What Is Amplitude In Ultrasonic Welding?

To understand what amplitude is, you must first know how does ultrasonic welding work. First, ultrasound converts electrical energy into mechanical energy through the piezoelectric effect. Typically, this high-frequency vibration is related to machine power and frequency. The distance between the vibration peak point and the original position is called the amplitude. The ultrasonic welding amplitude depends on the output power, the setting of the ultrasonic electric box, the enlargement ratio of the transducer, and the enlargement ratio of the welding sonotrode.

Amplitude in The Process Of Ultrasonic Welding

The main components of an ultrasonic welding machine are a power generator, converter, amplitude booster, and welding sonotrode. The power generator converts 50/60Hz mains power into 20-40Khz electrical energy. This energy is supplied to the converter, which converts the electrical energy into low-amplitude (1-100 μm) mechanical vibration using a disc-shaped piezoelectric ceramic, and the converter transmits the vibration to the amplitude booster. The amplitude booster amplifies the amplitude of the ultrasonic wave and continues to transmit it to the welding sonotrode. The welding sonotrode continues to amplify the amplitude of the ultrasonic wave and transmit it to the weldment.

amplitude in ultrasonic welding
amplitude in ultrasonic welding2

Influencing Factors

Amplitude is the first choice of process parameters for plastics in ultrasonic welding, and materials have a suitable amplitude range under specific ultrasonic welding. Within a suitable amplitude range, the increase of the amplitude is conducive to the diffusion of ultrasonic energy, thereby improving the welding strength. However, the influence of amplitude on welding quality does not fully satisfy the above rules.

In addition, the amplitude required for ultrasonic plastic welding is also affected by the working type of welding and the frequency of the welding equipment. Insertion and riveting require larger amplitudes, while flat welding requires smaller amplitudes. For specific welding amplitudes, you can consult our Knmtech professional team.

Ultrasonic Welding Components

ultrasonic generator

Ultrasonic power supply, also known as ultrasonic electric box, ultrasonic generator. The main function is to drive the ultrasonic transducer to vibrate. The ultrasonic power supply converts the mains AC (190-240V, 50/60Hz) into high-frequency high-voltage signals, which are then converted into high-frequency mechanical vibrations through the transducer system.

ultrasonic transducer

The ultrasonic transducer is an energy conversion device whose function is to convert the input electrical power into mechanical power (ie, ultrasonic waves) and transmits it out, while it consumes a small part of the power (less than 10%).


The ultrasonic booster is a functional component that cooperates with an ultrasonic transducer to change the amplitude of ultrasonic vibration. The main function of the booster is to change the amplitude of the transducer (usually increase), improve the vibration speed ratio, improve the efficiency, improve the mechanical quality factor, strengthen the heat resistance, expand the adaptable temperature range, and prolong the service life of the transducer.

ultrasonic sonotrode

The ultrasonic sonotrode is the component that finally outputs the ultrasonic energy to the plastic workpiece in the welding operation. It connects with the plastic workpiece and transmits the ultrasonic vibration energy to the plastic workpiece. The production process of the sonotrode needs to be precise. The common sonotrodes are classified according to different characteristics, including engraving sonotrode, full-wavelength sonotrodes, composite sonotrodes, pressure plate sonotrodes, vacuum sonotrodes, cutting sonotrodes, etc.


The function of the fixture is to fix and support the workpiece. The fixture needs to be positioned accurately, firm, and stable, which will directly affect the operation of the workpiece and affect the welding operation.

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