Resistance Spot Welding (RSW) Working Principle and Advantages-disadvantages

Resistance Spot Welding (RSW) Working Principle 

Resistance Spot welding is comparatively modern welding process. It came in to the field of welding in between years 1900 - 1905. It is  a most widely used resistance welding method. The main purpose of resistance spot welding method is to  join two to four light gauge overlapping metal sheets (which can have thickness up to 3 mm) . 

At first the job is cleaned  and  all types of contaminants like grease, oil, dirt , scale and paint are removed. The surface pf the electrodes are also made very clean.  For clamping the metal sheets together two copper electrodes are used at the same time.  The current passes through electrodes and then into the metal sheets.  Because of the resistance, heat is generated in the air gap within the contact points. Since copper is great conductor heat is dissipated to the metal so quickly. As the metal (workpiece) is a poor conductor of heat in comparison to the copper electrode the heat remains in the air gap.  So the heat remains in the one place creating a strong effect and the metal is melted at that desired spot. The period of heat dissipation is very small and at this time metal gets melted and then become solid and thus the joint is formed. 

Working Principle of resistant spot welding (rsw)

Steps involved in Resistance Spot Welding are shown by the following diagram 

Steps involved in Resistance Spot Welding

Advantages of Resistance Spot Welding 

  • Comparatively Low cost
  • Resistance Spot Welding (RSW) method doesn't need highly skilled worker. 
  • Distortion or warping of parts is eliminated though it leaves some depressions or indentation. 
  • The joint made is highly uniform. 
  • Automatic or semi-automatic operation both can be done. 
  • There is no need for edge preparation. 
  • Welding can be done in quick succession. It just needs a few seconds to make the joint. 

Disadvantages of RSW

  • The equipment cost is high so it can has an effect on the initial cost. 
  • Skilled welders or technicians are needed for the maintenance and controlling.   
  • Some metals need special surface preparation for making the RSW a success. 
  • The thick jobs are not easy to weld. 

Applications of Resistance Spot Welding 

  • Spot welding of thick steel plates has been done and it has replaced the need for riveting. 
  • The welding of two or more sheet metals can be joined by mechanical means more economically by using the spot welding methods. We don't need gas tight joints. 
  • Spot welding can be used for attaching braces, pads or clips with cases, bases and covers which are mainly product of sheet metal forming.
  • Automobile and aircraft industries relies greatly of spot welding these days. 
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