What is resistance welding?

Resistance welding is a process in which metal parts are joined together by applying heat and pressure. Two electrodes conduct an electrical current through the metals, melting them together.

• The basic process? Copper electrodes hold the pieces of metal to be joined together under pressure. When an electrical current passes through the electrodes, it heats up the metal, causing it to melt at the point of contact. Once the current stops, the molten metals cool and solidify, fusing the pieces together.
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• What are the advantages? Resistance welding is fast, efficient, and economical. It needs no filler metals or shielding gasses, so there is little waste or mess. The welds are very strong, often as strong as or stronger than the base metals. Resistance welding also works well for high-volume production and is commonly used in auto manufacturing.
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• What are the variables to keep in mind? The four main factors that determine the quality and strength of a resistance weld are the amount of current applied, the length of time the current flows, the pressure applied by the electrodes, and the surface area of the electrode tips. So, by carefully controlling these variables, manufacturers can produce consistently high-quality welds.

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The 6 main types of resistance welding

To make things a little more complicated, resistance welding isn’t just one thing; it’s six. So, how do you spot the differences, and what is each type good for? 

Let’s take a look: 

• Resistance Spot Welding (RSW). RSW is probably the most common type. It uses two copper electrodes to apply pressure and current to the materials, heating and fusing them together. RSW is fantastic for joining sheet metal and is used extensively in the automotive industry.
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• Resistance Seam Welding (RSE). RSE is similar to RSW but uses two wheel-shaped electrodes to create a continuous weld seam. It's often used to join the seams of cans, air ducts, or tubing.
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• Projection Welding (RPW). RPW uses projections or bumps on one material that are fused to the second material. The projections help concentrate the current and pressure, which allows for stronger welds. RPW is popular for joining racks, cabinets, and appliances.
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• Flash Welding (RFW). RFW rapidly heats the materials by passing an electrical current between them, then forcing the heated ends together under pressure. The flash of heat and light is where it gets the name. RFW works well for joining rails, rods, and pipes.
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• Upset Welding (RUW). RUW is kind of the opposite of RFW. The materials are clamped together and current is applied, heating them from the contact area out. Pressure is then applied to "upset" or deform the materials, increasing the surface area of the weld. RUW is good for joining wires or rods.
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• Percussion Welding (RPW). RPW joins metals using a rapid discharge of electrical energy and pressure. The materials are struck together, creating both heat and a weld in a fraction of a second. RPW can join most metal combinations and is often used where very rapid production is needed.

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How does it work?

In sum, resistance welding works by passing an electrical current through the metals to be joined while pressure is applied. 

Here’s what the entire process looks like in a nutshell: 

• To carry out resistance welding, you place two pieces of metal between two electrodes. The electrodes are connected to a power supply that provides the necessary current and pressure.
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• When you turn the power on, the current flows through the conductive metals. But metals are not perfectly conductive, so there is some resistance, which generates heat. The longer the current flows and the higher the current, the hotter the metals become. At the same time, the electrodes apply pressure to the metals.
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• Once the metals have reached a high enough temperature to melt, you turn off the power. The molten areas fuse together as the metals cool under pressure. This forms a strong weld without needing additional filler materials. The key is using the correct amount of current, time, and pressure to heat and join the metals properly without causing damage.

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What is resistance welding used for?

Resistance welding is used in many industrial applications where strong, permanent joints are necessary. 

Some of the most common uses include:

• The auto industry relies heavily on resistance welding for assembling vehicle bodies and components. Spot welding is frequently used to join steel body panels, while seam and projection welding are used to join tailored blanks and attach brackets. All in all, resistance welding allows high-speed, automated assembly of vehicles.
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• The aerospace industry uses resistance welding, especially spot welding, to assemble aircraft components like wings, fuselages, and engine parts. The welding process must produce extremely strong yet lightweight joints to meet safety standards. As such, resistance welding is suitable for joining aluminum alloys commonly used in aircraft.
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• Makers of appliances like refrigerators, washers and dryers, ovens, and dishwashers use resistance welding to join sheet metal components. The welding process allows fast mass production of steel cabinets and parts. Resistance seam welding is often used to join edges of sheet metal, while spot welding attaches brackets and joins overlapping sheets.
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• Resistance welding has many uses in general metal fabrication. It’s ideal for joining ferrous metals like steel in applications where strength and appearance are priorities. Uses include joining structural steel in building storage tanks, pressure vessels, pipes and tubing, and metal shelving.

Can resistance welding be automated?

Absolutely! Resistance welding is ideal for automation and is used extensively in manufacturing. 

Why? Due to the controlled and repetitive nature of resistance welding processes, which means that robots and automated equipment can easily be programmed to perform the necessary steps.

How? Automated resistance welding systems use articulated robotic arms equipped with welding electrodes to handle and maneuver workpieces through the welding process. 

The robot is programmed to clamp workpieces together under the proper pressure and for the correct amount of time while electric current flows to form a strong bond.

Automating resistance welding offers many benefits:

• Speed and productivity go through the roof. Robotic welders can work continuously without breaks, completing hundreds of welds per hour. This significantly boosts manufacturing throughput.
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• Superhuman consistency and quality. Robots always perform the exact same programmed motions and apply consistent pressure during each weld. The net result is higher quality, uniform welds.
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• Costs go down. Although automated welding systems have high upfront costs, they can save money in the long run through increased productivity, less wasted materials, and reduced labor costs.
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• Your working environment gets safer. Automated welding removes humans from hazardous welding areas, reducing the risk of injury from high voltages, fumes, and heavy equipment — and yes, also burning someone or bumping an employee on the noggin.
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• They can keep going and going and going. Automated welding systems can run 24 hours a day, 7 days a week without stopping (except for scheduled maintenance breaks). This allows for maximum utilization of equipment and resources.
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• Fast return of ROI. This is not common knowledge, but automation typically offers a blazing ROI of just 1-3 years. 

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Summing up

The takeaway? Resistance welding is a versatile, efficient, and easily automated process that joins metals using electricity and pressure. 

With so many types to choose from, resistance welding offers solutions for all kinds of manufacturing and fabrication needs, from big to small.

It’s up to you to see whether you want to get in on the automation action. Assess your needs and workflow, budget accordingly, and start reaping the added benefits of resistance welding and robotic automation!

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Next steps

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• Safety-centric engineering: Collaboration is key! From advanced sensors to integrated safety protocols, RO1 prioritizes a secure working environment where robots and humans thrive side-by-side.

• Intelligence that grows with you: RO1's cutting-edge AI (comparable to GPT-4) allows it to constantly learn and refine its processes, adapting to your specific needs and maximizing long-term efficiency gains.

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Our dedicated team is committed to supporting a smooth transition as you incorporate RO1's transformative capabilities into your workflow. Discover its potential firsthand with our 30-day risk-free trial!