Choosing Between Spot and Seam Welding for Your Project

When it comes to resistance welding, two of the most common and effective techniques are spot welding and seam welding. While they both fall under the umbrella of resistance welding, they serve distinct purposes depending on the application, materials, and performance requirements of your project. Understanding the difference can help you make informed decisions during the design and manufacturing stages. 

What Is Spot Welding? 

Spot welding is a resistance welding method where two or more metal sheets are joined together by applying pressure and heat to a specific point using copper alloy electrodes. The heat generated by electrical resistance at the contact point forms a molten weld nugget that solidifies to create a strong bond. 

Characteristics: 

• Welds are created at individual, spaced intervals 
• Ideal for overlapping sheet metals 
• Commonly used for automotive, aerospace, and appliance industries 
• Faster setup for small, repetitive welds 

Spot welding schematic: copper electrodes clamp overlapping sheets; current generates a molten nugget that solidifies into a strong localized weld. 

Weld Appearance: 

• Series of circular marks (weld nuggets) 
• Discrete, localized joints 

What Is Seam Welding? 

Seam welding, also known as continuous resistance welding, uses a similar principle to spot welding but replaces electrodes with rotating wheels. As the workpiece passes between the wheels, continuous or overlapping spot welds are formed along the seam of the materials. 

Characteristics: 

• • Creates a continuous, leak-tight weld 
  • Ideal for long, linear joints and cylindrical parts 
  • Commonly used in the production of fuel tanks, mufflers, and sealed containers 

Seam welding schematic: rotating electrodes roll over overlapping sheets, forming overlapping weld nuggets into a continuous seam. 

Weld Appearance: 

• • Uniform seam 
  • Overlapping spot welds or solid line depending on settings 
    
    

Spot Welding vs. Seam Welding: Key Differences 

Which Is Right for Your Project? 

Choosing between spot and seam welding comes down to the specifics of your application: 

Use Spot Welding If: 

• • You require quick, repetitive welds on sheet metal parts 
  • The joint doesn’t need to be airtight 
  • Your component design favors discrete weld points 

Use Seam Welding If: 

• • You need a continuous weld for sealing 
  • The part is cylindrical or has a long linear joint 
  • Structural integrity and leak prevention are critical 

At Associated Spot Welders (ASW), we specialize in both spot and seam resistance welding, serving industries where precision, repeatability, and certification compliance are non-negotiable. Our team can review your design and recommend the most cost-effective and performance-driven solution for your project. 

Ready to Discuss Your Welding Needs? 

Whether you're building aerospace components or producing commercial enclosures, ASW has the tools, experience, and certifications—including AWS D17.2—to deliver. Contact us today to find the right resistance welding process for your application.