Tool-free 3D joining technique for automotive headlights

Collaboration objective

Development of a process based on transmission laser welding without the need for extensive prior clamping of the headlight assembly parts. The joint section is designed to build a snap-on connection intrinsically providing the necessary joining pressure. No clamping tools are necessary. As part of the project, this new process has been demonstrated with a prototype and subsequently all operational parameters have been verified with regards to reproducibility and quality of the process.

Process development

Thorough R&D efforts and optimization of essential process parameters such as laser power and working distance have shown that hermetic sealing can be achieved by creating homogeneous material joints.

Observed esthetic limitations, caused by material flow at the joint, limit the application of this method to areas with no visual exposure. In areas where appearance is secondary, however, this method opens up new possibilities for creating hermetically sealed materials.

By taking an integral approach throughout product and process development, new process and cost optimization opportunities arise with the implementation of the tool-free laser transmission welding.

Functional and esthetic design aspects of automotive headlights require great flexibility of the welding process. In addition, the mechanical design has to take into consideration the need to irradiate the joint area with a laser. The requirements have been addressed by allowing for a large bulge (up to 65 degrees) of the plastic end disks of the prototypes.

The quality of the welding joint has been verified by testing the quality of the seal in a water bath and through analysis of the disk‘s settling behavior.

Process Parameters

Laser power up to 400 W
Working distance 230 mm
Processing time 40 sec
Seal integrity up to 15 J/mm

Development benefits

This newly developed method has been proven to be applicable to complex joint shapes and can be utilized in other applications as well as with other products. The project helped to gain insights with regards to the design of the joint sections, which are essential for the optimization of process parameters in similar applications. This enables the production of welding joints that meet the most demanding requirements.

As the development efforts have shown, knowledge of the optical properties of the welding assembly’s transparent part enables the irradiation strategy to be optimized, thereby substantially improving the mechanical properties of the welding joint.