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Development of a new laser welding technique for joining different types of polymers.

Final Report Summary - PLASWELD (Development of a new laser welding technique for joining different types of polymers)

The use of lasers in materials welding has increased in recent years due to the speed, accuracy and flexibility of this technique. But when applied to plastics in joining applications, lasers have limitations due to the inherent properties of these materials and it is still not sufficiently applied by plastic goods manufacturers. There are many methods established for joining plastics, each with its own advantages and disadvantages, but the most important disadvantage of the application of laser welding techniques is that the materials to be welded should be compatible to give a stable seam when cold. On the other hand, laser welding is the fastest welding method known but the dispensing and assembling activities are an important part of the welding process in terms of time consumption. Therefore, to take advantage of the laser welding speed it is necessary to optimize the dispensing and assembling operations.

The cooperative project PLASWELD aimed to develop a completely new, innovative and automated dispensing-assembling-laser welding process to make possible joining chemically incompatible plastic materials, using a new concept of polymeric absorbing inter-layer applied with a high tech dispensing system.

The following developments were made in the frame of the project:
- New compounds were developed for the four selected applications, with carbon black as absorbing additive when needed.
- Injection moulds were developed for the overinjection process and for the manufacturing of a modified cap for the PROCOPLAST case.
- Prototype plastic rectangular sample with different materials were injected for testing purposes.
- Overinjection trials were set up and transferred at sites of industrial partners.
- Overinjection trials were made on real parts for PROCOPLAST case.
- A welding and testing campaign was continued during all the second year.
- A clamping device was realised in order to ensure the scale up of the welding process.

All the objectives of the project have been reached: the process has been defined and validated for different applications. All the parameters linked with the composition of the materials, the injection and overinjection processes, and the laser welding process itself, have been analysed and optimised.

Furthermore, the consortium has established a methodology in order to help for the development of new applications, not only from a technical point of view (control of the processing parameters), but also from an economical point of view (cost calculation of the manufacturing and assembly processes, comparison between several assembly processes).

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