Resistance Projection Welding (RPW) Advantages and Disadvantages

Working Principle of Resistance Projection Welding (RPW)

In resistance projection welding (RPW), small projections are formed on one or both pieces of the base metal to obtain contact at a point which localize the current flow and concentrate the heat. Under pressure, the heated and softened projections collapse and a weld is formed. Projection on the upper component is pressed against the lower component by electrode force. The projection collapses and a fused weld nugget are formed with the application of current. This technique is of special value in mounting attachments to surfaces of which the back side is inaccessible to a welding operator.

Read : 

• Different Types of Welding Defects 

Advantages of resistance projection welding 

• Simultaneous operation can be done i.e. more than one welds can be made. 
• Projection welding has this advantage that it can weld metals of thickness which is not suitable for spot welding. 
• Projection welding electrodes have a longer life when compared to spot welding electrodes. Its because projection welding electrodes have to withstand less wear and less heating.  
• Resistance projection welding is not limited to sheet to sheet joints. 
• Projection welding can be done in specific points which are desired to be welded. 
• In difficult welding work projection welding gives a better heat balance. 
• Projection welding saves electricity because it needs less current to produce heat. So it reduces the shrinkage and distortion defects.  

Disadvantages of RPW 

• All types of metals cannot be welded using projection method. Metal thickness and composition is a big question. 
• All the metals are not strong enough to support the projections. Some brasses and coppers cannot be welded satisfactorily using projection welding. 
• There is an extra operation which is called forming of projection. 
• Projections need to have same heights for a appropriate welding. 

Applications

• Resistance Projection welding is used in Automobile sector. 
• Projection welding is used in refrigeration works ( mass production of condensers, gratings, racks etc.)

Please Read more about welding: 

• Gas Metal Arc Welding (GMAW) or MIG Welding
• Flux shielded metal arc welding process principle
• Tungsten Inert Gas welding or TIG welding 
• Advantages and Disadvantages of Submerged arc welding 
• Submerged Arc Welding Working Principles and Uses 
• Resistance Seam Welding (RSEW)
• Resistance Spot Welding