time, a high electric current is passed through the workpieces.

• When the raised portions touch the second workpiece of metal, the electric current flows through the contact points, which heats and fuses the two metal workpieces together.

Advantages of Projection Welding

Projection welding has the following advantages −

• There is no limitation on the metal thickness, i.e., metal of any thickness can be welded with the projection welding.

• With projection welding, more than one welds are done at a time. Hence, more output is obtained.

• In the projection welding, less current is passed through the electrodes and low pressure is applied. Thus, the electrode life is increased.

• Projection welding gives good heat balance while welding process.

• The weld with good furnished appearance is obtained in the projection welding.

Disadvantages of Projection Welding

The disadvantages of projection welding are as −

• The process of projection formation is complicated and time consuming.

• It requires highly skilled welders.

• Projection welding cannot be applied to all types of workpieces.

• Equipment used for projection welding are expensive.

Applications of Projection Welding

Some applications of projection welding are as follows −

• Projection welding is used for welding studs, nuts to plates, etc.

• Projection welding is also used in automobile industries, ship building works and sheet metal works, etc.

• It is also used for welding the parts of refrigerator, grills, condensers, etc.