Welded Securely All Round
Bühler Motor GmbH, Nürnberg, employs laser welding to reliably weld the housing for an auxiliary water pump. This housing is made from 40% glass-filled polyphthalamide (PPA). Auxiliary water pumps distribute hot water for the passenger compartment and regulate the temperature of the internal combustion engine when idling. As a result, the housing is exposed to temperatures of –30°C to +140°C.
During laser welding, the laser beam passes through a material that is transparent to the radiation from the laser and is absorbed at the surface of the second material, where it is converted into heat. Contact between the two materials results in conduction of heat to the transparent material, which then melts, and within a fraction of a second the weld seam forms.
The standard welding system (Model: ProWeld; Supplier: Prolas GmbH) in a stand-alone design was modified specifically to weld the auxiliary water pump. However, by exchanging part-specific components, changing the programming and adapting the process, it can also weld other variants.
To monitor the quality of the welding process, the laser welding system is equipped with an integral online process control system. This system measures the temperature change during welding and adjusts the laser output within defined limits in order to ensure high weld seam quality. Air inclusions in the transparent component, gaps between the components and different penetration depths are identified in this way. In addition, welding of defective components is prevented by a measuring device that confirms the laser transparency of the components prior to welding.