Resistance Welders by Avio

A resistance welding machine is composed of a welding power supply, a weld head and an electrode. The welding power supply controls a welding current, the weld head exerts a material holding pressure while the electrode applies welding current and local pressure to the part being welded. Various types of Welding Power supplies (Weld Timer plus Transformer) and Welding Heads are available to meet a wide variety of applications.

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Waveforms and Characteristics of Power Supplies

Welding Power Supplies have several operational characteristics that are configured by the control method used. It is important to select a Welding Power Supply based on the material type and/or shape of the work pieces being welded.

Welding Current Waveform for Each Type of Welding Power Supply


Welding Power Supply Characteristics

Excellent Good   Inferior


A.C. D.C. Transitor Inverter
Performance No weld Splatter*  
Stability to Power Fluctation
Welding Speed (Cycle Time)  
Power Source Capability    
Main Application

Between weldable plates

Magnetic head

For the parts requiring no deformation nor discoloring

Motor brush

Super fine wire

Lead wire of sensors

For the parts requiring no weld splatter*

Electron Gun

* Weld Splatter: Dust or Slag produced during welding, Welding slag.

Welding Theory

For Resistance Welding it is very important to concentrate heat at the junction of the objects to be welded. A method to accomplish this task is to utilize the specific material properties of the weld object and the weld electrode. This is especially important when welding objects of different material properties as shown in the adjacent figure.

By using an electrode of the same shape and material as the weld junction, the weld "nugget" has a tendency to move into the lower electrical conductivity material. To shift the "nugget" location shown as the material fusion temperature threshold in curve (c) towards the material to material junction of the work piece requires maintaining a heat balance. To accomplish this task:

  1. For the lower electric conductivity material side: cool the electrode selected to be of larger diameter than the desired nugget size and made of high electric conductivity material.
  2. For higher electric conductivity material side: use a small diameter electrode made of low electric conductivity material.


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