Ultrasonic Spot Welding

How does the ultrasonic welding work

[box type=”info” align=”” class=”” width=””]Ultrasonic welding works on the basic principle of energy of ultrasonic wave. It’s the process of connecting two parts to form a finished component. This process relies on the high-frequency ultrasonic vibrations produced and applied to the parts through the horn. These vibrations are generated by the ultrasonic system, which sends an alternating current. The ultrasonic energy melts the contact point between the two parts, creating a joint. Ultrasonic welding technology is generally known and is essentially a solid-state bonding process carried out at an ambient temperature, without soldiers or fluxes.[/box]

Ultrasonic welding machine principle
Ultrasonic welding machine principle

Ultrasonic Welding Step by Step

The following steps can describe the basic process of ultrasonic welding:

  1. The parts to be welded are placed in the anvil or fixture.
  2. The horn contacts the parts to be welded.
  3. Pressure is applied to keep the horn in contact with the welded materials and to hold them together.
  4. The horn delivers ultrasonic vibrations to heat the materials. The vibrations move less than a millimeter, either up-and-down or side-to-side.
  5. The materials are welded together.
  6. The horn gets retracted, and the welded materials can be removed from the anvil.

The welding times applied pressures, and temperatures are controlled by a computer or microprocessor within the welding apparatus. And what actually happens during the welding process depends on the nature of the materials.

How does the ultrasonic welding work

The ultrasound converter converts the electrical signal from the generator into mechanical vibrations. They, in turn, are directed to the workpiece to be welded via the booster and the sonotrode under specific pressure.

The mechanical vibrations generate frictional heat at the workpiece’s defined joints, which causes the material to melt and bonds the parts together.

During a brief cooling phase, a clamping force is applied to fuse the plasticized material. The pieces welded together with ultrasonic energy are immediately available for further processing.

Depending on the application, the sonotrodes can weld vertically, horizontally, and continuously.

Ultrasonic Welding Components:

The ultrasonic vibrations are produced by a series of components, including generator(power supply), converter, booster, and horn, which ultimately transmit mechanical vibrations to the two parts that need to be welded.

Generator(Power Supply):

The ultrasonic welding needs a high frequency and high voltage power supply. This power is needed by the transducer to generate vibrations.

hcsonic ultrasonic generator
hcsonic ultrasonic generator

The transducer is a device that can convert high-frequency electric signals into high-frequency mechanical vibration. This is connected with the welding head: the converter or piezoelectric transducer used in this welding process.

Ultrasonic transducer
Ultrasonic transducer
Booster and Horn:

The transducer’s mechanical vibration is supplied to the booster, which amplifies this vibration and supplies it to the horn. Horn is a device that supplies this amplified vibration to the welding plates.

Ultrasonic booster and round flange
Ultrasonic booster and horn
Fixture or clamping devices:

This device is essential in ultrasonic welding. This uses either electrical, hydraulic, pneumatic, or mechanical energy to hold the plates into the desire location.


  • Adopting the hot melt effect, the product has increased water resistance, lighter weight, and easier folding.
  • Ultrasonic welding technology does not require flammable fuels and open flames, so it’s a safer process compared to other welding methods.
  • The ultrasonic welding technology sets itself apart with fast welding speeds, high welding strength, and good sealing performance.
  • Ultrasonic welding is a clean, efficient, and repeatable process that produces strong, integral bonds while consuming very little energy.
  • The cooling time is rapid, and the pieces do not need to remain inside the tool for a long period of time to dry or cure the welding joint.
  • Ultrasonic welding machines can cut textiles while welding and realize automatic edge banding.
  • This type of welding is not dangerous to humans. Indeed the vibration is called ultrasonic because they are higher than those that the human ear can hear.
  • The welding process is clean because it doesn’t use harmful solvents or glues while also not damaging the product.
  • This ultrasonic welding technology is also easy to implement in a production process and has a low fault rate. continuous production without interruption


Ultrasonic assembly is widely accepted and is used in the automotive, medical, electrical and electronic, communications, appliance, consumer products, toys, textile, and packaging industries. It is an economical process that can significantly increase production and lower assembly costs. Ultrasonic Welders can be easily integrated into an automation manufacturing environment and provide unprecedented repeatability, reliability, and accuracy to the process.


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