What is Ultrasound in plastics?

Ultrasound in plastics refers to the use of high-frequency acoustic waves, typically above 20 kHz, for processes such as bonding, cutting, inspection, or cleaning of plastic components. Within the plastic transformation industry, the most common application is ultrasonic welding, a technique that joins two thermoplastic parts by generating localized heat through molecular friction—without the need for adhesives, screws, or additional materials.

Ultrasonic welding works by converting electrical energy into high-frequency mechanical vibrations, which are transmitted through a tool called a sonotrode. These vibrations are applied to the contact surfaces between the parts to be joined, generating internal frictional heat that melts the material at the interface. Once the vibrations stop, pressure is maintained briefly to allow the plastic to cool and solidify, forming a strong, clean, and fast bond.

This process is particularly efficient for compatible thermoplastic materials and is widely used in sectors such as automotive, electronics, packaging, medical, and consumer goods. Ultrasound enables high-precision bonding in very short cycles, making it a highly competitive technology for serial production.

Beyond welding, ultrasound is also used in other plastic-related processes:

• Ultrasonic cutting: useful for precisely cutting plastic parts or films while minimizing burrs or thermal deformation. It is ideal for thin materials or multilayer composites.

• Ultrasonic staking or insertion: allows for the insertion of metal inserts or the formation of localized joining points without damaging surrounding plastic.

• Ultrasonic cleaning: using cavitation in liquids, this method removes residues, grease, or particles from plastic surfaces, especially in technical or medical applications.

• Ultrasonic inspection: to a lesser extent, ultrasound can also be used for non-destructive testing of plastic parts to detect internal defects or structural failures.

One of the main benefits of ultrasound in plastics is its speed and energy efficiency, since heat is generated only at the interface and there is no need to heat the entire part. Additionally, because it is a clean process without direct contact with hot elements, the risk of contamination, deformation, or surface damage is significantly reduced—an essential factor in precision components or products for sensitive industries like medical or food.

However, not all polymers are equally suitable for ultrasonic welding. The materials must have similar melting points and good ability to transmit ultrasonic waves. Therefore, it is essential to choose the right type of plastic and design parts with proper joint geometry, contact areas, and energy directors that help concentrate heat in the desired zone.

In summary, ultrasound in plastics is a versatile, precise technology that is deeply integrated into modern manufacturing. Its ability to produce fast, strong bonds without external materials makes it an ideal solution for optimizing processes, reducing assembly times, and improving the final quality of technical and industrial plastic products.