company news about Ultrasonic Riveting Technology

Ultrasonic riveting and forming:

The ultrasonic riveting makes possible an interlocking bonding of two thermoplastics or of thermoplastics with dissimilar materials, e. g. thermoset materials or metals.

In this process the sonotrode serves as a re-forming tool. It determines the forming of the riveting pin.

During the holding time (cooling phase) the sonotrode serves also as fixation stamp, thus the melted material cools down under pressure.

Advantages of ultrasonic riveting:

1. A firm and seamless joint is achieved by overcoming the resilience of plastic materials
2. Short processing time
3. Low stress bonding
4. Rapid heat removal by a cold ultrasonic generator; ultrasonic generator is also used as a fixed mark
5. Deeper areas of plastic parts can also be achieved using riveted ultrasonic generators
6. Repeatable thickening technique; different materials can be riveted
7. Use a basic ultrasonic probe with a spiral riveted ultrasonic probe; therefore, one head can perform multiple riveting steps
8. No connection elements

Disadvantages of ultrasonic riveting:

1. Long process times and short cycle sequences lead to warming up of the riveting sonotrode. Here the sonotrode tip should be ventilated.
2. Electronic components are very sensitive against ultrasonic waves. It can lead to destruction of the elements.
3. If the parts to be riveted have thin walls, the visible side can show shiny spots and imprints
4. If the parts to be riveted have thin walls and also in case of hooks or clips the ultrasonic waves can lead to fissuring

An optimal riveting joint should be based on the following preconditions:

1. Principally provide radiuses or rounded punctures at the riveting root; this will reduce the indenting effect
2. Do not exceed the relation of pin diameter and pin length of 1:2 in full pins, otherwise use hollow pins (see attachment ‘design of riveting head’)
3. For easier parts assembly use inclined insertion surface
4. When riveting reinforced plastics and bondings with metal parts the riveting sonotrodes have to be wear-resistant

In the following there are listed some established sonotrode materials:

1. Hardened steel sonotrodes
2. Hardened Ferrotitanite sonotrodes
3. Titanium sonotrodes with coated riveting surface

Moreover, for an optimum riveting joint not only the sonotrode form and the material to be riveted are important, but also the process parameters like:

1. amplitude
2. melting time
3. contact force
4. contact speed
5. cooling time