Introduction of Ultrasonic Plastic Welding
Ultrasonic welding adopts ultrasonic plastic welding technology, which converts high-frequency electrical energy into mechanical vibration energy through ultrasonic transducers, and then transmits the mechanical vibration energy to the welding head by changing the amplitude through a banner device. When the welding head approaches the surface of the processed product, ultrasonic waves are automatically generated, causing micro amplitude high-frequency vibration on the surface of the processed product. Friction with the surface of the processed product converts it into heat, melting the processed product before welding. Due to the spot welding operation, welding is relatively more perfect, and different welding effects can be obtained by replacing the welding head.
What is ultrasound?
From the chirping of birds to the screams of broken glass - sounds are not just what we can hear with our ears. It is generated by the mechanical vibration of an object. This occurs not only in air, but also in every elastic medium, including gases, liquids, and solids.
Ultrasonic waves are an example of how humans cannot hear all types of sound. High frequency sound waves are used in industry and medicine, which cannot be heard.
Sound waves are classified according to their frequency (wave number per second). For example, the range of ultrasound is from 20 kHz to 1 GHz. Ultrasonic welding uses frequencies ranging from 20 kHz to 70 kHz. The lowest range can still be heard by human ears. This is because the range of audible sound (at least for humans) is only 16 Hz to 20 kHz. At most, oscillations exceeding this value are considered vibrations.
How does ultrasonic welding work?
When ultrasonic vibration strikes a material (such as plastic), the molecular chains begin to oscillate. Molecules begin to move and rub against each other. This generates energy (known as frictional heat). For thermoplastic materials, this process can cause them to start melting. Ultrasonic welding utilizes this principle. After a brief holding time under additional pressure, various materials (components) can be welded together at the molecular level in the connection area.
What is ultrasonic welding suitable for?
Ultrasonic welding occurs within seconds without the need for any auxiliary tools such as adhesives or screws. Ultrasonic waves are used for manufacturing packaging, automotive parts, toys, and more, for example, through:
1. Connect injection molded parts (such as toys)
2. Embedded membranes (such as filter membranes used in medical components)
3. Integrating leather, non-woven fabric, and textiles (such as air filters in cars)
4. Stack different types of materials together (such as for airbags)
5. Use forming technology to create shape fitting connectors (such as magnet contacts in chargers)
6. Counterhead socket and magnet (e.g. encapsulated magnet for activating sensors)
Ultrasonic welding system
A complete ultrasonic welding system consists of various components. Active components generate vibrations, transmit vibrations, and apply them to welded joints. Passive components absorb the force generated and fix the components in the appropriate position, especially at the welding joints where the supporting components are connected together.
Components:
The ultrasonic generator
Ultrasonic transducer
Ultrasonic amplitude rod
Ultrasonic tool head
The combination of transducers, amplitude rods, and ultrasonic generators forms a so-called stack.
Process technology: Energy focusing principle
In order to accurately melt the components, it is necessary to concentrate the vibration energy at one point. This is called energy focusing. This specific point is where heat development is strongest and melting occurs - used to define low-energy welding processes.
Types of energy focusing
Everything is a matter of shape: in order to concentrate vibration energy at the correct point, the geometric shape of the parts or tools to be welded must be designed accordingly. For component integration focusing, energy directors (EDs) focus energy on the material itself. For focusing tool geometry, the shape of the tool is suitable for specific applications.
What materials can be welded using ultrasonic waves?
Generally speaking, most thermoplastic materials (plastics that can be molded when heated) can be welded using ultrasonic waves. The harder the material, the better. In addition to plastics, different non-ferrous metals such as aluminum, nickel, brass, and copper are also suitable for ultrasonic welding.
