Ultrasonic Welding

Ultrasonic energy has been used to bond thermoplastics for over 70 years. Ultrasonic welding is often chosen when parts are too large, complex or expensive to be cast in one piece. In ultrasonic plastic welding, a vibrating motion on the horn side (amplitude) is transferred to the part. The vibrations move through the part and create friction at the interface between the parts. This creates heat, which causes the plastic to melt and join the two parts together. After cooling, a weld is formed. The ultrasonic welding of plastic is used to weld a component onto or into a plastic product. Ultrasonic welding creates qualitative welds between the two parts and your plastic product is tension-free.

How does ultrasonic welding work?

Ultrasonic welding of plastics is the joining or deformation of thermoplastics using heat generated by high-frequency mechanical movement. It is accomplished by converting high-frequency electrical energy into high-frequency mechanical motion. That mechanical movement, along with the applied force, creates frictional heat at the opposing surfaces of the plastic parts (join zone) so that the plastic material melts and forms a molecular bond between the parts.

Advantages of ultrasonic welding

There are many benefits to using ultrasonic assembly. It is a fast, clean, efficient and repeatable process that produces strong, integral connections while consuming very little energy. No solvents, adhesives, mechanical fasteners or external heat are required. The finished assemblies are strong and clean. Difficult materials can be assembled ultrasonically. The assembly of parts is done quickly because the energy transferred to the joint and released as heat is very rapid and confined to the immediate vicinity of the joint. The rapid dissipation of heat makes this process significantly faster than other assembly methods.

Are all plastic materials suitable for ultrasonic welding?

To glue two thermoplastic parts together, the materials must be chemically compatible. Otherwise, although both materials can fuse together, there will be no molecular bond. A good example would be trying to weld polyethylene to polypropylene. These two semi-crystalline materials have a similar appearance and many physical properties in common. However, they are not chemically compatible and therefore cannot be welded together. Similar thermoplastics (i.e. materials with the same chemical properties) do weld together. For example, an ABS part will weld to another ABS part. Chemically dissimilar thermoplastics are only compatible if their melting temperatures are within 6 C and they have a similar molecular structure. For example, it is likely that an ABS part can be welded to an acrylic part because their chemical properties are compatible. In general, only similar amorphous polymers have an excellent probability of being welded together. The chemical properties of each semi-crystalline material make eachone compatible only with itself.

When choosing ultrasonic welding, you must take into account the weldability of the type of plastic and the plastic welding geometry that protrudes on your product. Not all types of plastics are weldable. We have the knowledge for this and are happy to help you. We ensure that the right material is used for your product with correct welding geometry dimensions. Get in touch with us to learn more!

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