Ultrasonic Riveting Technology

Ultrasonic Riveting Technology

Date:Sep 06, 2019

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.

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Advantages of ultrasonic riveting:


solid and seamless fitting joint by overcoming the return elasticity of the plastic material

short process times

low-stress bondings

quick thermal drain via the cold sonotrode; the sonotrode simultaneously serves as fixation stamp

also deeper areas of a plastic component can be reached with the riveting sonotrodes

reproducible bolding technology; dissimilar materials can be riveted

use of basic sonotrodes with screw-in riveting sonotrodes; thus several riveting steps are possible with one head

no connection elements

 

Disadvantages of ultrasonic riveting:


Long process times and short cycle sequences lead to warming up of the riveting sonotrode. Here the sonotrode tip should be ventilated.

Electronic components are very sensitive against ultrasonic waves. It can lead to destruction of the elements.

If the parts to be riveted have thin walls, the visible side can show shiny spots and imprints

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:


Principally provide radiuses or rounded punctures at the riveting root; this will reduce the indenting effect

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’)

For easier parts assembly use inclined insertion surface

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:


Hardened steel sonotrodes

Hardened Ferrotitanite sonotrodes

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:


amplitude

melting time

contact force

contact speed

cooling time


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