Project MLP-X-4

Objective
After the success in the realization of the project 4500+ we dealt with the construction of the pipe. Here we discovered that the metal layer as a supporting element of the characteristics has to be focused on. When comparing the processes of butt welding and ultrasonic welding it became clear that both processes of the existing technology cannot be improved considerably. This experience caused consideration how the weld seam could be constructed differently in order to open up new possibilities in production.

System comparison
In ultrasonic welding the high level of safety due to the wide overlap of the metal layer proved to be an advantage. However, it is the reason for a bulge in the layer thickness in the welding area. Though, the low thermal load of the plastic material in production is an advantage. Butt welding shows a homogeneous feature in the curve. However, any possibility of full penetration welding of the material cannot be eliminated completely during the welding process. This would destroy the material’s oxide surface and require particular attention in production as to thermal characteristics. Due to diffusion, the destruction of the oxide surface offers the medium an additional contact surface. Furthermore, there is a minimum limit of material thickness for the process.

Research question and experimental set-up
These results lead to the question whether a combination of both systems would bring about the respective advantages. In an experimental set-up defined for the first time worldwide a laser was used for welding the overlapping layers.

Outcomes
The experimental set-up showed that the welding of the overlapping layers is possible. Modifications in the set-up then revealed that both the control of the laser intensity and the material thickness can be varied, so that the following overall result can be presented: The control of the welding intensity is possible in extremely small steps. This allows the adjustment of the welding depth subject to the material thickness. Thus, full penetration welding could be avoided and the side of the layer facing the medium is thermally not affected. Furthermore, the overlapping allows a highly exact guidance of the layers, which holds the welding process absolutely steady.

Further proceeding
In the pre-series we will have to examine how the process can be realized in practice.