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Resistance Welding

What is Resistance Welding?

Resistance welding is a thermo-electric process in which heat is generated at the interface of the parts to be joined by passing an electrical current through them under controlled pressure (force) for a precisely controlled time. The term “resistance” welding comes from the fact that the resistance of the workpieces and electrodes are used in combination or contrast to generate heat at their interface.

While AMADA WELD TECH didn’t invent resistance welding, it perfected it and was the first to apply it to welding small microelectronic modules in the early 1950’s. Today, AMADA WELD TECH offers a broad range of core resistance welding power supply technologies, including:

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resistance welding, resistance spot welding, micro welding
  • Linear DC Welders
  • High Frequency Inverter Welders
  • Mid Frequency Inverter Welders
  • Capacitive Discharge (CD) Welders
  • Alternating Current (AC) Inverter Welders
  • Thermocouple Welders
  • Weld Heads & Actuators, Monitors & Checkers, Electrodes & Accessories

Each technology type supports specific application needs and performance characteristics.

How Does Resistance Welding Work (Basic Principle)?

The process works by:

  1. Holding the parts securely between electrodes
  2. Applying controlled force
  3. Passing high current at low voltage through the parts for a set amount of time.

 Four Key Resistance Welding Process Variables

To achieve consistent, best-in-class results, four parameters must be closely monitored and controlled:

  • Materials — conductivity, thermal properties, surface condition.
  • Energy & Time — current and power delivered by a welding power supply.
  • Force — pressure applied by electrodes.

 Materials Suitable for Resistance Welding

The physical metallurgy of the materials to be welded determines the application of the process variables. In general, there are two categories of metals: “Conductive” (such as aluminum, copper, silver and gold), and “Resistive” (steel, nickel, Inconel, titanium, tungsten, molybdenum) with a third, small, middle ground category occupied primarily by brass.

Resistance welding can join a wide range of metals depending on electrical and thermal properties:

  • Steel and stainless steels
  • Nickel and its alloys
  • Copper and copper alloys
  • Aluminum and aluminum alloys
  • Other conductive metals

To determine whether your materials are suitable for resistance welding, please refer to our Material Weldability App.

How Does the Welding Power Supply Work (Energy)?

Energy is supplied by a power supply with either an internal or external transformer which both powers and controls the application of heat and time in the resistance welding process. In simple terms, it:

  • Receives and transforms electrical energy
  • Modulates power delivery
  • Executes a programmed weld schedule
  • Controls current, time, and other attributes

Advanced welders can store and recall unique weld schedules, enabling precise, repeatable welds across production runs. Output power ranges from small micro spot welders to systems capable of hundreds of thousands of amps capable of addressing both small and large welding applications.

 How Does Force Affect Resistance Welding?

A key parameter of resistance welding is weld pressure or force. The proper and consistent application of force:

  • Improves mating between workpieces
  • Increases electrical contact paths
  • Reduces interface resistance
  • Helps break oxide layers between materials
  • Enables repeatable weld quality through consistent resistance and heat balance

Optimum welds are achieved when the applied force is precise, repeatable, controlled by time schedule, used to fire the power supply, and regulated both to reduce the initial impact and not to become excessive after the weld.

Types of Resistance Welding Processes

Resistance welding encompasses several distinct processes, each suited to specific applications and geometries:

Resistance Spot Welding

A thermo-electric process where heat is generated at the interface of overlapping parts by passing current through them under force, creating a weld “nugget” at one or more spot locations.

Resistance Seam Welding

Similar to spot welding but produces seams by overlapping or rolling spot welds along a joint line — often using wheel or disc electrodes.

Projection Welding

Projections (low thermal mass islands) are one method of insuring proper heat balance in difficult spot welding applications when there exists a 5:1 size difference between the parts to be welded. By providing a projection on the surface of one of the workpieces, weld current and force can be focused into the small area of the projection to produce heat at the desired weld location. Projection welding is effective even if the weldments are thick.

Where is Resistance Welding Used?

Resistance welding is widely used in applications where fast cycle time, high repeatability, and controlled heat input are required. Key industries include automotive, aerospace, electronic components, medical devices, and battery manufacturing where reliable, repeatable welds are essential.

Resistance Welding Products

Power Supplies

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Linear DC Welders

High Frequency Inverter Welders

Mid Frequency Inverter Welders

Capacitive Discharge (CD) Welders

Alternating Current (AC) Inverter Welders

Alternating Current (AC) Welders

Thermocouple Welders

Weld Heads & Actuators

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Motorized Electromagnetic

Motorized Servo

Pneumatic

Manual

Compacting

Handpieces

Footswitches

Monitors & Checkers

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Desktop

Handheld Weld Monitors & Checkers

Accessories

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Electrodes

Consumables

Weld Cables

Integrated Systems

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