How Does Ultrasonic Plastic Welding Work?

The ultrasonic welding machine uses high-frequency vibration waves to transmit to the surfaces of two objects to be welded, and under pressure, the surfaces of the two objects are rubbed against each other to form fusion.

The Principle Of The Ultrasonic Welding Machine

When the ultrasonic wave of the ultrasonic plastic welding machine acts on the thermoplastic plastic contact surface, it will generate tens of thousands of high-frequency vibrations per second. This high-frequency vibration with a certain amplitude transmits the ultrasonic energy to the welding area through the upper weldment. Due to the large acoustic resistance in the welding area, that is, the interface between the two welding, local high temperatures will be generated. As the poor thermal conductivity of the plastic, it cannot be distributed in time, and it gathers in the welding area, causing the contact surface of the two plastics to melt rapidly. After a certain pressure is applied, the materials are fused into one. When the ultrasonic wave stops working, let the pressure continue for a few seconds to make it solidify and form, thus forming a strong molecular chain to achieve the purpose of welding.

ultrasonic plastic welding principle

The Main Application Scope

1. Medical industry: (precision) filter, T-tube, dosing tee, white blood cell filter, self-destructing syringe, etc.
2. Daily necessities industry: cosmetic mirror, cosmetic box (box), lighter, nail clipper box, lens fixing in the powder box, ABS suitcase, etc.
3. Toy industry: flash balls, toy guns, key chains, dolls, plastic gifts, and various types of plastic toys.
4. Packaging industry: anti-counterfeiting wine bottle caps, self-sealing bags, blister packaging boxes, packaging tapes, ordinary battery packaging, etc.

Characteristics of Ultrasonic Plastics Welding Machine

  1. Ultrasonic welding plastic requires thermoplastics.
  2. It does not require additives, but the welding speed is fast and the weld strength is high.
  3. While achieving good welding quality, the welding is irreversible due to the design of the weld seam.
  4. Low cost, clear operation, easy to mass produce.
How Does Ultrasonic Plastic Welding Work
ultrasonic welding machine

Precautions for The Ultrasonic Welding Machine

1. The welding machine directly uses 220v mains power, so the body should be properly grounded before power-on, and the grounding resistance should be less than 4 ohms.
2. When the mains voltage change is greater than 10%, an AC voltage stabilizer should be installed on the machine to ensure the efficient and safe operation of the welding machine.
3. When the ultrasonic sound is generated, the upper welding sonotrode shall not be contacted with the lower welding die, the fixture, and the worktable, so as to avoid damage to the parts.

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 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.

ultrasonic welding setting amplitude
Which parameter settings affect the effect of ultrasonic welding?

During the welding process of the ultrasonic plastic welding machine, the welding parameters will affect the welding results. These parameters include amplitude, welding distance, welding pressure, welding energy, and trigger pressure.

ultrasonic welding setting parameters

What are the common welding modes of the ultrasonic welding machine?

The simplest and most commonly used mode is the time mode, where ultrasonic energy is applied for a predetermined period of time without regard to other parameters. Another commonly used mode is the energy mode, which usually requires a microprocessor-based controller to measure and record the energy input during the welding process and calculate the energy. In this mode, ultrasonic vibration is maintained until the energy delivered to the part reaches a fixed value.

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