Ultrasonic welding in auto parts: Daytime Running Lights

2019-08-28 11:41:42

Ultrasonic application involved the assembly of daytime running lights. A clear plastic lens had to be welded to a plastic body with a hermetic seal. The complex 3D shape and class A surface were a challenge to weld. The customer also needed a cost-efficient system that could accommodate many variants for various car models.

To solve the problem, technician developed a composite sonotrode separated into two elements: a carrier-block sonotrode and a number of individually screwed-in tips. Each tip is a different height to fit its lens exactly.

To guarantee correct vibration, the carrier sonotrode was designed with the help of FEA and tuned for the correct frequency, idling power and amplitude. In addition, each tip was designed, manufactured and tuned like a stand-alone sonotrode. The tips include features for various interfering contours. For instance, some tips have cutouts to accommodate raised lettering on a component. All this influences how the sonotrode vibrates.

To ensure that the tips vibrate correctly, they were individually tested and adjusted in a pains-taking and time-consuming manual process. Under load simulation, the completed composite sonotrode was laser-measured and any corrections were performed by CNC machining. Special software measures up to 100 points to create the amplitude profile. Once calibrated, the composite sonotrodes worked beautifully and have been sold repeatedly.

To assemble model variants, all parts of the ultrasonic system form a “quick-change tooling frame” that can be detached from the main machine and exchanged with a different frame. During the startup phase, assembly was performed with one machine and multiple tooling frames. As variants increased, the customer only needed to purchase additional tooling frames. Cost-intensive components, such as ultrasonic generators, controls and safety systems, can be used with multiple tool frames for various daytime running lights.

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