Ultrasonic welding, its operation

Ultrasonic welding is an innovative welding technique used to join materials together quickly and accurately. This method uses high-frequency vibrations to fuse materials together without the need for additional adhesives or additives. However, there is an important difference between ultrasonic welding of metals and plastics. In this blog, we discuss how both methods work, their advantages and their applications. Learn more about ultrasonic welding.

See also our other blogs on ultrasonic welding: Ultrasonic Welding, Our New Technique and Ultrasonic Welding: Types and Applications. These blogs provide insight into how the ultrasonic welding principle works for both plastics and metals.

If you have any questions, please feel free to contact us. We will be happy to assist you. You can call us directly at +31 492 830126 or send an email to contact@bseni.nl.

How does ultrasonic welding work on plastics?

When welding thermoplastics, high-frequency sound waves (usually between 20 and 40 kHz) are used to generate mechanical vibrations. These vibrations cause friction between the surfaces to be welded, resulting in an increase in temperature at the contact point. This causes the materials to melt and form a strong bond after cooling. Watch a video on ultrasonic welding of plastics here.

The main machine components in ultrasonic welding of plastics are:

• Generator: Converts electrical energy into high-frequency vibration.
• Transducer: Converts electrical energy to mechanical vibration.
• Booster: Enhances vibrations.
• Sonotrode: Transfers vibrations to the material.
• Anvil (support): Holds materials in place.
• Vibration amplitude: The amplitude of vibration is usually between 10 and 100 microns and determines how much movement occurs at the molecular level.
• Direction of vibration: In plastic welding, the direction of vibration is usually parallel to the weld surface, which ensures maximum friction generation.
• Energy input: Energy input should be carefully controlled to prevent overheating and degradation of the plastic.

How does ultrasonic welding work on metals?

Ultrasonic welding of metals requires a different approach from plastics. Metals do not melt like thermoplastics, but ultrasonic vibrations cause local plastic deformation and welding by diffusion and friction. This results in a strong, solid joint without the need for additives or external heating. Watch a video on ultrasonic welding of metals.

The main components in ultrasonic welding of metals are similar to those in plastics, but the vibration amplitude and energy input differ to correctly join the metal structure without melting. More on the differences in welding.

The distinction from plastic welding is found in:

• Vibration amplitude: The amplitude is usually lower than for plastics, usually between 1 and 25 microns, to allow controlled deformation of the metal.
• Direction of vibration: In metal welding, an inclined or oscillating motion is often used, which ensures maximum material fusion at the molecular level.
• Energy input: The energy input must be higher than for plastics because metals have a higher density and melting temperature. This is achieved through a combination of pressure and vibration.

Main differences between plastic and metal welding

In summary, the differences in ultrasonic welding of plastics and metals can be described as follows:

1. Melting process: plastics melt and flow together, while metals form a solid bond via pressure and friction.
2. Vibration frequency: For plastics, the frequency is usually between 20-40 kHz, while metals require lower frequencies and higher energy density.
3. Vibration amplitude: Plastic welding requires a greater amplitude than metal welding.
4. Direction of vibration: Plastics are usually welded in a parallel motion, while metals require an oscillating or inclined motion.
5. Energy input: Metal welding requires a higher energy input because of the greater resistance and higher melting temperatures of metals.
6. Application:Plastic welding is often used in the packaging and automotive industries, while metal welding is more often used in the electronics and battery industries.

Advantages

Ultrasonic welding has many advantages over other joining techniques. These have been mentioned before, but here is a list of them again:

• Speed: Welding occurs within a few milliseconds to seconds.
• No additives: There is no need for solder, glue or additional materials.
• Energy efficiency: The technology consumes less energy than conventional welding technologies.
• Environmentally friendly: No chemicals or solvents required.
• Strong and consistent joints: The welds are uniform and reliable. More about the benefits.

Applications

Ultrasonic welding is a technique that has been available for decades and has undergone strong development over the years. Due to the advantages of this technique, ultrasonic welding has made its appearance in many industries such as:

• Automotive: Connecting plastic components and metal contacts.
• Medical industry: production of sterile plastic and metal parts.
• Electronics: Welding of battery connections, wire connections and circuit boards.
• Packaging industry: Sealing plastic packaging and aluminum foils. More on applications.

Conclusion

Ultrasonic welding is a versatile and efficient welding method that can be used for both plastics and metals. Although the basic principles remain the same, the exact methods vary by material and therefore the equipment required. The vibration amplitude, vibration direction and energy input play a crucial role in the success of the welding process. Thanks to its speed, reliability and environmental benefits, ultrasonic welding remains a popular choice in various industries. Want to learn more about ultrasonic welding and which method best suits your application? Then get in touch with us.

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