What Is Resistance Welding

Resistance welding joins two similar or dissimilar metals together. It uses high current, pressure, and heat to create the bond.

The Main Advantage

You don’t need extra material to complete the weld. This makes resistance welding reliable, repeatable, and cost-effective.

Types of Resistance Welding

Several forms exist, including spot, seam, projection, flash, and upset welding. Each type differs by the electrodes used. The electrodes apply pressure and conduct current to the weld point.

Manufacturers make electrodes from copper-based alloys. These materials offer superior conductive properties. Water flows through cavities inside the electrode to cool the tooling during operation.

Resistance Spot Welding

Resistance Projection Welding

Spot welding creates welds using heat from electrical current resistance. The process also applies force to push workpieces together over a defined time.

The electrode face geometries focus welding current at the desired location. They also apply force to the workpieces. The materials heat up, combine, and form a weld nugget.

Projection welding uses heat from electrical current resistance. It applies force over a defined time period.

How It Works
The process localizes welds at predetermined points. It uses projections, embossments, or intersections to focus heat generation. The weld current generates resistance at the contact point. The projections collapse and form the weld nugget.

Common Uses

Solid projections: Welding fasteners to parts
Embossments: Joining sheet or plate material
Intersections: Cross-wire welding applications.

The wire intersections localize heat generation. The wires set down into one another and form a weld nugget.

Resistance Seam Welding

Resistance Upset Welding

Seam welding is a subset of spot welding. It uses wheel-shaped electrodes to deliver force and current.
The workpiece rolls between the electrodes while current flows. Your weld settings determine the result. You can create overlapping welds that form a complete seam. Or you can create individual spot welds at defined intervals.

Upset welding uses heat from electrical current resistance. It applies force to push workpieces together.

Key Difference from Flash Welding
The workpieces already make firm contact with one another. No flashing occurs. You apply pressure before starting the current. You maintain pressure until the process completes.

How Resistance Welding Works

1. Pressure Application

Electrodes or welding tips hold the parts together under mechanical pressure.

2. Current Passage

A high electrical current passes through the joint area. The system controls the timing precisely. Current encounters resistance at contact points and within the material. This generates heat.

3. Heat Generation

The heat level depends on three factors:

The square of the current
The resistance of the materials
The time the current flows

Joule’s Law of Heating: Q = I² · R · t

Where:

Q = heat generated
I = current
R = resistance
t = time

4. Welding

The materials heat to their melting or near-melting point. The applied pressure fuses the materials together at the interface.

5. Cooling

The current turns off. You maintain pressure while the weld cools. This forms a solid bond.

Types of Resistance Welding Machines

Different machine configurations suit different manufacturing needs. Choose your machine based on part size, production volume, and application requirements.

Rocker Arm Welders

Rocker arm machines use a pivoting arm to bring the upper electrode down. They offer excellent accessibility for irregular-shaped parts. These welders work well for low to medium production volumes.

Benchtop Welders

Benchtop units mount directly to a work surface. They provide a compact footprint for smaller parts. These machines suit prototype work and light production runs.

Press-Type Welders

Press welders use a direct vertical stroke for electrode movement. They deliver consistent, parallel pressure across the weld area. This design handles high production volumes and heavy-duty applications.

Capacitor Discharge (CD) Welders

CD welders store electrical energy in capacitors. They release this energy in an extremely short pulse. This produces minimal heat-affected zones and works well for heat-sensitive materials. You can weld thin to thick materials without warping or distortion.

Common Applications

Engineers design resistance welding machines for automotive, aerospace, and industrial applications. Automation gives manufacturers highly controlled and repeatable results. This allows companies to staff production lines readily.

Advantages of Resistance Welding

High Speed

Resistance welding works very fast. This makes it suitable for mass production.

Clean Process

A correctly calibrated weld produces little to no sparks, smoke, or fumes. This beats arc welding significantly.

Consistency

The correct welding control provides uniform and repeatable welds. You must control parameters appropriately.

No Filler Material

Resistance welding doesn’t require filler metal. This reduces costs and simplifies the process.

More Questions? We’re happy to help, give us a call at (937)-253-3300.