Resistance welding (RW) is a process you’ve seen, but may not even have noticed. It’s one of the secret ingredients of the world of manufacturing.

TL;DR: It’s a process where electrical current runs through a metal, which resists the electrical flow to the point of nearly melting. It’s pretty popular because it’s quick, reliable, and has low distortion.

Today, we’ll give you a quick lowdown on how this cool (well, hot) process works its magic, and the industries making the most of it. 

We’ll cover: 

• What is resistance welding? 
• What are the pros and cons of using it? 
• What are the other types of resistance welding? 
• Electric resistance welding
• Some real-world applications of resistance welding 
• Resistance welding vs. other methods
• Technological innovations and future developments

Let’s dive right in! 

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What is resistance welding?

Resistance welding is a fusion welding process that generates heat by passing an electrical current through metal. 

Here’s how the whole thing works: 

1. The metal pieces resist the flow of electricity, which causes them to heat up and melt at the point of contact. Once the current is removed, the metal pieces fuse together as they cool.
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2. Two pieces of metal are pressed together and clamped by electrodes. An electrical current passes through the electrodes, heating the metal pieces and melting them at the point of contact. The current is then stopped, and the molten metal hardens, fusing the pieces together. 
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3. The amount of heat generated depends on the amount of electrical current, its duration, and the resistance of the metal. The trick is to apply enough current for a long enough time to melt the metal without overheating the surrounding area.

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Resistance welding pros 

• Fewer welding mistakes: Resistance welding is a fast, efficient process that produces strong, high-quality welds with few flaws, such as porosity or slag inclusion. The concentrated heat and pressure fuse materials together at a molecular level.
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• It can cost less: Resistance welding necessitates very little joint preparation and uses inexpensive equipment, so it is very cost-effective. Consumables are also cheap since they only require electricity and electrodes. 
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• High production rates: Resistance welding is also perfect for high-volume production because the equipment can cycle quickly. 

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6 types of resistance welding 

There are various types of resistance welding making the rounds. Let’s break them down in more detail: 

1. Resistance Spot Welding (RSW) 

Spot welding uses the heat generated by an electrical current to join metal sheets together. Electrodes clamp the metal sheets together, and an electric current is passed between them to create heat and form a weld nugget. Industries often use spot welding to join body panels in automotive manufacturing.

2. Resistance Seam Welding (RSEW) 

Seam welding is similar to spot welding but joins larger sections, like the seams of cans, drums, or beams. Multiple spot welds are made along the joint line to create a continuous weld. Seam welding requires equipment to automatically feed and clamp the workpieces.

3. Resistance Projection Welding (RPW)

Projection welding uses raised surfaces, called projections, that concentrate the current and generate heat. The projections melt and join the metal pieces together. Projection welding is often used to join crossed wires or attach brackets to metal surfaces.

4. Flash Welding (FW)

Flash welding passes a high current through the joint area of two metal parts to quickly heat and join them. The rapid heating causes the metal to flash, or melt, at the joint. The flashing metal is then forced together under pressure to form a weld. Flash welding is useful for joining rods, bars, tubes, and rails.

5. Percussion Welding (PW)

Percussion welding rapidly heats two metal surfaces through a series of high-current discharges. The heat causes the metals to melt instantly at the joint, and the pieces are then forced together under high pressure. Percussion welding can join dissimilar metals and is often used for welding wire to terminals.

By concentrating heat at the joint area, these welding methods avoid melting the entire workpiece. The concentrated heating also allows for fast cycle times, reducing energy.

6. Upset Welding (UW) 

This is a solid-state welding process. In upset welding, the parts being joined are heated by the resistance generated by the flow of current through the parts at their interface, and then immediately forged together to create a bond. This process does not require any filler metal, and the heat is generated internally, resulting in minimal distortion and a strong, high-quality weld.

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Electric resistance welding: Principles & applications

Electric resistance welding (ERW) keeps things simple and effective: It uses high current and pressure to fuse metal parts without filler, which makes it fast, clean, and an ideal choice for high-volume operations. 

Here’s what makes it special:

• It skips the filler and shielding gas: Unlike MIG or TIG welding, ERW relies solely on current and pressure to create heat and bond materials.
  
  
• Weld quality depends on three key factors: Current, time, and force need to be balanced. Too much current burns through, while too little force weakens the weld.
  
  
• Perfect for high-speed jobs: ERW is a go-to for sheet metal fabrication, wire manufacturing, and pipeline welding, where you have to get super high levels of consistency. 

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Real-world industries that benefit from resistance welding 

Resistance welding is a common process used in many industries and for countless products we use daily. 

Here are some real-world examples of resistance welding in action: 

• The auto industry relies heavily on resistance welding for assembling vehicle bodies and parts. Spot welding, in particular, is used to join sheet metal panels together for car doors, hoods, trunk lids, and panels. Seam welding is also used on longer joints. These techniques are fast, efficient, and create strong bonds between panels.
  
  For instance, Ford Motor Company's Dearborn plant has flawlessly delivered over 600 million resistance welds on aluminum F-150 pickup truck beds since 2013, with each assembly requiring an average of 83 precision welds.

• Makers of appliances like refrigerators, washers, dryers, and ovens also leverage resistance welding in their assembly lines. The process is ideal for joining sheet metal and creating airtight seals — both important for appliances. Spot welding and seam welding are commonly used.
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• Resistance welding, especially spot welding, is a standard in aircraft manufacturing. It is used to assemble the aluminum alloy sheet metal that makes up aircraft fuselages, wings, and other components. The high-strength welds it produces are essential for aircraft safety and durability.
  
  Indeed, in September 2024, Airborne Technologies achieved certification as a Lockheed Martin (LMCO) supplier for resistance welding, authorizing them to perform spot welding on LMCO products in strict compliance with American Welding Society specifications.

• Microspot welding joins very small electronic components, like wires, contacts, and microchips. The miniaturized process allows precise welds to be made without damaging heat-sensitive electronics. Resistance welding is also used for soldering some components onto printed circuit boards (PCBs).
  
  EWI engineers recently tested a resistance spot welding technique using capacitive discharge power supply for lithium battery assembly, providing precise control and real-time quality monitoring capabilities not available with ultrasonic or laser processes.

• For large infrastructure projects like bridges, skyscrapers, and pipelines, resistance welding offers speed, strength, and efficiency. The process is suitable for welding thick steel plates and beams, as well as joining pipes for transporting liquids and gases.
  
  For example, for London's 6 Bevis Marks building, Skanska installed massive transfer beams weighing up to 38 tons using special site welding procedures to deal with potential hydrogen cracking, demonstrating the critical importance of resistance welding in creating durable structural connections.

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Common challenges in resistance welding

Even resistance welding has its share of headaches. From worn-out electrodes to unpredictable material behavior, staying ahead of these challenges means fewer bad welds and less downtime.

Here’s where things get tricky:

• Electrode degradation slows everything down: Worn electrodes reduce weld quality and increase cycle time. Regular maintenance, cleaning, and on-time replacement keep things moving along.
  
  
• Material compatibility can throw curveballs: Aluminum, stainless steel, and other metals respond differently to resistance welding. Dialing in the right current, pressure, and weld time prevents errors.
  
  
• Process optimization makes or breaks weld consistency: Different conditions — like varying material thickness or electrode wear — impact weld quality. Fine-tuning machine settings and monitoring feedback means you’ll get much more stable results. 

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Technological innovations & automated resistance welding

Resistance welding isn’t stuck in the past, and we can prove it. 

Here’s what’s pushing resistance welding forward:

• Robotic welding systems that never clock out: Robotic arms equipped with parallel grippers are handling high-speed, high-volume jobs like welding chassis. Auto manufacturers like Tesla are using robotic welding systems to maintain near-flawless production lines. Check out our manual welding vs. robot welding comparison here.
  
  
• AI-driven monitoring to keep things sharp: AI-powered monitoring systems analyze real-time data, adjusting parameters like current, pressure, and weld time on the fly. This means fewer mistakes, less rework, and near-perfect welds more consistently,
  
  
• Fully automated welding lines bringing Industry 4.0 to life: IoT-connected systems track machine performance, analyze weld data, and alert operators before things go south. 

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Resistance welding vs. other welding methods

So how does resistance welding stack up against the competition? It’s faster and more cost-effective than many alternatives, but like everything in manufacturing, it’s not a one-size-fits-all solution.

Here’s how it compares:

The future of automated resistance welding

As automation, AI, and IoT take center stage, resistance welding is becoming smarter, faster, and more adaptable. Companies that embrace these changes will thrive, and those that don’t, well, they’ll go the way of the dodo. 

Here’s what’s coming next:

• AI that fine-tunes weld quality automatically: Future systems will analyze welds in real time and adjust parameters like current, pressure, and timing to eliminate defects and improve consistency. Fewer errors, more efficiency.
  
  
• Cobots taking precision to the next level: Collaborative robots will handle high-precision welding tasks safely and quickly. Equipped with adaptive grippers, they’ll make operations smoother and reduce the strain on human operators.
  
  
• IoT monitoring that stops problems before they start: Smart systems will track machine performance, detect potential failures, and schedule maintenance before things go wrong. Less downtime, more uptime.
  
  
• Fully automated lines: Industry 4.0 is already changing the whole play, but future welding lines will self-adjust for speed and accuracy, reducing the need for human intervention while maintaining high levels of quality. 

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Summing up

Resistance welding is a super common manufacturing process that you've definitely encountered, even if you didn't realize it at the time. 

But now is the time to ask yourself: Is resistance welding the right process for your fab shop? To find out, you’ll have to assess your current industry, niche, application — and budget!

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Next steps 

RO1 by Standard Bots reshapes resistance welding with top-tier automation, making it accessible to fab shops of every size.

• Budget-friendly innovation: RO1 offers unmatched value, with features comparable to premium robots at a significantly lower price.
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• Revamp your workflow: Experience precision and speed like never before with RO1's 6-axis arm and robust payload capacity.
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• Prioritizing safety: RO1 fosters a collaborative, human-centric workspace with its intuitive safety features.
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• Smarter over time: Harnessing AI similar to GPT-4, RO1 continually learns and optimizes, ensuring continued efficiency gains. It does more than weld, it can adapt to a wide variety of shop floor jobs. 

Our team partners with you for a smooth transition and helps you maximize the potential of your RO1 automation. Take advantage of our 30-day risk-free trial and witness the transformation!